Pretreatment method of styrene butadiene rubber wastewater

Abstract

The invention relates to a pretreatment method of styrene butadiene rubber wastewater, and belongs to the technical field of chemical wastewater treatment. The problem that the total nitrogen is difficult to stably reach the standard due to high organic nitrogen content in the butadiene styrene rubber discharged wastewater in the prior art is solved. The method comprises the following steps: S1, adjusting the pH value of the butadiene styrene rubber wastewater to 2.0-5.0 by using acid; s2, adding a COD (Chemical Oxygen Demand) degradation agent, an oxidizing agent and a catalyst into the butadiene styrene rubber wastewater, and uniformly stirring to obtain a mixed solution; s3, putting the mixed solution into a microwave field for microwave treatment to obtain pretreated wastewater. According to the method, the specific pollutant dinitrile diamine formaldehyde condensate in the butadiene styrene rubber wastewater can be effectively degraded, the biodegradability of the wastewater is improved, meanwhile, part of COD is removed, the subsequent biochemical treatment difficulty is reduced, and discharged sewage subjected to biochemical treatment stably meets the GB31571-2015 direct discharge water quality standard that the total nitrogen is smaller than or equal to 15 mg / L and the COD is smaller than or equal to 50 mg / L.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical wastewater treatment, and in particular relates to a pretreatment method for styrene-butadiene rubber wastewater. Background Art

[0002] More than 10 kinds of nitrogen-containing additives are used in the production process of styrene-butadiene rubber, which affect the total nitrogen index of the discharged sewage to varying degrees, and the one with the greatest impact is dinitrile diamine formaldehyde condensation. Dinitrile diamine formaldehyde condensation is a high molecular flocculant. In the coagulation process of styrene-butadiene rubber, it is used to destroy the emulsifying function of the emulsifier on the surface of latex particles, release polymer particles and aggregate into larger particles, so that they can be separated from the water. The amount of dinitrile diamine formaldehyde condensation in the polymerization process is 0.22% to 0.24% (w / w), which contributes the most to the total nitrogen index of sewage and contains difficult-to-degrade CN-, which is the main reason for the high total nitrogen content in sewage treatment plants. According to instrumental analysis, dinitrile diamine formaldehyde condensation exists in the entire process of the biochemical treatment system, and the concentration remains basically unchanged. Even after two-stage A / O treatment, it is still difficult for the discharged sewage to reach the technical index of total nitrogen ≤15mg / L.

[0003] Microwave technology is a chemical intensification technology that has emerged in recent years. Microwave radiation can cause the internal molecules of the heated substance to collide with each other to generate heat energy, increase the activation entropy of the reactants, and increase the reaction rate at an order of magnitude level. The microwave catalytic oxidation method is to quickly activate the active sites on the catalyst surface through high-intensity and short-pulse microwave radiation, so that organic pollutants can be quickly adsorbed to the catalyst surface and catalytically oxidized and degraded, thereby achieving the purpose of removing organic pollutants. The microwave catalytic oxidation method has the advantages of thorough oxidation, fast processing speed, low operating cost, and no secondary pollutants. CN116425351 A discloses a microwave-assisted Fenton method for treating high-concentration organic wastewater, which can reduce the COD of 2700 mg / L in high-concentration organic wastewater to 150-540 mg / L, and the COD removal rate reaches more than 80%, but the embodiment does not involve the removal of characteristic pollutants dinitrile diamine formaldehyde condensate and total nitrogen in styrene-butadiene rubber wastewater. The test results of using this technology to treat styrene-butadiene rubber wastewater show that the concentration of dinitrile diamine formaldehyde condensation products, a characteristic pollutant in the wastewater after treatment, does not change much, and the purpose of reducing organic nitrogen therein cannot be achieved; and the microwave radiation time is more than 6 minutes, with high energy consumption and large investment. CN 104291506 B discloses a method for treating rubber accelerator wastewater with microwave-enhanced micro-electrolysis combined oxidation. First, the wastewater to be treated (COD is 6000-8000 mg / L) is adjusted to pH value, hydrogen peroxide is added for oxidation, and then it enters a micro-electrolysis reactor for treatment, and air is introduced at the same time. After the treated water enters a microwave reactor for treatment, lime emulsion is added to adjust the pH value and stand, and the lower layer of emulsion is released. The COD of the treated water is 300-500 mg / L. This method has a complicated process, and the amount of the lower layer of emulsion is large, so it can only be used for hazardous waste treatment, and the treatment cost is high. Summary of the invention

[0004] In view of this, the present invention provides a pretreatment method for styrene-butadiene rubber wastewater, which can effectively degrade dinitrile diamine formaldehyde condensation products, a characteristic pollutant in styrene-butadiene rubber wastewater, improve the biodegradability of wastewater, and completely solve the pressure that the total nitrogen content of the discharged wastewater is difficult to stably meet the standard. At the same time, part of the COD is removed to reduce the difficulty of subsequent biochemical treatment, so that the discharged wastewater after biochemical treatment can stably meet the GB31571-2015 direct discharge water quality standard of total nitrogen ≤15mg / L and COD ≤50mg / L.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0006] The present invention provides a method for pretreating styrene-butadiene rubber wastewater, comprising the following steps:

[0007] S1. Using acid to adjust the pH value of styrene-butadiene rubber wastewater to 2.0-5.0;

[0008] S2. COD degradation agent, oxidant and catalyst were added to the styrene-butadiene rubber wastewater, and stirred to obtain a mixed solution; the COD degradation agent contained 2wt% to 3wt% of sodium chlorate and 0.1wt% to 0.3wt% of citric acid;

[0009] S3. placing the mixed liquid into a microwave field for microwave treatment to obtain pretreated wastewater.

[0010] Preferably, it further comprises S4, adjusting the pH value of the pretreated wastewater to neutral with alkali, and then sending the pretreated wastewater to the A / O biochemical system for treatment to obtain wastewater that meets the discharge standards;

[0011] More preferably, in step S4, the base is sodium hydroxide.

[0012] Preferably, in step S1, the content of dinitrile diamine formaldehyde condensate in the styrene-butadiene rubber wastewater is 86.2-92.2 mg / L, the total nitrogen is 91.1-98.6 mg / L, the COD is 455-478 mg / L, the pH value is 5.0-6.5, and the water temperature is 55-70°C.

[0013] Preferably, in step S1, the acid is hydrochloric acid or sulfuric acid.

[0014] Preferably, in step S2, the COD degradation agent is added at a concentration of 20 to 300 mg / L; more preferably, the COD degradation agent is added at a concentration of 30 to 50 mg / L.

[0015] Preferably, in step S2, the oxidant is hydrogen peroxide, and the added concentration is 2.0 to 6.0 g / L; more preferably, the added concentration is 3.0 to 4.0 g / L.

[0016] Preferably, in step S2, the catalyst is ferric chloride or ferrous sulfate, and the added concentration is 20 to 180 mg / L; more preferably, the added concentration is 60 to 120 mg / L;

[0017] Preferably, in step S3, the microwave treatment conditions are: microwave frequency is 915 MHz, microwave power is 100-800 W, microwave treatment time is 30 s-180 s, and pH value of treated wastewater is 2.0-5.0;

[0018] More preferably, the microwave power is 200-500 W, the microwave treatment time is 60 s-120 s, and the pH value of the treated wastewater is 3.0-4.0.

[0019] The principle of the present invention is:

[0020] The pretreatment method of styrene-butadiene rubber wastewater of the present invention comprises the following steps: adding a COD degradation agent whose main components are sodium chlorate and citric acid; the sodium chlorate, as an oxidant, can undergo oxidation reaction with organic matter and can also play a catalytic role under acidic conditions to accelerate the degradation rate of the organic matter; and the citric acid, as a stabilizer, can control the reaction rate of the degradation agent.

[0021] The pretreatment method of styrene-butadiene rubber wastewater of the present invention comprises the following steps: adjusting the pH value and adding a COD degradation agent, an oxidant and a catalyst to the styrene-butadiene rubber wastewater, subjecting the styrene-butadiene rubber wastewater to microwave field treatment, so that polar molecules in the styrene-butadiene rubber wastewater absorb microwaves, increase their movement speed, and increase the probability of collision and contact between water molecules and pollutant molecules, thereby rapidly completing the oxidation process, significantly degrading pollutants, reducing the difficulty of subsequent biochemical treatment, and ensuring that the COD and total nitrogen in the discharged sewage stably meet the standards.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The pretreatment method of styrene-butadiene rubber wastewater of the present invention adopts a COD degradation agent + microwave catalytic oxidation method to treat the styrene-butadiene rubber wastewater, so that the dinitrile diamine formaldehyde condensate and other organic matter therein are degraded, and the total nitrogen and COD of the discharged wastewater after biochemical treatment meet the direct discharge water quality standard of GB31571-2015;

[0024] (2) The pretreatment method of styrene-butadiene rubber wastewater of the present invention can increase the B / C of styrene-butadiene rubber wastewater from 0.1 to above 0.4;

[0025] (3) The pretreatment method of styrene-butadiene rubber wastewater of the present invention can reduce the concentration of dinitrile diamine formaldehyde condensate in styrene-butadiene rubber wastewater from 86.2 to 92.2 mg / L to 1.2 to 3.0 mg / L, COD from 455 to 478 mg / L to 80 to 120 mg / L, and total nitrogen from 91.1 to 98.6 mg / L to 2.0 to 4.0 mg / L;

[0026] (4) After the pretreated wastewater obtained by the pretreatment method of styrene-butadiene rubber wastewater of the present invention enters the biochemical system for treatment, the total nitrogen in the effluent is 0.5-1.8 mg / L and the COD is 15-35 mg / L;

[0027] (5) The pretreatment method of styrene butadiene rubber wastewater of the present invention has reaction conditions consistent with the water quality of styrene butadiene rubber wastewater, fully utilizes the acidity and heat energy of styrene butadiene rubber wastewater, saves the amount of acid used, and shortens the microwave irradiation time;

[0028] (6) The pretreatment method of styrene-butadiene rubber wastewater of the present invention is simple to operate and has a stable treatment effect, eliminating the pressure of subsequent biochemical treatment to meet the discharge standards. After biochemical treatment, the wastewater can stably meet the GB31571-2015 direct discharge water quality standards of total nitrogen ≤15 mg / L and COD ≤50 mg / L. DETAILED DESCRIPTION

[0029] In order to further understand the present invention, preferred embodiments of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0030] The pretreatment method of styrene-butadiene rubber wastewater of the present invention comprises the following steps:

[0031] S1. Using acid to adjust the pH value of styrene-butadiene rubber wastewater to 2.0-5.0;

[0032] S2. Add COD degradation agent, oxidant and catalyst to the styrene-butadiene rubber wastewater and stir to obtain a mixed solution;

[0033] S3. placing the mixed solution into a microwave field for microwave treatment to obtain pretreated wastewater;

[0034] S4. After adjusting the pH value of the pretreated wastewater to neutral with alkali, the pretreated wastewater is sent to the biochemical system for treatment to obtain wastewater that meets the discharge standards.

[0035] The styrene-butadiene rubber wastewater of the present invention refers to the wastewater from the process of generating styrene-butadiene rubber by reacting butadiene with styrene, and is the wastewater discharged after using polymer (dinitrile diamine formaldehyde condensate) and sulfuric acid as coagulants to separate rubber from latex and convert soap into organic acid. The dinitrile diamine formaldehyde condensate in the styrene-butadiene rubber wastewater is 86.2-92.2 mg / L, the total nitrogen is 91.1-98.6 mg / L, the COD is 455-478 mg / L, the pH value is 5.0-6.5, and the water temperature is 55-70°C.

[0036] In step S1 of the present invention, there is no particular limitation on the acid, and the acid may be selected according to the needs of those skilled in the art, such as hydrochloric acid, sulfuric acid, etc.

[0037] In step S2 of the present invention, the COD degradation agent contains 2wt% to 3wt% of sodium chlorate and 0.1wt% to 0.3wt% of citric acid. Sodium chlorate, as an oxidant, can react with organic matter to produce an oxidation reaction. Under acidic conditions, it can also act as a catalyst to accelerate the degradation rate of organic matter. Citric acid, as a stabilizer, can control the reaction rate of the degradation agent. The addition concentration of the COD degradation agent is 20 to 300 mg / L, preferably 30 to 50 mg / L. There are no special restrictions on other components in the COD degradation agent, such as water, or a common component of the COD degradation agent in the prior art.

[0038] In step S2 of the present invention, the oxidant is hydrogen peroxide, and the added concentration is 2.0 to 6.0 g / L, preferably 3.0 to 4.0 g / L.

[0039] In step S2 of the present invention, the catalyst is ferric chloride or ferrous sulfate, and the added concentration is 20 to 180 mg / L, preferably 60 to 120 mg / L.

[0040] In step S3 of the present invention, the microwave treatment conditions are: microwave frequency of 915MHz, microwave power of 100-800W, microwave treatment time of 30s-180s, and pH value of treated wastewater of 2.0-5.0; preferably, microwave power of 200-500W, microwave treatment time of 60s-120s, and pH value of treated wastewater of 3.0-4.0. During the microwave treatment process, polar molecules in styrene-butadiene rubber wastewater absorb microwaves, the movement speed increases, and the collision and contact probability of water molecules and pollutant molecules increases, so that the oxidation process is completed quickly, the pollutants are significantly degraded, the difficulty of subsequent biochemical treatment is reduced, and the COD and total nitrogen of the discharged wastewater are ensured to be stable and meet the standards.

[0041] The terms used in the present invention generally have the meanings commonly understood by those of ordinary skill in the art, unless otherwise specified.

[0042] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with embodiments.

[0043] In the following examples, various processes and methods not described in detail are conventional methods known in the art. The materials, reagents, devices, instruments, equipment, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources. The water samples in the examples are all wastewater produced by styrene-butadiene rubber devices, with a B / C ratio of 0.1, a pH value of 5.0-6.5, a water temperature of 55-70°C, a COD of 455-478 mg / L, a total nitrogen of 91.1-98.6 mg / L, and a dinitrile diamine formaldehyde condensate of 86.2-92.2 mg / L.

[0044] Comparative Example 1

[0045] Take 300mL of water sample and put it into a 500mL beaker, adjust the pH value to 3.0 with concentrated sulfuric acid, add COD degradation agent to the water sample, COD degradation agent contains 2wt% sodium chlorate and 0.3wt% citric acid, the addition concentration is 200mg / L, stir for 2min, let stand for 30min, and take the supernatant for water quality analysis. After analysis, the COD of the supernatant is 388mg / L, COD removal rate is 15.6%; total nitrogen is 86.7mg / L, total nitrogen removal rate is 8.7%, dinitrile diamine formaldehyde condensate is 82.1mg / L, dinitrile diamine formaldehyde condensate removal rate is 6.7%; B / C is 0.18.

[0046] Comparative Example 2

[0047] Take 300mL of water sample and put it into a 500mL beaker, adjust the pH value to 3.0 with concentrated sulfuric acid, add 2g / L H2O2 and 30mg / L FeSO4·7H2O to the water sample, stir evenly, and put it into a microwave oven. Microwave frequency 915MHZ, microwave power 100W, magnetic stirring and irradiation for 30s, take out the water sample, adjust the pH to 7.5 with NaOH (30wt%), let it stand for 30min, and take the supernatant for water quality analysis. After analysis, the dinitrile diamine formaldehyde condensate in the supernatant is 74mg / L, with a removal rate of 15.9%; total nitrogen is 89.2mg / L, with a removal rate of 5.1%; COD is 386.7mg / L, with a removal rate of 15.9%; B / C is 0.22. The first-stage AO biochemical effluent contains dinitrile diamine formaldehyde condensate of 72.1 mg / L, total nitrogen of 64.3 mg / L and COD of 88.6 mg / L.

[0048] Comparative Example 3

[0049] Take 300mL of water sample and put it into a 500mL beaker, adjust the pH value to 3.0 with concentrated sulfuric acid, add 3g / L H2O2 and 60mg / L FeSO4·7H2O to the water sample, stir evenly, and put it into a microwave oven. Microwave frequency 915MHZ, microwave power 200W, magnetic stirring and irradiation for 60s, take out the water sample, adjust the pH to 7.5 with NaOH (30wt%), let it stand for 30min, and take the supernatant for water quality analysis. After analysis, the dinitrile diamine formaldehyde condensate in the supernatant is 68.6mg / L, and the removal rate is 22.0%; the total nitrogen is 76.7mg / L, and the removal rate is 18.4%; the COD is 344.1mg / L, and the removal rate is 25.2%; the B / C is 0.26. The first-stage AO biochemical effluent contains dinitrile diamine formaldehyde condensate at 68.5 mg / L, total nitrogen at 55.1 mg / L, and COD at 73.4 mg / L.

[0050] Example 1

[0051] Take 300mL water sample and put it into a 500mL beaker, adjust the pH value to 3.0 with concentrated sulfuric acid, add COD degradation agent to the water sample, the COD degradation agent contains 2wt% sodium chlorate and 0.3wt% citric acid, the addition concentration is 50mg / L, stir for 2min, then add 3.5g / L H2O2, 80mg / L FeSO4·7H2O, stir evenly, put it into a microwave oven, microwave frequency 915MHZ, microwave power 300W, magnetic stirring and irradiation for 90s, take out the water sample, adjust the pH to 7.5 with NaOH (30wt%), let it stand for 30min, take the supernatant for water quality analysis. After analysis, the dinitrile diamine formaldehyde condensate in the supernatant is 2.0mg / L, the removal rate is 97.7%; the total nitrogen is 2.9mg / L, the removal rate is 96.9%; COD is 74mg / L, the removal rate is 83.9%; B / C is 0.42. The first-stage AO biochemical effluent contains dinitrile diamine formaldehyde condensate at 1.6 mg / L, total nitrogen at 1.2 mg / L, and COD at 36.7 mg / L.

[0052] Example 2

[0053] Take 300mL water sample and put it into a 500mL beaker, adjust the pH value to 4.0 with concentrated sulfuric acid, add COD degradation agent to the water sample, the COD degradation agent contains 3wt% sodium chlorate and 0.2wt% citric acid, the addition concentration is 30mg / L, stir for 2min, then add 6g / L H2O2, 140mg / L FeSO4·7H2O, stir evenly, put it into a microwave oven, microwave frequency 915MHZ, microwave power 300W, magnetic stirring and irradiation for 90s, take out the water sample, adjust the pH to 7.5 with NaOH (30wt%), let it stand for 30min, take the supernatant for water quality analysis. After analysis, the dinitrile diamine formaldehyde condensate in the supernatant is 2.8mg / L, the removal rate is 96.8%; the total nitrogen is 3.5mg / L, the removal rate is 96.3%; the COD is 94mg / L, the removal rate is 79.6%; B / C is 0.40. The first-stage AO biochemical effluent contains dinitrile diamine formaldehyde condensate at 2.5 mg / L, total nitrogen at 2.8 mg / L, and COD at 40.7 mg / L.

[0054] From the analysis results of Comparative Examples 1-3 and Examples 1-2, it can be seen that the pretreatment method of styrene-butadiene rubber wastewater of the present invention adopts COD degradation agent + microwave catalytic oxidation method to treat styrene-butadiene rubber wastewater, so that the dinitrile diamine formaldehyde condensation product and other organic matter therein can be degraded, and the total nitrogen and COD of the discharged wastewater after treatment by the A / O biochemical system meet the direct discharge water quality standard of GB31571-2015; and the synergistic effect of COD degradation agent + microwave catalytic oxidation method treatment is required to achieve the effect.

[0055] Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the embodiments. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. The obvious changes or modifications derived from them are still within the protection scope of the invention.

Claims

1. A method for pretreating styrene-butadiene rubber wastewater, characterized in that: Here are the steps: S1. Using acid to adjust the pH value of styrene-butadiene rubber wastewater to 2.0-5.0; S2. Adding a COD degradation agent, an oxidant and a catalyst to the styrene-butadiene rubber wastewater, stirring uniformly to obtain a mixed solution, wherein the COD degradation agent contains 2wt% to 3wt% of sodium chlorate and 0.1wt% to 0.3wt% of citric acid; S3. placing the mixed solution into a microwave field for microwave treatment to obtain pretreated wastewater.

2. The pretreatment method for styrene-butadiene rubber wastewater according to claim 1, characterized in that: The process also includes S4, wherein after the pH value of the pretreated wastewater is adjusted to neutral with alkali, the pretreated wastewater is sent to an A / O biochemical system for treatment to obtain wastewater that meets discharge standards.

3. The pretreatment method for styrene-butadiene rubber wastewater according to claim 2, characterized in that: In step S4, the alkali is sodium hydroxide.

4. The pretreatment method for styrene-butadiene rubber wastewater according to any one of claims 1 to 3, characterized in that: In step S1, the content of dinitrile diamine formaldehyde condensate in the styrene-butadiene rubber wastewater is 86.2-92.2 mg / L, the total nitrogen is 91.1-98.6 mg / L, the COD is 455-478 mg / L, the pH value is 5.0-6.5, and the water temperature is 55-70°C.

5. The pretreatment method for styrene-butadiene rubber wastewater according to any one of claims 1 to 3, characterized in that: In step S1, the acid is hydrochloric acid or sulfuric acid.

6. The pretreatment method for styrene-butadiene rubber wastewater according to any one of claims 1 to 3, characterized in that: In step S2, the COD degradation agent is added at a concentration of 20 to 300 mg / L; And / or, the oxidant is hydrogen peroxide, and the added concentration is 2.0 to 6.0 g / L; And / or, the catalyst is ferric chloride or ferrous sulfate, and the addition concentration is 20-180 mg / L.

7. The pretreatment method for styrene-butadiene rubber wastewater according to claim 6, characterized in that: In step S2, the concentration of the COD degradation agent added is 30-50 mg / L; And / or, the concentration of the oxidant added is 3.0-4.0 g / L; And / or, the catalyst is added at a concentration of 60 to 120 mg / L.

8. The pretreatment method for styrene-butadiene rubber wastewater according to claim 1, characterized in that: In step S3, the microwave treatment conditions are: microwave frequency is 915 MHz, microwave power is 100-800 W, microwave treatment time is 30 s-180 s, and pH value of treated wastewater is 2.0-5.

0.

9. The pretreatment method for styrene-butadiene rubber wastewater according to claim 8, characterized in that: The microwave power is 200-500W, the microwave treatment time is 60s-120s, and the pH value of the treated wastewater is 3.0-4.0.