Field

Disclosed herein is a process for producing an absorbent for use in absorption of hydrocarbon-based and aqueous-based contaminants . The absorbent finds particular , though not exclusive , use in the treatment of contaminated soils , beaches , ground and the like .

Background

The extensive use of hydrocarbon-based products such as petrol , diesel , and oils , and other contaminant products such as paints and pesticides , has led to contamination of soil and the natural environment through either accidental spills , illegal dumping or unsustainable management of such products . Contamination of sites by such products creates significant health concerns , as well as causing extensive damage to natural ecosystems .

As a consequence , remediation of contaminated sites has become an important factor in land management practices . In this regard, removal of pollutants such as petrol , diesel , oils , paints , and pesticides from soil , beaches and other land areas directly contributes to a healthier, more habitable site . For example , removal of contaminants in soil directly contributes to clean water and sanitation by prevention of pollutants leaching into water-courses and landfill . Enhancing soil quality via remediation contributes to growth of better quality food and agricultural products .

Remediation and spill clean-up products typically contain an absorbent for absorbing the contaminant . Various types of absorbents have been used in remediation/spill clean-up products including kaolin, clay, activated charcoal , cellulose and peat . However, the scale at which remediation/spill clean-up products are often required means that the cost for absorbents can be prohibitive .

More recently, bioremediation has been increasingly used for treating contaminated sites , particularly for sites contaminated with hydrocarbon-based pollutants . Bioremediation involves using microorganisms which are capable of absorbing, breaking down and/or metabolising pollutants to safer , less environmentally damaging compounds . Bioremediation is sustainable , has less ecological impact , is often cheaper , is scalable , and provides a permanent solution through destruction of contaminants .

However, the environment at contaminated sites is harsh and not generally supportive of microbial activity . As a consequence , maintaining microbial activity and/or microbial numbers during bioremediation in contaminated sites can be challenging . Moreover , nutrient formulations which may be suitable for supporting microbial populations during bioremediation are not as reliable , particularly at the scale required for bioremediation to be effective in a sustainable manner .

What is needed are products able to be produced at large scale in a cost-effective manner that are suitable for environmental remediation, and in particular bioremediation .

Summary

The inventors have developed a process for producing an absorbent at a scale that is economically viable for use in bioremediation, and which effectively supports microbial activity . The absorbent produced by the process also ensures the contaminants are contained which reduces the time , cost and ris ks involved in achieving desired results from bioremediation .

A first aspect provides a process for producing an absorbent for absorption of hydrocarbon-based and aqueous-based contamination, comprising the steps of : a . providing acidified cotton dust ; b . combining the acidified cotton dust with a neutralising agent in an amount sufficient to neutralise the acidified cotton dust .

A second aspect provides a process for producing a bioremediation product for absorption and reduction of hydrocarbon-based and aqueous-based contamination, comprising the steps of : a . providing acidified cotton dust ; b . combining the acidified cotton dust with a neutralising agent in an amount sufficient to neutralise the acidified cotton dust to produce an absorbent ; c . introducing one or more microbial strains into the absorbent .

A third aspect provides a process for producing an absorbent for absorption of hydrocarbon-based and aqueous-based contamination, comprising the steps of : a . providing acidified cotton dust ; b . combining the acidified cotton dust with magnesium oxide in an amount sufficient to neutralise the acidified cotton dust to produce an absorbent .

The process of the third aspect may further comprise a step : c . introducing one or more microbial strains into the absorbent .

The inventors have surprisingly discovered that neutralised cotton dust can act as a contaminant absorbent in its own right , but additionally can act as a suitable carrier for bioremediation-type microorganisms ( e . g . by enabling them to overcome many barriers so they survive and thrive in the often harsh environment of contaminated sites ) . Further , the inventors have identified that cotton dust is able to attract hydrocarbons and act as a host to support microbes so the microbes are more effective in reducing these contaminants quickly . Brief Description of the Drawing

Non-limiting examples of specific embodiments of the process will now be described, including with reference to Figure 1 , which is a flow diagram showing an embodiment of the process described herein .

Detailed Description

In one embodiment , there is provided a process for producing an absorbent for absorption of hydrocarbon-based and aqueous-based contamination, comprising the steps of : a . providing acidified cotton dust ; b . combining the acidified cotton dust with a neutralising agent in an amount sufficient to neutralise the acidified cotton dust .

As used herein, acidified cotton dust has the same meaning as acidified cotton linters . Cotton linters are very short fibres , typically fibres remaining on cotton seed after the cotton ginning process . The cotton linters are removed from the seed by treating the cotton seed ( coated with linters ) with acid to produce acidified cotton linters and de-linted cotton seed .

The acidified cotton dust is typically a waste product that may be produced from any cotton that is treated with an acid under conditions which convert a part of the cotton to a dust .

In one embodiment , the treatment acid is a gas . In one embodiment , the acid is HC1 , Sulfuric acid or nitric acid . In one embodiment , the acid is HC1 or sulphuric acid . In one embodiment , the acid is HC1 . In one embodiment , the acid is sulphuric acid . In one embodiment , the acid is nitric acid . In one embodiment , the acidified cotton dust is produced by treating cotton linters with an acid under conditions to convert the cotton linters to a dust . For example , cotton linters on the surface of cottonseed may be treated with an acid to remove the linters when preparing the cotton seed for planting . The acidified cotton dust produced from such delinting of cottonseed can form a feedstock to the process described herein . Thus , acidified cotton dust , which is usually a waste product produced during preparation of cottonseed for planting, can find advantageous use in the process described herein . As acidified cotton dust is a waste product of the cotton industry, it can be obtained economically in large scale , and the process also reduces the need for the acidified cotton dust to be disposed of .

The neutralising agent that is combined with the acidified cotton dust may be powdered, particulate , or in solution . In one embodiment , the neutralising agent is a powder or particulate . In such embodiments , the neutralisation is achieved by applying water to the combination of acidified cotton and powder or particulate .

A neutralising agent may be selected such that , once it has neutralised the acidified cotton dust , its by-product is suitable to form part of the resultant absorbent . For example , its by-product may be environmentally benign, neutral or even beneficial .

In selecting a neutralising agent that is not adverse to the environment and which is beneficial to bacterial growth and/or metabolism, the inventors have found that microbial activity can be preserved or even stimulated .

In one embodiment , the neutralizing agent comprises a metal that is beneficial to microbial viability . In one embodiment , the metal is an alkaline earth metal or alkali metal . In one embodiment, the metal is selected from magnesium, calcium and sodium. In one embodiment, the neutralizing agent comprises a metal salt such as MgO, NaOH, CaO, Mg (OH) 2, CaCOs, Ca(OH)2, or MgCOs . The neutralizing agent may comprise a combination of two or more of such salts.

In one embodiment, the neutralising agent comprises MgO.

Australian Patent No. 687186 describes the use of ammonia (NH3) to neutralise cotton acidified with sulfuric acid, resulting in an absorbent containing ammonium sulphate. However, anhydrous ammonia is a hazardous gas which is toxic, corrosive and flammable. The effects of breathing in anhydrous ammonia range from lung irritation to severe respiratory injuries, with possible fatality at higher concentrations. Anhydrous ammonia is also corrosive to the skin, eyes and lungs. Therefore, the use of large quantities of ammonia requires specialised handling and storage conditions .

As described herein, the inventors have found that, in contrast to ammonia, alkaline earth metal salts and/or alkali metal salts such as MgO are safer and easier to store and handle, and have a high neutralising capacity. Importantly, the inventors have found that most magnesium salts formed during production (i.e. , manufacture) of the absorbent are readily soluble in water, thus ensuring a rapid, clean and efficient neutralising operation without subsequent sludge disposal problems .

It has been discovered that the magnesium salts that are produced in the absorbent product as disclosed herein do not adversely affect the environment, and also, the absorbent that is produced provides enhanced support for microorganisms in bioremediation applications. In this regard, as described in the Examples, use of an absorbent made by the process described herein results in: an increase in soil bacterial abundance by more than 1000-fold; establishment of introduced bacterial strains within environments with large numbers of indigenous bacteria to encourage increase in beneficial bacteria; an increase in soil dehydrogenase enzyme activity to the levels detected in uncontaminated soil ; rapid breakdown of hydrocarbons (hydrocarbon chain length from C6-C40 , BTEX and naphthalene! ) ; improved water retention capacity of soil ; a maintained pH within the levels ideal for microbial activity;

Without wishing to be bound by theory, the inventors believe that the combination of the cellulose from the cotton and the cation of the neutralising agent serves to support microbial activity in harsh contaminated environments .

Typically, the MgO is added to the acidified cotton as a powder , which is reacted by applying water to the acidified cotton and MgO powder combination .

In one embodiment , the powder is a mineral powder comprising MgO . In one embodiment , the mineral powder comprising MgO comprises reactive calcined technical grade MgO .

In one embodiment , the calcined technical grade MgO is a composition which comprises at least 95% MgO w/w % , typically at least 96% , more typically at least 97% w/w % .

In one embodiment , the calcined technical grade MgO has a mean particle size of 3-8 microns . The inventors have found that a mean particle size of 3-8 microns provides improved neutralisation . In one embodiment, the MgO is applied in an amount in the range of from 1 to 10%, 2 to 9%, 2 to 8%, 2 to 7%, or 2 to 6%, by weight MgO per kg acidified cotton dust. Typically, the MgO is applied in an amount in the range of from 2 to 6% by weight MgO per kg cotton dust .

In one embodiment, the calcined technical grade MgO comprises MgO, CaO, SiO2, Fe2Os, and AI2O3. In one embodiment, the calcined technical grade MgO comprises MgO, CaO, SiO2, Fe2Os, and AI2O3, with a mean particle size of 3-8 microns .

In one embodiment, the calcined technical grade MgO comprises the components and properties set out in Table 1.

Table 1

In one embodiment , the process further comprises the step of introducing to the absorbent one or more microbial strains .

As used herein, introducing one or more microbial strains to an absorbent refers to adding one or more microbial strains to the absorbent that are in addition to any microbial strains that are indigenous or naturally associated with the absorbent . In some embodiments , the one or more microbial strains are from species exogenous to the absorbent , in that they are species not naturally associated with the absorbent . In some embodiments , the one or more microbial strains are from species indigenous to the absorbent , in that they are from species that are naturally associated with the absorbent , but are added in addition to the naturally occurring population of microbes already in the absorbent . In some embodiments , the one or more microbial strains comprises a mixture of strains from exogenous and indigenous species . The introduced strains may be blended or otherwise mixed with the absorbent .

The inventors have found that establishment of introduced microbial strains , typically introduced bacterial strains , within environments with large numbers of indigenous bacteria encourages an increase in beneficial bacteria . Typically, at least one of the one or more microbial strains is capable of utilising one or more hydrocarbons in the hydrocarbon-based contamination.

In one embodiment, the one or more microbial strains are bacterial strains.

In one embodiment, the one or more microbial strains are a consortium of bacterial strains .

Typically, the bacterial strains are typical bacterial strains that are naturally associated with oil-bearing plants . Examples of oil-bearing plants include cotton, peanut, rice, corn, and soybeans .

In one embodiment, the one or more bacteria strains introduced into the absorbent comprise a strain or strains from at least one species, typically from at least 2, 3, 4, or 5 species selected from Pseudomonas aeruginosa, Bacillus subtilis, Sphingobium yanoikuyae, Phenylobacterium sp. , and Ochrobactrum intermedium.

In one embodiment, the one or more bacterial strains introduced into the absorbent comprise a strain or strains from at least one species, typically at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 species selected from Pseudomonas aeruginosa, Bacillus subtilis, Sphingobium yanoikuyae, Phenylobacterium sp. , Ochrobactrum intermedium, Staphylococcus sp. , Burkholderia lata, Stenotrophomonas maltophilia, Klebsiella sp. , Paenibacillus polymyxa, Pseudomonas veronii, Delftia lacustris, Burkholderia cepacia, Bacillus velezensis, and Pseudomonas putida.

In one embodiment, the one or more bacteria strains introduced into the absorbent comprise at least one strain from each of the species Pseudomonas aeruginosa, Bacillus subtilis, Sphingobium yanoikuyae, Phenylobacterium sp. , and Ochrobactrum intermedium. In one embodiment , the one or more bacterial strains introduced into the absorbent comprise at least one strain from each of the species Pseudomonas aeruginosa , Bacillus subtilis , Sphingobium yanoikuyae , Phenylobacterium sp . , Ochrobactrum intermedium, Staphylococcus sp . , Burkholderia lata, Stenotrophomonas maltophilia , Klebsiella sp . , Paenibacillus polymyxa, Pseudomonas veronii , Delftia lacustris , Burkholderia cepacia, Bacillus velezensis , and Pseudomonas putida .

In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense , i . e . to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the process .

Example

Figure 1 is a diagram showing the steps for producing a bioremediation product . In the process , fuz zy cotton seed, which is produced by the removal of cotton from the seed by ginning, is the source of cotton linters . The fuz zy cotton seed is heated in a high temperature oven to remove long linter fibres . However, it will be appreciated by those skilled in the art that any methods used in the cotton processing industry for removing long linter fibres may be used to remove the long linter fibres .

The cotton seed containing the remaining short fibres is treated with concentrated HC1 gas , resulting in an acidified cotton dust having a pH of less than 1 . Acidified cotton dust may be obtained commercially from various cotton processing plants .

The acidified cotton dust is then blended with a neutralizing agent comprising MgO, and a small amount of water added sufficient to produce a neutralizing effect . This results in the production of an absorbent with a pH of greater than 5 . The resultant absorbent can be packaged as a product ready for distribution .

Optionally, the absorbent is subsequently blended with fine wood fibres to produce a product for packaging .

Additionally, the absorbent can be subsequently blended with a consortia of bacteria including Pseudomonas aeruginosa , Bacillus subtilis , Sphingobium yanoikuyae , Phenylobacterium sp . , Ochrobactrum intermedium, Staphylococcus sp . , Burkholderia lata , Stenotrophomonas maltophilia , Klebsiella sp . , Paenibacillus polymyxa , Pseudomonas veronii , Delftia lacustris , Burkholderia cepacia, Bacillus velezensis , and Pseudomonas putida .

Nutrients such as ammonium nitrate or other nitrogen sources are added at this stage to assist in support of the bacteria .

The resulting bioremediation product is then packaged ready for distribution .

It will be understood to persons s killed in the art that many modifications may be made without departing from the spirit and scope of the process as disclosed herein .

The present application claims priority from Australian provisional application no . 2022902760 the entirety of which is incorporated herein by reference .