Treatment method of PMA production wastewater

Abstract

The invention provides a treatment method of PMA production wastewater, and belongs to the technical field of wastewater treatment. The method is characterized in that dichloromethane is used as an extraction agent to perform multistage extraction on the PMA production wastewater, and the method specifically comprises the following steps: (1) adding dichloromethane into the PMA production wastewater and oscillating; standing, and separating out an organic phase and a water phase; (2) retaining an organic phase, and performing next-stage extraction on a water phase by using dichloromethane; and (3) mixing the extracted organic phases, rectifying, and separating PMA, IPMA and DPMA. The CODcr value of the treated wastewater is reduced to 13000-15000 mg / L, the CODcr removal rate is as high as 74%, PMA, IPMA and DPMA components can be effectively separated out, and up-to-standard discharge and resource utilization of the PMA production wastewater are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, in particular to a method for treating PMA production wastewater. Background Art

[0002] Propylene glycol methyl ether acetate (2-Acetoxy-1-methoxypropane, referred to as PMA), the molecular formula is C6H 12 O3 is an important low-toxic high-grade industrial solvent. PMA has a multi-functional group structure. The same molecule contains both non-polar and polar parts. The functional groups of these two parts not only restrict and repel each other, but also play their own inherent roles. Therefore, it has a certain solubility for both polar and non-polar substances.

[0003] PMA production wastewater mainly includes organic pollutants such as PMA, IPMA (propylene glycol paramethyl ether acetate), DPMA (dipropylene glycol methyl ether acetate), toluene, xylene, acetic acid, etc. The CODcr value in the wastewater is generally 40,000-50,000 mg / L, and it cannot be discharged directly.

[0004] At present, the traditional treatment method is often to use multiple independent treatment systems to treat various types of wastewater in PMA production wastewater, without organically combining various types of wastewater or treatment systems, resulting in equipment waste and cost increase, and overall poor economic efficiency. In addition, using a single method to treat PMA production wastewater often cannot meet the discharge standards, and multiple methods need to be combined to achieve the treatment effect, and the general distillation method cannot effectively separate PMA, IPMA, DPMA and other components.

[0005] In order to ensure that the treated wastewater can meet the discharge standards and realize the resource utilization of wastewater, it is urgent to develop a more efficient PMA production wastewater treatment method, which is of great significance for improving the environment and enhancing the competitiveness of PMA production enterprises. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a method for treating PMA production wastewater, in which dichloromethane is used as a single extractant to directly extract the PMA production wastewater, and the CODcr value of the treated wastewater is reduced to 13000-15000 mg / L, the CODcr removal rate is as high as 74%, and the PMA, IPMA and DPMA components can be effectively separated, thereby achieving the standard discharge and resource utilization of the PMA production wastewater.

[0007] The technical solution of the present invention is as follows:

[0008] A method for treating PMA production wastewater uses dichloromethane as an extractant to perform multi-stage extraction on the PMA production wastewater.

[0009] Preferably, the method specifically comprises the following steps:

[0010] (1) adding dichloromethane to PMA production wastewater for shaking; standing to separate the organic phase and the aqueous phase;

[0011] (2) retaining the organic phase, and extracting the aqueous phase again with dichloromethane;

[0012] (3) The organic phases after extraction are mixed and distilled to separate PMA, IPMA and DPMA.

[0013] Preferably, the volume ratio of dichloromethane to PMA production wastewater in step (1) is 1: (1-1.5).

[0014] Further preferably, the volume ratio of dichloromethane to PMA production wastewater in step (1) is 1:1.

[0015] Preferably, the shaking conditions in step (1) are: shaking at 20-25° C. for 20-30 min.

[0016] Preferably, the standing time in step (1) is 10 to 15 minutes.

[0017] Preferably, the distillation method in step (3) is to place the organic phase in a distillation tower for distillation.

[0018] Preferably, the multi-stage extraction is a three-stage extraction.

[0019] Beneficial effects:

[0020] The present invention uses dichloromethane as a single extractant to directly extract PMA production wastewater, and the CODcr value of the treated wastewater is reduced to 13000-15000 mg / L, the CODcr removal rate is as high as 74%, and the PMA, IPMA and DPMA components can be effectively separated, thereby achieving the standard discharge and resource utilization of PMA production wastewater. DETAILED DESCRIPTION

[0021] The following is explained in conjunction with specific embodiments:

[0022] Example 1: Determination of extraction times

[0023] Test 1:

[0024] Take 400 mL of PMA production wastewater with a CODcr value of 46806 mg / L, add 400 mL of dichloromethane in a volume ratio of 1:1, and oscillate at 25°C for 30 minutes; after standing for 10 minutes, separate the organic phase and the aqueous phase to obtain organic phase 1 and aqueous phase 1.

[0025] The aqueous phase 1 was subjected to secondary extraction: 350 mL of aqueous phase 1 was taken, 350 mL of dichloromethane was added, and the mixture was shaken at 25° C. for 30 min; after standing for 10 min, the organic phase and the aqueous phase were separated to obtain organic phase 2 and aqueous phase 2.

[0026] The aqueous phase 2 was subjected to three-stage extraction: 300 mL of aqueous phase 2 was taken, 300 mL of dichloromethane was added, and the mixture was shaken at 25° C. for 30 min; after standing for 10 min, the organic phase and the aqueous phase were separated to obtain organic phase 3 and aqueous phase 3.

[0027] The CODcr values ​​in water phase 1, water phase 2 and water phase 3 were measured respectively, and the CODcr removal rate was calculated. The results are shown in Table 1 below:

[0028] Table 1. CODcr removal rate at different extraction times

[0029] Group CODcr(mg / L) CODcr removal rate (%) PMA production wastewater 46806 / Water phase 1 27147 42 Water phase 2 17318 63 Water phase 3 12170 74

[0030] Test 2:

[0031] Take 400 mL of PMA production wastewater with a CODcr value of 47755 mg / L, add 400 mL of dichloromethane in a volume ratio of 1:1, and oscillate at 22°C for 30 minutes; after standing for 10 minutes, separate the organic phase and the aqueous phase to obtain organic phase 1 and aqueous phase 1.

[0032] The aqueous phase 1 was subjected to secondary extraction: 350 mL of aqueous phase 1 was taken, 350 mL of dichloromethane was added, and the mixture was shaken at 22° C. for 30 min; after standing for 10 min, the organic phase and the aqueous phase were separated to obtain organic phase 2 and aqueous phase 2.

[0033] The aqueous phase 2 was subjected to three-stage extraction: 300 mL of aqueous phase 2 was taken, 300 mL of dichloromethane was added, and the mixture was shaken at 22° C. for 30 min; after standing for 10 min, the organic phase and the aqueous phase were separated to obtain organic phase 3 and aqueous phase 3.

[0034] The CODcr values ​​in water phase 1, water phase 2 and water phase 3 were measured respectively, and the CODcr removal rate was calculated. The results are shown in Table 2 below:

[0035] Table 2. CODcr removal rate at different extraction times

[0036] Group CODcr(mg / L) CODcr removal rate (%) PMA production wastewater 47755 / Water phase 1 28653 40 Water phase 2 19297 60 Water phase 3 13547 72

[0037] As shown in Tables 1 and 2, after three-stage extraction of PMA production wastewater with dichloromethane, the removal rate of CODcr can be as high as 74%. Therefore, the three-stage extraction method is used to treat PMA production wastewater in the future.

[0038] Example 2: Treatment of PMA production wastewater

[0039] (1) Take 400 mL of PMA production wastewater with a CODcr value of 47200 mg / L, add 400 mL of dichloromethane in a volume ratio of 1:1, and shake at 25°C for 30 minutes; after standing for 10 minutes, separate to obtain organic phase 1 and aqueous phase 1.

[0040] (2) Perform secondary extraction on aqueous phase 1: take 350 mL of aqueous phase 1, add 350 mL of dichloromethane, and shake at 25° C. for 30 min; after standing for 10 min, separate the organic phase and the aqueous phase to obtain organic phase 2 and aqueous phase 2.

[0041] The aqueous phase 2 was subjected to three-stage extraction: 300 mL of aqueous phase 2 was taken, 300 mL of dichloromethane was added, and the mixture was shaken at 25° C. for 30 min; after standing for 10 min, the organic phase and the aqueous phase were separated to obtain organic phase 3 and aqueous phase 3.

[0042] (3) The organic phase 1, the organic phase 2 and the organic phase 3 after extraction are mixed and placed in a distillation tower for distillation to separate dichloromethane, PMA, IPMA and DPMA.

[0043] It was determined that the CODcr value in the water phase 3 was 12694 mg / L, and the CODcr removal rate was 73%.

[0044] Example 3: Treatment of PMA production wastewater

[0045] (1) Take 300 mL of PMA production wastewater with a CODcr value of 47755 mg / L, add 300 mL of dichloromethane in a volume ratio of 1:1, and shake at 22°C for 20 minutes; after standing for 10 minutes, separate to obtain organic phase 1 and aqueous phase 1.

[0046] (2) Perform secondary extraction on aqueous phase 1: take 250 mL of aqueous phase 1, add 250 mL of dichloromethane, and shake at 22° C. for 20 min; after standing for 10 min, separate the organic phase and the aqueous phase to obtain organic phase 2 and aqueous phase 2.

[0047] The aqueous phase 2 was subjected to three-stage extraction: 200 mL of aqueous phase 2 was taken, 200 mL of dichloromethane was added, and the mixture was shaken at 22° C. for 20 min; after standing for 10 min, the organic phase and the aqueous phase were separated to obtain organic phase 3 and aqueous phase 3.

[0048] (3) The organic phase 1, the organic phase 2 and the organic phase 3 after extraction are mixed and placed in a distillation tower for distillation to separate dichloromethane, PMA, IPMA and DPMA.

[0049] It was determined that the CODcr value in the water phase 3 was 13547 mg / L and the CODcr removal rate was 72%.

[0050] Example 4: Treatment of PMA production wastewater

[0051] (1) Take 300 mL of PMA production wastewater with a CODcr value of 46122 mg / L, add 200 mL of dichloromethane in a volume ratio of dichloromethane to PMA production wastewater of 1:1.5, and shake at 20°C for 30 minutes; stand for 10 minutes and separate to obtain organic phase 1 and aqueous phase 1.

[0052] (2) Perform secondary extraction on aqueous phase 1: take 250 mL of aqueous phase 1, add 167 mL of dichloromethane, and shake at 20° C. for 30 min; after standing for 10 min, separate the organic phase and the aqueous phase to obtain organic phase 2 and aqueous phase 2.

[0053] The aqueous phase 2 was subjected to three-stage extraction: 200 mL of aqueous phase 2 was taken, 133 mL of dichloromethane was added, and the mixture was shaken at 20° C. for 30 min; after standing for 10 min, the organic phase and the aqueous phase were separated to obtain organic phase 3 and aqueous phase 3.

[0054] (3) The organic phase 1, the organic phase 2 and the organic phase 3 after extraction are mixed and placed in a distillation tower for distillation to separate dichloromethane, PMA, IPMA and DPMA.

[0055] It was determined that the CODcr value in the water phase 3 was 14900 mg / L and the CODcr removal rate was 68%.

[0056] Comparative Example:

[0057] Experimental group: Take 400mL of PMA production wastewater with a CODcr value of 47200mg / L, add 400mL of dichloromethane at a volume ratio of 1:1, and oscillate at 25℃ for 30min; after standing for 10min, separate the organic phase and the aqueous phase.

[0058] Control group 1: The difference from the experimental group is that dichloromethane is replaced by dichloroethane; other experimental conditions are the same as the experimental group, and the organic phase and the aqueous phase are separated.

[0059] Control group 2: The difference from the experimental group is that dichloromethane is replaced by carbon tetrachloride; other experimental conditions are the same as the experimental group, and the organic phase and the aqueous phase are separated.

[0060] The CODcr values ​​of the water phase in the experimental group and the control group 1 and 2 were measured respectively, and the CODcr removal rate was calculated. The results are shown in Table 3 below:

[0061] Table 3. CODcr removal rate under different extractants

[0062]

[0063] It can be seen from Table 3 that, compared with ethylene dichloride and carbon tetrachloride, the removal rate of CODcr in the wastewater is the highest when dichloromethane is used as the extractant to extract PMA production wastewater.

Claims

1. A method for treating PMA production wastewater, characterized in that: Using dichloromethane as the extractant, PMA production wastewater was subjected to multi-stage extraction.

2. The processing method according to claim 1, characterized in that The specific steps include: (1) adding dichloromethane to PMA production wastewater for shaking; standing to separate the organic phase and the aqueous phase; (2) retaining the organic phase, and extracting the aqueous phase again with dichloromethane; (3) The organic phases after extraction are mixed and distilled to separate PMA, IPMA and DPMA.

3. The processing method according to claim 2, characterized in that: The volume ratio of dichloromethane to PMA production wastewater in step (1) is 1: (1-1.5).

4. The processing method according to claim 2, characterized in that: The volume ratio of dichloromethane and PMA production wastewater in step (1) is 1:

1.

5. The processing method according to claim 2, characterized in that: The shaking conditions in step (1) are: shaking at 20-25° C. for 20-30 min.

6. The processing method according to claim 2, characterized in that: The standing time in step (1) is 10 to 15 minutes.

7. The processing method according to claim 2, characterized in that: The distillation method in step (3) is to place the organic phase in a distillation tower for distillation.

8. The processing method according to claim 1, characterized in that: The multi-stage extraction is a three-stage extraction.

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