A method for catalytic oxidation treatment of 1,2-hexanediol production wastewater

Abstract

The present application belongs to the field of fine chemical wastewater treatment, and particularly relates to a method for catalytic oxidation treatment of 1,2-hexanediol production wastewater. A catalyst and hydrogen peroxide are added to the wastewater to be treated for oxidation reaction, and a calcium salt flocculant is added under alkaline conditions for flocculation and precipitation, thereby realizing removal of 1,2-hexanediol and COD. The present application uses an activated carbon loaded peroxo-phosphotungstic acid quaternary ammonium salt catalyst, which has high oxidation catalytic activity, and further flocculation treatment by calcium hydroxide can effectively remove residual 1,2-hexanediol in 1,2-hexanediol production wastewater. The present application not only solves the activity inhibition of 1,2-hexanediol on microorganisms, but also reduces the organic matter content of the wastewater and improves the biodegradability of the wastewater. The method of the present application is simple to operate, low in cost, and has a wide commercial application prospect.

Description

Technical Field

[0001] The invention belongs to the field of fine chemical wastewater treatment, and particularly relates to a method for treating 1,2-hexanediol production wastewater by catalytic oxidation. Background Art

[0002] 1,2-Hexanediol is a colorless, odorless liquid and an important raw material for pesticides such as pyrethroids and cyclic musks. It is also widely used in cosmetics due to its excellent moisturizing and antiseptic properties.

[0003] Using 1-hexene as the raw material and hydrogen peroxide as the oxygen source, an epoxidation intermediate is generated in the presence of an inorganic solid acid catalyst. This is then hydrolyzed under an inorganic acid catalysis to yield the product, 1,2-hexanediol. During production, the product undergoes distillation for purification, generating a large amount of wastewater with a COD concentration of approximately 1000 mg / L. The organic matter contained in this wastewater is primarily 1,2-hexanediol, which is highly toxic to microorganisms and can inhibit their activity. Even after dilution, biochemical treatment is ineffective, failing to meet relevant environmental protection requirements. Due to the inhibitory effect of 1,2-hexanediol on microorganisms, the 1,2-hexanediol-containing wastewater obtained from distillation is not suitable for direct biological treatment. Currently, no treatment methods for 1,2-hexanediol-containing wastewater have been reported. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings, the present invention provides a method for catalytic oxidation treatment of 1,2-hexanediol production wastewater. The present invention adopts activated carbon-supported peroxyphosphotungstate quaternary ammonium salt catalyst, which can effectively treat 1,2-hexanediol in the wastewater, avoids the inhibition of 1,2-hexanediol in the wastewater on microorganisms in the biochemical treatment tank, and improves the biodegradability of the wastewater.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for treating 1,2-hexanediol production wastewater by catalytic oxidation comprises adding a catalyst and hydrogen peroxide to the wastewater to be treated for oxidation reaction, adding a calcium salt flocculant under alkaline conditions for flocculation and precipitation, thereby achieving the removal of 1,2-hexanediol and COD.

[0007] Furthermore, a catalyst is added to the wastewater to be treated, hydrogen peroxide is added dropwise at 60-70°C, the catalyst is filtered out after reacting for 2-3 hours, the pH is adjusted to 12.0-13.0, a calcium salt flocculant is added, the reaction is carried out at 80-90°C for 1-2 hours, and the precipitate is filtered out after cooling to room temperature, thereby achieving the removal of 1,2-hexanediol and COD.

[0008] Preferably, a catalyst is added to the wastewater to be treated, hydrogen peroxide is added dropwise at 65°C, the catalyst is filtered out after reacting for 2.5 hours, the pH is adjusted to 12.5, a calcium salt flocculant is added, the reaction is carried out at 85°C for 1.5 hours, and the precipitate is filtered out after cooling to room temperature, thereby achieving the removal of 1,2-hexanediol and COD.

[0009] The amount of the catalyst added is 0.05-0.15% of the mass of the wastewater to be treated; preferably, the amount of the catalyst added is 0.1% of the mass of the wastewater;

[0010] The amount of hydrogen peroxide added is 0.4-0.6% of the mass of the wastewater to be treated; preferably, the amount of hydrogen peroxide added is 0.5% of the mass of the wastewater;

[0011] The amount of calcium salt flocculant aqueous solution added is 0.8-1.2% of the mass of the wastewater to be treated.

[0012] The calcium salt flocculant is one or more of calcium carbonate, calcium chloride, calcium hydroxide, and calcium oxide. The preferred calcium salt flocculant is calcium hydroxide.

[0013] The catalyst is an activated carbon-supported quaternary ammonium peroxyphosphotungstate catalyst;

[0014] The preparation method of the activated carbon-supported peroxyphosphotungstic acid quaternary ammonium salt catalyst comprises the following steps: dissolving phosphotungstic acid in distilled water, adding hydrogen peroxide to obtain a peroxyphosphotungstic acid solution; simultaneously adding benzyltriethylammonium chloride to ethanol, and then adding activated carbon to obtain a benzyltriethylammonium chloride ethanol solution; adding the peroxyphosphotungstic acid solution to the benzyltriethylammonium chloride ethanol solution, maintaining the temperature and stirring, cooling and allowing to stand, filtering, and drying to obtain the activated carbon-supported peroxyphosphotungstic acid quaternary ammonium salt catalyst.

[0015] The amount of distilled water used is 8 to 12 times the mass of phosphotungstic acid, and the amount of hydrogen peroxide used is 1.3 to 1.7 times the mass of phosphotungstic acid;

[0016] The amount of benzyltriethylammonium chloride used is 1.2 to 1.4 times the mass of phosphotungstic acid, the amount of ethanol used is 8 to 12 times the mass of benzyltriethylammonium chloride, and the amount of activated carbon used is 3.5 to 4.5 times the mass of phosphotungstic acid.

[0017] The preferred conditions are: the amount of distilled water is 10 times the mass of phosphotungstic acid, the amount of hydrogen peroxide is 1.5 times the mass of phosphotungstic acid, the amount of benzyltriethylammonium chloride is 1.3 times the mass of phosphotungstic acid, the amount of ethanol is 10 times the mass of benzyltriethylammonium chloride, and the amount of activated carbon is 4.0 times the mass of phosphotungstic acid.

[0018] In the catalyst preparation method, the process conditions are: holding temperature of 70-78°C, holding stirring time of 4-8 hours, cooling to 15-25°C, standing for 12-24 hours, drying temperature of 220-230°C, and drying time of 4-5 hours. The preferred conditions are: holding temperature of 78°C, holding stirring time of 6 hours, cooling to 20°C, standing for 18 hours, drying temperature of 225°C, and drying time of 4.5 hours.

[0019] The principle of the present invention is that 1,2-hexanediol in wastewater undergoes a degradation reaction under the action of a catalyst and hydrogen peroxide, and is degraded into aldehyde compounds. The aldehyde degradation products undergo a polymerization reaction under the catalysis of calcium hydroxide, and are flocculated and precipitated, and then filtered and removed, so that the content of organic matter such as 1,2-hexanediol in the wastewater is reduced, thereby achieving the purpose of reducing the COD of the wastewater. At the same time, the inhibitory effect of 1,2-hexanediol in the wastewater on microorganisms is also weakened, which is beneficial to the final biochemical treatment.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] This method utilizes activated carbon-supported quaternary ammonium peroxyphosphotungstate catalyst, which exhibits high oxidative catalytic activity. Further flocculation with calcium hydroxide effectively removes residual 1,2-hexanediol from 1,2-hexanediol production wastewater. The method also achieves a COD removal rate exceeding 70%, eliminating the inhibitory effect of 1,2-hexanediol on microbial activity while also reducing the organic matter content of the wastewater and improving its biodegradability. The method is simple to operate, low-cost, and has broad prospects for commercial application. DETAILED DESCRIPTION

[0022] The present invention will be further explained below through specific examples.

[0023] The main component of the wastewater to be treated is 1,2-hexanediol, the COD of the wastewater is about 1000 mg / kg, and the content of 1,2-hexanediol is 0.042%.

[0024] Example 1

[0025] Weigh 5.0g of phosphotungstic acid into a beaker, add 50g of distilled water to dissolve, stir and add 7.5g of 30% w / w hydrogen peroxide, and stir at room temperature for 30 minutes to obtain a peroxyphosphotungstic acid solution. Weigh 6.5g of benzyltriethylammonium chloride into a three-necked flask, add 65g of ethanol, stir to dissolve, and then add 20.0g of activated carbon to obtain a benzyltriethylammonium chloride ethanol solution. At room temperature, add the peroxyphosphotungstic acid solution dropwise to the benzyltriethylammonium chloride ethanol solution, heat to 78°C and reflux gently, stir for 6 hours, cool to 20°C, let stand for 18 hours, filter, rinse the filter cake with water and ethanol, respectively, and air dry the filter cake at 225°C for 4.5 hours to obtain an activated carbon-supported peroxyphosphotungstic acid quaternary ammonium salt catalyst.

[0026] Example 2

[0027] Weigh 5.0g of phosphotungstic acid and place it in a beaker. Add 40g of distilled water to dissolve it. Stir and add 6.5g of 30% w / w hydrogen peroxide. Stir at room temperature for 30 minutes to obtain a peroxyphosphotungstic acid solution. Weigh 6.0g of benzyltriethylammonium chloride and place it in a three-necked flask. Add 72g of ethanol and stir to dissolve it. Then add 22.5g of activated carbon to obtain a benzyltriethylammonium chloride ethanol solution. At room temperature, add the peroxyphosphotungstic acid solution dropwise to the benzyltriethylammonium chloride ethanol solution. Heat to 75°C, stir for 8 hours, cool to 25°C, let stand for 24 hours, filter, rinse the filter cake with water and ethanol, respectively, and air dry the filter cake at 230°C for 4 hours to obtain an activated carbon-supported peroxyphosphotungstic acid quaternary ammonium salt catalyst.

[0028] Example 3

[0029] Weigh 5.0g of phosphotungstic acid into a beaker, add 60g of distilled water to dissolve, then stir and add 8.5g of 30% w / w hydrogen peroxide. Stir at room temperature for 30 minutes to obtain a peroxyphosphotungstic acid solution. Weigh 7.0g of benzyltriethylammonium chloride into a three-necked flask, add 56g of ethanol, stir to dissolve, and then add 17.5g of activated carbon to obtain a benzyltriethylammonium chloride ethanol solution. At room temperature, add the peroxyphosphotungstic acid solution dropwise to the benzyltriethylammonium chloride ethanol solution, heat to 76°C, stir for 4 hours, cool to 15°C, let stand for 12 hours, filter, rinse the filter cake with water and ethanol, respectively, and air dry the filter cake at 220°C for 5 hours to obtain the catalyst.

[0030] Example 4

[0031] 500 g of 1,2-hexanediol production wastewater was placed in a 1 L three-necked flask, 0.5 g of the catalyst prepared in Example 1 was added, the mixture was stirred and heated to 65°C, 2.5 g of 30% hydrogen peroxide was added dropwise, the reaction was continued for 2.5 h, the temperature was lowered, and the catalyst was filtered out.

[0032] Add saturated sodium hydroxide aqueous solution to the filtrate to adjust the pH to 12.50, add 5.0 g of 10% calcium hydroxide aqueous solution, stir and heat to 85°C, keep the temperature for reaction for 1.5 hours, cool to room temperature, filter out the flocculated precipitate, and obtain treated wastewater.

[0033] The treatment effect is: the wastewater COD removal rate is 82%, the content of 1,2-hexanediol in the treated wastewater is 0.007%, and the treated wastewater can be used for subsequent microbial treatment.

[0034] Example 5

[0035] 500 g of 1,2-hexanediol production wastewater was placed in a 1 L three-necked flask, 0.25 g of the catalyst prepared in Example 2 was added, the mixture was stirred and heated to 70°C, 3.0 g of 30% hydrogen peroxide was added dropwise, the reaction was continued for 3.0 h, the temperature was lowered, and the catalyst was filtered out.

[0036] Add saturated sodium hydroxide aqueous solution to the filtrate to adjust the pH to 12.00, add 6.0 g of 10% calcium hydroxide aqueous solution, stir and heat to 80°C, keep the temperature for reaction for 2.0 h, cool to room temperature, filter out the flocculated precipitate, and obtain pretreated wastewater.

[0037] The treatment effect is: COD removal rate is 73%, the content of 1,2-hexanediol after pretreatment is 0.011%, and the treated wastewater can be used for subsequent microbial treatment.

[0038] Example 6

[0039] 500 g of 1,2-hexanediol production wastewater was placed in a 1 L three-necked flask, 0.75 g of the catalyst prepared in Example 3 was added, the mixture was stirred and heated to 60°C, 2.0 g of 30% hydrogen peroxide was added dropwise, the reaction was continued for 2.0 h, the temperature was lowered, and the catalyst was filtered out.

[0040] Add saturated sodium hydroxide aqueous solution to the filtrate to adjust the pH to 13.00, add 4.0 g of 10% calcium hydroxide aqueous solution, stir and heat to 90°C, keep the temperature for reaction for 1.0 h, cool to room temperature, filter out the flocculated precipitate, and obtain pretreated wastewater.

[0041] The treatment effect is: COD removal rate is 79%, the content of 1,2-hexanediol wastewater after pretreatment is 0.008%, and the treated wastewater can be used for subsequent microbial treatment.

[0042] Comparative Example 1

[0043] The difference from Example 4 is that the catalyst used is conventional phosphotungstic acid, and the other conditions are the same as those in Example 4, specifically:

[0044] Take 500g of 1,2-hexanediol production wastewater and place it in a 1L three-necked flask, add 0.5g of conventional catalyst phosphotungstic acid, stir and heat to 65℃, add 2.5g of 30% hydrogen peroxide dropwise, continue the reaction for 2.5h, cool down and filter out the catalyst.

[0045] Add saturated sodium hydroxide aqueous solution to the filtrate to adjust the pH to 12.50, add 5.0 g of 10% calcium hydroxide aqueous solution, stir and heat to 85°C, keep the temperature for reaction for 1.5 hours, cool to room temperature, filter and obtain treated wastewater.

[0046] The treatment effect is: the wastewater COD removal rate is 3%, the content of 1,2-hexanediol in the treated wastewater is 0.040%, and the treated wastewater has an inhibitory effect on microorganisms and cannot be used for subsequent microbial biochemical treatment.

[0047] Comparative Example 2

[0048] The difference from Example 4 is that the preparation method of activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst is different, and other conditions are the same as in Example 4, specifically:

[0049] Weigh 5.0g of phosphotungstic acid into a beaker, add 50g of distilled water to dissolve, then stir and add 7.5g of 30% w / w hydrogen peroxide. Stir at room temperature for 30 minutes to obtain a peroxyphosphotungstic acid solution. Weigh 9.4g of hexadecyltrimethylammonium chloride into a three-necked flask, add 65g of ethanol, stir to dissolve, and then add 20.0g of activated carbon to obtain a hexadecyltrimethylammonium chloride ethanol solution. At room temperature, add the peroxyphosphotungstic acid solution dropwise to the hexadecyltrimethylammonium chloride ethanol solution. Heat to 78°C and reflux gently, stir for 6 hours, cool to 20°C, let stand for 18 hours, filter, rinse the filter cake with water and ethanol, respectively, and air dry the filter cake at 225°C for 4.5 hours to obtain the activated carbon-supported peroxyphosphotungstic acid quaternary ammonium salt catalyst.

[0050] Take 500 g of 1,2-hexanediol production wastewater and place it in a 1L three-necked flask, add 0.5 g of the catalyst prepared in the previous step, stir and heat to 65°C, add 2.5 g of 30% hydrogen peroxide dropwise, continue the reaction for 2.5 hours, cool down and filter out the catalyst.

[0051] Add saturated sodium hydroxide aqueous solution to the filtrate to adjust the pH to 12.50, add 5.0 g of 10% calcium hydroxide aqueous solution, stir and heat to 85°C, keep the temperature for reaction for 1.5 hours, cool to room temperature, filter out the flocculated precipitate, and obtain treated wastewater.

[0052] The treatment effect is: the wastewater COD removal rate is 16%, the content of 1,2-hexanediol in the wastewater after pretreatment is 0.032%, and the treated wastewater inhibits the growth of microorganisms and cannot be used for subsequent biochemical treatment.

[0053] As can be seen from Comparative Examples 1 and 2, when the catalyst of Comparative Example 1 uses conventional phosphotungstic acid, the treatment effect is poor, and the treated wastewater cannot be used for subsequent microbial biochemical treatment. In Comparative Example 2, when hexadecyltrimethylammonium chloride ethanol is used instead of benzyltriethylammonium chloride ethanol solution to prepare activated carbon-supported peroxyphosphomolybdic acid quaternary ammonium salt catalyst, the COD and 1,2-hexanediol treatment effect of the wastewater is poor, and the treated wastewater cannot be used for subsequent microbial biochemical treatment. The embodiment of the present invention uses activated carbon-supported peroxyphosphotungstic acid quaternary ammonium salt catalyst with high oxidation catalytic activity, and further flocculation treatment with calcium hydroxide can effectively remove residual 1,2-hexanediol in 1,2-hexanediol production wastewater.

Claims

1. A method for treating 1,2-hexanediol production wastewater by catalytic oxidation, characterized in that: A catalyst and hydrogen peroxide are added to the wastewater to be treated for oxidation reaction, and a calcium salt flocculant is added under alkaline conditions for flocculation and precipitation, thereby achieving the removal of 1,2-hexanediol and COD; The catalyst is an activated carbon-supported quaternary ammonium peroxyphosphotungstate catalyst; The preparation method of the activated carbon-supported peroxyphosphotungstic acid quaternary ammonium salt catalyst comprises the following steps: dissolving phosphotungstic acid in distilled water, adding hydrogen peroxide to obtain a peroxyphosphotungstic acid solution; simultaneously adding benzyltriethylammonium chloride to ethanol, and then adding activated carbon to obtain a benzyltriethylammonium chloride ethanol solution; adding the peroxyphosphotungstic acid solution to the benzyltriethylammonium chloride ethanol solution, maintaining the temperature and stirring, cooling and allowing to stand, filtering, and drying to obtain the activated carbon-supported peroxyphosphotungstic acid quaternary ammonium salt catalyst.

2. The method for treating 1,2-hexanediol production wastewater by catalytic oxidation according to claim 1, characterized in that: Add a catalyst to the wastewater to be treated, add hydrogen peroxide dropwise at 60~70℃, react for 2~3h, filter out the catalyst, adjust the pH to 12.0~13.0, add a calcium salt flocculant, react at 80~90℃ for 1~2h, cool to room temperature, and filter out the precipitate to achieve the removal of 1,2-hexanediol and COD.

3. The method for treating 1,2-hexanediol production wastewater by catalytic oxidation according to claim 2, characterized in that: A catalyst was added to the wastewater to be treated, and hydrogen peroxide was added dropwise at 65°C. After reacting for 2.5 hours, the catalyst was filtered out, the pH was adjusted to 12.5, a calcium salt flocculant was added, and the reaction was carried out at 85°C for 1.5 hours. After cooling to room temperature, the precipitate was filtered out to remove 1,2-hexanediol and COD.

4. The method for treating 1,2-hexanediol production wastewater by catalytic oxidation according to claim 1 or 2, characterized in that: The amount of catalyst added is 0.05-0.15% of the mass of the wastewater to be treated; The amount of hydrogen peroxide added is 0.4~0.6% of the mass of the wastewater to be treated; The amount of calcium salt flocculant aqueous solution added is 0.8~1.2% of the mass of the wastewater to be treated.

5. The method for treating 1,2-hexanediol production wastewater by catalytic oxidation according to claim 4, characterized in that: The calcium salt flocculant is one or more of calcium chloride, calcium hydroxide and calcium oxide.

6. The method for treating 1,2-hexanediol production wastewater by catalytic oxidation according to claim 1, characterized in that: During the preparation of activated carbon-supported peroxyphosphotungstic acid quaternary ammonium salt catalyst, the amount of distilled water used is 8 to 12 times the mass of phosphotungstic acid, and the amount of hydrogen peroxide used is 1.3 to 1.7 times the mass of phosphotungstic acid; The amount of benzyltriethylammonium chloride used is 1.2 to 1.4 times the mass of phosphotungstic acid, the amount of ethanol used is 8 to 12 times the mass of benzyltriethylammonium chloride, and the amount of activated carbon used is 3.5 to 4.5 times the mass of phosphotungstic acid.

7. The method for treating 1,2-hexanediol production wastewater by catalytic oxidation according to claim 1, characterized in that: During the preparation process of the activated carbon-supported peroxyphosphotungstate quaternary ammonium salt catalyst, the insulation temperature is 70~78°C and the insulation time is 4~8h; the temperature is lowered to 15~25°C and allowed to stand for 12~24h, and the drying temperature is 220~230°C and the drying time is 4~5h.

8. The method for treating 1,2-hexanediol production wastewater by catalytic oxidation according to claim 6, characterized in that: During the preparation of activated carbon-supported peroxyphosphotungstic acid quaternary ammonium salt catalyst, the amount of distilled water used was 10 times the mass of phosphotungstic acid, and the amount of hydrogen peroxide used was 1.5 times the mass of phosphotungstic acid; The amount of benzyltriethylammonium chloride used is 1.3 times the mass of phosphotungstic acid, the amount of ethanol used is 10 times the mass of benzyltriethylammonium chloride, and the amount of activated carbon used is 4.0 times the mass of phosphotungstic acid.

9. The method for treating 1,2-hexanediol production wastewater by catalytic oxidation according to claim 7, characterized in that: During the preparation process of the activated carbon-supported peroxyphosphotungstate quaternary ammonium salt catalyst, the holding temperature is 78°C and the holding time is 6 hours; the temperature is lowered to 20°C and allowed to stand for 18 hours, and the drying temperature is 225°C and the drying time is 4.5 hours.