The present application refers to an aqueous solution for cleaning soil and/or water from organic and/or inorganic contaminants, said solution comprising a pre-activated peroxydisulfate and/or monoperoxysulfate, the use of this solution as well as of pre-activated peroxydisulfate and/or monoperoxysulfate for the removal of contaminants from soil and/or water, as well as to a process for the oxidative removal of contaminants from soil and/or water with activated peroxydisulfate and/or monoperoxysulfate.

The presence of organic and inorganic contaminants in soil and water, such as ground water or wastewater is a widespread problem especially after industrial use. When for example new buildings are under construction, the soil, soil vapour and ground water is to be analyzed to ensure any later contamination of habitants or users of the building. Especially in cases where former industrial areas are changed to be living areas, high pollution of soil with for example so called volatile organic compounds (VOC) are documented. Further, contaminations with PAH, mineral oils, hydrocarbons, PFAS and other organic or inorganic contaminants are monitored.

Volatile organic compounds (VOC) are organic chemicals that have a high vapour pressure at room temperature. High vapour pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a trait known as volatility.

Some VOCs are dangerous to human health or cause harm to the environment. Anthropogenic VOCs are regulated by law, especially indoors, where concentrations are the highest. Most VOCs are not acutely toxic but may have long-term chronic health effects.

The European Union defines a VOC as "any organic compound having an initial boiling point less than or equal to 250 °C measured at a standard atmospheric pressure of 101.3 kPa". This definition is also to be applied in the present application.

Additionally, not only volatile contaminants are present in soil or water, but also non-volatile contaminants are observed. Examples for non-volatile contaminants are PAH, long-chain alkanes (e.g. mineral oils or derivatives thereof), or PFAS.

Further, not only organic but also inorganic contaminants need to be removed or at least the concentration should be reduced in soil and/or water. Examples are ammonium compounds, cyanides or sulfide compounds.

It is known that at least some of these organic and inorganic contaminants can be removed by oxidation processes, in which the organic compound is oxidized mainly into CO and CO2 as well as nitrates and/or sulfates, where appropriate. It is known that such an oxidation may be performed for example with persulfate. But the persulfate alone is assumed being not reactive enough, so that other oxidants, such as hydrogen peroxide or other peroxides or metal oxides have to be added as well, as for example disclosed in EP 1 115 512 Bl.

Using metal ions in such a process has the disadvantage that an inorganic impurity is added to the soil and/or water. Additionally, reduction of permeability due to clogging as a result of metal precipitation is a problem resulting from the addition of metal ions. Further, the effectivity of the process is strongly depending on temperature of the soil/water as well as the pH value of the soil. Accordingly, there is still the requirement of removal of different kind of contaminants from soil in a fast and easy manner. Especially, no further contaminants should be added, which would allow an in-situ removal of contaminants from soil and/or water.

Surprisingly it was found that an aqueous solution of activated peroxydisulfate and/or monoperoxysulfate can be used for the removal of contaminants from soil and/or water, and that the activated peroxydisulfate and/or monoperoxysulfate is stable over time.

Accordingly, the peroxydisulfate and/or monoperoxysulfate can be pre-activated at any time and later used without any additional modification of the peroxydisulfate and/or monoperoxysulfate or the soil/water to be cleaned. In contrast to prior methods, it is not necessary to heat the soil or water to be cleaned. But the aqueous solution with the pre-activated peroxydisulfate and/or monoperoxysulfate can be used at any time at any place, which allows in-situ processes avoiding the transport and disposal of soil and/or ground water and/or wastewater and/or process water. A solution comprising the pre-activated peroxydisulfate and/or monoperoxysulfate was found to be stable over time and even after 2 weeks of storage at room temperature, the activity was sufficient to remove essentially all organic contaminants from soil and water.

Peroxydisulfate is also known as persulfate. Monoperoxysulfate is also known as monosulfate.

The object of the present invention is in a first embodiment solved by an aqueous solution for cleaning soil and/or water from organic and/or inorganic contaminants, said solution comprising a pre-activated peroxydisulfate and/or monoperoxysulfate wherein the peroxydisulfate and/or monoperoxysulfate is activated at least 15 minutes, especially at least 0.5 hours, preferably at least 1 hour, preferred at least 2 hours, preferably at least 4 hours, especially at least 6 hours prior to use. Accordingly, the peroxydisulfate and/or monoperoxysulfate can for example be activated 10 or 12 hours or even 24 hours in advance. For example, the activation may be performed at one day and the use can be at the next day. Alternatively, the activation may be performed over night and the use is at the next day.

In a second embodiment, the object of the present invention is solved by the use of pre-activated sulfate or persulfate for removal of organic and oxidizable inorganic contaminants from soil and/or water, wherein the sulfate is activated at least 15 minutes, especially at least 0.5 hours, preferably at least 1 hour, preferred at least 2 hours, especially at least 4 hours, preferably at least 6 hours, especially preferred 10 or 12 hours, in preference 24 hours prior to use.

In a third embodiment, the object of the present invention is solved by the use of an aqueous solution as defined above for removal of organic and oxidizable inorganic contaminants from soil and/or water, wherein the sulfate is activated at least 15 minutes, especially at least 0.5 hours, preferably at least 1 hour, preferred at least 2 hours, especially at least 4 hours, preferably at least 6 hours, especially preferred 10 or 12 hours, in preference 24 hours prior to use.

In a fourth embodiment, the object of the present invention is solved by a process for the removal of organic and/or inorganic contaminants from soil and/or water comprising:

• Providing an aqueous solution according to the first embodiment,

• Contacting soil and/or water with the aqueous solution in an amount effective to react with and remove organic as well as inorganic contaminants.

These embodiments as well as preferred features will be explained in more detail in the following. It is to be noted that each feature can be combined with each other or several of them without limitation. Further, each feature is valid for each and every embodiment alone or in any combination. It was surprisingly found that it is possible to provide an aqueous solution of a pre-activated sulfate or persulfate, which is stable for a long time. Activation within the meaning of the present invention is an increase in the redox potential of the solution. The activation results in an increase in the redox potential of preferably at least 50 mV, especially of at least 100 mV, more preferably of at least 150 mV, especially preferred of at least 200 mV. This activation can be observed by monitoring the redox potential. The activation can be observed by a sudden increase in the redox potential, a so called "Redox jump".

The obtained activated redox potential was surprisingly found to remain stable for at least 15 minutes, especially at least 0.5 hours, preferably at least 1 hour, preferred at least 2 hours, preferably for at least 4 hours, especially for at least 6 hours, especially preferred for at least 10 hours, even more preferred for at least 12 hours or 24 hours. Surprisingly it was found that event after two weeks of storage at ambient conditions, the aqueous solution was still activated, i.e. has a redox potential which is higher compared to a non-activated solution.

The redox potential is determined of an aqueous solution and can be measured during the activation, so that the state of activation can be observed. The redox potential is measured of an aqueous solution of the peroxydisulfate and/or mono-peroxysulfate. It is determined relative to standard hydrogen electrode as reference electrode. Common methods of determination of the redox potential are known to the skilled person. As the redox potential is depending on the concentration of the peroxydisulfate and/or monoperoxysulfate as well as the water used as solvent, absolute values cannot be mentioned. But as a jump in the redox potential is clearly visible in the measurement, the activated state can be clearly and unambiguously observed.

The aqueous solution of the present invention comprises a pre-activated peroxydisulfate and/or monoperoxysulfate. Accordingly, a source of peroxydisulfate and/or monoperoxysulfate is needed. Preferably, the monopersulfate is originating from peroxomonosulfuric acid (Caro's acid, H2SO5) or its salts, or sulfuric acid (H2SO4) or its salts. The salts are preferably the ammonium, alkaline or earth alkaline salts, especially the ammonium, sodium and potassium salts. Preferably, the persulfate is originating from peroxydisulfuric acid (Marshall's acid, H2S2O8) or its salts, especially its ammonium, alkaline or earth-alkaline salts, preferably the sodium and potassium salt.

The aqueous solution may comprise one or more peroxydisulfate and/or monoperoxysulfate. Accordingly, one source for monopersulfate may be present for pre-activation. It is also possible, that two or more sources of monopersulfate are present. Of course, also one or more sources of persulfate may be present. It is also within the scope of the invention that one or more sources of monopersulfate as well as one or more sources of persulfate are present. Preferably, the aqueous solution comprises at least one persulfate, preferably one persulfate.

The source for the peroxydisulfate and/or monoperoxysulfate is selected such that the solubility in water is high to achieve a high concentration of pre-activated peroxydisulfate and/or monoperoxysulfate in the solution. Further, the route of activation is relevant.

The activation may be performed for example by thermal treatment or treatment with radiation or chemically. It is within the scope of the present invention that first the peroxydisulfate and/or monoperoxysulfate is activated and afterwards solved in water or, alternatively, that the first, the peroxydisulfate and/or monoperoxysulfate is solved in water and that the aqueous solution is afterwards activated. After applying heat to the peroxydisulfate and/or monoperoxysulfate, this is allowed to cool to room temperature without actively cooling it. If the expression peroxydisulfate and/or monoperoxysulfate is used in this application, it has the meaning of peroxydi sulfate and/or monoperoxysulfate.

The thermal activation and the activation via radiation, especially via UV radiation are preferred, especially in cases where a persulfate is used. In a very preferred embodiment, sodium persulfate, i.e. NazSzOs is used and thermally activated or activated via radiation.

It is assumed that the activation results in the formation of SOU ^2- radicals (sulphate radicals). Surprisingly it was found that these are stable and do not rereact with each other or further components in the aqueous solution.

If the sodium persulfate is activated with hydrogen peroxide, the following reaction may occur:

The sulphate radicals catalyse the formation of the hydroxy radicals and vice versa. The hydroxy radical is more reactive compared with the sulphate radicals. Accordingly, the hydroxy radical reacts with the contaminants in soil and/or water. The sulphate radical can afterwards react with the more persistent contaminants.

If Fe(II) or Fe(II) citrate are used for activation, the following reaction may occur:

During thermally activation, the following assumed reaction of the persulfate occurs: S2O8 ² ' — 2 SO4'

Accordingly, two sulfate radicals -SOU’ are obtained. The same is true for an activation with radiation, especially UV radiation. Sulfate radicals are known to be strong oxidizing agents with a redox potential UH of about 2.6 V. Further, the sulfate radical has a high persistence and thus, a large radius of influence (ROI).

Due to the fact, that in cases where the persulfate is present in the solution, thermal or UV activation are preferred, as these result in the formation of two sulfate radicals, whereas the activation with peroxides, metal salts or alkaline compounds results in the formation of only one sulfate radical.

It was surprisingly found that the activated state of peroxydisulfate and/or monoperoxysulfate with an increased redox potential is stable at room temperature, i.e. a storage in a common container at temperatures from 15 °C and 30 °C, especially from 18 °C and 25 °C is possible.

The present invention further provides for a process for the removal of contaminants from soil comprising:

• Providing an aqueous solution, said solution comprising a pre-activated peroxydisulfate and/or monoperoxysulfate, wherein the peroxydisulfate and/or monoperoxysulfate is activated at least 15 minutes, especially at least 0.5 hours, preferably at least 1 hour, preferred at least 2 hours, preferably at least 4 hours, especially at least 6 hours, especially preferred at least 10 hours, preferred at least 12 hours, especially preferably at least 24 hours prior to use,

• Contacting soil and/or water with the aqueous solution in an amount effective to react with and remove organic as well as inorganic contaminants. The present invention therefore provides for the first time a process which allows reducing or even eliminating different kind of contaminants, especially oxidizable contaminants in a fast and easy manner. This can be done in a conventional way by transporting the contaminated soil and/or water to a predefined place and perform the treatment at this place. In this embodiment, the contaminated soil is for example irrigated with the aqueous solution containing the preactivated peroxydisulfate and/or monoperoxysulfate. If water is contaminated, the aqueous solution of the invention may be simply added to a tank or other storage means for the water. Mixing helps for a better reaction and is thus preferred - for both, the soil and water. In case of water, this may also flow through specific pipes and the aqueous solution of the invention is added so that the mixing is performed due to the flow of the liquids, for example.

In a preferred embodiment, the aqueous solution of the invention containing the pre-activated peroxydisulfate and/or monoperoxysulfate is added to the soil and/or water at the position of origin. This means, that the soil and/or water remains on site. The aqueous solution of the invention containing the pre-activated peroxydisulfate and/or monoperoxysulfate is added to the soil and/or water. This can be for example performed by irrigation. This helps for a removal of oxidizable contaminants especially in an upper soil layer. But as usually the organic contaminants are also present in lower soil layers, the contacting can take place by injecting the pre-activated peroxydisulfate and/or monoperoxysulfate into deeper soil layers, especially to a depth where the concentration of oxidizable contaminants is high.

In any way, the soil and/or water may also actively be mixed with each other to allow for a better contacting between the soil and/or water and the aqueous solution. The mixing can be performed in any manner suitable for the respective situation. The water, from which contaminants can be removed, is for example ground water, wastewater or any other process water. Especially ground water can be treated in combination with soil. Accordingly, the process of the present invention allows for the removal of oxidizable contaminants from soil and ground water in one step.

Oxidizable contaminants which can effectively be removed with the process of the present invention are any organic or inorganic compound, which can be destroyed into a non-contaminant by an oxidation process. Various contaminants are known to be destroyed by chemical oxidation. All of them can also be removed or the concentration can be at least reduced significantly with the method and solution of the present invention.

Preferably, the oxidizable contaminant is selected from volatile organic compounds (VOC), non-volatile organic compounds, reduced inorganic compounds as well as mixtures of these.

Volatile organic compounds (VOC) are organic chemicals that have a high vapour pressure at room temperature. High vapour pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a trait known as volatility. The European Union defines a VOC as "any organic compound having an initial boiling point less than or equal to 250 °C measured at a standard atmospheric pressure of 101.3 kPa". This definition is also to be applied in the present application. Examples for VOC, which often occur as pollutant in soil are HVCH, HHC or BTEX or other substituted monoaromats.

Non-volatile organic contaminants are for example PAH, HC hydrocarbons (i.e. long-chain alkanes, in gasoline, kerosene or diesel, or PFAS. Even though gasoline and kerosene are mixtures, which may also comprise volatile compounds (e.g. hydrocarbons with 5 to 9 C-Atoms), they are usually mentioned to be nonvolatile organic contaminants.

Reduced inorganic compounds which can be treated with the pre-activated peroxydisulfate and/or monoperoxysulfate, i.e. with the aqueous solution of the present invention, are within the meaning of the present invention, for example, ammonium compounds, sulfide compounds or cyanides.

The initialism BTX refers to mixtures of benzene, toluene, and the three xylene isomers, all of which are aromatic hydrocarbons. The xylene isomers are distinguished by the designations ortho - (or o -), meta - (or m -), and para - (or p - ) as indicated in the adjacent diagram. If ethylbenzene is included, the mixture is referred to as BTEX.

Substituted monoaromats are aromatic cyclic compounds with only one aromatic ring. They are substituted in at least one position with for example a halogen or a hydroxy group.

Halogenated hydrocarbons (HHC) are organic compounds containing at least one covalently bonded atom of any halogen. If the halogen is a chlorine, they a called chlorinated hydrocarbons (CHC). These are organic compounds containing at least one covalently bonded atom of chlorine. The chloroalkane class (alkanes with one or more hydrogens substituted by chlorine) provides common examples.

A polycyclic aromatic hydrocarbon (PAH) is a hydrocarbon — a chemical compound containing only carbon and hydrogen — that is composed of multiple aromatic rings. The group is a major subset of the aromatic hydrocarbons. The simplest of such chemicals are naphthalene, having two aromatic rings, and the three-ring compounds anthracene and phenanthrene. The terms polyaromatic hydrocarbon or polynuclear aromatic hydrocarbon are also used for this concept. HVHH is the abbreviation for Highly Volatile Halogenated Hydrocarbons. If the halogen is a chlorine, they are called HCVH, which is the abbreviation for Highly Volatile Chlorinated Hydrocarbons.

In general, these are derivatives of methane, ethane and ethene in which hydrogen atoms are substituted by halogen atoms, namely chlorine, fluorine, chlorine, bromine atoms. HCVH are not so much a group of substances in the strict chemical sense, but rather a term from the environmental sciences, under which substances are grouped that have or have had a comparable technical application significance (solvents, etc.), that show similar behaviour in the environment, and that have a similar chemical composition (solvents etc.), which show similar behaviour in the environment (e.g. comparatively high volatility) and which can be analyzed together (e.g. vapour space gas chromatography).

A subgroup of HCVH are the CFC and HCFC. Chlorofluorocarbons (CFC) and hydrochlorofluorocarbons (HCFC) are fully or partly halogenated paraffin hydrocarbons that contain only carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivative of methane, ethane, and propane. They are also commonly known by the DuPont brand name Freon.

The most common representative is dichlorodifluoromethane (R.-12 or Freon- 12). Many CFCs have been widely used as refrigerants, propellants (in aerosol applications), and solvents. Because CFCs contribute to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs) including R.-410A and R-134a.

Per- and polyfluoroalkyl substances (PFASs, also perfluorinated alkylated substances) are synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. As such, they contain at least one perfluoroalkyl moiety, -CnFzn-. According to OECD, there are at least 4730 different PFAS with at least three perfluorinated carbons. A U.S. Environmental Protection Agency (EPA) toxicity database, DSSTox, even lists 8163 PFAS. A subgroup, the fluorosurfactants or fluorinated surfactants, have a fluorinated "tail" and a hydrophilic "head" and are thus surfactants. They are more effective at reducing the surface tension of water than comparable hydrocarbon surfactants. They include perfluorocarboxylic acids such as the perfluoroocta noic acid (PFOA). Further common PFAS-contaminants of soil and/or water are for example PFBA (perfluorobutyric acid), PFPeA (perfluoropentanoic acid), PFHxA (perfluorohexanoic acid), PFHpA (perfluoroheptanoic acid), PFNA (perfluorononanoic acid), PFDeA (perfluorodecanoic acid), PFUnA (perfluoroundecanoic acid), PFDoA (perfluorododecanoic acid).

Accordingly, the most common pollutants, such as petroleum hydrocarbons, BTEX, benzene, phenols, PAHs, MTBE, tert-butyl alcohol, chlorinated ethenes, carbon tetrachloride, chloroform, methylene chloride, chlorinated ethanes, trichloroethane, dichlorethane, chlorobenzene, PCBs, energetic (RDX, HMX), explosives, pesticides or even 1,4-dioxane, can be removed with the aqueous solution of the present invention.

It was surprisingly found, that thermally activated persulfate is able to reduce such organic contaminants in soil without the need of addition of further metal ions or any other oxidizing agent, such as for example hydrogen peroxide. Accordingly, in a preferred embodiment, the process of the present invention is performed without addition of metal ions and/or oxidizing agents to the soil in a timely relationship with the addition of the thermally activated persulfate. Hence, there is no addition of metal ions or additional oxidizing agents to soil prior or after the contacting with the thermally activated persulfate. Additionally, no metal ions or oxidizing agents are added to the soil together with the thermally activated persulfate. Of course, oxidizing agent in this context means any oxidizing agent different from persulfate. A further advantage of the process of the present invention is that it can be performed at more or less any temperature. Accordingly, there is no need for heating the soil or the persulfate after the thermal activation. This makes the process of the present invention also more economic compared to previously known proceedings. Further, the applicability of the process is increased, as any soil can be treated at any position. The only limitation being the fact, that the thermally activated persulfate is somehow to be spread over the soil or injected into it. This is performed by using a solution of the persulfate. Accordingly, the temperature has to be such that the solution is liquid.

In a preferred embodiment, the temperature of the soil and/or the solution comprising the thermally activated persulfate is in the range from 40 ° to 5 °C, preferably from 30 °C or from 25 °C to 10 °C at the moment of contact. The temperature of the persulfate solution and the soil is independent from each other. Preferably, the temperature difference between the soil and the persulfate solution is 20 °C or less, especially 15 °C or less.

The process of the present invention is based on the fact that pre-activated persulfate is present in a solution and that this solution is contacted with organic contaminants. These contaminants are oxidized essentially to CO, CO2, and N2, as well as NOs’, and SO4 ² ’ .

The thermal activation of the persulfate can be performed prior or after adding it to a solvent for obtaining the respective solution. Accordingly, the process of the present invention may comprise the following steps in the following order:

• Providing a source of peroxydisulfate and/or monoperoxysulfate,

• activation said peroxydi sulfate and/or monoperoxysulfate,

• Preparing a solution comprising said pre-activated persulfate, and

• Contacting soil and/or water with the solution of the pre-activated persulfate in an amount effective to react with and oxidize contaminants, wherein the activation of the peroxydisulfate and/or monoperoxysulfate is preferably performed by heating the persulfate in the absence of metal ions and/or oxidizing agents and afterwards cooling to room temperature.

In an alternative embodiment, the process of the present invention may comprise the following steps in the following order:

• Providing a source of peroxydisulfate and/or monoperoxysulfate,

• Preparing a solution comprising said peroxydisulfate and/or monoperoxysulfate,

• activating said solution of peroxydisulfate and/or monoperoxysulfate,

• Contacting soil and/or water with the solution of the pre-activated peroxydisulfate and/or monoperoxysulfate in an amount effective to react with and oxidize contaminants, wherein the activation of the peroxydisulfate and/or monoperoxysulfate is preferably performed by heating the persulfate in the absence of metal ions and/or oxidizing agents and afterwards cooling to room temperature

A suitable source for persulfate are alkaline or earth alkaline persulfate salts. Especially in cases where the organic contaminants are HCVH, the alkaline metal can react with the chlorine. For example, if the alkaline salt is a sodium or potassium salt, i.e. sodium or potassium persulfate is used, NaCI or KCI are formed. Both can remain in soil without toxic or otherwise harmful effect to flora and/or fauna or animals or human beings. Accordingly, in a preferred embodiment, the persulfate is sodium persulfate or potassium persulfate, especially sodium persulfate.

The selection of suitable persulfate sources is mainly depending on the fact that the process should be cost effective and that no additional harmful substances should be added to the soil. The process can be performed independent of the pH of the soil and/or water. The relevant factor of the process of the present invention is the pre-activation of the peroxydi sulfate and/or monoperoxysulfate. The successful activation can be monitored by measuring the redox potential of the peroxydisulfate and/or monoperoxysulfate. After thermal treatment, irradiation or application of other suitable activation techniques, an increase in the redox potential can be monitored. The increase of the redox potential is preferably at least 50 mV, especially at least 100 mV, preferably at least 200 mV. In some cases, the increase in the redox potential may even be up to 250 mV or more, and even 300 mV. The absolute increase of the redox potential is of course depending on the concentration of the aqueous solution. But concentration which are sufficient for the intended use usually show the above-mentioned increase if the activation is successful.

For an effective thermal activation, the persulfate or a solution comprising the persulfate is especially heated to a temperature of at least 30 °C and less than 100 °C, especially preferred from 40 °C to 80 °C, preferably from 50 °C to 65 °C. The heating is preferably performed over a time of 5 minutes to 120 minutes, especially from 10 minutes to 90 minutes, preferably from 15 minutes to 60 minutes.

Surprisingly it was found that the thermal activation is especially effective, if the solution or persulfate is not actively cooled after the heating, but is allowed to cool to room temperature by itself.

Preferably, the activation is stable for at least 48 hours, which allows the thermal activation of the persulfate at one place, transporting it to the soil to be treated and performing the treatment. It was surprisingly found that in preferred embodiments, the persulfate remains activated for at least 6 hours, especially at least 10 hours, preferably at least 12 hours, especially preferred at least 24 hours, more preferably for at least 1 week, especially for at least 2 weeks. This also allows a storage of the activated persulfate and its use step after step with intermediate control of success.

The pre-activated peroxydisulfate and/or monoperoxysulfate allows an effective removal of contaminated soil and/or water. In preferred embodiments, at least 40 wt.-% of the organic contaminants in the volume of the treated soil, especially at least 60 wt.-%, preferably at least 70 wt.-%, especially at least 75 wt.-% of the organic contaminants in the soil are oxidized.

Depending on the contamination, it is even possible removing all of the contaminants from soil and ground water or other types of water, i.e. the reduction of contaminants can be up to 100 wt.-%, such as 98 wt.-% or 99 wt.-%.

If the contamination is still too high after a first injection, this can be repeated resulting in a higher reduction of the contaminants.

Using an aqueous solution, allows the application in soil being in contact with ground water. The presence of ground water has in such an embodiment the advantage that it spreads the pre-activated peroxydisulfate and/or monoperoxysulfate over a certain area. Accordingly, in case of in-situ injection of an aqueous solution of a pre-activated peroxydisulfate and/or monoperoxysulfate at a position, the peroxydisulfate and/or monoperoxysulfate is active in an area starting from the point of injection and extending to the flow direction of the ground water.

The concentration of the peroxydisulfate and/or monoperoxysulfate in the aqueous solution is depending on the concentration of the organic contaminants in the soil and/or water. If groundwater is present in the soil, the concentration of peroxydisulfate and/or monoperoxysulfate in the inventive aqueous solution will be more or less diluted in the soil. Accordingly, the concentration of the peroxydisulfate and/or monoperoxysulfate in the aqueous solution can be up to its saturation concentration. Typical concentrations of for example sodium persulfate, which is a preferred source for persulfate in the aqueous solution, in water are for example 50 to 500 g/L, such as 50 to 300 g/L or 100 to 200 g/L. The pre-activated peroxydisulfate and/or monoperoxysulfate has further the advantage, that it mainly reacts with contaminants dissolved in soil and/or water. Natural organic matter (NOM), which is also present mainly in soil, is less affected, as the affinity of the pre-activated peroxydisulfate and/or monoperoxysulfate is higher towards the dissolved contaminants compared to NOM.

In a further aspect, the present invention refers to the use of pre-activated persulfate for oxidative removal of organic contaminants from soil and/or water. The persulfate is preferably pre-activated by thermal treatment including heating up to an activation temperature and allowing it to cool to room temperature without active cooling it.

In the following example, the present invention is explained in more detail but without limiting the scope of the invention.

Examples:

1. Determination of redox potential a) Sodium persulfate was dissolved in water in concentrations of 500 g/L down to 1 g/L. The solutions were heated to 60 °C. The temperature was kept constant for about 15 minutes. After, the solution was allowed to cool to room temperature.

The redox potential was measured at the beginning, during heating, during cooling and for the next 14 days. The results are shown in Fig. 1. b) Sodium persulfate was dissolved in water in concentrations von 200 g/L and 20 g/L. The solutions were heated to 40 °C. The temperature was kept constant for about 45 minutes. After, the solution was allowed to cool to room temperature.

The redox potential was measured at the beginning, during heating, during cooling and for the next 14 days. The results are shown in Fig. 2.

When comparing Fig. 1 and 2, it is obvious, that the redox potential is increasing over time. The time needed for a full thermal activation is depending on the temperature. If a higher temperature is chosen, the time for heating may be shorter compare to lower temperature. Nevertheless, also heating to 40 °C for about 45 minutes is sufficient for a thermal activation. The increase of the redox potential is slow at the beginning. After about 1000 minutes, a strong increase can be monitored, which hints to a chain reaction of formation of the sulfate radicals -SOT.

2. Removal of HCVH from soil

A solution of sodium persulfate with a concentration of 200 g/L was prepared and activated overnight. The solution was afterwards injected into the soil through respective drilling holes. The injection took place in a depth of 6 m to 10 m below ground. 50 Litres of solution were added.

The concentration of HCVH was monitored. Within 3 weeks a reduction of about 66 wt.-% of HCVH was observed.

This shows that also on-situ oxidation of contaminants in soil can effectively performed. The final overall reduction of impurities can be controlled by several subsequent injections. Compared to other techniques, the present invention provides a process in which contaminants can effectively be reduced without the need of metal ions in a fast and easy manner.