CA2762060A1 - Process for decontamination of soils polluted with metals, pentachlorophenol, dioxins and furans and contaminants removal from leachates - Google Patents
Process for decontamination of soils polluted with metals, pentachlorophenol, dioxins and furans and contaminants removal from leachates Download PDFInfo
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- CA2762060A1 CA2762060A1 CA 2762060 CA2762060A CA2762060A1 CA 2762060 A1 CA2762060 A1 CA 2762060A1 CA 2762060 CA2762060 CA 2762060 CA 2762060 A CA2762060 A CA 2762060A CA 2762060 A1 CA2762060 A1 CA 2762060A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/08—Reclamation of contaminated soil chemically
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/02—Extraction using liquids, e.g. washing, leaching, flotation
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Description
PROCESS FOR DECONTAMINATION OF SOILS POLLUTED WITH
METALS, PENTACHLOROPHENOL, DIOXINS AND FURANS AND
CONTAMINANTS REMOVAL FROM LEACHATES
FIELD OF THE INVENTION
The present invention generally relates to wood treating sites and more particularly to a method of decontamination. More specifically, this invention relates to a process for decontaminating soil polluted by metals, pentachlorophenol, dioxins and furans and extracting contaminants from contaminated solutions.
BACKGROUND OF THE INVENTION
To increase wood lifetime, chemical treatments are often applied to particularly protect wood against insects and fungi. Main chemical preservatives are Chromated Copper Arsenate (CCA), Pentachlorophenol (PCP) and polychlorined dibenzodioxins and dibenzofurans (PCDDF). Many of the chemical preservatives are toxic to organisms and are consequently harmful if released into the environment.
The number of wood treating sites in Canada has remained around 65 for many years (Morris et Wang 2006) but the number of sites where pole are stored is much higher. In the U.S., more than 60 sites were ranked on the list of national priority intervention (US Congress 1995). In Scandinavian countries, more than 500 wood treating sites are contaminated by metals or pentachlorophenol or dioxins and furans, with direct impacts on the environment (Ottosen et al. 2002).
Due to the lack of appropriate technologies for soil remediation, selected approaches were chemical stabilization and solidification or excavation and disposal of contaminated soils.
There is currently and will continue to be a need for techniques for remediating wood treating sites.
There are some known techniques for dealing with soil that has been contaminated with one or more preservatives such as CCA or PCP or PCDDF. Such techniques fall under the general categories of incineration, dechlorination, thermal desorption, solvent extraction, bioremediation and soil washing.
Destructive methods such as incineration, dechlorination, thermal desorption and separation methods such as extraction with organic solvents are effective to remove organic contaminants such as pentachlorophenol and dioxins and furans, but do not allow a decontamination of metal from soils (Sahle-Demessie et al. 2000).
Bioremediation techniques were used for pentachlorophenol and polycyclic aromatic hydrocarbons removal from soil but are less effective for removing metals, dioxins and furans form soils (Patent Biotrol , USEPA 1992).
Soil washing is the best technique for decontamination of soils polluted with metals, pentachlorophenol and dioxins and furans, but the known techniques are often ineffective or have process costs that make them non-applicable at industrial scale.
In this regard, Riveiro-Huguet and Marshall (2011) describe a process including an ultrasonic leaching step with surfactants and chelatants which cost approach 137, 000 US$ per t of treated soil.
There are a variety of disadvantages and challenges related to the known techniques for decontaminating soil from wood treating sites. Main disadvantages are process efficiency for organic compounds or metals and cost-effectiveness.
There is indeed a need for a technology that overcomes at least one of the disadvantages of what is known in the field.
SUMMARY OF THE INVENTION
The present invention responds to the above need by providing a process for the decontamination of soil containing wood-preservative contaminants.
Accordingly, the invention provides a process for decontamination of soil contaminated with preservative comprising contaminants, which include metals or pentachlorophenol or dioxins and furans. In one embodiment, the process comprises:
contacting the soil with water and an inorganic base at a concentration between about 0.1 M and about 2 M and optionally a surfactant at a concentration between about 0.05 % and 5 %, at a temperature lower than about 100 C, to solubilise at least a portion of the contaminant present in the soil, thereby producing a contaminant-rich solution and contaminant-poor soil;
and separating the contaminant-rich solution from the contaminant-poor soil.
The present invention also responds to the above need by providing a process for contaminants extraction from a contaminated solution.
Accordingly, in another embodiment, the invention provides a process for extraction of all contaminants present in soil leachate comprising:
contacting the contaminated solution with a coagulant at a pH favoring precipitation of pentachlorophenol, copper, chromium and arsenic; and/or contacting the contaminated solution with an activated carbon or an ion exchange resin favoring pentachlorophenol, dioxins and furans extraction.
Additional embodiments, aspects and features of the present invention will be described and defined herein.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig 1 is a flowchart of the process according to an embodiment of the present invention.
Fig 2 is a graph of As, Cr, Cu and PCP solubilization from wood treating site soil after leaching by several chemical reagents.
Figs 3a and 3b are graphs of As, Cr, Cu and PCP solubilization from wood treating site soil after sodium hydroxide leaching at various base concentration and pulp density.
Figs 4a and 4b are graphs of As, Cr, Cu and PCP solubilization from wood treating site soil after sodium hydroxide leaching at various temperature and reaction time.
Fig 5 is a graph of PCDDF solubilization from wood treating site soil after sodium hydroxide leaching with several surfactants according to optimized parameters.
Fig 6 is a graph of As, Cr, Cu and PCP removal yields after precipitation step with various volume of coagulant.
Fig 7a and 7b are a graph of As, Cr, Cu and PCP removal yields after contacting soil leachates with several adsorbents or ion exchange resins.
Fig 8 is a graph of As, Cr, Cu, PCP and PCDDF removal yields after contacting soil leachates with best adsorbents, ion exchange resins or after optimised precipitation step.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Process embodiments of the present invention provide an effective and economical technique to remove contaminants from soil and to treat the resulting leachate solutions. In one optional aspect of the process embodiments of the present invention, they are used in relation to soil containing arsenic, chromium, copper, pentachlorophenol, dioxins and furans.
Definitions "About", when qualifying the value of a variable or property - such as concentration, temperature, pH, particle size and so on - means that such variable or property can vary within a certain range depending on the margin of error of the method or apparatus used to evaluate such variable or property. For instance, the margin of error for temperature may range between 1 C to 5 C.
"Contaminated soil" means a soil that may be in any state, granular or powder form and so on, which has at some time been in contact with a wood preservative to thereby become "contaminated". It should be understood that the contaminated soil may be mixed with uncontaminated soil at various point in the process in order to form an overall soil quantity to meet certain governmental or environmental standards.
"Preservative" means a compound for treating wood in order to increase its useful lifetime or compound which come from decomposition of initial compound.
Preservatives may include a fungicide component and an insecticide component to combat those two factors that so often lead to the deterioration of wood.
There are many different types of preservatives that have been used to treat wood.
"Inorganic base" means abase lacking a carbon atom and may be a hydroxide or a carbonate of sodium, potassium or calcium or a combination of such bases. It should also be understood that the inorganic base may be a used or recycled base.
"Surfactant" means a compound that lowers the surface tension of a liquid or that between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants. Surfactants can have a cationic, anionic, both anionic and cationic or neutral head and can be synthetic or a biosurfactant.
"Contacting", when pertaining to the contaminated soil and the inorganic base and water, means that those elements contact each other so as to enable diffusion of the contaminants from the soil phase into the alkaline solution phase. The "contacting"
will often be referred to as leaching herein and may include techniques such as soaking, batch mixing, trickling, spraying, continuous flow-by, or various combination of such contacting techniques.
"Separating", when pertaining to the contaminant-rich solution and the contaminant-poor soil, means any suitable solid-liquid separation technique.
"Arsenic" (As), "chromium" (Cr), "copper" (Cu), unless specified otherwise, each means a compound containing the given element and may include solubilised ions, complexes, derivatives, isomers, as the case may be. For instance, the term "chromium" may include chromium III and chromium VI; "arsenic" may include arsenate in association with CCA or solubilised in an aqueous medium; while "copper" may include the element in association with CCA, solubilised, or in its pure metallic form upon recovery. Thus, these elements should be read with a mind to their relationship with the process steps, process conditions and other interacting compounds.
"Pentachlorophenol" (PCP), "dioxins and furans" (PCDDF) unless specified otherwise, each means a compound containing the given compounds and may include solubilised ions, complexes, derivatives, isomers, as the case may be.
For instance, the term "pentachlorophenol" may include all chlorophenols such as dichlorophenol, trichlorophenol and tetrachlorophenol; "dioxins and furans"
may include all 210 isomers of polychlorined dibenzodioxins and polychlorined dibenzofurans. Thus, these compounds should be read with a mind to their relationship with the process steps, process conditions and other interacting compounds.
"Contaminant-rich solution" means a solution containing the contaminants removed from the contaminated soil during a leaching step. It should also be understood that for subsequent treatment of the solution to remove or recover contaminants, the contaminant-rich solution from the initial step may be combined with solutions from other leaching or washing steps to form an overall contaminant-rich solution.
Thus, the contaminant-rich solution may be combined with other streams, or be subjected to various other steps before it is treated to recover one or more of the contaminants.
Embodiments of the processes In an optional embodiment of the process, it includes at least one inorganic base leaching and the surfactant step to solubilise arsenic, chromium, copper, pentachlorophenol, dioxins and furans from the soil, followed by at least one treatment step for the recovery of metals and organic compounds from the alkaline leachates resulting from the leaching and washings steps. Smaller yield of removal for PCDDF can be obtained if only the inorganic base is used. The decontaminated soil and the contaminants extracted from the soil may be safely disposed.
Fig 1 shows a flow diagram of the various stages of one embodiment of the process.
According to an embodiment of the present invention, the first phase of the process includes contacting the soil with water and an inorganic base at a concentration between about 0.1 M and about 2 M and a surfactant at a concentration between about 0.05 % and 5 % at a temperature lower than 100 C, to solubilise at least a portion of contaminants present in the soil, thereby producing a contaminant-rich solution and contaminant-poor soil. This contacting step may also be called a primary alkaline leaching step. More particularly, this leaching step includes basification of soil by a mixture of an inorganic base and water.
Before this leaching treatment, soil can be crushed or screened, so as to obtain for instance soil having a size inferior to about 1 cm, preferably inferior to about 0.6 mm.
According to one embodiment of the process, the soil content of the mixture is adjusted to a range between about 20 and about 200 g/L of solution.
In one optional embodiment of the present invention, the inorganic base is sodium hydroxide and is added so as to obtain a concentration ranging between about 0.1 M
and about 2 M. The inorganic base used as a leaching agent may be sodium, potassium or calcium base, used base, recycled base or a combination thereof.
In one optional embodiment of the present invention, the surfactant is an amphoteric biosurfactant cocamidopropylbetaine and is added so as to obtain a concentration ranging between about 0.05 % and about 5 %. The surfactant used may have cationic, anionic, both anionic and cationic or neutral head and can be synthetic or a biosurfactant, or a combination thereof.
The alkaline solution is then mixed for a period sufficient to adequately solubilise contaminants present in the soil. Typically, this period ranges from about 0.5 to about 24 h.
The mixture is maintained at a temperature below about 100 C. According to one optional aspect of the invention, the temperature may range between about 20 C
and about 80 C.
There may also be a single leaching step or several sequential steps that employ the same or different bases and surfactants and concentrations of the bases and surfactants. The leaching steps can be operated in batch, semi-continuous or continuous mode in tank reactors.
After the leaching steps, the soil is separated from the solution, thereby obtaining the contaminant-poor soil and the contaminant-rich alkaline leachate. The separation of soil from the liquid fraction can be done by decantation, filtration, centrifugation, or another other standard technique of solid-liquid separation.
According to an embodiment of the present invention, there is a second phase of the process including washing of the soil to remove residual solubilised contaminants.
The washing of the soil can be done by rinsing the solids resulting from a previous filtration step or by mixing the solids re-suspended in the washing solution, followed by a step of solid-liquid separation. The washing of the soil can be done in one or more steps with water, a dilute alkaline solution, or an acid solution. The different washing steps may be performed with the same or different washing solutions.
The alkaline leachates from the first phase and the spent washing liquids may then be combined to obtain a solution containing the totality of the target contaminants.
Some or all of the washing waters can also be directly used as process water for the operation of the initial leaching steps for a subsequent batch or quantity of contaminated soil.
According to an embodiment of the present invention, the process may also have a third phase including treating the alkaline leachates, the spent washing liquids or a combination of these solutions, to recover at least one of the contaminants.
The combination of the alkaline leachates and the spent washing liquids will be generally referred to here as the "contaminant solution", which contains the solubilised contaminants. It should be understood however that the solution treated to recover solubilised contaminants may be the alkaline leachate or the spent washing liquid only. The metal recovery from the solution includes one or a combination of the following techniques: chemical precipitation, ion exchange, solvent extraction and adsorption. After the contaminated solution has been treated to remove contaminants, it may for example be used as process water for the operation of the leaching steps.
In another optional embodiment of the process, pentachlorophenol, copper, chromium and arsenic may be simultaneously removed from the solution by a total precipitation technique using an iron salt (e.g. ferric chloride or sulfate) with a strong acid (e.g. sulfuric acid). Organic compounds such as pentachlorophenol, dioxins and furans can be removed from the solution by using ion exchange resins or activated carbons.
The decontaminated soil and the contaminants extracted from the soil can be safely disposed of or recycled.
Embodiments of the present invention provide a number of advantages.
Advantages will be understood as per the above and the examples and experimental data obtained through the extensive studies presented below.
For instance, the use of inorganic base and surfactant, such as sodium hydroxide and cocamidopropylbetaine respectively allows good metal, pentachlorophenol, dioxins and furans solubilization yields from soil at a low chemical cost. The relatively low temperature (< 100 C) used during the operation of the leaching steps can be reached at low energy cost. Furthermore, the addition of at least one washing step after the leaching steps is useful to remove the dissolved contaminants still present in the soil.
EXAMPLES, EXPERIMENTATION & ADDITIONAL INFORMATION
The embodiments of the present invention will be further comprehended and elaborated in light of the following examples and results, which are to be understood as exemplary and non-limiting to what has actually been invented.
General Methodology The following describes the general methodology of examples of an embodiment of the process of the present invention.
Soil characterisation Four soils (F1, Si, S2 and S3) coming from confidential origins in the province of Quebec (Canada) were used in following examples. Metals and metalloids analysis was performed by inductive coupled plasma with atomic emission spectroscopy (ICP-AES) (Varian, model Vista-AX simultaneous ICP-AES) after a mineralisation of soil according to CEAEQ method (MA. 205 ¨ Met/P 1.0). Arsenic, chromium, copper, pentachlorophenol, dioxins and furans were analysed in the different soil fractions to determine where contaminants are located.
The measured concentrations for the four soils are between 50 and 250 mg kg-1 for As, 35 and 220 mg kg-1 for Cr, 80 and 350 mg kg-1 for Cu, 2.5 and 30 mg kg-1 for PCP, 1200 and 6300 ng kg-1 for PCDDF-TEQ.
Soil decontamination The soil decontamination examples were conducted to determine the efficient and economical design and operation of an embodiment of an alkaline leaching process to remove, for example, As, Cu, Cr, PCP and PCDDF from wood treating sites soil.
In one example related to the first phase of the process, mineral acids (sulfuric, hydrochloric and nitric) and bases (calcium, potassium and sodium hydroxide), an organic acid (lactic acid) and ethanol were evaluated for PCP and CCA
solubilization. Mineral acid and bases concentration was fixed at 1N. Lactic acid and ethanol concentration were respectively fixed at 25% v/v in relation to water and 50%
v/v in relation to water as proposed in literature. For experiments, soil samples were passed through a 1 mm or 6 mm sieve. Assays were carried out in triplicates on ten or hundred grams of soil for a 10% (w v-1) pulp density (PD) at room temperature (T
= 22 2 C). After shaking at 200 revolutions per minute (rpm) (Orbital shaker, Lab-line Environ-Shaker, model 3528) or stirring at 500 rpm using a magnetic Teflon-covered bar, soil and washing solutions were separated by vacuum (0.5 bar) filtration on Whatman 934-AH membrane (pore size = 1.5 pm). Soil was then dried at 60 C
and analysed. Leaching solutions were prepared with analytical grade reagents diluted in deionised water. All glassware was thoroughly washed.
Further studies were performed on a broad range of bases concentration. The improved alkaline condition was kept constant for the subsequent experiments.
Other studies were performed on pulp density, temperature and reaction time to optimised decontamination.
Anionic surfactant (SDS), non-ionic surfactants (Brij35, TVV80, and TX100) and amphoteric surfactants (CAS and BW) were evaluated for contaminants removal.
Assays were conducted on the four soils on the 6 mm fraction with the optimal experimental conditions. Soils were analysed before and after treatment to estimate removal yields of contaminants.
Chemical precipitation and coagulation Coagulation experiments occurred in 250 mL beaker with magnetic stirring at rpm using a Teflon-covered bar. Leachate pH was initially stabilized to the appropriate pH by adding sulfuric acid solution. Then, ferric sulfate solution Fe2(SO4)3 was added into the 100 or 200 mL leachates. The pH was re-adjusted after ferric sulfate addition. Solutions were mixed together at 250 rpm for 30 min, and then settled down for 24 h. The supernatant was collected and filtrated on Whatman 934AH membranes for further soluble metals and pentachlorophenol analysis.
Industrial ferric sulfate solution from Environnement EagleBrook Canada Ltee (Varennes, Canada) containing 160 g Fe/L was used.
Ion exchange resin and adsorbent Experiments regarding ion exchange resin and adsorbent assessed the potential of ion exchange and adsorption for selective recovery of contaminants.
Experiments were conducted in batch mode. Five grams of resin or adsorbent were mixed with 250 mL soil leachate in 500 mL Erlenmeyer flasks and shake at 200 revolutions per minute (rpm) (Orbital shaker, Lab-line Environ-Shaker, model 3528) for 24 h to ensure that chemical equilibrium was attained. Thereafter, liquid to solid separation was made by filtration onto Whatman 934AH filter.
Ion exchange resins studied are anionic (Lewatit MP500, Lewatit SR7, Amberlite 1RA900), cationic (Lewatit TP207), adsorption (Lewatit F036, Lewatit VPOC, Lewatit AF5).
Adsorbent studied are granular, medium or fine anthracite (anthra G, anthra M
and anthra F), Norit, Aquamerik and Darco granular activated carbon (CAG N, CAG A, and CAG D), powdered activated carbon (CAP), alumina and silica.
Analytical techniques Metals and metalloids analysis was performed by inductive coupled plasma with atomic emission spectroscopy (ICP-AES) (Varian, model Vista-AX simultaneous ICP-AES) according to CEAEQ method (MA. 205¨Met/P 1.0). Soils were digested by aqua regia (1/4 of nitric acid for 3/4 of hydrochloric acid) at 80 C during 8 h. Analysis was controlled using reference certified solutions obtained from SCP science and yttrium was used as internal standard.
PCP analysis was performed by gas chromatography with mass spectroscopy (GC-MS) (Perkin Elmer, model Clarus 500, with column type of DB-5 30 mm * 0.25mm *
0.25 pm) according to CEAEQ method (MA. 400 Phe 1.0). Samples were extracted with Soxhlet in methylene chloride during 12 h, extracted in sodium hydroxide, then derivate with anhydrous acetate and finally extracted in methylene chloride.
Phenanthrene c110 was used as internal standard.
Analysis of 17 major polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans was performed using CEAEQ method (MA.400-DF 1.0) by GC-MS
(Perkin Elmer, model Clarus 500 with RTX-Dioxin column of 60 m * 0.25 mm *
0.25 pm). Samples were extracted with toluene and then were purified and concentrated using multilayer silica columns eluted with hexane and alumina column eluted in three fractions with mixtures of hexane and dichloromethane. The quantification was performed with carbon 13C-labeled analogs.
Economic aspect The chemical costs associated to the decontamination of wood treating sites soils were calculated on the basis of the following unitary prices.
The sodium hydroxide (99.9% pure powder) was estimated at a cost of 500 US$/t and the cocamidopropylbetaine (solution at 35% w/w) was calculated at a cost of 1000 US$/t.
The sulfuric acid (solution at 93% w/w) was evaluated at a cost of 80 US$/t and the ferric sulfate solution (160 g Fe/L) at a cost of 500 US$/t.
Example 1: Selection of the leaching reagent Several "extractants" were tested for metal and pentachlorophenol extraction from soil. Solubilization assays carried in triplicates on Fl soil are presented in Fig 2.
Evaluation of both organic and inorganic acids, bases and ethanol shows that sulfuric and lactic acids give the best CCA removal yields and sodium and potassium hydroxide the best PCP removal yields. In order to design a remediation process, performance and cost are two principal criteria in terms of leaching reagents.
Lactic acid is more expensive than sulfuric acid with costs of approximately 1 200 and 94 $US/t respectively (ICIS Chemical Business, 28 August 2006) but acidic conditions did not allow PCP solubilization. Sodium hydroxide was chosen for next assays as he allow PCP, As and Cu solubilization and is cheaper than potassium hydroxide.
But at the initial stage of experimentation, it did not allow more than 53%
removal yield for As.
Example 2: Effect of operating parameters Figure 3 and 4 presents the influence of operating parameters on CCA and PCP
removal. Figure 3a and 3b present the influence of base concentration and pulp density on CCA and PCP removal. On Figure 3a, sodium hydroxide concentration form 0.1 to 2 M, causes an increase of CCA and PCP solubilization with a maximum obtain at 1 M for PCP with a removal yield of 90%. Increasing to 2M the base concentration raises arsenic and copper extraction with removal yields of 60%
and 40% respectively. As shown in Figure 3b, variation of soil PD from 5 to 20% (w v-1) causes considerable decrease of CCA and PCP removal. Temperature and reaction time are significant parameters in chemical processes. To assess influence of these variables, tests were done at four different temperatures: 20, 40, 60 and 80 C
and five different time: 1, 2, 4, 8 and 24 h. Figure 4a and 4b present the influence of temperature and time reaction on CCA and PCP removal. As show in Figure 4a, an increase of temperature between 20 to 80 C causes an increase of CCA and PCP
solubilization to 75% and 65% for PCP and As respectively. In Figure 4b, evolution of CCA removal decreased when time varied from 1 to 2 h. After 4 h, removals increased slowly. Gain in metals extraction is relatively low for increasing cost when base concentration exceeds 1 M. The pulp density content is an important parameter as it influences capital costs by varying the size of the leaching reactor.
Therefore, 1M sodium hydroxide is a good compromise between performances and low costs with 10% pulp density.
On Optimal operating conditions were determined from these results to improve solubilization performance at low operating costs. For further assays, sodium hydroxide concentration is fixed at 1M, temperature at 80 C, soil PD at 10%
(w1(1) and reaction time at 2 h.
Example 3: Evaluation of surfactant for PCDDF solubilization Assays were conducted on Si soil with an anionic (sodium dodecyl succinate), two amphoteric (cocamidopropyl hydroxysultaIne CAS and betaine BW) and four non-ionic (Brij-35, Igepal-CA720, Tween-80, Triton-X100) surfactants. Experimental parameters determined previously were used. Figure 5 presents PCDDF
solubilization at surfactant concentration of 1 g kg"1 (1%). SDS, Tween 80 and Triton X100 allow the best PCDDF removal which approaches 60% with only one leaching step. In other experiments, it was show that some surfactants reduce or enhance PCP and CCA solubilization.
Best results were obtained for the amphoteric surfactant BW which increases PCP
and CCA solubilization. Otherwise it shows acceptable removal yields for PCDDF
and has advantages to be non-toxic and biodegradable.
Example 4: Leaching process characteristics and cost Since alkaline soil washing with surfactant seems to be a promising method to treat soils contaminated with both organic and inorganic pollutants, process was tested on the four contaminated soils. For the purpose of an optional embodiment of the process, the parameters for leaching of wood treating site soil were selected as follows:
1. Soil content: 100 g/L;
2. Base type and concentration: 0.75 M NaOH;
3. Temperature: 80 C;
4. Reaction time: 2 h;
METALS, PENTACHLOROPHENOL, DIOXINS AND FURANS AND
CONTAMINANTS REMOVAL FROM LEACHATES
FIELD OF THE INVENTION
The present invention generally relates to wood treating sites and more particularly to a method of decontamination. More specifically, this invention relates to a process for decontaminating soil polluted by metals, pentachlorophenol, dioxins and furans and extracting contaminants from contaminated solutions.
BACKGROUND OF THE INVENTION
To increase wood lifetime, chemical treatments are often applied to particularly protect wood against insects and fungi. Main chemical preservatives are Chromated Copper Arsenate (CCA), Pentachlorophenol (PCP) and polychlorined dibenzodioxins and dibenzofurans (PCDDF). Many of the chemical preservatives are toxic to organisms and are consequently harmful if released into the environment.
The number of wood treating sites in Canada has remained around 65 for many years (Morris et Wang 2006) but the number of sites where pole are stored is much higher. In the U.S., more than 60 sites were ranked on the list of national priority intervention (US Congress 1995). In Scandinavian countries, more than 500 wood treating sites are contaminated by metals or pentachlorophenol or dioxins and furans, with direct impacts on the environment (Ottosen et al. 2002).
Due to the lack of appropriate technologies for soil remediation, selected approaches were chemical stabilization and solidification or excavation and disposal of contaminated soils.
There is currently and will continue to be a need for techniques for remediating wood treating sites.
There are some known techniques for dealing with soil that has been contaminated with one or more preservatives such as CCA or PCP or PCDDF. Such techniques fall under the general categories of incineration, dechlorination, thermal desorption, solvent extraction, bioremediation and soil washing.
Destructive methods such as incineration, dechlorination, thermal desorption and separation methods such as extraction with organic solvents are effective to remove organic contaminants such as pentachlorophenol and dioxins and furans, but do not allow a decontamination of metal from soils (Sahle-Demessie et al. 2000).
Bioremediation techniques were used for pentachlorophenol and polycyclic aromatic hydrocarbons removal from soil but are less effective for removing metals, dioxins and furans form soils (Patent Biotrol , USEPA 1992).
Soil washing is the best technique for decontamination of soils polluted with metals, pentachlorophenol and dioxins and furans, but the known techniques are often ineffective or have process costs that make them non-applicable at industrial scale.
In this regard, Riveiro-Huguet and Marshall (2011) describe a process including an ultrasonic leaching step with surfactants and chelatants which cost approach 137, 000 US$ per t of treated soil.
There are a variety of disadvantages and challenges related to the known techniques for decontaminating soil from wood treating sites. Main disadvantages are process efficiency for organic compounds or metals and cost-effectiveness.
There is indeed a need for a technology that overcomes at least one of the disadvantages of what is known in the field.
SUMMARY OF THE INVENTION
The present invention responds to the above need by providing a process for the decontamination of soil containing wood-preservative contaminants.
Accordingly, the invention provides a process for decontamination of soil contaminated with preservative comprising contaminants, which include metals or pentachlorophenol or dioxins and furans. In one embodiment, the process comprises:
contacting the soil with water and an inorganic base at a concentration between about 0.1 M and about 2 M and optionally a surfactant at a concentration between about 0.05 % and 5 %, at a temperature lower than about 100 C, to solubilise at least a portion of the contaminant present in the soil, thereby producing a contaminant-rich solution and contaminant-poor soil;
and separating the contaminant-rich solution from the contaminant-poor soil.
The present invention also responds to the above need by providing a process for contaminants extraction from a contaminated solution.
Accordingly, in another embodiment, the invention provides a process for extraction of all contaminants present in soil leachate comprising:
contacting the contaminated solution with a coagulant at a pH favoring precipitation of pentachlorophenol, copper, chromium and arsenic; and/or contacting the contaminated solution with an activated carbon or an ion exchange resin favoring pentachlorophenol, dioxins and furans extraction.
Additional embodiments, aspects and features of the present invention will be described and defined herein.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig 1 is a flowchart of the process according to an embodiment of the present invention.
Fig 2 is a graph of As, Cr, Cu and PCP solubilization from wood treating site soil after leaching by several chemical reagents.
Figs 3a and 3b are graphs of As, Cr, Cu and PCP solubilization from wood treating site soil after sodium hydroxide leaching at various base concentration and pulp density.
Figs 4a and 4b are graphs of As, Cr, Cu and PCP solubilization from wood treating site soil after sodium hydroxide leaching at various temperature and reaction time.
Fig 5 is a graph of PCDDF solubilization from wood treating site soil after sodium hydroxide leaching with several surfactants according to optimized parameters.
Fig 6 is a graph of As, Cr, Cu and PCP removal yields after precipitation step with various volume of coagulant.
Fig 7a and 7b are a graph of As, Cr, Cu and PCP removal yields after contacting soil leachates with several adsorbents or ion exchange resins.
Fig 8 is a graph of As, Cr, Cu, PCP and PCDDF removal yields after contacting soil leachates with best adsorbents, ion exchange resins or after optimised precipitation step.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Process embodiments of the present invention provide an effective and economical technique to remove contaminants from soil and to treat the resulting leachate solutions. In one optional aspect of the process embodiments of the present invention, they are used in relation to soil containing arsenic, chromium, copper, pentachlorophenol, dioxins and furans.
Definitions "About", when qualifying the value of a variable or property - such as concentration, temperature, pH, particle size and so on - means that such variable or property can vary within a certain range depending on the margin of error of the method or apparatus used to evaluate such variable or property. For instance, the margin of error for temperature may range between 1 C to 5 C.
"Contaminated soil" means a soil that may be in any state, granular or powder form and so on, which has at some time been in contact with a wood preservative to thereby become "contaminated". It should be understood that the contaminated soil may be mixed with uncontaminated soil at various point in the process in order to form an overall soil quantity to meet certain governmental or environmental standards.
"Preservative" means a compound for treating wood in order to increase its useful lifetime or compound which come from decomposition of initial compound.
Preservatives may include a fungicide component and an insecticide component to combat those two factors that so often lead to the deterioration of wood.
There are many different types of preservatives that have been used to treat wood.
"Inorganic base" means abase lacking a carbon atom and may be a hydroxide or a carbonate of sodium, potassium or calcium or a combination of such bases. It should also be understood that the inorganic base may be a used or recycled base.
"Surfactant" means a compound that lowers the surface tension of a liquid or that between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants. Surfactants can have a cationic, anionic, both anionic and cationic or neutral head and can be synthetic or a biosurfactant.
"Contacting", when pertaining to the contaminated soil and the inorganic base and water, means that those elements contact each other so as to enable diffusion of the contaminants from the soil phase into the alkaline solution phase. The "contacting"
will often be referred to as leaching herein and may include techniques such as soaking, batch mixing, trickling, spraying, continuous flow-by, or various combination of such contacting techniques.
"Separating", when pertaining to the contaminant-rich solution and the contaminant-poor soil, means any suitable solid-liquid separation technique.
"Arsenic" (As), "chromium" (Cr), "copper" (Cu), unless specified otherwise, each means a compound containing the given element and may include solubilised ions, complexes, derivatives, isomers, as the case may be. For instance, the term "chromium" may include chromium III and chromium VI; "arsenic" may include arsenate in association with CCA or solubilised in an aqueous medium; while "copper" may include the element in association with CCA, solubilised, or in its pure metallic form upon recovery. Thus, these elements should be read with a mind to their relationship with the process steps, process conditions and other interacting compounds.
"Pentachlorophenol" (PCP), "dioxins and furans" (PCDDF) unless specified otherwise, each means a compound containing the given compounds and may include solubilised ions, complexes, derivatives, isomers, as the case may be.
For instance, the term "pentachlorophenol" may include all chlorophenols such as dichlorophenol, trichlorophenol and tetrachlorophenol; "dioxins and furans"
may include all 210 isomers of polychlorined dibenzodioxins and polychlorined dibenzofurans. Thus, these compounds should be read with a mind to their relationship with the process steps, process conditions and other interacting compounds.
"Contaminant-rich solution" means a solution containing the contaminants removed from the contaminated soil during a leaching step. It should also be understood that for subsequent treatment of the solution to remove or recover contaminants, the contaminant-rich solution from the initial step may be combined with solutions from other leaching or washing steps to form an overall contaminant-rich solution.
Thus, the contaminant-rich solution may be combined with other streams, or be subjected to various other steps before it is treated to recover one or more of the contaminants.
Embodiments of the processes In an optional embodiment of the process, it includes at least one inorganic base leaching and the surfactant step to solubilise arsenic, chromium, copper, pentachlorophenol, dioxins and furans from the soil, followed by at least one treatment step for the recovery of metals and organic compounds from the alkaline leachates resulting from the leaching and washings steps. Smaller yield of removal for PCDDF can be obtained if only the inorganic base is used. The decontaminated soil and the contaminants extracted from the soil may be safely disposed.
Fig 1 shows a flow diagram of the various stages of one embodiment of the process.
According to an embodiment of the present invention, the first phase of the process includes contacting the soil with water and an inorganic base at a concentration between about 0.1 M and about 2 M and a surfactant at a concentration between about 0.05 % and 5 % at a temperature lower than 100 C, to solubilise at least a portion of contaminants present in the soil, thereby producing a contaminant-rich solution and contaminant-poor soil. This contacting step may also be called a primary alkaline leaching step. More particularly, this leaching step includes basification of soil by a mixture of an inorganic base and water.
Before this leaching treatment, soil can be crushed or screened, so as to obtain for instance soil having a size inferior to about 1 cm, preferably inferior to about 0.6 mm.
According to one embodiment of the process, the soil content of the mixture is adjusted to a range between about 20 and about 200 g/L of solution.
In one optional embodiment of the present invention, the inorganic base is sodium hydroxide and is added so as to obtain a concentration ranging between about 0.1 M
and about 2 M. The inorganic base used as a leaching agent may be sodium, potassium or calcium base, used base, recycled base or a combination thereof.
In one optional embodiment of the present invention, the surfactant is an amphoteric biosurfactant cocamidopropylbetaine and is added so as to obtain a concentration ranging between about 0.05 % and about 5 %. The surfactant used may have cationic, anionic, both anionic and cationic or neutral head and can be synthetic or a biosurfactant, or a combination thereof.
The alkaline solution is then mixed for a period sufficient to adequately solubilise contaminants present in the soil. Typically, this period ranges from about 0.5 to about 24 h.
The mixture is maintained at a temperature below about 100 C. According to one optional aspect of the invention, the temperature may range between about 20 C
and about 80 C.
There may also be a single leaching step or several sequential steps that employ the same or different bases and surfactants and concentrations of the bases and surfactants. The leaching steps can be operated in batch, semi-continuous or continuous mode in tank reactors.
After the leaching steps, the soil is separated from the solution, thereby obtaining the contaminant-poor soil and the contaminant-rich alkaline leachate. The separation of soil from the liquid fraction can be done by decantation, filtration, centrifugation, or another other standard technique of solid-liquid separation.
According to an embodiment of the present invention, there is a second phase of the process including washing of the soil to remove residual solubilised contaminants.
The washing of the soil can be done by rinsing the solids resulting from a previous filtration step or by mixing the solids re-suspended in the washing solution, followed by a step of solid-liquid separation. The washing of the soil can be done in one or more steps with water, a dilute alkaline solution, or an acid solution. The different washing steps may be performed with the same or different washing solutions.
The alkaline leachates from the first phase and the spent washing liquids may then be combined to obtain a solution containing the totality of the target contaminants.
Some or all of the washing waters can also be directly used as process water for the operation of the initial leaching steps for a subsequent batch or quantity of contaminated soil.
According to an embodiment of the present invention, the process may also have a third phase including treating the alkaline leachates, the spent washing liquids or a combination of these solutions, to recover at least one of the contaminants.
The combination of the alkaline leachates and the spent washing liquids will be generally referred to here as the "contaminant solution", which contains the solubilised contaminants. It should be understood however that the solution treated to recover solubilised contaminants may be the alkaline leachate or the spent washing liquid only. The metal recovery from the solution includes one or a combination of the following techniques: chemical precipitation, ion exchange, solvent extraction and adsorption. After the contaminated solution has been treated to remove contaminants, it may for example be used as process water for the operation of the leaching steps.
In another optional embodiment of the process, pentachlorophenol, copper, chromium and arsenic may be simultaneously removed from the solution by a total precipitation technique using an iron salt (e.g. ferric chloride or sulfate) with a strong acid (e.g. sulfuric acid). Organic compounds such as pentachlorophenol, dioxins and furans can be removed from the solution by using ion exchange resins or activated carbons.
The decontaminated soil and the contaminants extracted from the soil can be safely disposed of or recycled.
Embodiments of the present invention provide a number of advantages.
Advantages will be understood as per the above and the examples and experimental data obtained through the extensive studies presented below.
For instance, the use of inorganic base and surfactant, such as sodium hydroxide and cocamidopropylbetaine respectively allows good metal, pentachlorophenol, dioxins and furans solubilization yields from soil at a low chemical cost. The relatively low temperature (< 100 C) used during the operation of the leaching steps can be reached at low energy cost. Furthermore, the addition of at least one washing step after the leaching steps is useful to remove the dissolved contaminants still present in the soil.
EXAMPLES, EXPERIMENTATION & ADDITIONAL INFORMATION
The embodiments of the present invention will be further comprehended and elaborated in light of the following examples and results, which are to be understood as exemplary and non-limiting to what has actually been invented.
General Methodology The following describes the general methodology of examples of an embodiment of the process of the present invention.
Soil characterisation Four soils (F1, Si, S2 and S3) coming from confidential origins in the province of Quebec (Canada) were used in following examples. Metals and metalloids analysis was performed by inductive coupled plasma with atomic emission spectroscopy (ICP-AES) (Varian, model Vista-AX simultaneous ICP-AES) after a mineralisation of soil according to CEAEQ method (MA. 205 ¨ Met/P 1.0). Arsenic, chromium, copper, pentachlorophenol, dioxins and furans were analysed in the different soil fractions to determine where contaminants are located.
The measured concentrations for the four soils are between 50 and 250 mg kg-1 for As, 35 and 220 mg kg-1 for Cr, 80 and 350 mg kg-1 for Cu, 2.5 and 30 mg kg-1 for PCP, 1200 and 6300 ng kg-1 for PCDDF-TEQ.
Soil decontamination The soil decontamination examples were conducted to determine the efficient and economical design and operation of an embodiment of an alkaline leaching process to remove, for example, As, Cu, Cr, PCP and PCDDF from wood treating sites soil.
In one example related to the first phase of the process, mineral acids (sulfuric, hydrochloric and nitric) and bases (calcium, potassium and sodium hydroxide), an organic acid (lactic acid) and ethanol were evaluated for PCP and CCA
solubilization. Mineral acid and bases concentration was fixed at 1N. Lactic acid and ethanol concentration were respectively fixed at 25% v/v in relation to water and 50%
v/v in relation to water as proposed in literature. For experiments, soil samples were passed through a 1 mm or 6 mm sieve. Assays were carried out in triplicates on ten or hundred grams of soil for a 10% (w v-1) pulp density (PD) at room temperature (T
= 22 2 C). After shaking at 200 revolutions per minute (rpm) (Orbital shaker, Lab-line Environ-Shaker, model 3528) or stirring at 500 rpm using a magnetic Teflon-covered bar, soil and washing solutions were separated by vacuum (0.5 bar) filtration on Whatman 934-AH membrane (pore size = 1.5 pm). Soil was then dried at 60 C
and analysed. Leaching solutions were prepared with analytical grade reagents diluted in deionised water. All glassware was thoroughly washed.
Further studies were performed on a broad range of bases concentration. The improved alkaline condition was kept constant for the subsequent experiments.
Other studies were performed on pulp density, temperature and reaction time to optimised decontamination.
Anionic surfactant (SDS), non-ionic surfactants (Brij35, TVV80, and TX100) and amphoteric surfactants (CAS and BW) were evaluated for contaminants removal.
Assays were conducted on the four soils on the 6 mm fraction with the optimal experimental conditions. Soils were analysed before and after treatment to estimate removal yields of contaminants.
Chemical precipitation and coagulation Coagulation experiments occurred in 250 mL beaker with magnetic stirring at rpm using a Teflon-covered bar. Leachate pH was initially stabilized to the appropriate pH by adding sulfuric acid solution. Then, ferric sulfate solution Fe2(SO4)3 was added into the 100 or 200 mL leachates. The pH was re-adjusted after ferric sulfate addition. Solutions were mixed together at 250 rpm for 30 min, and then settled down for 24 h. The supernatant was collected and filtrated on Whatman 934AH membranes for further soluble metals and pentachlorophenol analysis.
Industrial ferric sulfate solution from Environnement EagleBrook Canada Ltee (Varennes, Canada) containing 160 g Fe/L was used.
Ion exchange resin and adsorbent Experiments regarding ion exchange resin and adsorbent assessed the potential of ion exchange and adsorption for selective recovery of contaminants.
Experiments were conducted in batch mode. Five grams of resin or adsorbent were mixed with 250 mL soil leachate in 500 mL Erlenmeyer flasks and shake at 200 revolutions per minute (rpm) (Orbital shaker, Lab-line Environ-Shaker, model 3528) for 24 h to ensure that chemical equilibrium was attained. Thereafter, liquid to solid separation was made by filtration onto Whatman 934AH filter.
Ion exchange resins studied are anionic (Lewatit MP500, Lewatit SR7, Amberlite 1RA900), cationic (Lewatit TP207), adsorption (Lewatit F036, Lewatit VPOC, Lewatit AF5).
Adsorbent studied are granular, medium or fine anthracite (anthra G, anthra M
and anthra F), Norit, Aquamerik and Darco granular activated carbon (CAG N, CAG A, and CAG D), powdered activated carbon (CAP), alumina and silica.
Analytical techniques Metals and metalloids analysis was performed by inductive coupled plasma with atomic emission spectroscopy (ICP-AES) (Varian, model Vista-AX simultaneous ICP-AES) according to CEAEQ method (MA. 205¨Met/P 1.0). Soils were digested by aqua regia (1/4 of nitric acid for 3/4 of hydrochloric acid) at 80 C during 8 h. Analysis was controlled using reference certified solutions obtained from SCP science and yttrium was used as internal standard.
PCP analysis was performed by gas chromatography with mass spectroscopy (GC-MS) (Perkin Elmer, model Clarus 500, with column type of DB-5 30 mm * 0.25mm *
0.25 pm) according to CEAEQ method (MA. 400 Phe 1.0). Samples were extracted with Soxhlet in methylene chloride during 12 h, extracted in sodium hydroxide, then derivate with anhydrous acetate and finally extracted in methylene chloride.
Phenanthrene c110 was used as internal standard.
Analysis of 17 major polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans was performed using CEAEQ method (MA.400-DF 1.0) by GC-MS
(Perkin Elmer, model Clarus 500 with RTX-Dioxin column of 60 m * 0.25 mm *
0.25 pm). Samples were extracted with toluene and then were purified and concentrated using multilayer silica columns eluted with hexane and alumina column eluted in three fractions with mixtures of hexane and dichloromethane. The quantification was performed with carbon 13C-labeled analogs.
Economic aspect The chemical costs associated to the decontamination of wood treating sites soils were calculated on the basis of the following unitary prices.
The sodium hydroxide (99.9% pure powder) was estimated at a cost of 500 US$/t and the cocamidopropylbetaine (solution at 35% w/w) was calculated at a cost of 1000 US$/t.
The sulfuric acid (solution at 93% w/w) was evaluated at a cost of 80 US$/t and the ferric sulfate solution (160 g Fe/L) at a cost of 500 US$/t.
Example 1: Selection of the leaching reagent Several "extractants" were tested for metal and pentachlorophenol extraction from soil. Solubilization assays carried in triplicates on Fl soil are presented in Fig 2.
Evaluation of both organic and inorganic acids, bases and ethanol shows that sulfuric and lactic acids give the best CCA removal yields and sodium and potassium hydroxide the best PCP removal yields. In order to design a remediation process, performance and cost are two principal criteria in terms of leaching reagents.
Lactic acid is more expensive than sulfuric acid with costs of approximately 1 200 and 94 $US/t respectively (ICIS Chemical Business, 28 August 2006) but acidic conditions did not allow PCP solubilization. Sodium hydroxide was chosen for next assays as he allow PCP, As and Cu solubilization and is cheaper than potassium hydroxide.
But at the initial stage of experimentation, it did not allow more than 53%
removal yield for As.
Example 2: Effect of operating parameters Figure 3 and 4 presents the influence of operating parameters on CCA and PCP
removal. Figure 3a and 3b present the influence of base concentration and pulp density on CCA and PCP removal. On Figure 3a, sodium hydroxide concentration form 0.1 to 2 M, causes an increase of CCA and PCP solubilization with a maximum obtain at 1 M for PCP with a removal yield of 90%. Increasing to 2M the base concentration raises arsenic and copper extraction with removal yields of 60%
and 40% respectively. As shown in Figure 3b, variation of soil PD from 5 to 20% (w v-1) causes considerable decrease of CCA and PCP removal. Temperature and reaction time are significant parameters in chemical processes. To assess influence of these variables, tests were done at four different temperatures: 20, 40, 60 and 80 C
and five different time: 1, 2, 4, 8 and 24 h. Figure 4a and 4b present the influence of temperature and time reaction on CCA and PCP removal. As show in Figure 4a, an increase of temperature between 20 to 80 C causes an increase of CCA and PCP
solubilization to 75% and 65% for PCP and As respectively. In Figure 4b, evolution of CCA removal decreased when time varied from 1 to 2 h. After 4 h, removals increased slowly. Gain in metals extraction is relatively low for increasing cost when base concentration exceeds 1 M. The pulp density content is an important parameter as it influences capital costs by varying the size of the leaching reactor.
Therefore, 1M sodium hydroxide is a good compromise between performances and low costs with 10% pulp density.
On Optimal operating conditions were determined from these results to improve solubilization performance at low operating costs. For further assays, sodium hydroxide concentration is fixed at 1M, temperature at 80 C, soil PD at 10%
(w1(1) and reaction time at 2 h.
Example 3: Evaluation of surfactant for PCDDF solubilization Assays were conducted on Si soil with an anionic (sodium dodecyl succinate), two amphoteric (cocamidopropyl hydroxysultaIne CAS and betaine BW) and four non-ionic (Brij-35, Igepal-CA720, Tween-80, Triton-X100) surfactants. Experimental parameters determined previously were used. Figure 5 presents PCDDF
solubilization at surfactant concentration of 1 g kg"1 (1%). SDS, Tween 80 and Triton X100 allow the best PCDDF removal which approaches 60% with only one leaching step. In other experiments, it was show that some surfactants reduce or enhance PCP and CCA solubilization.
Best results were obtained for the amphoteric surfactant BW which increases PCP
and CCA solubilization. Otherwise it shows acceptable removal yields for PCDDF
and has advantages to be non-toxic and biodegradable.
Example 4: Leaching process characteristics and cost Since alkaline soil washing with surfactant seems to be a promising method to treat soils contaminated with both organic and inorganic pollutants, process was tested on the four contaminated soils. For the purpose of an optional embodiment of the process, the parameters for leaching of wood treating site soil were selected as follows:
1. Soil content: 100 g/L;
2. Base type and concentration: 0.75 M NaOH;
3. Temperature: 80 C;
4. Reaction time: 2 h;
5. Leaching / rinsing step: 3 /1; and 6. Surfactant type and concentration: 3 % BW.
Table 1 gives the removal yields of PCP, CCA and PCDDF evaluated on pollutant concentrations in the soil before and after treatment.
Table 1: Removal yields of PCP, CCA and PCDDF for the four soils after three sodium hydroxide leaching step and 1 rinsing step with surfactant BW at concentration of 3 g kg-1. t = 120 min, T = 80 C, NaOH = 0,75M, PD = 10% (w V') Contaminant in mg/kg Fl soil As Cr Cu PCP PCDDF
Treated fraction 52,0 60,6 81,5 2,12 1394 After treatment 20,66 55,6 49,61 0,49 270 Solubilisation 59% 8% 41% 77% 81%
Si Contaminant in mg/kg soil As Cr Cu PCP PCDDF
Treated fraction 90,6 67,2 143 8,06 1375 After treatment 6,63 22,6 19,9 1,35 147 Solubilisation 92% 66% 91% 83% 89%
Contaminant in mg/kg 52 soil As Cr Cu PCP PCDDF
Treated fraction 262 199 346 7,01 3730 After treatment 62,1 152,0 185,4 0,61 874 Solubilisation 74% 21% 48% 91% 77%
Contaminant in mg/kg soil As Cr Cu PCP PCDDF
Treated fraction 91,1 83,0 148 47,2 6289 After treatment 13,5 54,2 66,7 0,92 603 Solubilisation 84% 34% 58% 98% 90%
This chemical leaching allows good metals solubilization with average removal yields of 77% for As, 32% for Cr and 60% for Cu. Moreover, it allows very good organic pollutants solubilization with average removal yields of 87% for PCP and 84%
for PCDDF. Cost associated to chemical leaching depends of sodium hydroxide concentration. For Fl and S1 soils, base concentration of 0.5 M allows sufficient soil decontamination according to Quebec regulation on contaminated soil. For S2 soil, a base concentration of 1 M is needed and for S3 soil, a base concentration of 0.75 M.
In those cases, cost associated to chemical leaching for the treatment of 1 t of dry soil is between 145 US$ and 265 US$.
This estimate does not take into account the possibility of recycling the final alkaline leachate after contaminant removal. This alkaline leaching has good potential for industrial application. A closed loop system may also further lower operational costs.
=
Example 5: Coagulation and precipitation of soil leachate using sulfuric acid and ferric sulfate Contaminants concentration in mixture of leachate from the four soil are 4.53 mg/L of As, 0.79 mg/L of Cr, 3.95 mg/L of Cu, 1.83 mg/L of PCP and 127 ng/L of PCDDF-TEQ. Precipitation was studied to recover PCP and CCA from leachates. Figure 6 presents removal yields during precipitation step with various volume of ferric sulfate solution containing 160 g Fe/L. Addition of 2 mL of ferric solution on 100 mL
of soil leachate with pH adjustment using sulfuric acid remove 98% of As, 92% of Cu and 85% of PCP. Pentachlorophenol precipitation depends of pH which control equilibrium between pentachlorophenate anion and the protonate form and so its solubility (Lee et al., 1990). Decreases of pH reduce solubility of pentachlorophenol due to its pKa = 4.75 (for acidic pH solubility is less than 20 mg/L whereas for alkaline pH solubility is up to 200 g/L). Arsenic coagulation is due to both the precipitation of iron arsenate (FeAs04.2H20) and the adsorption of arsenic onto hydrous ferric oxides. In the aqueous phase, soluble chromium is able to precipitate as Cr(OH)3. Copper is able to precipitate as hydroxides Cu(OH)2 and co-precipitate with ferric hydroxides (Janin et al., 2009b, 2009c). The presence of the three metals in solution influences individual precipitation behaviour of arsenic, chromium and copper. This could be explained by metal-metal interactions as arsenic, chromium and copper are able to form mixed compounds like Cu3(As04)2.2H20 and CuCrat (Blais et al., 2008).
Pentachlorophenol, copper, chromium and arsenic may be simultaneously removed from the solution by a total precipitation technique using an iron salt (e.g.
ferric sulfate) with a strong acid (e.g. sulfuric acid). Due to low cost of sulfuric acid, process cost for treatment of leachate produced during decontamination of 1 t of soil is less than 30 US$.
Example 6: Contaminant removal by ion exchange and adsorption with batch mode experiments Figure 7a and 7b show As, Cr, Cu and PCP removal yields after contacting soil leachates with several adsorbents or ion exchange resins.
100 mL of soil leaching were used and a mass of resin and adsorbent of 5 g were added. According to Figure 7a, adsorbents studied (anthracite, granular activated carbon, powdered activated carbon, alumina and silica) allow to remove PCP and some copper but are all enable to remove arsenic and chromium. Activated carbon powder and Norit granular activated carbon give the best removal yield (98%) for PCP. Ion exchange resins studied in Figure 7b are anionic, cationic or adsorption resin. All resins allow removal of pentachlorophenol. Anionic resins show the best removal yields for metal removal. Removal yields for Cu, Cr and PCP with Lewatit SR7 approach 83%, 41% and 99% respectively.
Ion exchange and adsorption on activated carbon are usually selective separation technologies and could be highly specific. Selective separation technologies are useful for contaminants extraction. Activated carbons are often used for organic pollutants removal whereas resins are mainly used for ionic compounds extraction.
Anionic resins were chosen due to ionic form of metals and PCP in soil leachate. In such alkaline conditions, pentachlorophenol, arsenic, copper and chromium are mainly on anionic form. Pentachlorophenol form is PCP due to pH, speciation of arsenic was analysed and show that 98% is on pentavalent oxidation state (As043-), Norkus et al. (1996 and 2004) have demonstrate that copper and chromium form anionic complex with hydroxide: Cu(OH)42- and Cr(OH)4" respectively.
Best adsorbent and ion exchange resin were compared to precipitation for contaminants removal from soil leachate including dioxins and furans extraction. As, Cr, Cu, PCP and PCDDF removal yields after contacting soil leachates with Lewatit SR7, Lewatit VPOC, Norit activated carbon, powder activated carbon or after optimised precipitation step are presented in Figure 8. 100 mL of soil leaching and 5 g of resin or adsorbent or 2 mL of ferric sulfate (160 g Fe/L) were used.
Lewatit SR 7, Lewatit VPOC and Norit granular activated carbon allow the best extractions of PCDDF with removal yields of 97%, 93% and 91% respectively whereas precipitation step remove less than 20% of PCDDF.
According to present invention, extraction of all contaminants present in soil leachate could be achieve with contacting the contaminated solution with a coagulant at a pH
favoring precipitation of pentachlorophenol, copper, chromium and arsenic and contacting the contaminated solution with an activated carbon or an ion exchange resin favoring pentachlorophenol, dioxins and furans extraction.
Table 1 gives the removal yields of PCP, CCA and PCDDF evaluated on pollutant concentrations in the soil before and after treatment.
Table 1: Removal yields of PCP, CCA and PCDDF for the four soils after three sodium hydroxide leaching step and 1 rinsing step with surfactant BW at concentration of 3 g kg-1. t = 120 min, T = 80 C, NaOH = 0,75M, PD = 10% (w V') Contaminant in mg/kg Fl soil As Cr Cu PCP PCDDF
Treated fraction 52,0 60,6 81,5 2,12 1394 After treatment 20,66 55,6 49,61 0,49 270 Solubilisation 59% 8% 41% 77% 81%
Si Contaminant in mg/kg soil As Cr Cu PCP PCDDF
Treated fraction 90,6 67,2 143 8,06 1375 After treatment 6,63 22,6 19,9 1,35 147 Solubilisation 92% 66% 91% 83% 89%
Contaminant in mg/kg 52 soil As Cr Cu PCP PCDDF
Treated fraction 262 199 346 7,01 3730 After treatment 62,1 152,0 185,4 0,61 874 Solubilisation 74% 21% 48% 91% 77%
Contaminant in mg/kg soil As Cr Cu PCP PCDDF
Treated fraction 91,1 83,0 148 47,2 6289 After treatment 13,5 54,2 66,7 0,92 603 Solubilisation 84% 34% 58% 98% 90%
This chemical leaching allows good metals solubilization with average removal yields of 77% for As, 32% for Cr and 60% for Cu. Moreover, it allows very good organic pollutants solubilization with average removal yields of 87% for PCP and 84%
for PCDDF. Cost associated to chemical leaching depends of sodium hydroxide concentration. For Fl and S1 soils, base concentration of 0.5 M allows sufficient soil decontamination according to Quebec regulation on contaminated soil. For S2 soil, a base concentration of 1 M is needed and for S3 soil, a base concentration of 0.75 M.
In those cases, cost associated to chemical leaching for the treatment of 1 t of dry soil is between 145 US$ and 265 US$.
This estimate does not take into account the possibility of recycling the final alkaline leachate after contaminant removal. This alkaline leaching has good potential for industrial application. A closed loop system may also further lower operational costs.
=
Example 5: Coagulation and precipitation of soil leachate using sulfuric acid and ferric sulfate Contaminants concentration in mixture of leachate from the four soil are 4.53 mg/L of As, 0.79 mg/L of Cr, 3.95 mg/L of Cu, 1.83 mg/L of PCP and 127 ng/L of PCDDF-TEQ. Precipitation was studied to recover PCP and CCA from leachates. Figure 6 presents removal yields during precipitation step with various volume of ferric sulfate solution containing 160 g Fe/L. Addition of 2 mL of ferric solution on 100 mL
of soil leachate with pH adjustment using sulfuric acid remove 98% of As, 92% of Cu and 85% of PCP. Pentachlorophenol precipitation depends of pH which control equilibrium between pentachlorophenate anion and the protonate form and so its solubility (Lee et al., 1990). Decreases of pH reduce solubility of pentachlorophenol due to its pKa = 4.75 (for acidic pH solubility is less than 20 mg/L whereas for alkaline pH solubility is up to 200 g/L). Arsenic coagulation is due to both the precipitation of iron arsenate (FeAs04.2H20) and the adsorption of arsenic onto hydrous ferric oxides. In the aqueous phase, soluble chromium is able to precipitate as Cr(OH)3. Copper is able to precipitate as hydroxides Cu(OH)2 and co-precipitate with ferric hydroxides (Janin et al., 2009b, 2009c). The presence of the three metals in solution influences individual precipitation behaviour of arsenic, chromium and copper. This could be explained by metal-metal interactions as arsenic, chromium and copper are able to form mixed compounds like Cu3(As04)2.2H20 and CuCrat (Blais et al., 2008).
Pentachlorophenol, copper, chromium and arsenic may be simultaneously removed from the solution by a total precipitation technique using an iron salt (e.g.
ferric sulfate) with a strong acid (e.g. sulfuric acid). Due to low cost of sulfuric acid, process cost for treatment of leachate produced during decontamination of 1 t of soil is less than 30 US$.
Example 6: Contaminant removal by ion exchange and adsorption with batch mode experiments Figure 7a and 7b show As, Cr, Cu and PCP removal yields after contacting soil leachates with several adsorbents or ion exchange resins.
100 mL of soil leaching were used and a mass of resin and adsorbent of 5 g were added. According to Figure 7a, adsorbents studied (anthracite, granular activated carbon, powdered activated carbon, alumina and silica) allow to remove PCP and some copper but are all enable to remove arsenic and chromium. Activated carbon powder and Norit granular activated carbon give the best removal yield (98%) for PCP. Ion exchange resins studied in Figure 7b are anionic, cationic or adsorption resin. All resins allow removal of pentachlorophenol. Anionic resins show the best removal yields for metal removal. Removal yields for Cu, Cr and PCP with Lewatit SR7 approach 83%, 41% and 99% respectively.
Ion exchange and adsorption on activated carbon are usually selective separation technologies and could be highly specific. Selective separation technologies are useful for contaminants extraction. Activated carbons are often used for organic pollutants removal whereas resins are mainly used for ionic compounds extraction.
Anionic resins were chosen due to ionic form of metals and PCP in soil leachate. In such alkaline conditions, pentachlorophenol, arsenic, copper and chromium are mainly on anionic form. Pentachlorophenol form is PCP due to pH, speciation of arsenic was analysed and show that 98% is on pentavalent oxidation state (As043-), Norkus et al. (1996 and 2004) have demonstrate that copper and chromium form anionic complex with hydroxide: Cu(OH)42- and Cr(OH)4" respectively.
Best adsorbent and ion exchange resin were compared to precipitation for contaminants removal from soil leachate including dioxins and furans extraction. As, Cr, Cu, PCP and PCDDF removal yields after contacting soil leachates with Lewatit SR7, Lewatit VPOC, Norit activated carbon, powder activated carbon or after optimised precipitation step are presented in Figure 8. 100 mL of soil leaching and 5 g of resin or adsorbent or 2 mL of ferric sulfate (160 g Fe/L) were used.
Lewatit SR 7, Lewatit VPOC and Norit granular activated carbon allow the best extractions of PCDDF with removal yields of 97%, 93% and 91% respectively whereas precipitation step remove less than 20% of PCDDF.
According to present invention, extraction of all contaminants present in soil leachate could be achieve with contacting the contaminated solution with a coagulant at a pH
favoring precipitation of pentachlorophenol, copper, chromium and arsenic and contacting the contaminated solution with an activated carbon or an ion exchange resin favoring pentachlorophenol, dioxins and furans extraction.
Claims (58)
1. A process for decontamination of soil contaminated with a preservative comprising contaminants, comprising contacting the soil with water, an inorganic base at a concentration between about 0 1 M and about 2 M at a temperature lower than about 100°C, to solubilise at least a portion of the contaminants present in the soil, thereby producing a contaminant-rich solution and contaminant-poor soil; and separating the contaminant-rich solution from the contaminant-poor soil
2. The process of claim 1, wherein the step of contacting the soil includes also contacting with a surfactant at a concentration optionally between about 0.05 % and about 5 % by weight.
3 The process of claim 1 or 2, wherein the contaminants include metals or organic compounds or combinations thereof
4. The process of claim 3, wherein the contaminants include .
metals;
pentachlorophenol;
dioxins and furans; or derivatives, analogues, or isomers of such contaminants; or combinations thereof.
metals;
pentachlorophenol;
dioxins and furans; or derivatives, analogues, or isomers of such contaminants; or combinations thereof.
5. The process of claim 4, wherein the contaminants include:
pentachlorophenol (PCP) and derivatives thereof, and/or polychlorined dibenzodioxins and dibenzofurans (PCDDFs) and isomeric analogues thereof.
pentachlorophenol (PCP) and derivatives thereof, and/or polychlorined dibenzodioxins and dibenzofurans (PCDDFs) and isomeric analogues thereof.
6. The process of any one of claims 1 to 5, wherein the contaminants come from preservatives including Chromated Copper Arsenate (CCA), Pentachlorophenol (PCP) and/or polychlorined dibenzodioxins and dibenzofurans (PCDDF).
7. The process of any one of claims 1 to 6, wherein, prior to the contacting step, the soil is crushed or screened.
8. The process of claim 7, wherein the soil is crushed or screened so as to have particle size inferior to about 1 cm.
9. The process of claim 8, wherein the soil is crushed or screened so as to have particle size inferior to about 0.6 mm.
10. The process of any one of claims 1 to 9, wherein the soil, the water, the inorganic base and the surfactant form an alkaline mixture, and soil content of the alkaline mixture is adjusted to a range between about 20 g/L and about 200 g/L of the total mixture.
11. The process of any one of claims 1 to 10, wherein the inorganic base comprises sodium hydroxide.
12. The process of any one of claims 1 to 11, wherein the inorganic base comprises a sodium, potassium or calcium base, a used base, or a recycled base or a combination thereof.
13. The process of any one of claims 1 to 12, wherein the surfactant comprises an amphoteric biosurfactant.
14. The process of any one of claims 1 to 13, wherein the surfactant is an amphoteric biosurfactant.
15. The process of any one of claims 1 to 14, wherein the surfactant comprises cocamidopropylbetaine.
16. The process of any one of claims 1 to 15, wherein the surfactant is cocamidopropylbetaine.
17. The process of any one of claims 1 to 16, wherein the surfactant comprises a cationic, anionic, both anionic and cationic or neutral head, or a combination thereof.
18. The process of any one of claims 1 to 17, wherein the surfactant is synthetic or a biosurfactant, or a combination thereof.
19. The process of any one of claims 1 to 18, comprising mixing the alkaline mixture for a period sufficient to adequately solubilise the contaminants present in the soil.
20. The process of claim 19, wherein the mixing of the alkaline mixture is performed for about 0.5 to about 24 h.
21. The process of any one of claims 1 to 20, wherein the temperature of the alkaline mixture is between about 20°C and about 80°C.
22. The process of any one of claims 1 to 21, wherein the step of contacting producing the contaminant-rich solution and the contaminant-poor soil, is performed in a single leaching step.
23. The process of any one of claims 1 to 21, wherein the step of contacting producing the contaminant-rich solution and the contaminant-poor soil, is performed in multiple leaching steps.
24. The process of claim 23, wherein the multiple leaching steps are performed sequentially.
25. The process of claim 24, wherein the sequential leaching steps utilize the same or different inorganic bases.
26. The process of claim 25, wherein the sequential leaching steps utilize the same or different concentrations of the inorganic base(s).
27. The process of any one of claims 24 to 26, wherein the sequential leaching steps utilize the same or different surfactants.
28. The process of claim 27, wherein the sequential leaching steps utilize the same or different concentrations of the surfactant(s).
29. The process of any one of claims 23 to 28, wherein the leaching steps are operated in batch, semi-continuous or continuous mode in tank reactors.
30. The process of any one of claims 1 to 29, wherein, after the leaching step or steps, the contaminant-poor soil is separated from the contaminant-rich solution by decantation, filtration, centrifugation, or another technique of solid-liquid separation, or a combination thereof.
31. The process of any one of claims 1 to 30, comprising washing the separated contaminant-poor soil to remove residual solubilised contaminants.
32. The process of claim 31, wherein the washing is done by rinsing the solids resulting from a previous filtration step or by mixing the solids re-suspended in the washing solution, followed by a step of solid-liquid separation.
33. The process of claim 31, wherein the washing is done in one or more steps with water, a dilute alkaline solution, or an acid solution.
34. The process of claim 31, wherein different washing steps are performed with the same or different washing solutions.
35. The process of claim 31, wherein the contaminant-rich solution and spent washing liquids are combined to obtain a solution containing the totality of the target contaminants.
36. The process of claim 31, wherein some or all of spent washing waters are directly used as process water for the operation of the initial leaching steps for a subsequent batch or quantity of contaminated soil.
37. The process of any one of claims 1 to 36, wherein the contaminant-rich solution and the spent washing liquids are referred to as alkaline leachate, which comprises at least a portion of the contaminant-rich solution or the spent washing liquids or a combination thereof, and wherein the process comprises treating at least a portion of the alkaline leachate to recover at least one of the contaminants therefrom.
38. The process of claim 37, wherein the recovered contaminant comprises a metal.
39. The process of claim 38, wherein at least a portion of the recovered metal comprises copper arsenic, chromium or copper or a combination thereof.
40. The process of claim 38, wherein at least a portion of the recovered metal is recovered in the form of mixed metalloid compounds and/or as pure metal.
41. The process of any one of claims 38 to 40, wherein the metal contaminant is recovered by means of chemical precipitation, ion exchange, solvent extraction or adsorption or a combination thereof.
42. The process of any one of claims 37 to 41, wherein, after the alkaline leachate has been treated to remove the at least one of the contaminants, the resulting treated solution is used as process water for the operation of the leaching step(s).
43. The process of any one of claims 1 to 42, wherein at least two of pentachlorophenol, dioxins and furans, copper, chromium and arsenic are simultaneously removed from the alkaline leachate.
44. The process of any one of claims 1 to 43, wherein all of pentachlorophenol, dioxins and furans, copper, chromium and arsenic are simultaneously removed from the solution.
45. The process of claim 43 or 44, wherein the removal is performed by a total precipitation technique using an iron salt
46 The process of claim 45, wherein the iron salt comprises ferric chloride or sulfate.
47. The process of claim 45 or 46, wherein the total precipitation technique also uses a strong acid
48 The process of claim 47, wherein the strong acid comprises sulfuric acid.
49. The process of claim 37, wherein the alkaline leachate is treated to remove at least one organic compound
50. The process of claim 43, wherein the organic compound comprises pentachlorophenol, dioxins and furans or a combination thereof
51 The process of claim 49 or 50, wherein the organic compound is removed by means of chemical precipitation, ion exchange, solvent extraction or adsorption or a combination thereof
52 The process of claim 49 or 50, wherein the organic compound is removed from the alkaline leachate by means of ion exchange resins or activated carbons or a combination thereof.
53. The process of any one of claims 1 to 52, wherein the decontaminated soil and/or the contaminants extracted from the soil and/or alkaline leachate are disposed of or recycled.
54. A process for contaminant extraction from a contaminated solution, comprising:
contacting the contaminated solution with a coagulant at a pH favoring precipitation of pentachlorophenol, copper, chromium and arsenic, and/or contacting the contaminated solution with an activated carbon or an ion exchange resin favoring pentachlorophenol, dioxins and furans extraction.
contacting the contaminated solution with a coagulant at a pH favoring precipitation of pentachlorophenol, copper, chromium and arsenic, and/or contacting the contaminated solution with an activated carbon or an ion exchange resin favoring pentachlorophenol, dioxins and furans extraction.
55. The process of claim 54, comprising at least one step or feature as defined in any one of claims 1 to 46 for producing the contaminated solution and/or treating any of the resulting streams or fractions of the process.
56. A process as defined in any one of claims 1 to 55, comprising at least one step or feature as defined in the present description and/or figures for treating the contaminated soil, the contaminated solution, the contaminants and/or any of the resulting streams or fractions of the process.
57. A process for decontamination of soil contaminated with a preservative comprising contaminants, the contaminants comprising metals and/or organic compounds, wherein:
the metals include, for example, arsenic, chromium, copper, and/or other metal species; and the organic compounds include, for example, pentachlorophenol and derivatives thereof, dioxins and furans such as polychlorined dibenzodioxins and dibenzofurans and isomeric analogues thereof, and/or other organic species;
the metals and organic compounds optionally coming from preservatives, for example, Chromated Copper Arsenate (CCA), Pentachlorophenol (PCP) and/or polychlorined dibenzodioxins and dibenzofurans (PCDDF).
wherein the process comprises the steps of:
contacting the soil with water, an inorganic base with or without a surfactant at a temperature lower than about 100°C, the concentrations of the inorganic base and the optional surfactant being sufficient to enable solubilization a substantial amount of the contaminants present in the soil, thereby producing a contaminant-rich solution and contaminant-poor soil; and separating the contaminant-rich solution from the contaminant-poor soil.
the metals include, for example, arsenic, chromium, copper, and/or other metal species; and the organic compounds include, for example, pentachlorophenol and derivatives thereof, dioxins and furans such as polychlorined dibenzodioxins and dibenzofurans and isomeric analogues thereof, and/or other organic species;
the metals and organic compounds optionally coming from preservatives, for example, Chromated Copper Arsenate (CCA), Pentachlorophenol (PCP) and/or polychlorined dibenzodioxins and dibenzofurans (PCDDF).
wherein the process comprises the steps of:
contacting the soil with water, an inorganic base with or without a surfactant at a temperature lower than about 100°C, the concentrations of the inorganic base and the optional surfactant being sufficient to enable solubilization a substantial amount of the contaminants present in the soil, thereby producing a contaminant-rich solution and contaminant-poor soil; and separating the contaminant-rich solution from the contaminant-poor soil.
58. The process of claim 57, comprising at least one step or feature as defined in any one of the claims 1 to 56 and/or the present description and/or figures.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2762060 CA2762060A1 (en) | 2011-12-16 | 2011-12-16 | Process for decontamination of soils polluted with metals, pentachlorophenol, dioxins and furans and contaminants removal from leachates |
| PCT/CA2012/050904 WO2013086641A1 (en) | 2011-12-16 | 2012-12-17 | Process for decontamination of soils polluted with metals, pentachlorophenol, dioxins and furans and contaminants removal from leachates |
| CA2857703A CA2857703A1 (en) | 2011-12-16 | 2012-12-17 | Process for decontamination of soils polluted with metals, pentachlorophenol, dioxins and furans and contaminants removal from leachates |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2762060 CA2762060A1 (en) | 2011-12-16 | 2011-12-16 | Process for decontamination of soils polluted with metals, pentachlorophenol, dioxins and furans and contaminants removal from leachates |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2762060A1 true CA2762060A1 (en) | 2013-06-16 |
Family
ID=48611770
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2762060 Abandoned CA2762060A1 (en) | 2011-12-16 | 2011-12-16 | Process for decontamination of soils polluted with metals, pentachlorophenol, dioxins and furans and contaminants removal from leachates |
| CA2857703A Abandoned CA2857703A1 (en) | 2011-12-16 | 2012-12-17 | Process for decontamination of soils polluted with metals, pentachlorophenol, dioxins and furans and contaminants removal from leachates |
Family Applications After (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2857703A Abandoned CA2857703A1 (en) | 2011-12-16 | 2012-12-17 | Process for decontamination of soils polluted with metals, pentachlorophenol, dioxins and furans and contaminants removal from leachates |
Country Status (2)
| Country | Link |
|---|---|
| CA (2) | CA2762060A1 (en) |
| WO (1) | WO2013086641A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108906348B (en) * | 2018-03-05 | 2023-10-10 | 中国标准化研究院 | Separation device and separation method for separating microplastic and cellulose crystals in soil |
| CN114393021B (en) * | 2021-12-27 | 2022-11-29 | 中国科学院沈阳应用生态研究所 | Thermal desorption and stabilization synergic remediation method for composite contaminated soil |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2628642A1 (en) * | 2008-04-08 | 2009-10-08 | Institut National De La Recherche Scientifique (Inrs) | Process for decontamination of chromated copper arsenate treated wood |
-
2011
- 2011-12-16 CA CA 2762060 patent/CA2762060A1/en not_active Abandoned
-
2012
- 2012-12-17 WO PCT/CA2012/050904 patent/WO2013086641A1/en active Application Filing
- 2012-12-17 CA CA2857703A patent/CA2857703A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO2013086641A1 (en) | 2013-06-20 |
| CA2857703A1 (en) | 2013-06-20 |
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