A method for treating isooctyl thioglycolate wastewater

Abstract

The present invention provides a method for treating isooctyl thioglycolate wastewater, wherein the isooctyl thioglycolate wastewater is passed through a fixed bed adsorption column equipped with an adsorbent material, and the effluent is collected; wherein the adsorbent material is a polystyrene-divinylbenzene resin modified with a carboxylic acid functional group. The present invention selects styrene-divinylbenzene modified with a carboxylic acid functional group, and the polarity of the resin is suitable for adsorbing isooctyl thioglycolate, which can effectively increase the adsorption capacity of the resin, so that the isooctyl thioglycolate in water can be effectively adsorbed, thereby improving adsorption efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of PVC additive fine chemical industry, and particularly relates to a method for treating isooctyl thioglycolate wastewater. Background Art

[0002] Isooctyl thioglycolate, also known as isooctyl thioglycolate or 2-hexylhexyl thioglycolate, has a chemical formula of HSCH2COOCH2CH(C2H5)(CH2)3CH3, a molecular weight of 204, a flash point of 118°C, and a density d420 of 0.9730-0.9737. It is a colorless, transparent liquid. Isooctyl thioglycolate is a primary raw material for the preparation of polyvinyl chloride (PVC) heat stabilizers (tin mercaptides and antimony mercaptides). It can also be used as a branching inhibitor during PVC resin polymerization and as a catalyst for the synthesis of bisphenol A. With the rapid increase in PVC production, the use of heat stabilizers (tin mercaptides and antimony mercaptides) has also increased. Therefore, isooctyl thioglycolate, as a primary raw material for PVC heat stabilizers, is in great demand in the market.

[0003] With the rapid development of PVC industry, pesticide, pharmaceutical and related industries, the market prospect of 2-ethylhexyl thioglycolate is very good.

[0004] Currently, the biggest problem facing domestic companies producing isooctyl thioglycolate is the treatment of production wastewater. The wastewater produced by isooctyl thioglycolate is characterized by high salt content, high COD, and a strong pungent odor. General oxidation, extraction, and evaporation treatment methods all have process incompleteness. High salt content in the wastewater affects the efficiency and service life of the oxidation catalyst, high COD affects the evaporation efficiency and the quality of the crystalline salt, and extraction will bring about secondary pollution (the loss of extractant and solvent will result in secondary contaminated water). On the other hand, the pungent odor of the wastewater produced by isooctyl thioglycolate is particularly strong, and the air pollution problem is particularly prominent, which has become a key problem that plagues the long-term survival and development of enterprises. Summary of the Invention

[0005] The present invention aims at the deficiencies in the above-mentioned prior art and provides a method for treating isooctyl thioglycolate wastewater, which can effectively treat isooctyl thioglycolate wastewater and make up for the deficiencies of the previous treatment methods.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for treating isooctyl thioglycolate wastewater comprises passing the isooctyl thioglycolate wastewater through a fixed bed adsorption column filled with an adsorption material, and collecting the effluent; wherein the adsorption material is a polystyrene-divinylbenzene resin modified with a carboxylic acid functional group.

[0008] Preferably, the flow rate of the isooctyl thioglycolate wastewater through the column is 1 to 1.5 BV / h, where BV is the volume of the adsorption material in the fixed bed adsorption column.

[0009] Preferably, the technical indicators of the adsorption material are shown in the following table:

[0010]

[0011] Preferably, the method specifically includes the following steps:

[0012] S1, passing the isooctyl thioglycolate wastewater through a fixed bed adsorption column filled with adsorption material, and collecting the effluent;

[0013] S2, the effluent was evaporated to collect salt;

[0014] S3, regenerating the fixed bed adsorption column filled with adsorption material.

[0015] Furthermore, S3 specifically includes:

[0016] S3.1, using water to replace the residual isooctyl thioglycolate wastewater in the fixed bed adsorption column;

[0017] S3.2, after water replacement, the residual water and wastewater mixture in the fixed bed adsorption column is drained with compressed nitrogen;

[0018] S3.3, after the mixed liquid is drained, the fixed bed adsorption column containing the adsorption material is regenerated.

[0019] Furthermore, in S3.1, the effluent obtained by water replacement is returned to S1.

[0020] Furthermore, S3.3 specifically includes:

[0021] S3.31, desorbing the fixed bed adsorption column using an organic solvent;

[0022] S3.32, after desorption is complete, use compressed nitrogen to drain the remaining organic solvent in the fixed bed adsorption column;

[0023] S3.33, after the residual organic solvent is drained, the fixed bed adsorption column is rinsed with water.

[0024] Furthermore, in S3.31, the organic solvent is isopropanol.

[0025] Furthermore, in S3.31, the amount of organic solvent used is 1-2 BV; the desorption flow rate is 0.5-0.75 BV / h, and BV is the volume of the adsorption material in the fixed bed adsorption column.

[0026] Furthermore, in S3.31, the desorption liquid obtained by desorption is distilled to recover the organic solvent.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention combines the physical properties of isooctyl thioglycolate and the polarity of the ester group. Since the polarity of the non-polar functional group of simple styrene-divinylbenzene is limited to the lipid group adsorption capacity, styrene-divinylbenzene modified with a weakly polar functional group is selected as the adsorption material. Due to the similar polarity, the styrene-divinylbenzene can effectively combine with the isooctyl thioglycolate, thereby increasing the adsorption capacity of the resin. In this way, the isooctyl thioglycolate in water can be effectively adsorbed, and the adsorption efficiency is improved. The high salt content in the wastewater basically has no effect on adsorption, and the high salt content also helps to promote adsorption, because when the salt content is high, the solubility of organic matter in water will decrease, the polarity will be weaker, which is conducive to the adsorption of resin, and effectively solves the problems of high salt, high COD and strong irritating odor in isooctyl thioglycolate wastewater. The treated water is colorless and odorless, and the COD meets the requirements for entering the evaporator, so as to maximize the utilization efficiency of the evaporator and avoid the problem of fouling caused by organic matter. The quality of the evaporated crystalline salt can be effectively guaranteed, which is far superior to the existing wastewater treatment methods on the market. This treatment method is easy to operate, convenient to maintain, safe and reliable to operate, does not require the addition of any chemical agents, has a short treatment time, significant adsorption effect, uses less and simple equipment, and has good treatment effect. It can bring considerable economic benefits to the plant while greatly reducing the environmental pressure of the plant.

[0029] Furthermore, it can be found from the experimental data that the column flow rate has a great influence on the treatment effect of isooctyl thioglycolate wastewater. When the column flow rate is 1 to 1.5 BV / h, the treatment effect of isooctyl thioglycolate wastewater is better.

[0030] Furthermore, water replacement and nitrogen purge can greatly reduce the amount of wastewater produced.

[0031] Furthermore, the effluent after replacing the isooctyl thioglycolate wastewater with water can be returned to the raw water tank for continued adsorption, thereby reducing material loss and avoiding the generation of secondary wastewater.

[0032] Furthermore, isopropyl alcohol is used as the organic solvent because it is used as the raw material in the on-site synthesis process. Therefore, isopropyl alcohol is selected to avoid introducing new solvents that may cause new environmental problems in the subsequent water quality and desorption liquid disposal, and is safer.

[0033] Furthermore, the study found that reducing the desorption flow rate can improve the desorption effect and reduce the amount of organic solvent used, with the lowest overall cost and the best desorption effect.

[0034] Furthermore, the obtained desorption liquid is distilled to recover the organic solvent, which can achieve the reuse of the organic solvent and reduce costs. DETAILED DESCRIPTION

[0035] In order to further understand the present invention, the present invention is described below in conjunction with embodiments. These descriptions are only for further explaining the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0036] The present invention aims to provide a method for treating isooctyl thioglycolate wastewater, which replaces the existing traditional water treatment process in the market, improves the incompleteness of the existing process treatment, treats the wastewater without introducing secondary pollution, has a high degree of automation, improves the production efficiency of the enterprise, reduces the production cost of the enterprise, and alleviates the environmental protection pressure of the factory.

[0037] The method for treating isooctyl thioglycolate wastewater of the present invention comprises the following steps:

[0038] Step 1. The wastewater after oil-water separation of isooctyl thioglycolate production water is passed through a fixed bed adsorption column equipped with adsorption material at a flow rate of 1 to 1.5 BV / h (BV is the volume of adsorption material in the fixed bed, i.e., bed volume or column volume). The adsorption material specifically adsorbs organic matter in the wastewater. The high salt content in the wastewater has little effect on adsorption, and the high salt content also helps to promote adsorption, obtaining qualified brine to the back-end evaporation system. The adsorption material is a polystyrene-divinylbenzene resin modified with carboxylic acid functional groups. The modification of carboxylic acid functional groups can increase hydrogen bond adsorption, which is beneficial to improving the adsorption removal rate and adsorption capacity.

[0039] When the flow rate through the column is controlled at 1-1.5 BV / h, 1 BV of adsorption material can treat 30 BV of isooctyl thioglycolate wastewater, and the TOC content of the column liquid meets the plant's technical requirements. When the flow rate through the column is controlled at 1.5 BV / h, 1 BV can treat 25 BV of isooctyl thioglycolate wastewater. Therefore, the experimental data shows that the flow rate through the column has a significant impact on the treatment effect of isooctyl thioglycolate wastewater. The fixed-bed adsorption column can treat 25-30 BV of isooctyl thioglycolate production wastewater.

[0040] Step 2. Use tap water to displace the isooctyl thioglycolate wastewater from the adsorption material that has absorbed organic matter. Remove the isooctyl thioglycolate wastewater from the pores of the adsorption material. Collect the wastewater displaced by tap water and return it to the raw water tank for continued adsorption, preventing secondary water contamination. The electrical conductivity of the tap water used is ≤50 microsiemens / cm.

[0041] Step 3. Drain the residual isooctyl thioglycolate wastewater in the fixed bed adsorption column of step 2 using 0.2 MPa compressed nitrogen;

[0042] Step 4. Desorb and regenerate the adsorbent material in the fixed bed adsorption column with 1-2 BV of organic solvent at a desorption flow rate of 0.5-0.75 BV / h. Collect the desorption liquid and recover the organic solvent through distillation. The still residue after distillation is solidified and then outsourced for treatment.

[0043] The inventors found in experiments that reducing the desorption flow rate can improve the desorption effect and reduce the amount of isopropyl alcohol solvent used. The preferred desorption flow rate is 1 BV / h, which minimizes the overall cost and achieves the best desorption effect.

[0044] In application, the choice of organic solvent can be based on what is available in the factory and is not limited to one or more of isopropyl alcohol.

[0045] Step 5. The organic solvent remaining in the adsorption material after desorption in step 4 is drained using 0.2 MPa compressed nitrogen, and the discharged desorption liquid is collected and returned to the distillation to recover the solvent.

[0046] Step 6. The adsorption material is rinsed with tap water at a temperature of 30 to 40°C to remove the residual organic solvent in the pores of the adsorption material. The organic solvent content is washed with water until it is less than 0.1%. The tap water used to clean the organic solvent can be collected in batches and reused in the next cycle. The distillation treatment is then determined based on the concentration of the organic solvent, which can effectively recover the organic solvent and reduce operating costs.

[0047] Step 7. Using the fixed bed adsorption column rinsed with tap water in step 6, repeat steps 1 to 5 until all the isooctyl thioglycolate production wastewater is treated.

[0048] The above-mentioned adsorption material is a weakly polar post-crosslinked adsorption material, a polystyrene-divinylbenzene resin modified with a carboxylic acid functional group, preferably Lanshen LS-200 adsorption material. The technical indicators of the adsorption material are shown in Table 1 below:

[0049] Table 1 Technical indicators of adsorption materials

[0050]

[0051] Example 1

[0052] The method for treating isooctyl thioglycolate wastewater of the present invention comprises the following steps:

[0053] Step 1. The wastewater after oil-water separation of isooctyl thioglycolate production water is passed through a fixed bed adsorption column filled with adsorption material at a flow rate of 0.5 BV / h; the adsorption material is Lanshen LS-200 adsorption material;

[0054] Step 2. Using tap water to displace the isooctyl thioglycolate wastewater from the adsorption material obtained in step 1, thereby removing the isooctyl thioglycolate wastewater from the pores of the adsorption material;

[0055] Step 3. Drain the residual isooctyl thioglycolate wastewater in the fixed bed adsorption column obtained in step 2 using 0.2 MPa compressed nitrogen;

[0056] Step 4. Desorb and regenerate the adsorbent material in the fixed-bed adsorption column with 1-2 BV of isopropyl alcohol (an organic solvent) at a desorption rate of 0.5 BV / h. Collect the desorbed liquid and distill it to recover the isopropyl alcohol. The residual product after distillation is solidified and then outsourced for disposal.

[0057] Step 5. Drain the organic solvent remaining in the adsorption material after desorption in step 4 using 0.2 MPa compressed nitrogen, and collect the discharged desorption liquid and return it to distillation to recover the organic solvent;

[0058] Step 6. The adsorption material is rinsed with tap water at a temperature of 30°C to remove the residual organic solvent in the pores of the adsorption material. The organic solvent content is washed with water until it is less than 0.1%. The regenerated fixed bed adsorption column is reused.

[0059] Example 2

[0060] The steps are the same as those in Example 1, except that the flow rate in step 1 is modified to 1.0 BV / h.

[0061] Example 3

[0062] The steps are the same as those in Example 1, except that the flow rate in step 1 is modified to 1.5 BV / h.

[0063] Example 4

[0064] The steps are the same as those in Example 1, except that the flow rate in step 1 is modified to 2.0 BV / h.

[0065] Example 5

[0066] The steps are the same as those in Example 1, except that the flow rate in step 1 is modified to 3.0 BV / h.

[0067] The adsorption removal rates of isooctyl thioglycolate by the resins of Test Examples 1-5 were 98%, 96%, 83%, 65%, and 48%, respectively. Since the adsorption principle of isooctyl thioglycolate in water on the resin is diffusion dialysis and intermolecular hydrogen bonding, the adsorption rate is one of the most critical factors affecting adsorption. The lower the adsorption rate, the better the adsorption effect. Combining the comprehensive analysis of adsorption effect and economic efficiency, the adsorption rate was finally determined to be 1 BV / h.

[0068] Comparative Example 1

[0069] The same as Example 2, except that the adsorption material is replaced by polystyrene-divinylbenzene.

[0070] Comparative Example 1 has an adsorption removal efficiency of only 55% for isooctyl thioglycolate, and the adsorption capacity is 25 kg / m 3 The adsorption removal efficiency of the resin loaded with carboxylic acid functional groups in Example 3 for isooctyl thioglycolate reached 96%, and the adsorption capacity was 50 kg / m3 , indicating that the polystyrene-divinylbenzene resin of the present invention can greatly improve the adsorption effect after loading the carboxylic acid functional group, and the adsorption amount is doubled.

[0071] Example 1:

[0072] The method for treating isooctyl thioglycolate wastewater provided by the present invention was used to demonstrate its process for producing wastewater from an isooctyl thioglycolate production enterprise in Weifang, Shandong Province. The test used isooctyl thioglycolate wastewater produced by the plant, and the TOC of the raw water was 8000-10000 mg / L. Comparative tests were conducted using advanced oxidation and extraction treatment methods currently on the market and the adsorption separation method provided by the present invention. After treatment with the adsorption separation method of the present invention, the TOC concentration in the effluent was lower than that of the other two treatment methods, and the secondary pollution and fatigue tests were also better than the other two treatment methods. There was no sign of performance degradation during adsorption and desorption, and no secondary wastewater was produced. The treatment effect exceeded the expected effect of the plant (see Table 1 below for comparative data). Currently, a set of 3 tons / hour industrial equipment is in stable operation, and the treatment effect is stable.

[0073] Table 1 Comparison of the effect data of three treatment methods

[0074] project Advanced Oxidation extraction Adsorption separation Remark Raw water TOC 8000-10000mg / L 8000-10000mg / L 8000-10000mg / L Experimental comparison data Water output cycle <500mg / L <400mg / L <200 mg / L Experimental comparison data Water discharge cycle 2 <650mg / L <450 mg / L <200 mg / L Experimental comparison data Three water cycles <720 mg / L <480 mg / L <200 mg / L Experimental comparison data Four cycles of water discharge <800mg / L <510 mg / L <200 mg / L Experimental comparison data Five water discharge cycles <900mg / L <570 mg / L <200 mg / L Experimental comparison data Ton of water, waste and other wastes treated 500g 1.2kg 0 Experimental comparison data

[0075] Example 2:

[0076] The present invention provides for the isooctyl thioglycolate wastewater treatment method in a certain isooctyl thioglycolate production enterprise in Nanjing, Jiangsu Province, and carries out process demonstration. The test plant produces isooctyl thioglycolate wastewater. Raw water TOC18000-25000mg / L. Direct evaporation is used to substantially eliminate treatment effect. Condensed water, centrifuge mother liquor and crystallized salt are not directly processed. Condensed water is blended and biochemically treated. Crystallized salt and centrifuge mother liquor are commissioned for processing. The factory handles the hazardous waste costs of this part of wastewater commissioned annually and is roughly about 3 million. Increase the cost and loss of the commissioned factory greatly reducing the treatment unit after the present invention. Save evaporation and biochemical costs. While bringing considerable economic benefits to the factory, reduce environmental pressure (data are shown in Table 2). This decolorization system and method have good separating effect, and system footprint is small, simple to operate, reliable in operation, easy to maintain, and runs for 24 hours continuously, and production efficiency is greatly improved.

[0077] Table 2 Comparison of various costs after adding the treatment device of the present invention

[0078] project Hazardous waste disposal costs Steam Fees Biochemical costs Recycling benefits Original treatment process 3 million / year 2.7 million / year 890,000 / year 0 / year Add adsorption process 100,000 / year 1.809 million / year 445,000 yuan / year 450,000 yuan / year

[0079] Compared with the prior art, the present invention has the following beneficial technical effects:

[0080] 1. According to the characteristics of isooctyl thioglycolate wastewater, polystyrene-divinylbenzene resin loaded with carboxylic acid functional groups was selected as the adsorption material to specifically adsorb organic matter in the wastewater. The high salt content in the wastewater basically has no effect on the adsorption, and the high salt content also helps to promote the adsorption. After the adsorption material is saturated with organic matter, it is rinsed with 1-2BV tap water, and the rinsing liquid is recovered and returned to the raw water tank for further adsorption, reducing secondary pollution of the water.

[0081] 2. The TOC removal efficiency for isooctyl thioglycolate wastewater is achieved by utilizing a lift pump, piping, and a fixed-bed adsorption column loaded with adsorbent material. No chemical agents are required for isooctyl thioglycolate wastewater treatment, resulting in a short treatment time and significant adsorption efficiency. The system utilizes minimal and simple equipment, and the entire system can be fully PLC-controlled. Therefore, the apparatus of the present invention can operate 24 hours a day without requiring downtime.

[0082] In summary, the present invention uses renewable adsorption materials to treat isooctyl thioglycolate production water wastewater, which has a simple structure, easy operation, convenient maintenance, safe and reliable operation, good treatment effect, can eliminate secondary pollution, bring considerable economic benefits, and reduce the environmental protection pressure of the factory area.

Claims

1. A method for treating isooctyl thioglycolate wastewater, characterized in that: Passing the isooctyl thioglycolate wastewater through a fixed bed adsorption column equipped with an adsorption material, and collecting the effluent; wherein the adsorption material is a polystyrene-divinylbenzene resin modified with a carboxylic acid functional group; The flow rate of isooctyl thioglycolate wastewater through the column is 1~1.5BV / h, where BV is the volume of the adsorption material in the fixed bed adsorption column; The technical indicators of the adsorption material are shown in the following table: 。 2. The method for treating isooctyl thioglycolate wastewater according to claim 1, wherein The specific steps include: S1, passing the isooctyl thioglycolate wastewater through a fixed bed adsorption column filled with adsorption material, and collecting the effluent; S2, the effluent was evaporated to collect salt; S3, regenerating the fixed bed adsorption column filled with adsorption material.

3. The method for treating isooctyl thioglycolate wastewater according to claim 2, wherein S3 specifically includes: S3.1, using water to replace the residual isooctyl thioglycolate wastewater in the fixed bed adsorption column; S3.2, after water replacement, the residual water and wastewater mixture in the fixed bed adsorption column is drained with compressed nitrogen; S3.3, after the mixed liquid is drained, the fixed bed adsorption column containing the adsorption material is regenerated.

4. The method for treating isooctyl thioglycolate wastewater according to claim 3, wherein In S3.1, the effluent obtained by water replacement is returned to S1.

5. The method for treating isooctyl thioglycolate wastewater according to claim 3, wherein S3.3 specifically includes: S3.31, desorbing the fixed bed adsorption column using an organic solvent; S3.32, after desorption is complete, use compressed nitrogen to drain the remaining organic solvent in the fixed bed adsorption column; S3.33, after the residual organic solvent is drained, the fixed bed adsorption column is rinsed with water.

6. The method for treating isooctyl thioglycolate wastewater according to claim 5, wherein: In S3.31, the organic solvent is isopropyl alcohol.

7. The method for treating isooctyl thioglycolate wastewater according to claim 5, wherein: In S3.31, the amount of organic solvent used is 1-2 BV; the desorption flow rate is 0.5~0.75 BV / h, and BV is the volume of the adsorption material in the fixed bed adsorption column.

8. The method for treating isooctyl thioglycolate wastewater according to claim 5, wherein: In S3.31, the desorption liquid obtained by desorption is distilled to recover the organic solvent.

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