CN113651507A - Method for removing heavy metals in livestock and poultry manure/biogas residues and EKR-PRB coupling device - Google Patents
Method for removing heavy metals in livestock and poultry manure/biogas residues and EKR-PRB coupling device Download PDFInfo
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/006—Electrochemical treatment, e.g. electro-oxidation or electro-osmosis
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
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- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/20—Nature of the water, waste water, sewage or sludge to be treated from animal husbandry
Abstract
The invention provides a method for removing heavy metals in livestock and poultry manure/biogas residues and an EKR-PRB coupling device, and relates to the technical field of agricultural environmental protection. The removal method provided by the invention organically combines leaching technology and electric chelating PRB technology by taking ethylene diamine tetraacetic acid and/or disodium ethylene diamine tetraacetate as an extracting agent. The solid phase pH value of the excrement/biogas residue treated by leaching technology is 6.1-8.0 by using ethylene diamine tetraacetic acid and/or disodium ethylene diamine tetraacetic acid as a leaching agent, the influence on the pH value of the excrement/biogas residue is small, and the obtained solid component can be directly used as a composting raw material; the leaching waste liquid is treated by EKR-PRB to realize the high-efficiency removal of heavy metals of Cu, Zn and Cd, and the obtained treatment liquid can be used as biogas liquid fertilizer for crops such as rice, vegetables and the like, so that the agricultural environmental risk of manure is reduced, and the operation is simple.
Description
Technical Field
The invention relates to the technical field of agricultural environment protection, in particular to a method for removing heavy metals in livestock and poultry manure/biogas residues and an EKR-PRB coupling device.
Background
The unreasonable use of feed additives in livestock breeding has caused the problem of high heavy metal residue in feces. The heavy metals in the livestock and poultry manure are mainly Cu, Zn and Cd. Heavy metals in the excrement are mainly treated by anaerobic digestion and aerobic composting, and organic matters in the livestock excrement can be converted into humus by decomposition of microorganisms in the anaerobic and aerobic fermentation processes, so that the effect of passivating the heavy metals is achieved. In addition, the migration capacity and the biological effectiveness of heavy metals can be further reduced by adding physical, chemical and biological passivators in the anaerobic and aerobic treatment links. However, the treatment method cannot reduce the total amount of heavy metals, and the passivated heavy metals still have the environmental risk of being released again after entering the farmland along with the organic fertilizer.
The organic matter content in the livestock and poultry manure/biogas residues is higher, and the heavy metals are firmly combined and are difficult to remove. Chemical and bioleaching technologies for removing heavy metals from livestock and poultry manure/biogas residues are researched more, and the removal rate of the heavy metals can be improved by acidifying the livestock and poultry manure/biogas residues. For example, the technological parameters for removing the heavy metals in the livestock and poultry manure by using sulfuric acid, hydrochloric acid and nitric acid are researched by the yakexin (see: yakexin, research on removal of the heavy metals in the livestock and poultry manure [ D ]. China university of mining (Beijing), 2010.), and the lower the pH of a reaction system is, the more beneficial the removal of the heavy metals is. Weak Xiaozhu and the like (see: Wenxiaxian, Liu east, Liao, Wang Zhendong, Liwenjiao, Dolerian and Lizhendong. research on removing heavy metal in pig manure by bioleaching with indigenous thiobacillus [ J ]. science and science of agricultural environment, 2018,37(11):2594 and 2602.) by leaching with thiobacillus thiooxidans, and the result also shows that the higher removal rate of the heavy metal can be realized only when the pH value of the manure is reduced to below 2. However, the method excessively acidifies the livestock manure in the process of removing heavy metals, so that the pH of the solid phase of the leached livestock manure is too low, and the method is not beneficial to the utilization of the compost in the later period. Therefore, there is a strong need to develop a method for effectively removing heavy metals with little influence on the pH of livestock and poultry manure/biogas residues.
Disclosure of Invention
In view of the above, the present invention provides a method for removing heavy metals from livestock and poultry manure/biogas residues and an EKR-PRB coupling device, and the method provided by the present invention has a small influence on the pH of livestock and poultry manure/biogas residues and a high removal rate for heavy metals.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for removing heavy metals in livestock and poultry manure/biogas residues, which comprises the following steps:
mixing the livestock and poultry manure/biogas residue with an extractant solution, carrying out leaching treatment, and carrying out solid-liquid separation to obtain a solid component and a leaching waste liquid; the lixiviant in the lixiviant solution comprises ethylene diamine tetraacetic acid and/or disodium ethylene diamine tetraacetate;
and carrying out EKR-PRB coupling treatment on the leaching waste liquid to obtain a treatment liquid.
Preferably, the heavy metal comprises one or more of Cd, Cu and Zn.
Preferably, the concentration of the leaching agent solution is 0.01-0.15 mol/L;
the solid-liquid ratio of the livestock and poultry manure/biogas residues to the leaching agent solution is 1kg: 5-10L.
Preferably, the leaching treatment temperature is 15-35 ℃, and the time is 10 min-24 h.
Preferably, the adsorption material adopted by the EKR-PRB coupling treatment comprises one or more of weak acid type ion exchange resin CH-90 with iminodiacetic acid functional groups, strong acid cation exchange resin CH-93 with amino methyl phosphonic acid functional groups, Katalox Light filter material with a manganese dioxide coating on the surface, biomass charcoal, natural rectorite and natural zeolite.
Preferably, the EKR-PRB coupling processing operation parameters include: the direct current voltage is 0.5-1V/cm, and the electrolysis time is 40-60 h.
The invention provides an EKR-PRB coupling device adopted by the removal method in the technical scheme, which comprises an electrolytic cell 1, a first electrode plate 21 and a second electrode plate 22 which are respectively arranged at two ends of the electrolytic cell 1, and a direct current power supply 3 connected with the first electrode plate 21 and the second electrode plate 22;
a treatment chamber 4, a PRB permeable wall 5 and an anode chamber 6 are arranged in the electrolytic cell 1; the PRB permeable wall 5 is filled with an adsorbing material 51;
a detachable isolation plate 61 is arranged in the anode chamber 6.
Preferably, sintered glass 52 is disposed on both sides of the adsorbent 51.
Preferably, the material of the first electrode plate 21 and the second electrode plate 22 includes titanium alloy, graphite, or stainless steel.
Preferably, the material of the detachable isolation plate 61 includes steel, teflon or polyvinyl chloride.
The invention provides a method for removing heavy metals in livestock and poultry manure/biogas residues, which comprises the following steps: mixing the livestock and poultry manure/biogas residue with an extractant solution, carrying out leaching treatment, and carrying out solid-liquid separation to obtain a solid component and a leaching waste liquid; the lixiviant in the lixiviant solution comprises ethylene diamine tetraacetic acid and/or disodium ethylene diamine tetraacetate; and carrying out EKR-PRB coupling treatment on the leaching waste liquid to obtain a treatment liquid. The removal method provided by the invention organically combines a leaching technology and an EKR-PRB technology, uses ethylene diamine tetraacetic acid and/or disodium ethylene diamine tetraacetic acid as an extracting agent, has a pH value of 6.1-8.0 of a solid component treated by the leaching technology, has little influence on the pH value of livestock and poultry manure/biogas residues, and can directly use the obtained solid component as a composting raw material; the leaching waste liquid is treated by EKR-PRB to realize the high-efficiency removal of heavy metals Cd, Cu and Zn, and the treating liquid obtained after the leaching waste liquid is treated by EKR-PRB can be used as biogas slurry fertilizer, especially as biogas slurry fertilizer for crops such as rice, vegetables and the like. The removal method provided by the invention reduces the agricultural environmental risk of manure; moreover, the removal method provided by the invention is simple to operate and suitable for large-scale application. As shown in the results of the examples, the removal rate of Cd, Cu and Zn in the livestock and poultry manure/biogas residues after leaching treatment is respectively 46%, 34% and 45%, and the average removal rate is reduced by 42%; after EKR-PRB treatment, Cd, Cu and Zn in the leaching waste liquid are respectively reduced by 99%, 40% and 72%, wherein Cd is less than or equal to 0.01mg/L, and the biogas liquid fertilizer can meet the agricultural requirements of crops such as rice, vegetables and the like.
The invention provides an EKR-PRB coupling device adopted by the method for removing heavy metals in livestock and poultry manure/biogas residues in the technical scheme. The device provided by the invention has a simple structure, can realize the efficient removal of heavy metals such as Cd, Cu and Zn in the livestock and poultry manure/biogas residues and the leaching waste liquid, does not influence the subsequent composting of the solid part, can be used as biogas liquid fertilizer of crops such as rice, vegetables and the like after the leaching waste liquid is treated by the EKR-PRB coupling device, and reduces the agricultural environmental risk of manure pollution.
Drawings
FIG. 1 is a schematic perspective view of an EKR-PRB coupling device for removing heavy metals from leach liquors;
FIG. 2 is a schematic plan view of an EKR-PRB coupling device used to remove heavy metals from leach liquors;
FIG. 3 is a diagram showing the effect of the type of leaching agent on the removal of solid-phase heavy metals from livestock and poultry manure/biogas residues;
FIG. 4 shows Na2A result graph of the influence of the concentration of the EDTA solution on the removal of heavy metals in the livestock and poultry manure/biogas residues;
FIG. 5 is a graph showing the effect of leaching time on the removal of heavy metals from animal manure/biogas residues;
FIG. 6 is a graph showing the effect of solid-liquid ratio on the removal of heavy metals from livestock and poultry manure/biogas residues;
FIG. 7 is a response surface diagram of factor interaction influencing the removal of Cd from the livestock manure/biogas residues;
FIG. 8 is a graph showing the effect of different voltages on the concentration of heavy metals remaining in the leach liquor;
FIG. 9 is a graph showing the effect of electrolysis time on the concentration of residual heavy metals in a leach liquor;
FIG. 10 is a graph showing the effect of adsorption material species on the removal of heavy metals from leach liquors.
Detailed Description
The invention provides a method for removing heavy metals in livestock and poultry manure/biogas residues, which comprises the following steps:
mixing the livestock and poultry manure/biogas residue with an extractant solution, carrying out leaching treatment, and carrying out solid-liquid separation to obtain a solid component and a leaching waste liquid; the lixiviant in the lixiviant solution comprises ethylene diamine tetraacetic acid and/or disodium ethylene diamine tetraacetate;
and carrying out EKR-PRB coupling treatment on the leaching waste liquid to obtain a treatment liquid.
In the present invention, all the raw material components are commercially available products well known to those skilled in the art unless otherwise specified.
The invention mixes the livestock and poultry manure/biogas residue with the leaching agent solution, and carries out solid-liquid separation after leaching treatment to obtain solid components and leaching waste liquid.
In the present invention, the livestock manure/biogas residue preferably comprises livestock manure and/or biogas residue. In the present invention, the lixiviant in the lixiviant solution comprises ethylenediaminetetraacetic acid (EDTA) and/or disodium ethylenediaminetetraacetate (Na)2EDTA); the lixiviant is an industrial grade pure commodity; the leaching agent is used for complexing heavy metals in the livestock and poultry manure/biogas residues to leaching waste liquid; the heavy metal preferably comprises one or more of Cd, Cu and Zn; the concentration of the leaching agent solution is preferably 0.01-0.15 mol/L, more preferably 0.01-0.1 mol/L, and further preferably 0.03-0.06 mol/L; the concentration of the lixiviant solution is controlled within the range, so that the pH value (6.1-8.0) of the livestock and poultry manure/biogas residue can not be obviously influenced under the condition of ensuring the removal rate of heavy metals in the livestock and poultry manure/biogas residue, subsequent compost is not influenced, the obtained lixiviant waste liquid can be used as biogas manure after subsequent treatment, and the economic cost can be reduced. In the invention, the solid-to-liquid ratio of the livestock and poultry manure/biogas residue to the leaching agent solution is preferably 1kg: 5-10L, more preferably 1kg: 5-7L, and further preferably 1kg: 5L; excessive use of the lixiviant solution can produce large amounts of waste liquor, thereby increasing the economic cost of post-treatment.
In the invention, the leaching temperature is preferably 15-35 ℃, and more preferably 20-25 ℃; in the embodiment of the present invention, the leaching treatment is preferably performed at room temperature; the leaching time is preferably 10min to 24h, more preferably 10min to 10h, even more preferably 10min to 4h, and most preferably 10 to 30 min; the leaching treatment is preferably carried out in an oscillator, and the oscillation speed of the oscillator is preferably 150-200 rpm, more preferably 160-190 rpm, and further preferably 170-180 rpm.
The leaching treatment is carried out under the conditions, the influence on the pH value of the livestock and poultry manure/biogas residues is small, the removal rates of heavy metals Cd, Cu and Zn are respectively 46%, 34% and 45%, the average removal rate is 42%, the subsequent composting use of the livestock and poultry manure/biogas residues is not influenced, and the treatment cost is low.
In the invention, the solid-liquid separation mode is preferably centrifugal separation, and the speed of the centrifugal separation is preferably 4000-5000 rpm, more preferably 4500 rpm; the time for centrifugal separation is preferably 8-10 min, and more preferably 9 min.
In the present invention, the solid component can be used directly for composting.
After the leaching waste liquid is obtained, EKR-PRB coupling treatment is carried out on the leaching waste liquid to obtain a treatment liquid.
In the invention, the adsorption material adopted by the EKR-PRB coupling (electric-permeable reactive wall coupling) treatment preferably comprises one or more of weak acid type ion exchange resin CH-90 with iminodiacetic acid functional groups, strong acid cation exchange resin CH-93 with amino methyl phosphonic acid functional groups, Katalox Light filter material with a manganese dioxide coating on the surface, biomass charcoal, natural rectorite and natural zeolite; the weak acid type ion exchange resin CH-90 with iminodiacetic acid functional group, the strong acid cation exchange resin CH-93 with aminomethylphosphonic acid functional group and the Katalox Light filter material with manganese dioxide coating on the surface are preferably purchased from Kohaisi (Beijing) science and technology Limited.
In the invention, the biomass charcoal is preferably obtained by self-making, and the biomass charcoal is preferably obtained by thermally cracking peanut shells in an oxygen-isolated manner. In the invention, the method preferably comprises the steps of crushing the peanut shells and sieving the crushed peanut shells before the oxygen-isolated thermal cracking, wherein the crushing mode is not particularly limited, and the peanut shells can be crushed to the particle size of less than or equal to 2 mm; the sieve mesh of the sieve adopted for sieving is preferably 2mm, and the part below the sieve is subjected to subsequent oxygen-isolated thermal cracking. In the invention, the oxygen-insulating heating cracking temperature is preferably 450-550 ℃, and more preferably 500 ℃; the oxygen-isolated heating cracking time is preferably 3.5-4.5 h, and more preferably 4 h.
In the present invention, the natural rectorite is preferably pulverized and sieved before use; the invention has no special limitation on the crushing and sieving, and the particle size of the natural rectorite can be less than or equal to 0.15 mm; in an embodiment of the invention, the screened mesh size is preferably 0.15 mm; the natural rectorite is preferably produced in Jingmen city, Hubei province.
In the present invention, the zeolite is preferably a natural zeolite, and the particle size of the zeolite is preferably less than or equal to 1 mm; the natural zeolite is preferably purchased from akaho constant mineral products ltd.
In the present invention, the operating parameters of the EKR-PRB coupling process preferably include: the DC voltage is preferably 0.5-1V/cm, more preferably 0.8-1V/cm, and further preferably 0.9-1V/cm; the electrolysis time is preferably 40 to 60 hours, more preferably 50 to 60 hours, and further preferably 55 to 60 hours. In the invention, in the EKR-PRB coupling treatment process, complex heavy metal anions in the leaching waste liquid can migrate to the anode chamber under the action of an electric field and are intercepted by PRB close to the anode chamber.
The invention provides an EKR-PRB coupling device adopted by the removal method in the technical scheme, which comprises an electrolytic cell 1, a first electrode plate 21 and a second electrode plate 22 which are arranged at two ends of the electrolytic cell 1, and a direct current power supply 3 connected with the first electrode plate 21 and the second electrode plate 22;
a treatment chamber 4, a PRB permeable wall 5 and an anode chamber 6 are arranged in the electrolytic cell 1; the PRB permeable wall 5 is filled with an adsorbing material 51;
a detachable isolation plate 61 is arranged in the anode chamber 6.
In the present invention, a schematic perspective view and a schematic plan view of the EKR-PRB coupling device are shown in FIG. 1 and FIG. 2, and the EKR-PRB coupling device will be described in detail with reference to FIGS. 1 to 2.
The EKR-PRB coupling device provided by the invention comprises an electrolytic bath 1. In the invention, a first electrode plate 21 and a second electrode plate 22 are respectively arranged at two ends of the electrolytic cell 1; the first electrode plate 21 and the second electrode plate 22 are made of titanium alloy, graphite or stainless steel. In the invention, a treatment chamber 4, a PRB permeable wall 5 and an anode chamber 6 are arranged in the electrolytic cell 1.
In the invention, the treatment chamber 4 and the anode chamber 6 are filled with leaching waste liquid; the leaching waste liquid in the anode chamber 6 can be recycled; for the convenience of subsequent sampling, the process chamber is preferably divided into five regions, S5, S4, S3, S2 and S1.
In the invention, the PRB permeable wall 5 is filled with an adsorbing material 51, and the adsorbing material 51 is used for intercepting EDTA complex heavy metal anions moving to the anode under the action of an electric field; sintered glass 52 is preferably disposed on both sides of the adsorbing material 51 to fix the adsorbing material 51; the sintered glass 52 is preferably purchased from a glass instrument factory such as east China.
In the invention, a detachable isolation plate 61 is arranged in the anode chamber 6; the material of the detachable isolation plate 61 preferably comprises steel, polytetrafluoroethylene or polyvinyl chloride PVC hard plastic; the removable partition plate 61 is preferably disposed at a side of the anode chamber 6 adjacent to the PRB permeable wall 5.
The size of the EKR-PRB coupled device is not particularly limited in the present invention; in the embodiment of the present invention, the dimensions of the first electrode plate 21 and the second electrode plate 22 are preferably 18cm × 10cm × 1mm (length × width × thickness); the size of the electrolytic cell 1 is preferably 30cm × 20cm × 10cm (length × width × height); the size of the processing chamber 4 is preferably 24cm × 20cm × 10cm (length × width × height); the dimensions of the PRB permeable walls 5 are preferably 20cm × 10cm × 4cm (length × width × thickness); the size of the sintered glass 52 is preferably 20cm × 10cm × 3mm (length × width × thickness); the size of the anode chamber 6 is preferably 2cm × 20cm × 10cm (length × width × height); the dimensions of the removable insulation panel 61 are preferably 20cm × 10cm × 1mm (length × width × thickness).
The EKR-PRB coupling device provided by the invention comprises a direct current power supply 3, wherein the direct current power supply 3 is electrically connected with the first electrode plate 21 and the second electrode plate 22.
The specific method for removing heavy metals in leaching waste liquid by using the EKR-PRB coupling device provided by the invention is described in the following with reference to FIGS. 1-2, and comprises the following steps: adding the leaching waste liquid into the anode chamber 6 and the treatment chamber 4, detaching the detachable isolation plate 61 to communicate the anode chamber 6 with the treatment chamber 4, introducing a direct-current power supply to carry out electrolysis, mounting the detachable isolation plate 61 to separate the anode chamber 6 from the treatment chamber 4 after the electrolysis, wherein the liquid in the treatment chamber can be used as biogas liquid fertilizer of crops such as rice, vegetables and the like, and the liquid in the anode chamber can be continuously used by electrolysis.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
(1) Leaching technology for removing heavy metals
Mixing livestock and poultry manure/biogas residue with Na with the concentration of 0.1mol/L2Mixing EDTA aqueous solution according to the solid-liquid ratio of 1:10(kg: L), leaching for 4h at room temperature, and centrifuging at 5000rpm for 8min to obtain solid components and leaching waste liquid, wherein the initial concentration of Cd in the livestock and poultry manure/biogas residue is 3.70mg/kg, the initial concentration of Cu is 27.1mg/kg, and the initial concentration of Zn is 172 mg/kg.
(2) EKR-PRB coupling technology for removing heavy metals
The EKR-PRB coupling device shown in fig. 1-2 is adopted, the leaching waste liquid is added to the anode chamber 6 and the treatment chamber 4 to reach the position 3/4 of the height, the detachable isolation plate 61 is detached to enable the anode chamber 6 and the treatment chamber 4 to be communicated, a direct-current power supply is introduced for electrolysis, after the electrolysis, the detachable isolation plate 61 is installed to enable the anode chamber 6 and the treatment chamber 4 to be separated, the treatment liquid obtained in the treatment chamber 4 can be used as biogas liquid fertilizer of crops such as rice, vegetables and the like, and the anode chamber liquid can be continuously electrolyzed and utilized.
In the EKR-PRB coupling device, the dimensions of the first electrode plate 21 and the second electrode plate 22 are 18cm × 10cm × 1mm (length × width × thickness); the size of the electrolytic cell 1 is 30cm × 20cm × 10cm (length × width × height); the size of the processing chamber 4 is 24cm × 20cm × 10cm (length × width × height); the dimensions of the PRB permeable wall 5 are 20cm × 10cm × 4cm (length × width × thickness), and the dimensions of the sintered glass 52 are 20cm × 10cm × 3mm (length × width × thickness); the anode chamber 6 has a size of 2cm × 20cm × 10cm (length × width × height), and the detachable partition plate 61 has a size of 20cm × 10cm × 1mm (length × width × thickness); the treatment chamber 4 is divided into five areas of S5, S4, S3, S2 and S1 on average for sampling, and after the samples are digested by nitric acid to be clear, the contents of Cd, Cu and Zn are measured by ICP-MS.
EKR-operating parameters of PRB coupling: the adsorption material used was weak acid type ion exchange resin CH-90 (abbreviated as resin CH-90, purchased from Kohaisi technologies, Inc., Kyoto) having iminodiacetic acid functional group at room temperature, DC voltage of 1V/cm and electrolysis time of 60 h.
Examples 2 to 13
The method of example 1 is used to remove heavy metals from livestock and poultry manure/biogas residues, and the conditions for removing step (1) of examples 2-13 are shown in table 1.
Comparative examples 1 to 4
Heavy metals in the livestock and poultry manure/biogas residues are removed by the method of the example 1, and the removing conditions of the step (1) of the comparative examples 1-4 are shown in the table 1.
TABLE 1 conditions for removing heavy metals by leaching technique in step (1) of examples 1 to 13 and comparative examples 1 to 4
The results of removing the heavy metals from the livestock manure/biogas residues in the step (1) of examples 1 to 14 and comparative examples 1 to 4 are shown in table 2 and fig. 3 to 6, wherein fig. 3 is the results of removing the heavy metals Cu and Zn from the livestock manure/biogas residues in the step (1) of examples 1 to 2 and comparative examples 1 to 4, fig. 4 is the results of removing the heavy metals Cd, Cu and Zn from the livestock manure/biogas residues in the step (1) of examples 1 and 3 to 6, fig. 5 is the results of removing the heavy metals Cd, Cu and Zn from the livestock manure/biogas residues in the step (1) of examples 1 and 7 to 12, and fig. 6 is the results of removing the heavy metals Cd, Cu and Zn from the livestock manure/biogas residues in the step (1) of examples 1 and 13 to 14.
TABLE 2 results of heavy metal removal rate of livestock and poultry excrements/biogas residues in step (1) of examples 1 to 14 and comparative examples 1 to 4
As can be seen from FIG. 3 and Table 2, EDTA and Na2The EDTA has obviously better effect on removing heavy metals in the livestock and poultry manure/biogas residues than other types of extractants, wherein Na is2EDTA has better water solubility than EDTA, Na2EDTA is the best leaching agent.
As can be seen from FIG. 4 and Table 2, Na is accompanied by2The removal rate of EDTA on heavy metals in the livestock and poultry manure/biogas residues is obviously increased due to the increase of the concentration of EDTA, wherein the EDTA has a great influence on Cd and Zn. However, due to Na2The pH value of the livestock manure/biogas residue can be reduced when the concentration of EDTA is too high, and when the concentration of EDTA is too high, Na is added2The solid component of the livestock and poultry manure/biogas residue has a pH value of 6.1 when the concentration of EDTA is 0.15mol/L and Na when the concentration is2Increasing the EDTA concentration increases the economic cost and lowers the pH further, which is not favorable for the composting of the solid components obtained after leaching (for example, when only Na is distinguished from the step (1) of example 12When the concentration of EDTA is increased to 0.2mol/L, the pH value of the solid component obtained after leaching treatment is 5.1, and the solid component has strong acidity to influence the use of subsequent compost).
As can be seen from FIG. 5 and Table 2, Na was added as the leaching time increased2The removing effect of EDTA on the heavy metals in the livestock and poultry manure/biogas residues is in a trend of increasing rapidly and then tending to be gentle, wherein a rapid increasing stage is arranged between 0 and 0.5h, and when leaching time is less than or equal to 30min, time cost is consumedLow.
As can be seen from fig. 6 and table 2, there is no significant difference between the three solid-to-liquid ratios, wherein the smaller the solid-to-liquid ratio, the less the leaching waste liquid is produced. Therefore, when the solid-to-liquid ratio is 1:5, the amount of the generated leaching waste liquid is the least, and the energy consumption of subsequent treatment is the least.
Example 15
Response surface method for optimizing leaching treatment technical parameters
With Na2EDTA as extractant, Na2The concentrations of EDTA aqueous solution are respectively 0.01mol/L, 0.02mol/L and 0.03mol/L, and the leaching time is respectively 10min, 20min and 30 min; the solid-liquid ratio is optimized by the combined process parameters of 1:5(kg: L), 1:6(kg: L) and 1:7(kg: L), and the specific parameter design is shown in Table 3.
TABLE 3 design of various technical parameters in response surface method
The parameters in the table 3 are submitted to Design Expert software, the experiment Design method adopts Box-Behnken Design, and the experiment scheme based on the Box-Behnken Design is shown in the table 4.
TABLE 4 Box-Behnken-based experimental design protocol
Setting 3 repeated tests for each experiment number, leaching at 180rpm and room temperature for 10-30 min, centrifuging at 5000rpm for 8min to obtain solid components and leaching waste liquid, measuring the content of heavy metal in the solid components, calculating the heavy metal removal rate (%) (initial solid phase heavy metal content-leached solid phase heavy metal content)/initial solid phase heavy metal content multiplied by 100) of the livestock and poultry manure/biogas residue, and removing the heavy metalThe results of the rate are filled in the result column corresponding to each experiment number for response surface model fitting, and the results are shown in fig. 7. As can be seen from FIG. 7, Na2The concentration of EDTA has great influence on the removal effect of Cd in the livestock and poultry manure/biogas residues, and the leaching time and the solid-liquid ratio have small influence. Increase Na2The EDTA concentration will significantly increase the removal rate of Cd, but will also lower the pH of the livestock manure/biogas residue and increase the economic cost. Taking comprehensive consideration, finally determining Na2The concentration of the EDTA solution was 0.01 mol/L. On the basis, the optimal technical process for responding to the fitting of the curved surface model comprises the following steps: na (Na)2The concentration of EDTA aqueous solution is 0.01mol/L, leaching time is 21min, solid-to-liquid ratio is 1:5, and the removal rate of Cd in the livestock and poultry manure/biogas residue in the step (1) is 46%.
Example 16
(1) Leaching technology for removing heavy metals
Mixing livestock and poultry manure/biogas residue with Na with the concentration of 0.01mol/L2Mixing EDTA solution according to the solid-to-liquid ratio of 1:5(kg: L), leaching for 21min at room temperature, and then centrifugally separating at 4000-5000 rpm for 8-10 min to obtain a solid component and a leaching waste liquid, wherein the initial concentration of Cd in the livestock and poultry manure/biogas residue is 3.70mg/kg, the initial concentration of Cu is 27.1mg/kg, the initial concentration of Zn is 172mg/kg, the removal rate of Cd is 46%, the removal rate of Cu is 34%, and the removal rate of Zn is 45%.
(2) EKR-PRB coupling technology for removing heavy metals
The EKR-PRB coupling device shown in fig. 1-2 is adopted, the leaching waste liquid is added to the anode chamber 6 and the treatment chamber 4 to reach the position 3/4 of the height, the detachable isolation plate 61 is detached to enable the anode chamber 6 and the treatment chamber 4 to be communicated, a direct-current power supply is introduced for electrolysis, after the electrolysis, the detachable isolation plate 61 is installed to enable the anode chamber 6 and the treatment chamber 4 to be separated, the treatment liquid obtained in the treatment chamber 4 can be used as biogas liquid fertilizer, and the anode chamber liquid can be continuously electrolyzed and utilized.
In the EKR-PRB coupling device, the dimensions of the first electrode plate 21 and the second electrode plate 22 are 18cm × 10cm × 1mm (length × width × thickness); the size of the electrolytic cell 1 is 30cm × 20cm × 10cm (length × width × height); the size of the processing chamber 4 is 24cm × 20cm × 10cm (length × width × height); the dimensions of the PRB permeable wall 5 are 20cm × 10cm × 4cm (length × width × thickness), and the dimensions of the sintered glass 52 are 20cm × 10cm × 3mm (length × width × thickness); the anode chamber 6 has a size of 2cm × 20cm × 10cm (length × width × height), and the detachable partition plate 61 has a size of 20cm × 10cm × 1mm (length × width × thickness); the treatment chamber 4 is divided into five areas of S5, S4, S3, S2 and S1 on average for sampling, and after the samples are digested by nitric acid to be clear, the contents of Cd, Cu and Zn are measured by ICP-MS.
EKR-operating parameters of PRB coupling: the adsorption material used was weak acid type ion exchange resin CH-90 (abbreviated as resin CH-90, purchased from Kohaisi technologies, Inc., Kyoto) having iminodiacetic acid functional group at room temperature, DC voltage of 1V/cm and electrolysis time of 60 h.
Examples 17 to 21
The removal of heavy metals from livestock and poultry manure/biogas residues by the method of example 16 was carried out under the EKR-PRB coupling conditions in step (2) of examples 17 to 21 shown in Table 5.
Comparative example 5
The heavy metals in the livestock manure/biogas residue were removed according to the method of example 16, and the EKR-PRB coupling treatment conditions of step (2) of comparative example 5 are shown in Table 5.
TABLE 5 conditions for removal of heavy metals by EKR-PRB coupling technique in examples 16 to 21 and comparative example 5
| Kind of adsorbent | Direct current voltage (V/cm) | Electrolysis time (h) | |
| Example 16 | Resin CH-90 | 0.5 | 24 |
| Example 17 | Resin CH-90 | 1 | 24 |
| Comparative example 5 | Resin CH-90 | 2 | 24 |
| Example 18 | Resin CH-90 | 1 | 12 |
| Example 19 | Resin CH-90 | 1 | 36 |
| Example 20 | Resin CH-90 | 1 | 48 |
| Example 21 | Resin CH-90 | 1 | 60 |
The residual heavy metal concentrations of the leaching waste liquids in the step (2) of examples 16 to 21 and comparative example 5 are shown in Table 6 and FIGS. 8 to 9, wherein FIG. 8 is the residual concentrations of heavy metals Cd, Cu and Zn in the leaching waste liquids in the step (2) of examples 16 to 17 and comparative example 5, and FIG. 9 is the residual concentrations of heavy metals Cd, Cu and Zn in the leaching waste liquids in the step (2) of examples 17 to 21. Lower residual heavy metal concentrations indicate better removal.
TABLE 6 residual heavy Metal concentration of leach liquors in examples 16 to 21 and step (2) of comparative example 5
| Cd(mg/L) | Cu(mg/L) | Zn(mg/L) | |
| Example 16 | 0.32 | 1.47 | 13.8 |
| Example 17 | 0.24 | 1.35 | 5.85 |
| Comparative example 5 | 0.04 | 0.74 | 4.14 |
| Example 18 | 0.28 | 1.58 | 9.11 |
| Example 19 | 0.09 | 1.31 | 4.77 |
| Example 20 | 0.04 | 1.28 | 4.36 |
| Example 21 | 0.003 | 1.13 | 4.22 |
As can be seen from fig. 8 and table 6, the concentration of heavy metals in the leach liquor decreased significantly as the voltage increased. However, in the experimental process, the current of the leaching waste liquid is too large under the treatment of 2V/cm voltage, the temperature is increased rapidly, the liquid evaporation is serious, and meanwhile, the corrosion of the electrode plate is also serious.
As can be seen from FIG. 9 and Table 6, under the action of direct current voltage electrolysis of 1V/cm, the concentration of heavy metals in the leaching waste liquid in the treatment chamber is reduced along with the increase of the electrolysis time, and after 60 hours of electrolysis, the removal rates of Cd, Cu and Zn in the leaching waste liquid are respectively 99%, 40% and 72%, wherein Cd is less than or equal to 0.01mg/L, and the biogas liquid fertilizer can meet the agricultural requirements of crops such as rice, vegetables and the like.
Example 22
Weak acid type ion exchange resin CH-90 (abbreviated as resin CH-90, purchased from Kahaisi, Beijing) science and technology Co., Ltd.) containing iminodiacetic acid functional group was added to the leaching waste liquid obtained in the step (1) of example 16 in a treatment volume ratio of 1% (g/mL), treated at 180rpm for 24 hours at room temperature, centrifuged at 2000rpm for 10 minutes, the resulting supernatant was digested with nitric acid to be clarified, and then the contents of Cd, Cu and Zn were measured by ICP-MS.
Example 23
Heavy metal ions were removed according to the method of example 22, which is different from example 22 in that the adsorbing material was a strongly acidic cation exchange resin CH-93 containing an aminophosphonic acid functional group (abbreviated as resin CH-93, purchased from Kahaisi, Beijing) science and technology Co., Ltd.).
Example 24
Heavy metal ions were removed according to the method of example 22, which is different from example 22 in that the adsorbing material was a Katalox Light filter (abbreviated as KL filter, purchased from kohaisi (beijing) science and technology ltd) with a manganese dioxide coating on the surface.
Example 25
The method of example 22 was followed to remove heavy metal ions, except that the adsorbent material was biomass charcoal.
The biomass charcoal is obtained by crushing peanut shells, sieving the crushed peanut shells by a 2mm sieve, and thermally cracking the sieved peanut shell powder at 500 ℃ in an oxygen-isolated manner for 4 hours.
Example 26
Heavy metal ions were removed according to the method of example 22, which is different from example 22 in that the adsorbing material was natural rectorite (produced in Jingmen city, Hubei province, and sieved through a 0.15mm sieve after pulverization, and the sieved part was taken out).
Example 27
Heavy metal ions were removed according to the method of example 22, which is different from example 22 in that the adsorption material was natural zeolite (purchased from Hexagon Hexatropic mineral products Co., Ltd., particle size <1 mm).
The removal effect of heavy metals in the leach liquors of examples 22 to 27 is shown in FIG. 10 and Table 7.
Table 7 results of heavy metal removal rates of leach liquors in examples 22 to 27
| Cd removal rate (%) | Cu removal rate (%) | Zn removal rate (%) | |
| Example 22 | 76.0 | 36.6 | 68.7 |
| Example 23 | 61.3 | 29.7 | 49.7 |
| Example 24 | 63.7 | 23.4 | 56.2 |
| Example 25 | 67.6 | 27.6 | 56.8 |
| Example 26 | 58.6 | 26.8 | 50.7 |
| Example 27 | 60.6 | 22.5 | 46.7 |
As can be seen from Table 7 and FIG. 10, under the same heavy metal removal conditions, the weak acid type ion exchange resin CH-90 with iminodiacetic acid functional group has better removal effect on Cd, Cu and Zn in leaching waste liquid than other 5 kinds of adsorbing materials, and the removal rate of the material on three kinds of heavy metals is Cd, Zn and Cu from high to low.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A method for removing heavy metals in livestock and poultry manure/biogas residues is characterized by comprising the following steps:
mixing the livestock and poultry manure/biogas residue with an extractant solution, carrying out leaching treatment, and carrying out solid-liquid separation to obtain a solid component and a leaching waste liquid; the lixiviant in the lixiviant solution comprises ethylene diamine tetraacetic acid and/or disodium ethylene diamine tetraacetate;
and carrying out EKR-PRB coupling treatment on the leaching waste liquid to obtain a treatment liquid.
2. The removal method of claim 1, wherein the heavy metal comprises one or more of Cd, Cu and Zn.
3. The removal method according to claim 1 or 2, wherein the concentration of the lixiviant solution is 0.01 to 0.15 mol/L;
the solid-liquid ratio of the livestock and poultry manure/biogas residues to the leaching agent solution is 1kg: 5-10L.
4. The removing method according to claim 1 or 2, wherein the leaching treatment is carried out at a temperature of 15 to 35 ℃ for 10min to 24 hours.
5. The removal method according to claim 1 or 2, wherein the EKR-PRB coupling treatment adopts an adsorption material comprising one or more of a weak acid type ion exchange resin CH-90 having an iminodiacetic acid functional group, a strong acid cation exchange resin CH-93 having an amino methanephosphonic acid functional group, a KataloxLight filter material having a manganese dioxide coating on the surface thereof, biomass charcoal, natural rectorite and natural zeolite.
6. The removal method according to claim 1 or 2, wherein the operating parameters of the EKR-PRB coupling process comprise: the direct current voltage is 0.5-1V/cm, and the electrolysis time is 40-60 h.
7. An EKR-PRB coupling device used in the removing method according to any one of claims 1 to 6, comprising an electrolytic cell (1), a first electrode plate (21) and a second electrode plate (22) respectively arranged at two ends of the electrolytic cell (1), and a DC power supply (3) connected with the first electrode plate (21) and the second electrode plate (22);
a treatment chamber (4), a PRB permeable wall (5) and an anode chamber (6) are arranged in the electrolytic cell (1); the PRB permeable wall (5) is filled with an adsorption material (51);
and a detachable isolation plate (61) is arranged in the anode chamber (6).
8. The device according to claim 7, characterized in that the adsorbing material (51) is provided with sintered glass (52) on both sides.
9. The device according to claim 7, wherein the material of the first electrode plate (21) and the second electrode plate (22) comprises titanium alloy, graphite or stainless steel.
10. The device according to claim 7, characterized in that the material of the removable insulation plate (61) comprises steel, polytetrafluoroethylene or polyvinyl chloride.
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