Coupling impurity removal method for high-concentration industrial waste salt solution

Abstract

The invention discloses a coupling impurity removal method for a high-concentration industrial waste salt solution. The method comprises the following steps: 1) dissolving industrial waste salt subjected to pyrolysis treatment in water to form a saturated solution, and precipitating or filtering to obtain a pretreated industrial waste salt solution; 2) mixing the pretreated industrial waste salt solution with an anionic or cationic surfactant, and stirring to obtain a solution containing emulsion particles; (3) adding a flocculating agent of which the charge is opposite to that of the anionic or cationic surfactant into the solution containing the emulsion particles, performing flocculation to form flocs, and removing the flocs to obtain flocculation process effluent; 4, a coagulation agent is added into the flocculation process effluent, stirring is carried out for coagulation, coagulation flocs are removed, and small-particle impurity removal is achieved.According to the method, demulsification and coagulation are not needed in sequence, the problem that the efficiency of removing particle impurities in a high-concentration salt solution through traditional flocculation / coagulation is low is solved, and the method is used for deep recycling and reusing of industrial pyrolysis waste salt.

Description

Technical Field

[0001] This invention belongs to the field of industrial hazardous waste resource utilization technology, and relates to a coupled impurity removal method for high-concentration industrial waste salt solutions. Background Technology

[0002] Industrial waste salt mainly comes from industries such as chemical, pharmaceutical, dye, and metallurgy. Its composition is complex, with sodium chloride and / or sodium sulfate as the main components, and it also contains a large amount of recalcitrant organic matter. Based on the organic matter content, it can be divided into high-organic-matter waste salt (such as pesticide waste salt) and low-organic-matter waste salt (such as chlor-alkali industrial salt mud), with significantly different treatment difficulties.

[0003] Currently, the main method for treating industrial waste salt is pyrolysis. After pyrolysis at 500-1000℃, the waste salt is landfilled as solid waste. Even after pyrolysis, the waste salt still contains 1-30% particulate carbon, oily substances, and colloids. Existing treatment processes primarily involve filtering the saturated solution of the pyrolyzed waste salt to remove impurities, followed by crystallization to obtain the industrial salt product. However, filtration suffers from severe clogging of the filter cloth / membrane, and residual oily substances reduce the hydrophilicity of the filter cloth / membrane, leading to high operating costs and a high failure rate.

[0004] Therefore, there is an urgent need for a method to deeply process industrial waste salt after pyrolysis in order to solve the above problems and reduce the production cost of industrial salt. Summary of the Invention

[0005] The purpose of this invention is to provide a coupled impurity removal method for high-concentration industrial waste salt solutions.

[0006] The present invention provides a coupled impurity removal method for high-concentration industrial waste salt solution, comprising the following steps: 1) dissolving the pyrolysis treated industrial waste salt in water to form a saturated solution, precipitating or filtering to obtain a pretreated industrial waste salt solution; 2) The pretreated industrial waste salt solution is mixed with anionic or cationic surfactant and stirred to obtain a solution containing emulsion particles; 3) Add a flocculant with the opposite charge to the anionic or cationic surfactant to the solution containing emulsion particles, and carry out flocculation. The flocculant neutralizes the surface of the surfactant and the surface of the particles, and also bridges the emulsion and particles to form flocs. The flocs are removed by precipitation or filtration, thus completing the removal of emulsion particles and large particulate impurities and obtaining effluent from the flocculation process. 4) Add coagulant to the effluent from the flocculation process, stir to coagulate, and remove the coagulated flocs by sedimentation or filtration to complete the removal of small particulate impurities.

[0007] The above method also includes: step 5) using activated carbon adsorption to remove residual organic matter from the system after step 4).

[0008] The above method also includes: step 6) removing impurity ions from the system after step 5) using an ion exchange resin.

[0009] In the above method, the industrial waste salt after pyrolysis contains 0-30% particulate carbon and 0-1% oil, which are free oil and the remainder are adsorbed oil.

[0010] In the above method, in step 1), the temperature of the saturated solution is controlled at 10~60 ℃ to promote the dissolution of salts and to initially precipitate and remove large particles and high-density insoluble matter. The pH of the pretreated industrial waste salt solution is adjusted to 5-9; Step 1) also includes adding calcium chloride to remove carbonic acid, silicate or fluoride ions based on water quality analysis results, or introducing CO2 under alkaline conditions to remove calcium / magnesium ions.

[0011] In the above method, step 1) further includes using an oil remover to pretreat the pretreated industrial waste salt solution when the pretreated industrial waste salt solution contains oily substances and the content is >500 mg / L, thereby removing most of the oily substances. These oily substances are mainly tar, phenols and other substances.

[0012] In the above method, in step 2), the anionic or cationic surfactant is selected from at least one of alkyl sodium sulfate surfactants, alkylbenzene sulfonate surfactants, polystyrene sulfonate surfactants, fatty alcohol polyoxyethylene ether sodium sulfate surfactants, polyoxyethylene ether sodium phosphate surfactants, alkyl acrylamide salt surfactants, and quaternary ammonium salt surfactants; the above compounds have different carbon chain lengths, specifically dodecyl or hexadecyl. The amount of the anionic or cationic surfactant added can be 5~500 mg / L of the pretreated industrial waste salt solution.

[0013] In the above method, in step 2), the temperature of the gradient stirring can be 0~60 ℃. First, the stirring speed can be 2000~100 rpm for 1~10 min to allow the surfactant and oil to combine and form a stable emulsion. Then, the stirring speed is 100~5 rpm, the number of stirring gradients can be set to 2~5, and the stirring time is 1~120 min. The gradient stirring breaks down and eliminates the oil-water interface film formed by the oil, so that the oil forms emulsion droplets or "emulsion-particulate" composite structures with a diameter of 0.1~100 μm.

[0014] In the above method, in step 3), the amount of flocculant added is 1~300 mg / L of the solution containing emulsion particles; The flocculant is selected from at least one of anionic polyacrylamide, cationic polyacrylamide, polydimethyldiallylammonium chloride, modified starch, xanthan gum, sodium carboxymethyl cellulose and chitosan; The flocculant has a molecular weight of 80,000 to 10,000,000 Da.

[0015] Step 3) further includes adding a coagulant aid based on the specific components of the effluent from the flocculation process; the coagulant aid can be selected from at least one of micro sand, bentonite, chalk, kaolin, sodium alginate, modified lignin, humic acid, phytic acid, chitosan, powdered activated carbon, powdered iron oxide, powdered alumina, and powdered calcium carbonate; the amount of coagulant aid added is 0.01% to 20% of the flocculant.

[0016] In the above method, in step 3), the reaction temperature of the charge neutralization flocculation is 0~60 ℃; through charge neutralization and bridging, emulsion particles and remaining large particulate impurities are captured and flocs are formed, thereby removing oily emulsion droplets, residual surfactants and large particulate carbon. The stirring is set as gradient stirring, with a speed of 2000~5 rpm, the number of stirring gradients is set to 2-5, and the settling time is 5~90 ​​min; specifically, it can be the following two methods: (1) 100~2000 rpm, 1 min; 5~50 rpm, 10~60 min; (2) 100~800 rpm, 1 min; 5~50 rpm, 10~60; 100~500 rpm, 1~5 min; 5~50 rpm, 10~60 min.

[0017] In the above method, in step 4), the coagulant is selected from at least one of polyaluminum ferric chloride, polyaluminum chloride, polyaluminum sulfate, polyferric chloride, polyferric sulfate zirconium chloride, and zirconium oxychloride; for the remaining small particulate impurities and colloidal particles, flocs are formed by net trapping, sweeping, and charge neutralization to remove them; The amount of coagulant added can be 10~800 mg / L of the effluent from the flocculation process.

[0018] In the above method, based on the specific components of the industrial waste salt solution, step 4) further includes adding a coagulation aid. The coagulation aid is selected from 0 to 5 of the following: micro sand, bentonite, chalk, kaolin, sodium alginate, modified lignin, humic acid, phytic acid, chitosan, powdered activated carbon, powdered iron oxide, powdered alumina, powdered calcium carbonate, ferrate, ozone, chlorine, sodium hypochlorite, perchloric acid, hydrogen peroxide, sodium persulfate, and sodium perdisulfate. The amount of coagulation aid added is 0.01% to 20% of the flocculant.

[0019] In the above method, in step 4), the reaction temperature for coagulation can be 0~60 degrees Celsius; The stirring speed can be 2000~5 rpm, the number of stirring gradients can be set to 2~5, and the sedimentation time is 5~90 ​​min. Specifically, the stirring can be carried out first at a speed of 20000~100 rpm for 1~10 min to allow the flocculant to fully dissolve and disperse; then at 100~5 rpm for 5~60 min to allow the floc particles to collide and grow, forming large floc particles, which is beneficial for sedimentation or filtration separation. However, the speed must be controlled to prevent large particles from being broken. The number of gradients can be increased, following the above principles. After stirring stops, sedimentation usually occurs. A high-density sedimentation tank can be used to accelerate sedimentation and continuous production. Filtration is rarely used, but there are cases where it is applicable.

[0020] In the above method, steps 3) and 4) include at least one of sedimentation, inclined tube settling, and filtration for removing flocs.

[0021] The present invention has the following beneficial effects: 1. The surfactant forms an emulsion or "emulsion-particulate" composite structure with the oil film, eliminating the need for demulsification before coagulation; 2. The pretreated industrial waste salt solution is prepared by adding surfactants and stirring to break down and eliminate the oil-water interface film formed by the oily substances, so that the oily substances form emulsion droplets or "emulsion-particulate" composite structures with a diameter of 0.1~100μm. 3. PAM effectively removes the above-mentioned substances by reacting with the solution containing emulsion particles and free surfactants through charge neutralization reaction and bridging with large particulate impurities to form flocs.

[0022] 4. This invention solves the problem of low efficiency in removing particulate impurities in high-concentration salt solutions using traditional flocculation / coagulation, and can be used for the deep recycling and reuse of industrial pyrolysis waste salt. Attached Figure Description

[0023] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0025] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0026] In this invention, the technical parameters of the industrial waste salt after pyrolysis treatment are shown in the table below:

[0027] The present invention provides a coupled impurity removal method for high-concentration industrial waste salt solutions, comprising the following steps: 1) dissolving the pyrolyzed industrial waste salt in water to form a saturated solution, precipitating or filtering to obtain a pretreated industrial waste salt solution; for example, when the free oil content is greater than 250, an oil separator is used for pretreatment; 2) The pretreated industrial waste salt solution is mixed with anionic or cationic surfactant and stirred to obtain a solution containing emulsion particles; 3) Add a flocculant with the opposite charge to the anionic or cationic surfactant to the solution containing emulsion particles, and carry out flocculation. The flocculant neutralizes the surface of the surfactant and the surface of the particles, and also bridges the emulsion and particles to form flocs. The flocs are removed by precipitation or filtration, thus completing the removal of emulsion particles and large particulate impurities and obtaining effluent from the flocculation process. 4) Add coagulant to the effluent from the flocculation process, stir to coagulate, and remove the coagulated flocs by sedimentation or filtration to complete the removal of small particulate impurities. 5) The system treated in step 4) is then subjected to activated carbon adsorption to remove residual organic matter; 6) The system after step 5) is treated with ion exchange resin to remove impurity ions.

[0028] Example 1 (Coal Chemical Waste Salt) Raw material: pyrolyzed sodium chloride (containing 8.2% tar-like substances, of which 0.43% are free oily substances and 12% are carbon particles, i.e., the free oily substances are 107.5 mg / L and the total oil content is 2173 mg / L).

[0029] Dissolution: Prepare a solution with a total solids concentration of 265 g / L (30℃).

[0030] deal with: 1) Adjust the pH to 7.5; 2) Add sodium dodecylbenzenesulfonate solution to bring the final concentration of the system to 125 mg / L, and stir (600 rpm × 1 min). 3) Add 100 mg / L (120 kDa) of cationic PAM and stir in stages (200 rpm × 1 min → 50 rpm × 15 min) to form 2.3 mm flocs (Zeta potential +12 mV). 4) Remove flocs by precipitation, add fresh polyaluminum ferric chloride solution to the supernatant to make the final concentration of the system 500 mg / L, stir in stages (100 rpm × 1 min → 50 rpm × 10 min), after stirring stops, use inclined tube sedimentation for 30 min, and then filter using microfiltration membrane. 5) Results: The effluent turbidity was 4.1 NTU, and the crystallization salt whiteness was 92.7%.

[0031] Example 2 (Fermentation Industrial Waste Salt) Raw material: Sodium sulfate after pyrolysis (containing 5.1% tar-like substances, of which 1% are free oily substances and 24% are carbon particles).

[0032] Dissolve: Prepare a TDS 230 g / L solution (40℃).

[0033] deal with: 1) Adjust the pH to 7.8; 2) Add sodium dodecyl sulfate solution to make the final concentration of the system 50 mg / L, and stir (400 rpm × 2 min); 3) Add 300 mg / L (160 kDa) of cationic PAM, stir in stages (300 rpm × 1 min → 50 rpm × 10 min) to form 3.6 mm flocs (Zeta potential +9 mV), allow to settle naturally for 5~10 min, and take the supernatant. 4) Mix 750 mg / L of polyaluminum ferric chloride with 150 mg / L of polyaluminum chloride, stir in stages (200 rpm×1min→50 rpm×15min), and let it settle naturally for 60 min; 5) Results: The effluent turbidity was 22.3 NTU, and the crystallization salt whiteness was 91.5%.

[0034] Example 3 (Alkaline industrial waste salt) Raw materials: pyrolyzed sodium chloride salt + sodium sulfate (containing 8.6% tar-like substances, of which 3.8% are free, 18% are carbon particles, and 10% are other insoluble substances).

[0035] Dissolve: Prepare a 230 g / L solution (40℃).

[0036] deal with: (1) Introduce CO2, stir, allow to settle, and discard the precipitate; (2) Use an oil separator to remove oily substances, so that the free oily substances in the effluent are <0.5%. (3) Adjust the pH to 7.2 using hydrochloric acid / sulfuric acid; (4) Add 150 mg / L cetyltrimethylammonium bromide (pH=7.0) and stir in a stepwise manner (500 rpm×2 min); (5) Add 500 mg / L (110 kDa) of anionic PAM and stir in stages (400 rpm × 1 min → 20 rpm × 20 min) to form 3.6 mm flocs (Zeta potential -8 mV). (6) Polyaluminum ferric chloride 750 mg / L + ferric chloride 50 mg / L + sodium ferrate 50 mg / L were mixed and stirred in stages (200 rpm×1 min→50 rpm×20 min). After natural sedimentation for 10 min, the mixture was filtered using a 1-micron filter cloth. (7) Activated carbon (iodine value 1100, filling amount 10 g / L, residence time 60 min) was subsequently used to further remove residual organic matter through adsorption.

[0037] Results: Effluent turbidity 18.5 NTU, crystallization salt whiteness 93.8%, TOC=30.2 mg / L.

Claims

1. A coupled method for removing impurities from a high-concentration industrial waste salt solution, comprising the following steps: 1) dissolving the pyrolyzed industrial waste salt in water to form a saturated solution, precipitating or filtering to obtain a pretreated industrial waste salt solution; 2) The pretreated industrial waste salt solution is mixed with anionic or cationic surfactant and stirred to obtain a solution containing emulsion particles; 3) Add a flocculant with the opposite charge to the anionic or cationic surfactant to the solution containing emulsion particles, and carry out flocculation. The flocculant neutralizes the surface of the surfactant and the surface of the particles, and also bridges the emulsion and particles to form flocs. The flocs are removed by precipitation or filtration, thus completing the removal of emulsion particles and large particulate impurities and obtaining effluent from the flocculation process. 4) Add coagulant to the effluent from the flocculation process, stir to coagulate, and remove the coagulated flocs by sedimentation or filtration to complete the removal of small particulate impurities.

2. The method according to claim 1, characterized in that, The method further includes: step 5) using activated carbon adsorption to remove residual organic matter from the system after step 4).

3. The method according to claim 2, characterized in that, The method further includes: step 6) removing impurity ions from the system after step 5) using an ion exchange resin.

4. The method according to any one of claims 1-3, characterized in that, The industrial waste salt after pyrolysis treatment contains 0-30% particulate carbon and 0-1% oil. In step 1), the temperature of the saturated solution is controlled at 10~60 ℃; The pH of the pretreated saturated industrial waste salt solution is adjusted to 5-9; Step 1) also includes adding calcium chloride to remove carbonate, silicate or fluoride ions based on water quality analysis results, or introducing CO2 under alkaline conditions to remove calcium / magnesium ions. And / or, step 1) further includes pretreatment with an oil remover when the pretreated industrial waste salt solution contains oily substances and the content is >250 mg / L.

5. The method according to any one of claims 1-4, characterized in that, In step 2), the anionic or cationic surfactant is selected from at least one of alkyl sodium sulfate surfactants, alkylbenzene sulfonate surfactants, polystyrene sulfonate surfactants, fatty alcohol polyoxyethylene ether sodium sulfate surfactants, polyoxyethylene ether sodium phosphate surfactants, alkyl acrylamide salt surfactants, and quaternary ammonium salt surfactants. The amount of the anionic or cationic surfactant added is 5~500 mg / L of the pretreated industrial waste salt solution; In step 2), the temperature of the gradient stirring is 0~60 ℃, and the stirring is first carried out at a speed of 2000~100 rpm for 1~10 min, and then at a speed of 100~5 rpm. The number of stirring gradients is set to 2~5, and the stirring time is 1~120 min.

6. The method according to any one of claims 1-5, characterized in that, In step 3), the amount of flocculant added is 1~300 mg / L of the solution containing emulsion particles; The flocculant is selected from at least one of anionic polyacrylamide, cationic polyacrylamide, polydimethyldiallylammonium chloride, modified starch, xanthan gum, sodium carboxymethyl cellulose and chitosan; The molecular weight of the flocculant is 80,000 to 10,000,000 Da; Step 3) further includes adding a coagulation aid based on the composition of the effluent from the flocculation process; the coagulation aid is selected from at least one of micro sand, bentonite, chalk, kaolin, sodium alginate, modified lignin, humic acid, phytic acid, chitosan, powdered activated carbon, powdered iron oxide, powdered alumina, and powdered calcium carbonate; the amount of the coagulation aid added is 0.01% to 20% of the flocculant.

7. The method according to any one of claims 1-6, characterized in that, In step 3), the reaction temperature for the charge neutralization flocculation is 0~60 ℃, and the pH of the system is 5~9; The stirring is set to gradient stirring, the stirring speed can be 2000~5 rpm, the number of stirring gradients can be set to 2~5, and the sedimentation time is 5~90 ​​min.

8. The method according to any one of claims 1-7, characterized in that, In step 4), the coagulant is selected from at least one of polyaluminum ferric chloride, polyaluminum chloride, polyaluminum sulfate, polyferric chloride, polyferric sulfate zirconium chloride, and zirconium oxychloride; The amount of coagulant added is 10~800 mg / L of the effluent from the flocculation process; Step 4) further includes adding a coagulation aid, which is selected from 0 to 5 of the following: micro sand, bentonite, chalk, kaolin, sodium alginate, modified lignin, humic acid, phytic acid, chitosan, powdered activated carbon, powdered iron oxide, powdered alumina, powdered calcium carbonate, ferrate, ozone, chlorine, sodium hypochlorite, perchloric acid, hydrogen peroxide, sodium persulfate, and sodium perdisulfate. The amount of coagulation aid added is 0.01% to 20% of the flocculant.

9. The method according to any one of claims 1-8, characterized in that, In step 4), the reaction temperature for coagulation is 0~60 ℃; The stirring speed is 2000~5 rpm, the number of stirring gradients is set to 2~5, and the settling time is 5~90 ​​min.

10. The method according to any one of claims 1-9, characterized in that, In steps 3) and 4), the method for removing flocs includes at least one of sedimentation, inclined tube settling, and filtration.

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