TECHNICAL FIELD

[0001] The present invention generally relates to the disposal and processing of electronic waste, and more particularly to a process for the recovery of a metallic fraction of electronic waste for valorization thereof.

BACKGROUND

[0002] Current technologies for the recovery of electronic waste are complex and require, for obvious reasons of profitability, high-capacity installations that include systems for controlling pollutant emissions (management of by-products, collection and dust treatment, process gas scrubbing, control of pollutant levels, etc.). The treatment of electronic waste by melting in a high-temperature furnace is the most common process on an industrial scale, such as the one used in the Horne foundry in Rouyn-Noranda, Quebec.

[0003] Melting processes have shown significant effectiveness in recovering precious metals, but there are still limitations with respect to hazardous emissions such as dioxins that are generated during the melting of electronic waste containing halogenated flame retardants; instant combustion of fines from organic matter that can occur before reaching metal extraction; and partial recovery and purity problems of precious metals that require further treatments in order to recover pure metals. For example, it is known that melting processes in foundries led to a 15 to 20% loss of valorizable metals, whereas other mechanical processes can lead to 20 to 25 % of loss of valorizable metals.

[0004] Disposal and processing of electronic waste present various challenges that still need to be addressed and there is thus a need for a technology that overcomes at least some of the remaining drawbacks of what is known in the field.

SUMMARY [0005] In one aspect, there is provided a process for recovering organic and metallic fractions from electronic waste, the process comprising: conditioning the electronic waste to produce a conditioned material; pyrolyzing the conditioned material to thermally decompose the conditioned material into a gaseous component and a solid component, wherein the solid component comprises an organic fraction and a metallic fraction; and separating the metallic fraction from the solid component to recover at least one of Al, Zn, Ni, Cu, Au, Ag, Pt, and Pd; wherein at least 95 wt% of the electronic waste is valorizable under the form of recovered metals, pyrolysis oil and value-added products.

[0006] In some implementations, the conditioning includes reducing a size of the electronic waste. For example, the conditioned material can be under particulate form, and the conditioning step can include crushing the electronic waste into particulates having a particle size between 500 pm and 1000 pm. The crushing can be performed to produce the particulates having substantially the same particle size.

[0009] In some implementations, the conditioning can include extracting a ferrous fraction from the electronic waste to produce a non-ferrous waste. Optionally, the conditioning can include admixing a potassium-containing additive with the non-ferrous waste to form the conditioned material that is sent to the subsequent pyrolysis. For example, the potassium-containing additive can include potassium carbonate (K2CO3) and potassium oxide (K2O).

[0011] In some implementations, pyrolyzing the conditioned material can include exposing the conditioned material to a temperature between 300°C and 500°C, in an oxygen-depleted atmosphere.

[0012] In some implementations, the process comprises isolating the gaseous component from the solid component after pyrolysis.

[0013] In some implementations, the process comprises removing at least a portion of contaminants from the gaseous component. Optionally, removing the at least a portion of the contaminants comprises filtering the gaseous component.

[0014] In some implementations, the process comprises condensing a condensable portion of the gaseous component to form pyrolysis oil. Optionally, the condensing is performed via indirect heat exchange based on circulation of a cooling fluid. Optionally, the cooling fluid has an inlet temperature between 20 and 25°C. The process can further include separating the pyrolysis oil and a non-condensable portion of the gaseous component. The process can further comprise combustion of the non-condensable portion of the gaseous component via flaring.

[0017] In some implementations, separating the metallic fraction from the solid component comprises separating a lighter fraction comprising aluminum, and a heavier fraction comprising at least one of Zn, Ni, Cu, Au, Ag, Pt, and Pd from the solid component based on density. For example, separating the lighter fraction and the heavier fraction from the solid component based on density comprises immersing the solid component in a liquid medium to recover the lighter fraction floating on the liquid medium, and the heavier fraction sinking in the liquid medium. For example, separating the metallic fraction from the solid component comprises separating aluminum from the solid component as part of the lighter fraction, and the heavier fraction comprising remaining metals from the solid component. Optionally, the process can include selecting the liquid medium having a density of at least 3950 kg/m3.

[0019] In some implementations, the process comprises separating the heavier fraction from the liquid medium via filtration. Optionally, the process comprises washing the heavier fraction. Optionally, the process further comprises separating at least one of Zn, Ni, Cu, Au, Ag, Pt, and Pd from the heavier fraction. Optionally, separating at least one of Zn, Ni, Cu, Au, Ag, Pt, and Pd from the heavier fraction comprises separating nickel and zinc via leaching with a first leaching agent, thereby producing a liquid stream comprising nickel and zinc ions, and a solid residue. Optionally, the first leaching agent is sulfuric acid.

[0020] In some implementations, the process comprises extracting each of the nickel ions and zinc ions via separate liquid-liquid extractions by contacting the liquid stream with a solvent in two different columns at two different pH.

[0021] In some implementations, the solid residue comprises at least one of Cu, Au, Ag, Pt, and Pd, and the process further comprises separating copper by leaching the solid residue with a second leaching agent to produce a second solid-liquid mixture comprising copper ions in solution and a copper-depleted solid residue. Optionally, the second leaching agent is sulfuric acid and leaching the solid residue comprises contacting the solid residue with a solution of sulfuric acid having a concentration of at least 95%.

[0022] In some implementations, the process comprises filtering the second solid-liquid mixture to separate the copper-depleted solid residue and a copper-containing solution. Optionally, the process comprises electroreduction of the copper-containing solution in an electrolytic cell to recover solid copper on the cathode.

[0023] In some implementations, the copper-depleted solid residue comprises at least one of Au, Ag, Pt, and Pd, and the process further comprises separating silver by leaching the copper-depleted solid residue with a third leaching agent to produce a third solid-liquid mixture comprising silver ions in solution and a silver-depleted solid residue. Optionally, the third leaching agent is nitric acid and leaching the copper-depleted solid residue comprises contacting the copper-depleted solid residue with a solution of nitric acid having a concentration of at least 65%.

[0024] In some implementations, the process comprises filtering the third solid-liquid mixture to separate the silver-depleted solid residue and a silver-containing solution. Optionally, the process comprises mixing the silver-containing solution with a reduction agent to form recoverable solid silver. Optionally, the reduction agent is ascorbic acid.

[0025] In some implementations, the process comprises co-adding an anionic surfactant with the reduction agent.

[0026] In some implementations, the process comprises adding ethanol to the silver- containing solution in a centrifugation unit to remove the anionic surfactant.

[0027] In some implementations, the silver-depleted solid residue comprises at least one of Au, Pt, and Pd, and the process further comprises separating the at least one of Au, Pt, and Pd by contacting the silver-depleted solid residue with a fourth leaching agent to produce a metal-enriched solution comprising Au ions, Pt ions, Pd ions or any combinations thereof. Optionally, the fourth leaching agent is aqua regia, or a sodium cyanide solution.

[0028] In some implementations, the process comprises extraction of gold from the metal-enriched solution. Optionally, the extraction of the gold from the metal-enriched solution comprises conditioning the metal-enriched solution by: heating the metal- enriched solution; acidifying the metal-enriched solution to produce a corrected solution; and filtering the corrected solution to produce a filtered solution.

[0029] In some implementations, the extraction of the gold from the metal-enriched solution further comprises precipitating gold by contacting the filtered solution with a precipitation agent to produce a gold-containing slurry comprising precipitated gold and a gold-depleted solution. Optionally, the precipitation agent is sodium metabisulfite.

[0030] In some implementations, the process comprises filtering the gold-containing slurry to separate the precipitated gold and the gold-depleted solution. Optionally, the gold-depleted solution further comprises platinum ions and the process further comprises extracting platinum from the gold-depleted solution.

[0031] In some implementations, extracting the platinum from the gold-depleted solution comprises precipitating a platinum-containing compound by contacting the gold-depleted solution with a second precipitation agent to produce a platinum-containing slurry comprising the platinum-containing compound and a platinum-depleted solution. Optionally, the second precipitation agent is ammonium chloride, and the platinum- containing compound is ammonium hexachloroplatinate.

[0032] In some implementations, the process comprises filtering the platinum-containing slurry to recover the platinum-containing compound and a platinum-depleted solution.

[0033] In some implementations, the process comprises calcining the platinum- containing compound to form a solid mixture including free platinum.

[0034] In some implementations, the process comprises adding water to the solid mixture to solubilize soluble elements in an aqueous solution while leaving the platinum in solid state, and further separating the platinum via filtration.

[0035] In some implementations, the platinum-depleted solution further comprises palladium ions and the process further comprises extracting palladium from the platinum-depleted solution. Optionally, extracting the palladium from the platinum- depleted solution comprises precipitating a palladium-containing compound by contacting the platinum-depleted solution with a third precipitation agent to produce a palladium-containing slurry comprising the palladium-containing compound and a palladium-depleted solution. Optionally, the third precipitation agent is a mixture of hydrochloric acid (pH=1) and ammonia (4<pH>5), and the palladium-containing compound is dichloro-diamine-palladium.

[0036] In some implementations, the process comprises filtering the palladiumcontaining slurry to recover the palladium-containing compound.

[0037] In some implementations, the process comprises calcining the palladiumcontaining compound to form a second solid mixture including free palladium.

[0038] In some implementations, the process comprises adding water to the second solid mixture to solubilize soluble elements in an aqueous solution while leaving the palladium in solid state, and further separating the palladium via filtration.

[0039] In some implementations, the pyrolyzing of the conditioned material is performed by exposing the conditioned material to microwave radiations.

[0040] While the invention will be described in conjunction with example embodiments, it will be understood that it is not intended to limit the scope of the invention to such embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included as defined by the present description. The objects, advantages and other features of the present invention will become more apparent and be better understood upon reading of the following non-restrictive description of the invention, given with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Implementations of the process are represented in and will be further understood in connection with the following figures.

[0042] Figure 1 is a schematic process flow diagram representing a conditioning of e- waste (e.g., circuit board waste) to produce a conditioned material, a pyrolysis of the conditioned material, a separation of a produced solid component, and a separation of the aluminum from the solid component.

[0043] Figure 2 is a schematic process flow diagram representing further implementations of the process including extraction and separation of each of the remaining metals forming a metallic fraction of the solid component. [0044] Figure 3 is a graph showing the percentage of crushed electronic waste (printed circuit boards) passing each sieve based on the ASTM standard for particle diameter (in pm).

[0045] Figure 4 is a schematic representation of an experimental pyrolysis set-up comprising a tubular furnace coupled to a FT-IR.

[0046] Figure 5 includes two photographs of liquid solutions (lixiviant and wash water) after the dissolution of precious metals in aqua regia.

[0047] Figure 6 is an X-ray diffractogram of solid residues of a PCB/K2CO3 mixture (A) 500°C, (B) 750oCXRD analysis of solid residues of PCB I K2CO3 mixtures.

[0048] Figure 7 includes two photographs of condensable phenolic products resulting from the pyrolysis of a PCB/K2CO3 mixture at 500°C (A), or 750°C (B).

[0049] Figure 8 is a FT-IR spectrum of gaseous products resulting from the pyrolysis of pure PCB between 275°C and 425°C.

[0050] Figure 9 is a FT-IR spectrum of gaseous products resulting from the pyrolysis of a PCB/K2CO3 mixture at 425°C.

[0051] Figure 10 is a graph of a microwave thermogravimetric analysis curve of waste printed circuit board pyrolysis providing weight loss (in %) vs. temperature (°C).

[0052] Figure 11 is a graph of a conventional thermogravimetric analysis curve of waste printed circuit board pyrolysis providing weight loss (in %) vs. temperature (°C) for four different heating rates.

DETAILED DESCRIPTION

[0053] The present techniques relate to the recovery of multiple components from electronic devices, e.g., circuit boards, and their valorization as metals and value-added products. The process implementations described herein have a low environmental impact, and yet are economically profitable, in comparison with typical handling or recycling steps to dispose electronic devices. More particularly, the present process implementations include pyrolysis and hydrometallurgical steps to recover precious metals and produce high-end products such as carbon black, oil and chemicals. For example, the chemicals that can be produced from the treatment of waste printed circuit boards include phenols. In another example, the chemicals that can be produced from the treatment of waste plastics (e.g., ABS and HIPS) include styrene.

[0054] The combination of process steps described herein allows for the decontamination of plastic waste by recovering metals and for the valorization of decontaminated plastic waste into value-added products, while minimizing losses to landfill, which are reduced to at most 5 wt%, at most 3 wt%, at most 2 wt%, at most 1 wt% or 0 wt%. Fractions of electronic equipment that are typically unrecovered and sent to land fill, such as core magnet from hard drive, can rather be recovered as rare earth metals by the present techniques. In other words, upon being processes by the process as encompassed herein, at least 95 wt% of the electronic waste can be valorized as recovered metals or as a value-added product derived from the recovered organic fraction. Valorization is to be understood herein as a direct reuse of the recovered fraction or as an additional step/stage producing value-added products from the recovered fraction.

[0055] For example, a solid component and a gaseous component are recovered by the present techniques, with the solid component containing metals, metal oxides (silica) and carbon black that can be recovered for further reuse. The gaseous component can be characterized as including a condensable portion and a non-condensable portion (syngas). The non-condensable portion includes valorizable products such as phenolic products. For example, the metals that are recovered via the present process can be directly reused as raw material, and the carbon black that is recovered via the present process can be used as a conductive or insulating agent in a variety of rubber, plastic, ink and coating applications.

[0056] It should be noted that the CO2 emissions that are generated in relation to each of the steps of the process can be reduced by further selecting low-impact or renewable sources of energy, such as hydroelectricity. For example, the present process when processing circuit board waste can reduce CO2 emissions by 1256 tonnes CChe in comparison with a scenario in which the electronic waste is sent to landfill locally or abroad. [0057] In addition, the present process facilitates recovering each and every one of the metals included in the e-waste, and via techniques that do not release harmful chemicals to the environment/atmosphere. The metals and other carcinogenic materials are thus prevented from being released in terrestrial and aquatic environments, in comparison to disposing e-waste in landfill. In addition, recovering metals from the e-waste avoids consuming natural metal resources. For example, a circuit board can include about 200 g per ton of gold.

[0058] In one aspect, there is provided a process for recycling electronic devices that includes a pre-treatment stage to prepare intrants for the subsequent steps, a pyrolysis stage to thermally decompose the prepared material into a gaseous component and a solid component comprising recoverable organic and metallic fractions. The process further includes a primary separation stage where the gaseous component is recovered separately from the solid component, the former being converted into pyrolysis oil. The process further includes a secondary separation stage comprising separating at least one of a non-metallic fraction, and a non-ferrous metallic fraction from the solid component. More details regarding each stage will be provided further below.

Conditioning

[0059] Conditioning of the electronic waste can be considered as a non-chemical pretreatment that prepares the electronic waste to facilitate optimal performance of the subsequent pyrolysis step. The conditioning of the electronic waste can include reducing a size of the electronic waste.

[0060] For example, the electronic waste can be conditioned in particulate form. For example, the particulates can have a particle size ranging from 500 pm to 1000 pm. For example, the particulates can have substantially the same particulate size. It should be noted that the particulates having substantially the same particulate size are to be understood as particulates having a particulate size that do not differ from one particulate to another particulate of the electronic waste by more than 10%.

[0061] Reducing a size of the electronic waste facilitates the subsequent pyrolysis thereof. Referring to the implementation illustrated in Figure 1, the conditioning can include crushing the electronic waste 2, such as waste printed circuit board, to produce the particulates. For example, the electronic waste can be conveyed (via Conveyor-01) to a hammer mill 4. In some implementations, size reduction can be performed to produce particulates having substantially the same particulate size. Homogeneity in size can favor homogeneity in temperature in a pyrolysis reactor that is used for the subsequent pyrolysis step.

[0062] The conditioning can further include extracting a magnetic fraction from the electronic waste. For example, referring to Figure 1, the particulates 6 can be conveyed to a ferromagnetic separator 8 including a magnet that attracts ferromagnetic fractions 10, while remaining fractions 12 separate out from Reservoir-04 based on gravity to form a non-ferrous waste. The extraction of the magnetic fractions (Fe-containing) 10 can include adjusting a rotation speed of the Conveyor-01 and a size of the particulates 6 resulting from crushing.

[0063] The conditioning can further include mixing the electronic waste with a potassium-containing additive to form a mixture that, when further subjected to pyrolysis conditions in a pyrolysis reactor, can trap any released hydrogen bromide. Organobromide compounds can be used in electric and electronic devices as a flame retardant, and thermal decomposition of such compounds releases hydrogen bromide that can present environmental and safety issues. Referring to Figure 1 , the present process makes use of the potassium-containing additive 14 to form solid potassium bromide upon capturing toxic hydrogen bromide that can be released in the pyrolysis reactor 16 in order to avoid contamination of the gaseous component 17 with hydrogen bromide.

[0064] Figure 1 thus shows an implementation where the conditioning includes crushing into particulates 6 of controlled size, removing the ferrous metallic fraction 10 and adding a potassium-containing additive 14 to the non-ferrous waste 12 to form the conditioned material 15 that is sent to subsequent pyrolysis in the pyrolysis reactor 16.

Pyrolysis

[0065] In some implementations, as seen in Figure 1, the pyrolyzing stage includes pyrolysis of the conditioned material 15 that is performed in the pyrolysis reactor 16 to thermally decompose the organic elements of the conditioned material 15 and facilitate release of the remaining metallic fractions. The pyrolyzing stage includes subjecting the conditioned material 15 to thermal decomposition temperatures of at most 500°C, optionally ranging from 300°C to 450°C, further optionally ranging from 300°C to 400°C, and under controlled atmosphere that is exempt of oxygen and at a pressure being atmospheric pressure or being optionally of at least 1 atm. The controlled atmosphere can be consisting of an inert gas. One skilled in the art will know how to adjust temperature and pressure in accordance with the nature of the electronic waste to be decomposed, for example, via thermal gravimetric analysis of a sample of the waste.

[0066] The techniques that are used to perform pyrolysis can vary and include conventional heating or microwave heating, to reach the targeted thermal decomposition temperature. The pyrolysis can be for example performed in a pyrolysis reactor that can be a rotary horizontal tube furnace (e.g., tube length up to 48", tube Diameter up to 10", Rotating speed up to 30 RPM, double-Shell Design to Ensure Low Outside Temperature), that deliver accurate temperature control, and excellent temperature uniformity. Alternatively, the pyrolysis can be performed in a pyrolysis reactor that is inserted in a multimode microwave oven for exposure to microwaves. Additional comparative results are provided in the further below experimental results section when conventional and microwave heating were tested.

[0067] Thermal decomposition of the conditioned e-waste 15 produces a gaseous component 17 and a solid component 18. The solid component includes a metallic fraction and an organic fraction that is also referred to as carbon black.

Primary separation

[0068] The process further includes a primary separation stage where the gaseous component and the solid component are separated from one another. For example, referring to Figure 1 , the gaseous component 17 can be recovered via a gas outlet located in an upper portion of the pyrolysis reactor 16, while the solid component 18 can be separately recovered via a solid outlet located in a lower portion of the pyrolysis reactor 16.

[0069] The process further includes condensing a condensable portion of the recovered gaseous component to form a pyrolysis oil. Still referring to Figure 1, the condensing is performed in a condensing unit 19 (or condenser) involving indirect heat exchange via circulation of a cooling fluid 19’ in closed loop to condense the condensable portion of the gaseous component 17, and the process can further include separating the pyrolysis oil 21 and a non-condensable portion 22 via a separator 20.

[0070] The condensable portion can include value-added products. The produced value- added products include mainly phenolic products (see experimental section) and can further include in lower concentrations other organic compounds, such as 1-Methyl-4-(1- methylethenyl)-benzene, 3-Phenyl-2-propenal. Non-condensable gases containing mainly hydrogen, methane, and carbon monoxide can be further produced.

[0071] For example, the cooling fluid 19’ can have an inlet temperature between optionally between 20°C and 25°C. For example, the cooling fluid 19’ can be water, ethylene glycol, or a mixture thereof. The heat that is transferred to the cooling fluid 19’ during condensation of the condensable portion of the gaseous component 17 into the pyrolysis oil 21 is further transferred to surrounding air in a cooling tower 19” so that the cooling fluid 19’ is cooled down and recycled to the condenser 19. The pyrolysis oil 21 can be stored in a dedicated oil tank.

[0072] The non-condensable portion 22 of the gaseous component, that is depleted in hydrocarbons, is separated after condensing. In some implementations, the process can include burning the non-condensable portion 22 off to atmosphere via a flaring system. The flaring system can be operatively connected to a pressure monitoring system that flares the non-condensable portion at the exit of the condenser when the monitored pressure reaches an upper threshold in the condenser. Optionally, a scrubber 23 can be used to clean the non-condensable portion 22 before burning thereof.

[0073] In some implementations, the process can include, prior to condensing, removing contaminants from the gaseous component to avoid subsequent contamination of the condensed pyrolysis oil. The removal of the contaminants can be performed via a filter that is positioned directly at the gas outlet of the pyrolysis reactor. The contaminants can be fine particles of carbon black and/or metals.

[0074] The solid component that is recovered from the pyrolysis reactor via the solid outlet includes an organic fraction and a metallic fraction. The process includes further separation of the fractions from the solid component based on physicochemical characteristics of such fractions. Separation of elements from the solid component is referred to as a secondary separation. More particularly, the process includes separation of the metallic fraction from the solid component, and the separation of the metallic fraction including extracting each and every one of the metals that are included in the metallic fraction of the solid component.

Secondary separation

[0075] The nature of the metals included in the solid component can vary in accordance with the e-waste that is processed. When the conditioning includes a ferromagnetic separation of the e-waste particulates, the metallic fraction can be characterized as being a non-ferrous metallic fraction that includes at least one of Al, Zn, Ni, Cu, Au, Ag, Pt, and Pd. The organic phase of the solid component can be referred to as carbon black. The solid component can further include other non-metal compounds such as potassium bromide, ceramics (aluminum oxide and/or silicon dioxide) or a combination thereof.

[0076] Various analysis techniques have been relied on to characterize the composition and structure of the recovered solid component. Based on SEM characterization, it was observed that the organic fraction (carbon black) was distributed as a thin volatile and hydrophobic layer onto metals which led to choosing a closed conveyor to avoid release of carbon black particles in surrounding atmosphere.

[0077] The following Table 1 provides a list of the compounds that can be found in the solid component along with their density in kg/m ³ .

Table 1 [0078] Ferrous metals can be present in the solid component in an implementation where the magnetic separation is performed after pyrolysis.

[0079] It should be noted that the solid component 18, before separation thereof into fractions, can be further grinded in a grinder 24 as seen in Figure 1, to in order to liberate the metals and enhance the subsequent density separation process.

[0080] The separation of the metallic fraction can include separating the aluminum from the solid component based on density. Density-based separation includes immersing the solid component in a liquid medium having a density that is selected in accordance with the density of the elements to be separated. More particularly, the density of the liquid medium can be selected between a lower density threshold corresponding to the density of a lighter fraction of the solid component to be separated, and an upper density threshold corresponding to the density of a heavier fraction of the solid component.

[0081] Separating aluminum from the solid component can thus include separating the lighter fraction from the solid component, with the lighter fraction including aluminum. The liquid medium can be selected to have a density that is above the density of aluminum oxide (3950 kg/m ³ ) and below the density of other metals of the solid component, e.g. below the density of zinc (7134 kg/m ³ ). For example, the liquid medium can be lithium heteropolytungstate (LST « Heavy liquid »).

[0082] Referring to Figure 1, the solid component 18 is immersed in a liquid medium 26, e.g. LST, having a density of at least 3950 kg/m ³ within a floating tank 27. It should be noted that a fluidized bed could be used in place of the floating tank to fulfill the same objective. The lighter fraction 28 can be recovered floating on the liquid medium, the heavier fraction 29 sinking in the liquid medium. The lighter fraction 28 thus includes the organic fraction of the solid component in addition to any ceramic and potassium bromide that the solid component can contain. It should be noted that ceramics, for example, would be absent from the solid component, when treating plastic waste such as ABS and/or HIPS. Separating the aluminum as part of the lighter fraction 28 thus includes immerging the solid component 25 in the liquid medium to recover the lighter fraction floating on the liquid medium, and the heavier fraction sinking in the liquid medium. The heavier fraction 29 can be then separated from the liquid medium and further washed before subsequent extraction of at least one of Zn, Ni, Cu, Au, Ag, Pt, and Pd that will be detailed further below.

[0083] The lighter fraction including aluminum can be further subjected to another density separation in order to recover aluminum that can represent 2 to 5% of the solid residue after pyrolysis.

Nickel and zinc extraction

[0084] The process can further include extraction of nickel and zinc from the recovered heavier fraction. Extraction of nickel and zinc are separated from the heavier fraction via leaching with a first leaching agent that can be sulfuric acid. The process can include preparing a solution of sulfuric acid including 10% (pH 1) to 33.5% (pH 0.5), further optionally at least 30% of sulfuric acid.

[0085] Referring to Figure 2, upon contacting the heavier fraction 29 with the first leaching agent 30, nickel and zinc are leached and dissolved as nickel, zinc and sulfate ions that are formed along with water, and a solid residue that is depleted in nickel and zinc is further formed. The contacting can be performed in a first leaching unit 31, which can include a paddle mixer, to mix the solids and the liquid, thereby optimizing leaching efficiency. A first liquid-solid mixture 32 can be recovered from the first leaching unit 31 and further sent to a filtration unit 33 to proceed with filtrating the first liquid-solid mixture 32. Filtration allows separation of the solid residue 34, and of a filtered liquid stream 35 that includes water, nickel ions (Ni ²⁺ ), zinc ions (Zn ²⁺ ), and sulfate ions (SCU ^2- ).

[0086] Although not illustrated in the Figures, nickel and zinc ions can be further extracted from the filtered liquid stream based on liquid-liquid extraction with an adequate solvent. For example, the solvent can be dialkyl phosphinic acid solvent, such as Cyanex® 272, that can extract up to 99,4% of zinc at a pH of 3,08 and up to 92,8 % of nickel at a pH of 7,47. In another example, the solvent can be Cyanex® 301. The process can include adjusting a pH of the liquid stream to remove at least 90% of the zinc and at least 90% of the nickel, in accordance with the selected solvent. Adjustment of the pH can be performed by adding sulfuric acid to the liquid stream. For example, the filtered liquid stream can be sent to a first column for contacting the solvent to extract zinc and form a zinc-depleted liquid stream. The pH of the zinc-depleted liquid stream can be sent to a second column for contacting the solvent and operate further extraction of nickel. An adjustable amount of a solution of diluted sulfuric acid can be added at each of the first and second columns to adjust a first pH in the first column and a second pH in the second column.

Copper extraction

[0087] The solid residue that is recovered from nickel and zinc extraction can further contain remaining metals that are valorizable, and more particularly can include at least one of Cu, Au, Ag, Pt, and Pd. In some implementations, the process further includes extracting copper via leaching of the solid residue with a second leaching agent. The second leaching agent can be sulfuric acid. The sulfuric acid can be provided in concentrated solution, in a concentration between 90% and 99%, preferably of at least 98%.

[0088] In the implementation shown in Figure 2, the solid residue 34 can be contacted with a solution of the second leaching agent 36 in a second leaching unit 37 that can be equipped with a paddle mixer. Upon contacting sulfuric acid as the second leaching agent, the copper from the solid residue forms copper sulfate (CuSOi) and sulfur dioxide (SO2). The solution can be at a pH between 0.5 and 1. The process can include maintaining the temperature at ambient conditions, between 18°C and 24°C, to minimize co-leaching silver with the copper. The yield of the copper leaching can be at least 75 wt% of the copper included in the electronic waste. The second leaching produces a second solid-liquid mixture 38 that can be filtered with filter 39 to recover a copper- containing solution 40, and a copper-depleted solid residue 41 that can further include remaining precious metals, such as at least one of Au, Ag, Pt, and Pd.

[0089] Still referring to Figure 2, the copper-containing solution 40, containing copper ions, is sent to an electroreduction step in an electrolytic cell 42 that can include a copper cathode and a platinum anode, thereby recovering copper 43 on the cathode and producing a liquid waste 44. The liquid waste can include or be sulfuric acid.

[0090] By relying on electrolysis that precipitates copper out of the liquid stream, at least 95 wt%, at least 96 wt%, at least 97 wt% or at least 98 wt% of the copper from the e-waste can thus be recovered.

Silver extraction [0091] The copper-depleted solid residue can include precious metals that are recoverable via further extraction depending on the nature of the precious metal that is to be extracted. The copper-depleted solid residue 41 can further include remaining precious metals, such as at least one of Au, Ag, Pt, and Pd. Referring to the implementation of Figure 2, the process includes extracting silver from the recovered copper-depleted solid residue 41 by leaching the copper-depleted solid residue 41 with a third leaching agent. The leaching can include mixing the copper-depleted solid residue 41 with a solution of the third leaching agent 45 in a third leaching unit (e.g., mixer) 46.

[0092] The third leaching agent can be nitric acid (HNOs) or hot concentrated sulfuric acid (H2SO4). For example, the solution of nitric acid can have a concentration between 30 and 70 vol. %. The third leaching can be performed at a solid/liquid ratio of 1 g/20 mL, a leaching time of 1 h, a temperature of 65 °C, and a stirring speed of 500 rpm to enable sufficient mixing. When nitric acid is used as leaching agent for silver, the formed third mixture comprises a silver-depleted solid residue, a silver-containing solution (silver nitrate) and gaseous nitric oxide (NO). Referring to Figure 2, a filtering system can include a solid filter 47 to separate the silver-depleted solid residue 48, and the silver- containing solution 49 released from an outlet of the third leaching unit 46, and further includes a gas filter 50 to prevent any nitric oxide to be released in atmosphere.

[0093] The process can further include recovering silver from the silver-containing solution by mixing the silver-containing solution with a reduction agent.

[0094] Referring to Figure 2, the silver-containing solution 49 can be mixed with ascorbic acid (CeHsOe) as the reduction agent 51 in a mixer 52 to perform reduction of silver metal. For example, the silver-containing solution can be an AgNCh solution having a concentration of 20 mg/mL, a ratio of n(C6H8O6)/n(AgNO3) can be of 1:3, and the reaction temperature was 60°C. However, because the reduction reaction can release an oxidizing agent, such as nitric acid that can oxidize the reduced silver, the process can include co-adding a film-forming agent 53 that surrounds the formed solid silver with a film preventing contact and oxidation with the released oxidizing agent. The filmforming agent 53 can be an anionic surfactant, such as sodium dodecyl benzene sulfonate (SDBS), that is diluted in water when added into the mixer 52. [0095] Still referring to Figure 2, the process can further include recovering the solid silver 55 by filtering the slurry 54 exiting the mixer 52. Optionally, before filtering the slurry, the process can include adding a solution of ethanol to the slurry and centrifuging the mixture to remove the protective film. Once filtrated, the solid silver 55 is dried in an oven at a temperature between 55 and 65°C, for example at 60°C.

Leaching of Gold, Palladium and Platinum

[0096] The silver-depleted solid residue can include at least one of Au, Pt, and Pd which can further be extracted. Each of these three precious metals can be leached by aqua regia (HNOs : 68% I HOI 37%) which is a strong leaching agent. The process can thus further include leaching the silver-depleted solid residue with a fourth leaching agent that can leach the Au, Pt and Pd together when all present in the solid component.

[0097] Referring to Figure 2, the silver-depleted solid residue 48 is contacted with aqua regia serving as the fourth leaching agent 56 in a fourth leaching unit 57 that can include another paddle mixer. The leaching of the remaining precious metals can be performed at a temperature between 75°C and 80°C. Upon leaching the precious metals into the aqua regia, another slurry 58 can be recovered from the leaching unit 57 via a solidliquid outlet. The remaining slurry 58 can for example include any undissolved metals, carbon black and silica. Any gas that can form during leaching, for example water vapor and NO, is filtered via a gas filter 59 provided at a gas outlet of the leaching unit 57. The formed slurry 58 comprises a solution that is enriched in precious metal ions which can be extracted in order to recover each of the precious metals separately for further valorization. Before proceeding to extraction of the precious metals, the process can include removing remaining solids 60 (e.g., undissolved metals, carbon black, silica) from the slurry 58 via filtration to recover the metal-enriched solution 61.

Gold extraction

[0098] Gold can be the first of the remaining precious metals to be extracted from the recovered metal-enriched solution.

[0099] In some implementations, extraction of gold can include conditioning the metal- enriched solution for preparation to the further extraction. The conditioning can include removal of the nitric acid from the solution, adjustment of the pH and further removal of any remaining solids. Referring to Figure 2, nitric acid can be removed from the metal- enriched solution 61 in a mixing unit 62 that is heated at a temperature between 80°C and 85°C to neutralise the Aqua regia solution and remove the nitric acid. An acidification agent, such as additional hydrochloric acid, can be further added via another stream 63 to the mixing unit 62 for re-acidification at a pH between 1 and 2.5, and production of a corrected solution 64. The corrected solution 64 is further filtrated via another filtration unit 65 to remove any remaining solid that is discarded as waste 66. A filtered solution 67, exiting the filtration unit 65, contains chloroauric acid and any other precious metals that were leaching by the aqua regia. In the case of an e-waste made of printed circuit board, the filtered solution can contain gold, platinum and palladium ions.

[00100] Before proceeding to the precipitation of gold, urea CO(NH2)2 can be added to the liquid stream to neutralise the nitric acid. Additional hydrochloric acid can be mixed to the neutralized solution for re-acidification and diluted with water. Optionally, the neutralized and diluted solution can be filtered again to remove any solids.

[00101] The extraction of gold can include contacting the filtered solution with a precipitation agent. Still referring to Figure 2, extraction of the gold from the filtered solution 67 is performed by contacting the filtered solution 67 with an aqueous solution of the precipitation agent 68 in a precipitation unit 69 (e.g., a mixer) at a pH between 1 and 2.5. The precipitation agent can be sodium metabisulfite (Na2S20s) which will precipitate gold while releasing sulfur dioxide (SO2) and forming sodium bisulfite (NaHSCh). The precipitation agent can alternatively be hydrazine hydrate, zinc and hydroquinone. A gas filter 70 can be used at a gas outlet of the precipitation unit to filter any toxic gas that can be released during precipitation (e.g., sulfur dioxide). A gold- containing slurry 71 is thus produced and solid gold 73 is recovered by filtering the gold- containing slurry 71 via a seventh filtration unit 72. The remaining gold-depleted liquid stream 74 exiting the filtration unit 72 includes hydrazine hydrate, zinc and hydroquinone.

Platinum extraction

[00102] The gold-depleted solution can further include at least one of platinum and palladium-based acids, which can further be recovered as precipitated solid metal according to the following. In the implementation where the gold-depleted solution 74 further contains platinum, as seen in Figure 2, a stream of ammonium chloride (NH4CI) can be added as a second precipitation agent 75 in a second precipitation unit 76 (e.g., a mixer) to form solid ammonium hexachloroplatinate ((NH^PtCfe). Such solid portion 77 can be filtered via filtration in an eighth filtration unit 78, thereby producing a platinum-depleted solution 79.

[00103] Extraction of platinum further includes calcining 80 the ammonium hexachloroplatinate at a calcination temperature of at least 500°C to decompose ammonium chloride, platinum and hydrochloric acid. As ammonium chloride is soluble, water can be added to the calcined mixture to solubilize ammonium chloride and recover platinum via additional filtration (not shown in Figure 2).

Palladium extraction

[00104] In some implementations, the platinum-depleted solution can contain palladium ions, and the process further includes extraction of the palladium from the platinum-depleted solution.

[00105] Referring to the implementation of Figure 2, the platinum-depleted solution 79 can be contacted with a third precipitation agent 81 in a third precipitation unit 82 (e.g., a mixer). The third precipitation agent can be a mixture of hydrochloric acid (pH=1) and ammonia (4<pH>5) to perform precipitation of solid dichloro-diamine- palladium (3(NH3)2(PdCl2)). The solid 84 can be recovered via filtration in another filtration unit 83. The filtered stream 88 is considered as a waste stream and can include residual metals that have not been recovered, depending on the nature of the processed electronic waste.

[00106] Extraction of the palladium further includes calcining the recovered solid to form a solid mixture including free solid palladium. Referring to Figure 2, the solid 84 (dichloro-diamine-palladium) can be calcined at a temperature of at least 800°C to release palladium, chloride, and hydrochloric acid. Although not shown in Figure 2, water can be added to solubilize soluble component of the calcined mixture and palladium can be separated with a final filtration.

[00107] It should be understood that any one of the above-mentioned aspects and implementations can be adapted to the nature of the e-waste to be processed. Although most of the implementations are described in relation to recovering components from circuit board waste (fiberglass reinforced epoxy resin composite (FR-4)), one skilled in the art will know that said process implementations can be used and adapted to other bromine-containing e-waste including acrylonitrile-butadiene-styrene (ABS-Br) and high-impact polystyrene (HIPS-Br).ln another example, the present techniques could also be applied to optical fiber waste. Mainly silica (SiCh), among the glasses, fused silica (amorphous silicon dioxide, SiCh) is the dominating base material in fiber optics (particularly for optical fiber communications), because it has a number of very favorable properties: Silica has a wide wavelength range with good optical transparency.

[00108] It should be noted that the same numerical references refer to similar elements. Furthermore, for the sake of simplicity and clarity, namely so as to not unduly burden the figures with several references numbers, not all figures contain references to all the components and features, and references to some components and features may be found in only one figure, and components and features of the present disclosure which are illustrated in other figures can be easily inferred therefrom. The embodiments, geometrical configurations, materials mentioned and/or dimensions shown in the figures are optional, and are given for exemplification purposes only. Therefore, the descriptions, examples, methods and materials presented in the claims and the specification are not to be construed as limiting but rather as illustrative only.

[00109] It is worth mentioning that throughout the following description when the article “a” is used to introduce an element it does not have the meaning of “only one” it rather means of “one or more”. It is to be understood that where the specification states that a component, feature, structure, or characteristic “may”, “might”, “can” or “could” be included, that particular component, feature, structure, or characteristic is not required to be included.

[00110] In the following description, the term “about” means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e., the limitations of the measurement system. It is commonly accepted that a 10% precision measure is acceptable and encompasses the term “about”. [00111] In the above description, an embodiment is an example or implementation of the inventions. The various appearances of “one embodiment,” “an embodiment” or “some embodiments” do not necessarily all refer to the same embodiments. Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment.

EXPERIMENTAL RESULTS

[00112] Printed circuit boards were used as the electronic waste to be treated by the present process. After being shredded and crushed, the conditioned electronic waste was analyzed to be characterized via 1) sieve analysis to determine a particle size distribution thereof, 2) elemental composition analysis (CHNSO), 3) immediate analysis (ash, volatile matter, fixed carbon, humidity) and 4) Neutron Activation Analysis (NAA) to determine metal concentrations.

CHARACTERIZATION

PARTICLE SIZE DISTRIBUTION OF PRINTED CIRCUIT BOARDS

[00113] The standard (ASTM B214-07) describes the standard method for sieve analysis for metallic samples, including sample preparation, procedure, and how to report the results. The ASTM standard provides a recommendation on the sample size used in the sieve analysis. If the bulk density of the material used is greater than 1.50 g / cm ³ , a sample size between 90 g and 110 g should be used. Otherwise, a smaller sample between 40 g and 60 g can be used. In the present case, the density of the printed circuit boards used is 1.86 g / cm ³ , which is why the sample size used is 100 g. The results of the sieve analysis are shown in the following table in terms of the percentage of the total weight of the sample which passed through different sieves.

Particle size analysis of printed circuit boards (sample size = 100 g)

Sieve Diameter Percentage of sample Percentage of sample passed number (pm) retained on each sieve (%) through each sieve (%)

3 2000 0 100

5 1000 3 97

7 850 6 91

10 500 27 64

12 300 35 29

15 180 24 5

19 106 3 2

Pan - 2 0 [00114] By analyzing the particle size distribution curve of the crushed printed circuit boards shown in Figure 3, it can be concluded that the distribution was not uniform due to the variation in the degree of release of the different components. More than 90% of the initial sample is less than 740 pm in size and more than 50% of the initial sample is less than 420 pm in size.

ELEMENTARY AND IMMEDIATE ANALYSIS OF PRINTED CIRCUIT BOARDS

[00115] Elemental Composition Analysis (CHNSO) was performed on four samples, using EuroVector's EA3000 Elemental Analyzer. Three analytical methods have been developed to analyze the presence of the following elements: 1 - Carbon, Hydrogen, Nitrogen (CHN); 2 - Oxygen (O); and 3 - Sulfur (S). The instrument's detection limit is 0.2 pg for Carbon, Hydrogen, Nitrogen (CHN) and 1 pg for Sulfur (S). The proximate analysis of the printed circuit boards was carried out with a thermogravimetric analyzer (TGA) (Q50 - TA Instruments) on 4 samples, based on the standard (TA-129) of TA Instruments. The sample was initially heated to 200°C and maintained at this temperature for 30 minutes under an inert atmosphere (N2) (the weight loss is directly associated here with the relative humidity of the sample expressed in%), then heated to 900°C and held for a further 30 min. under an inert atmosphere (N2) (weight loss is here associated with the presence of volatile species formed during thermal decomposition), and finally nitrogen was replaced by air for 10 minutes (weight loss associated with fixed carbon). The immediate analysis presented in the following table shows that the printed circuit boards (as raw electronic waste) contain a high concentration of ash rich in metals and metal oxides (67.35%). The humidity is relatively low, while the volatiles produced by organic compounds (epoxy resins + polymers) are high (20.15% of the initial mass). The mass percentage of carbon which is 21.05% is relatively high compared to other elements derived from elemental analysis.

Elementary and proximate analysis of printed circuit boards obtained by TGA and by the elementary analyzer EA3000

Mass fraction (%)

Elemental analysis

C 21.05 (± 0.34) H 2.09 (± 0.05)

N 0.78 (± 0.21)

S 0.03 (± 0.01)

O 1.63 (± 0.15)

Proximate analysis

Humidity 0.25 (± 0.07)

Volatile 20.15 (± 0.13)

Fixed carbon 9.95 (± 0.17)

^Ash 67.35 (± 0.32)

NEUTRONIC ACTIVATION ANALYSIS (NAA) OF PRINTED CIRCUIT BOARDS

[00116] Neutron Activation Analysis (NAA) is a non-destructive method used to determine the concentrations of elements in a sample. It is based on the conversion of stable isotopes of the elements into unstable radioactive isotopes by irradiation with neutrons in a nuclear reactor. The following presents the results of the neutron activation analysis of printed circuit boards carried out using a (Safe LOW-Power Kritical Experiment (SLOWPOKE) nuclear reactor.

[00117] High concentrations of certain elements have been detected, in particular: 1 - copper (15% by weight), an excellent electrical and thermal conductor; 2 - tin (5.2% by weight), used for soldering, and iron (4.9% by weight). Bromine from flame retardant (TBBPA) was also detected at a concentration of 5849 ppm. Other elements such as silicon (30% by weight), aluminum (2.6% by weight) and calcium (4.2% by weight) are most likely present in the form of oxides which make up epoxy resins. Despite the low concentrations of gold (387), silver (1063 ppm), platinum (544 ppm) and palladium (11.6 ppm), their relative content in electronic waste compared to that of ores mined to date makes them economically interesting to recover.

Chemical analysis by Neutron Activation of printed circuit boards

Concentration Concentration Concentration

Element Element Element (PPm) (PPm) (PPm) Si <300 000 Gd 311 W 3.44

Cu 150 856 Sr <300 Hg <3

Sn 51 574 Ru 226 Dy 1.7

Fe 49611 Gd <150 Sc 1.76

Ca 42 477 Cd <100 Cs 1.38

Al 25 985 La 93.5 Ta 0.52

Ni 12 494 Ce 71.9 In 0.354

Zn 8 759 Mn 46.7 Mo <25

Pb 7 686 Cr 46.4 Rb <12

Ti <6 000 Cl 38.3 U <5

Br 5 849 Eu <30 Ir <5

Ba 4 843 Nd 27 I <5

Mg 4 735 Co 19.7 Se <8

Ag 1 063 As 13.8 Yb <1

Na 905 V 12.7 Tb <0.6

Sb 643 Ga 10.9 Lu <0.2

Pt 544 Hf 10.5

Zr 540 Sm 4.71

K 399 Th 3.18

Au 387 Pd 11.6

[00118] As mentioned earlier, the concentrations of metals in printed circuit boards vary widely within a sample depending on the size of the particles. To study this phenomenon, and based on our particle size distribution, three samples of different particle sizes (<180 pm, 180-300 pm, 300-500 pm) derived from the initial sample were prepared and analyzed, as presented in the following table. Silicon, the main base metals (copper, tin, iron), and some precious metals (silver, platinum, palladium) follow the same behavior: as the size of the particles increases, their concentration becomes higher. In contrast, gold and bromine from the flame retardant are more concentrated in samples containing the smallest particles (<180 pm). Neutron Activation Analysis of Printed Circuit Boards with different particle sizes

< 180 m 180-300 pm 300-500 pm uement

Cone. Cone. Cone.

Si 255,188 283,927 < 330,000

Cu 72,856 179,365 176,807

Sn 21,764 35,362 44,259

Fe 61,261 64,066 76,735

Br 28,287 23,974 18,657

Au 523 277 251

Ag 3,090 4,562 6,712

Pd 861 1,281 1 ,469

Pt 575 923 1 ,527

PYROLYSIS OF PRINTED CIRCUIT BOARDS IN A TUBULAR OVEN

[00119] Using the experimental set-up illustrated in Figure 4, pyrolysis tests were carried out in a Lindberg I Blue tube furnace (M ™ 1200 ° C). A quartz reactor (internal diameter = 0.013 m, length = 0.254 m) was used, under an inert atmosphere (N2, 1000 ml I min.). A heating rate of 10°C/min. and an ambient temperature range of 750°C was considered. The liquid products were collected using a cold trap (acetone + dry ice), then analyzed qualitatively and quantitatively via GC/MS chemical analyzes. A high-resolution FT-IR analyzer (atmosFIR) is connected to the output of the cold trap, to analyze the non-condensable gases produced during the thermal decomposition of the samples, as shown in the following figure. The FT-IR analyzer is equipped with an integrated sampling control system that guarantees the analysis of the reactor outlet gas. Dry nitrogen at 1 bar and a flow rate of 3 l/min is connected to the inlet of the purge cell and is used as a reference gas, while the internal optics of the FT-IR is purged with a flow rate of 250 ml/min. A vacuum pump is connected to the output of the assembly to remove the gases produced by the sample to the fume hood. The sampling line is heated and insulated, without a cold zone. To protect the FT-IR analyzer cell from dust and other particles that may be present in the sample, the atmosFIR is equipped with an inlet filter. [00120] As concluded from the present analysis, the pyrolysis of printed circuit boards produces a solid residue rich in metals and metal oxides, mixed with carbon black (73.15%), while the liquid and gaseous products from the decomposition of the polymers and epoxy resins were about 21.69% and 5.16%, respectively, as shown in the following table.

Distribution of pyrolysis products from printed circuit boards at 75CPC

Product Mass fraction (%)

ANALYSIS OF LIQUID AND SOLID FLOWS AFTER LEACHING (see Figure 5)

Analysis of the liquid flow Analysis of the solid flow

After After

After HCI After HNO3 Aqua After HCI After HNO3 Aqua

Regia Regia

( vcone. , . (cone. , . (cone. (cone. . (cone, ppm) ^v . (cone, ppm) ^{v v} . ppm) ^v ’ ppm) ^v ’ ppm) ppm)

Cu - 171 788 3435 175294 3505 70.12

Ag - 1315.16 26.30 1342.00 26.84 0.54

Au - 6.60 271.85 284.00 277.40 5.55

Pd - 7.56 351.78 374.00 366.44 14.66

Pt - 3.19 172.72 185.00 181.81 9.09

PRODUCTION OF VALUE-ADDED GAS AND LIQUID PRODUCTS (PHENOL)

[00121] Referring to Figure 6, it can be observed by analyzing the X-ray diffractogram for the conditioned electronic waste (crushed printed circuit board (PCB) and K2CO3 mixture), that potassium bromide (KBr) is the major compound that was detected at a temperature of 500°C, which confirms the reaction between the carbonate of potassium (K2CO3) and HBr (g) released. Signals of copper bromide (CuBr) and iron, which did not react with HBr, were also identified at the same temperature. At a temperature of 750°C, potassium bromide (KBr) which formed at 500°C, was still the major compound that was detected, due to its thermal stability, while the majority of copper bromide (CuBr ) which formed at low temperature, evaporated.

ANALYSIS OF PRINTED CIRCUIT BOARDS (PCB) and PCB/K2CO3 MIXTURES (1 :1 wt/wt) PYROLYSIS CONDENSABLE PHENOLIC PRODUCTS

[00122] The presence of potassium carbonate (K2CO3) in the conditioned electronic waste sent to pyrolysis shows that the resulting pure phenol content has increased by comparing the same values to those obtained during the pyrolysis of PCB (see table below and Figure 7) at temperatures of 500 and 700°C.

Results of semi-quantitative analysis by GC-MS of condensable phenolic products of PCB and PCB/K2CO3 mixture

PCB PCB PCB/K2CO3 PCB/K2CO3

% wt in the % wt in the % wt in the % wt in the condensable condensable condensable condensable fraction fraction fraction fraction

T = 500°C T = 750°C T = 500°C T = 750°C

Phenol 1.0 26.2 53.0 78.4

2-bromophenol 0.9 29.9 12.9 18.3

4-bromophenol 15.9 6.9 0.0 0.0

2,4-dibromophenol 25.6 9.2 2.2 0.0

2,6-dibromophenol 44.8 16.9 31.0 3.3

2,4,6-tribromophenol 11.9 10.8 0.9 0.0

Total 100.0 100.0 100.0 100.0

GAS ANALYSIS OF PCB PYROLYSIS BY FT-IR

[00123] The gaseous products released during the decomposition of the PCBs were analyzed by the FT-IR, in order to study the effect of the process temperature on their emission. The major bands detected by FT-IR were those of hydrogen bromide (HBr) [2390-2730 cm’ ¹ ], phenol (C ₆ H ₆ O) [1350-1750 cm’ ¹ ], carbon monoxide (CO) [2060- 2200 cm ^-1 ], carbon dioxide (CO2) [2300-2390 cm-1], and water vapor (H2O) [1150-1260 cm ^-1 ], as shown in Figure 8.

[00124] Still referring to Figure 8, it was also observed that the band which corresponds to hydrogen bromide (HBr) was detected at 275°C. Its intensity increased significantly at 325°C, which means that HBr was released mainly in this temperature range (275-325°C). The band corresponding to phenol was very weak between 275 and 325°C, and reached a significant intensity at 425°C. Bands of carbon monoxide (CO) and carbon dioxide (CO2) were detected between 275 and 425°C.

[00125] The pyrolysis gases of PCB/K2CO3 mixture (1:1 wt/wt) was analyzed by the FT-IR, and Figure 9 shows that potassium carbonate (K2CO3) significantly reduced the release of hydrogen bromide (HBr) [2390-2730 cm ^-1 ] due to the gas - solid reaction leading to the formation of a stable potassium bromide (KBr).

PYROLYSIS BASED ON CONVENTIONAL HEATING vs. MICROWAVE HEATING

[00126] A microwave thermogravimetric analyzer was used to study the kinetics of waste printed circuit boards (WPCB) pyrolysis via microwaves compared to conventional TGA. The multimode microwave oven was a BP-211 from Microwave Research & Applica-tions, Inc. powered by 4 adjustable 800 W magnetrons working at a frequency of 2.45 GHz. The uniformity of the microwaves inside the cavity was achieved with 4 stirrer fans. The reactor was a quartz test tube of 1.3e-2 m ID and 0.254 m in length from Technical Glass Products, Inc. To limit heat losses to the surroundings and to minimize temperature gradients inside the receptor bed, the reactor was isolated with a layer of alumina silica isolation. The reaction temperature was measured with a custom-made infrared thermometer made from an infrared thermopile (model: TS105-10L5.5mm) from Measurement Specialties. The mass loss was measured with a 100 g micro load cell (model: CZL639HD) from Phidgets, Inc. A flow of 500 mL min ^-1 of nitrogen was continuously supplied to maintain an inert atmosphere and to purge the pyrolysis gases.

[00127] Referring to Figures 10 and 11, compared with a simulated conventional TGA incorporating a similar heating rate, the activation energy in microwave-induced pyrolysis is much smaller. This can be attributed to the internal-type heating style and a catalyst effect caused by the presence of microwave heating or microwave-metal discharges. A high disposal efficiency and low activation energy indicated by the microwave-induced pyrolysis of WPCBs makes the adoption of microwave technology an attractive approach for the disposal of WPCBs and waste electrical and electronic equipment (WEEE) materials in general.

Solid-State Rate and Integral Expressions for Different Reaction Models (the selected model in grey)

Kinetics parameters - Conventional TGA vs Microwave TGA Item 1. A process for recovering organic and metallic fractions from electronic waste, the process comprising: conditioning the electronic waste to produce a conditioned material; pyrolyzing the conditioned material to thermally decompose the conditioned material into a gaseous component and a solid component, wherein the solid component comprises an organic fraction and a metallic fraction; and separating the metallic fraction from the solid component to recover at least one of Al, Zn, Ni, Cu, Au, Ag, Pt, and Pd; wherein at least 95 wt% of the electronic waste is valorizable under the form of recovered metals, pyrolysis oil and value-added products.

Item 2. The process of item 1 , wherein the conditioning includes reducing a size of the electronic waste.

Item 3. The process of item 1 or 2, wherein the conditioned material is under particulate form, and the conditioning step comprises crushing the electronic waste into particulates having a particle size between 500 pm and 1000 pm.

Item 4. The process of item 3, wherein the crushing is performed to produce the particulates having substantially the same particle size.

Item 5. The process of any one of items 1 to 4, wherein the conditioning comprises extracting a ferrous fraction from the electronic waste to produce a non-ferrous waste.

Item 6. The process of item 5, wherein the conditioning comprises admixing a potassium-containing additive with the non-ferrous waste to form the conditioned material that is sent to the subsequent pyrolysis.

Item 7. The process of item 6, wherein the potassium-containing additive comprises potassium carbonate (K2CO3) and potassium oxide (K2O). Item 8. The process of any one of items 1 to 7, wherein pyrolyzing the conditioned material comprises exposing the conditioned material to a temperature between 300°C and 500°C, in an oxygen-depleted atmosphere.

Item 9. The process of any one of items 1 to 8, comprising isolating the gaseous component from the solid component after pyrolysis.

Item 10. The process of item 9, further comprising removing at least a portion of contaminants from the gaseous component.

Item 11. The process of item 10, wherein removing the at least a portion of the contaminants comprises filtering the gaseous component.

Item 12. The process of any one of items 1 to 11, further comprising condensing a condensable portion of the gaseous component to form pyrolysis oil.

Item 13. The process of item 12, wherein the condensing is performed via indirect heat exchange based on circulation of a cooling fluid.

Item 14. The process of item 13, wherein the cooling fluid has an inlet temperature between 20 °C and 25°C.

Item 15. The process of any one of items 1 to 14, further comprising separating the pyrolysis oil and a non-condensable portion of the gaseous component.

Item 16. The process of item 15, comprising combustion of the non-condensable portion of the gaseous component via flaring.

Item 17. The process of any one of items 1 to 16, wherein separating the metallic fraction from the solid component comprises separating a lighter fraction comprising aluminum, and a heavier fraction comprising at least one of Zn, Ni, Cu, Au, Ag, Pt, and Pd from the solid component based on density.

Item 18. The process of item 17, wherein separating the lighter fraction and the heavier fraction from the solid component based on density comprises immersing the solid component in a liquid medium to recover the lighter fraction floating on the liquid medium, and the heavier fraction sinking in the liquid medium. Item 19. The process of item 18, wherein separating the metallic fraction from the solid component comprises separating aluminum from the solid component as part of the lighter fraction, and the heavier fraction comprising remaining metals from the solid component.

Item 20. The process of item 18 or 19, comprising selecting the liquid medium having a density of at least 3950 kg/m ³

Item 21. The process of any one of items 17 to 20, comprising separating the heavier fraction from the liquid medium via filtration.

Item 22. The process of item 21 , comprising washing the heavier fraction.

Item 23. The process of any one of items 17 to 22, further comprising separating at least one of Zn, Ni, Cu, Au, Ag, Pt, and Pd from the heavier fraction.

Item 24. The process of item 23, wherein separating at least one of Zn, Ni, Cu, Au, Ag, Pt, and Pd from the heavier fraction comprises separating nickel and zinc via leaching with a first leaching agent, thereby producing a liquid stream comprising nickel and zinc ions, and a solid residue.

Item 25. The process of item 24, wherein the first leaching agent is sulfuric acid.

Item 26. The process of item 24 or 25, further comprising extracting each of the nickel ions and zinc ions via separate liquid-liquid extractions by contacting the liquid stream with a solvent in two different columns at two different pH.

Item 27. The process of any one of items 24 to 26, wherein the solid residue comprises at least one of Cu, Au, Ag, Pt, and Pd, and the process further comprises separating copper by leaching the solid residue with a second leaching agent to produce a second solid-liquid mixture comprising copper ions in solution and a copper-depleted solid residue.

Item 28. The process of item 27, wherein the second leaching agent is sulfuric acid and leaching the solid residue comprises contacting the solid residue with a solution of sulfuric acid having a concentration of at least 95%. Item 29. The process of item 27 or 28, comprising filtering the second solid-liquid mixture to separate the copper-depleted solid residue and a copper-containing solution.

Item 30. The process of item 29, comprising electroreduction of the copper-containing solution in an electrolytic cell to recover solid copper on the cathode.

Item 31. The process of any one of items 27 to 30, wherein the copper-depleted solid residue comprises at least one of Au, Ag, Pt, and Pd, and the process further comprises separating silver by leaching the copper-depleted solid residue with a third leaching agent to produce a third solid-liquid mixture comprising silver ions in solution and a silver-depleted solid residue.

Item 32. The process of item 31, wherein the third leaching agent is nitric acid and leaching the copper-depleted solid residue comprises contacting the copper-depleted solid residue with a solution of nitric acid having a concentration of at least 65%.

Item 33. The process of item 31 or 32, comprising filtering the third solid-liquid mixture to separate the silver-depleted solid residue and a silver-containing solution.

Item 34. The process of item 33, comprising mixing the silver-containing solution with a reduction agent to form recoverable solid silver.

Item 35. The process of item 34, wherein the reduction agent is ascorbic acid.

Item 36. The process of item 34 or 35, comprising co-adding an anionic surfactant with the reduction agent.

Item 37. The process of any one of items 34 to 36, comprising adding ethanol to the silver-containing solution in a centrifugation unit to remove the anionic surfactant.

Item 38. The process of any one of items 31 to 37, wherein the silver-depleted solid residue comprises at least one of Au, Pt, and Pd, and the process further comprises separating the at least one of Au, Pt, and Pd by contacting the silver-depleted solid residue with a fourth leaching agent to produce a metal-enriched solution comprising Au ions, Pt ions, Pd ions or any combinations thereof.

Item 39. The process of item 38, wherein the fourth leaching agent is aqua regia, or a sodium cyanide solution. Item 40. The process of item 38 or 39, comprising extraction of gold from the metal- enriched solution.

Item 41. The process of item 40, wherein the extraction of the gold from the metal- enriched solution comprises conditioning the metal-enriched solution by: heating the metal-enriched solution; acidifying the metal-enriched solution to produce a corrected solution; and filtering the corrected solution to produce a filtered solution.

Item 42. The process of item 41 , wherein the extraction of the gold from the metal- enriched solution further comprises precipitating gold by contacting the filtered solution with a precipitation agent to produce a gold-containing slurry comprising precipitated gold and a gold-depleted solution.

Item 43. The process of item 42, wherein the precipitation agent is sodium metabisulfite.

Item 44. The process of item 42 or 43, comprising filtering the gold-containing slurry to separate the precipitated gold and the gold-depleted solution.

Item 45. The process of any one of items 42 to 44, wherein the gold-depleted solution further comprises platinum ions and the process further comprises extracting platinum from the gold-depleted solution.

Item 46. The process of item 45, wherein extracting the platinum from the gold-depleted solution comprises precipitating a platinum-containing compound by contacting the gold- depleted solution with a second precipitation agent to produce a platinum-containing slurry comprising the platinum-containing compound and a platinum-depleted solution.

Item 47. The process of item 46, wherein the second precipitation agent is ammonium chloride, and the platinum-containing compound is ammonium hexachloroplatinate.

Item 48. The process of item 46 or 47, comprising filtering the platinum-containing slurry to recover the platinum-containing compound and a platinum-depleted solution. Item 49. The process of any one of items 46 to 48, comprising calcining the platinum- containing compound to form a solid mixture including free platinum.

Item 50. The process of item 49, comprising adding water to the solid mixture to solubilize soluble elements in an aqueous solution while leaving the platinum in solid state, and further separating the platinum via filtration.

Item 51. The process of any one of items 46 to 50, wherein the platinum-depleted solution further comprises palladium ions and the process further comprises extracting palladium from the platinum-depleted solution.

Item 52. The process of item 51, wherein extracting the palladium from the platinum- depleted solution comprises precipitating a palladium-containing compound by contacting the platinum-depleted solution with a third precipitation agent to produce a palladium-containing slurry comprising the palladium-containing compound and a palladium-depleted solution.

Item 53. The process of item 52, wherein the third precipitation agent is a mixture of hydrochloric acid (pH=1) and ammonia (4<pH>5), and the palladium-containing compound is dichloro-diamine-palladium.

Item 54. The process of item 52 or 53, comprising filtering the palladium-containing slurry to recover the palladium-containing compound.

Item 55. The process of any one of items 52 to 54, comprising calcining the palladiumcontaining compound to form a second solid mixture including free palladium.

Item 56. The process of item 55, comprising adding water to the second solid mixture to solubilize soluble elements in an aqueous solution while leaving the palladium in solid state, and further separating the palladium via filtration.

Item 57. The process of any one of items 1 to 56, wherein the pyrolyzing of the conditioned material is performed by exposing the conditioned material to microwave radiations.