CN107434285A - A kind of preparation method for being used to slow down the modified polyaluminium chloride of secondary fiber papermaking waste water hyperfiltration treatment fouling membrane - Google Patents

Abstract

The invention discloses a preparation method of modified polyaluminum chloride used for slowing down membrane fouling in ultrafiltration treatment of secondary fiber papermaking wastewater. The method comprises the following steps: (1) dissolving aluminum chloride and calcium chloride in deionized water, reacting under heating and stirring, taking the upper layer solution for aging to obtain liquid polyaluminum chloride; (2) dissolving sodium silicate After dissolving in deionized water, adjust the pH value to obtain a polysilicate solution; (3) Add the polysilicate solution to the liquid polyaluminium chloride, ripen, and dry to obtain ultrafiltration treatment for slowing down secondary fiber papermaking wastewater Membrane fouling of modified polyaluminium chloride. The modified polyaluminum chloride prepared by the method of the present invention is used to slow down the membrane fouling of the secondary fiber papermaking wastewater ultrafiltration treatment. While effectively reducing the membrane fouling, it also significantly reduces the turbidity of the effluent, improves the quality of the effluent, and maintains the membrane pollution. The flux improves the membrane separation efficiency, prolongs the service life of the membrane equipment, and improves the treatment efficiency of the membrane equipment.

Description

A modified polymer for slowing membrane fouling in ultrafiltration treatment of secondary fiber papermaking wastewater The preparation method of aluminum chloride

technical field

The invention belongs to the technical field of sewage treatment, and in particular relates to a preparation method of modified polyaluminum chloride used for slowing down membrane pollution of secondary fiber papermaking wastewater ultrafiltration treatment.

Background technique

Since the 1990s in my country, the proportion of secondary fibers in papermaking pulp has increased year by year. Compared with primary fibers, the use of secondary fibers can save resources and protect the environment, and has higher economic and social benefits. Due to the complex impurities contained in waste paper and the need to add various chemicals in the pulping and papermaking process, the wastewater from secondary fiber papermaking is complex and difficult to treat. There are three main pollutants in secondary fiber wastewater: COD mainly from lignin and hemicellulose in wastewater, TSS mainly formed by fine fibers and inorganic fillers, and chroma formed by inks and dyes. Therefore, how to deal with the secondary fiber wastewater generated in large quantities has become one of the problems to be solved urgently in the pulp and paper industry.

According to the country's strict discharge requirements for wastewater, most of them currently use a three-stage treatment process. Primary treatment uses physical or chemical methods to remove suspended particles or colloids in water; secondary treatment uses anaerobic or aerobic biological methods; tertiary treatment uses physical or chemical methods for advanced treatment, including the Fenton method , imitation enzyme catalyzed condensation treatment method, ecological method and membrane separation, among which membrane separation technology has become one of the most attractive water treatment technologies due to its excellent retention performance and easy operation. However, when the membrane separation technology is directly applied to the secondary treatment of effluent, the deposition of inorganic substances, the adsorption of organic molecules, the deposition of particulate matter, and the adhesion and growth of microorganisms will occur on the surface of the membrane or in the pores of the membrane, resulting in serious membrane fouling. The attenuation of membrane flux greatly restricts the development of membrane separation technology. In order to slow down membrane fouling, maintain its flux, and prolong membrane service life, it is necessary to introduce pretreatment.

Pretreatment refers to adding one or several substances to the raw material liquid, which is the change of the properties or solutes of the raw material liquid or pretreatment measures such as filtration and precipitation. Pretreatment technology should be able to effectively improve the quality of influent water, so as to achieve the purpose of protecting the ultrafiltration membrane. At present, the main pretreatment methods include centrifugation, prefiltration, sterilization, adsorption, oxidation and coagulation, among which coagulation as pretreatment can effectively slow down the occurrence of membrane fouling. Modified polyaluminum chloride has excellent charge neutralization and adsorption bridging capabilities, and can bridge fine floc particles such as tiny microorganisms and colloids to form larger flocs, preventing fine particles from clogging membrane pores, and can Effectively slow down membrane fouling caused by fine particles, improve membrane treatment efficiency, and improve effluent quality.

Using the coagulation process of modified polyaluminum chloride as the pre-membrane pretreatment process of secondary fiber papermaking wastewater can effectively prevent the decline of membrane flux, slow down membrane fouling and greatly prolong the service life of ultrafiltration membrane equipment , and improve the effluent quality of secondary fiber papermaking wastewater.

Contents of the invention

The purpose of the present invention is to address the deficiencies in the prior art, to provide a method for preparing a modified polyaluminum chloride used to slow down the membrane fouling of secondary fiber papermaking wastewater ultrafiltration treatment, the prepared modified polyaluminum chloride is used for Slow down membrane fouling and maintain membrane flux during ultrafiltration treatment of secondary fiber papermaking wastewater, prolong the service life of membrane equipment, and improve the treatment efficiency of membrane equipment.

The purpose of the present invention is achieved through the following technical solutions.

A preparation method of modified polyaluminum chloride for slowing down membrane fouling of secondary fiber papermaking wastewater ultrafiltration treatment, comprising the following steps:

(1) dissolving aluminum chloride and calcium chloride in deionized water, and reacting under heating and stirring; after the reaction is finished, take the upper layer solution for aging to obtain liquid polyaluminum chloride;

(2) After sodium silicate is dissolved in deionized water, the pH value is adjusted to obtain a polysilicate solution;

(3) Add polysilicic acid solution to liquid polyaluminum chloride, ripen at room temperature, and dry after ripening to obtain modified polyaluminum chloride (PAC) for slowing down membrane fouling of secondary fiber papermaking wastewater ultrafiltration treatment .

Further, in step (1), the aluminum chloride and calcium chloride are added in a molar ratio of 1:0.7-1.2.

Further, in step (1), the aluminum chloride used includes commercially available analytically pure crystalline aluminum chloride.

Further, in step (1), the solid-to-liquid ratio of the aluminum chloride to deionized water is 10-20:100-150 g/mL.

Further, in step (1), the reaction is carried out at 80-85° C. for 40-45 minutes.

Further, in step (1), the aging is stirring at 55-65° C. for 4-5 hours.

Further, in step (2), the adjustment of the pH value is to adjust the pH value to 5-6. After the pH value is adjusted to 5-6, a light blue color appears and the polymerization is stopped to obtain a polysilicic acid solution.

Further, in step (2), the solid-to-liquid ratio of the sodium silicate to deionized water is 5-6:50-75 g/mL.

Further, in step (3), the amount of the liquid polyaluminum chloride and the polysilicate solution is added at a molar ratio of Al/Si=0.7-1, preferably 0.7-0.9.

Further, in step (3), the aging is stirring at room temperature for 1-1.5 hours.

The modified polyaluminum chloride prepared by the method of the present invention is suitable for membrane treatment of various pulp and papermaking wastewater, especially for pulp and papermaking wastewater that is secondary fiber papermaking wastewater after biological treatment, and is especially suitable for membrane treatment as ultrafiltration Membrane treatment is a membrane treatment process, and the effect of synergistic use with cationic polyacrylamide (CPAM) is better.

Compared with prior art, the present invention has following advantage and beneficial effect:

The modified polyaluminum chloride prepared by the method of the present invention is used to slow down the membrane fouling of the secondary fiber papermaking wastewater ultrafiltration treatment. While effectively reducing the membrane fouling, it also significantly reduces the turbidity of the effluent, improves the quality of the effluent, and maintains the membrane pollution. The flux improves the membrane separation efficiency, slows down the fouling of the ultrafiltration membrane, prolongs the service life of the membrane equipment, and improves the treatment efficiency of the membrane equipment.

detailed description

The present invention will be described in further detail below in conjunction with specific examples, which are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

The experimental methods used in the following examples are conventional methods unless otherwise specified; the materials and reagents used are commercially obtained reagents and materials unless otherwise specified.

Example 1

The preparation of modified polyaluminum chloride specifically comprises the steps:

(1) Dissolve 10g of commercially available crystalline aluminum chloride and 5.83g of calcium chloride (the molar ratio of aluminum chloride to calcium chloride is 1:0.7) in 100mL of deionized water, and react under heating and stirring at 80°C for 40min; the reaction is over Afterwards, take the upper layer solution and stir it at 55°C for 4 hours to mature to obtain liquid polyaluminum chloride;

(2) After dissolving 5g of sodium silicate in 50mL of deionized water, adjust the pH value to 5 to obtain a polysilicate solution;

(3) Add 3.2g of polysilicate solution (molar ratio Al/Si=0.7) to 5.4g of liquid polyaluminum chloride, stir at room temperature for 1.2h for aging, dry after aging to prepare a solid, and obtain Modified polyaluminum chloride (PAC) for ultrafiltration treatment of membrane fouling in fiber and papermaking wastewater.

The prepared modified PAC is used to slow down the membrane pollution of secondary fiber papermaking wastewater ultrafiltration treatment, including the following steps:

Measure 200mL of secondary fiber papermaking wastewater after biological treatment, adjust the water sample to pH 9, add 2mL of commercially available polyaluminum chloride PAC to dissolve and prepare 100mg/L solution and modified polyaluminum chloride PAC to dissolve and prepare 100mg/L solution respectively. L solution was stirred for 10 minutes under the condition of rotating speed of 300r/min, and after standing for precipitation for 30 minutes, it entered the ultrafiltration membrane treatment system and operated for 10 minutes.

The system flux decay of adding commercially available polyaluminum chloride PAC is 45.3%, and the waste water TSS is reduced to 147mg/L by 246mg/L, and TSS removal rate is 40.24%; Adding the system flux decay of modified polyaluminum chloride PAC is 65.4%, the wastewater TSS was reduced from 246mg/L to 20mg/L, and the TSS removal rate was 93.90%.

The above results show that the prepared modified polyaluminum chloride has very significant turbidity removal performance.

Example 2

The preparation of modified polyaluminum chloride specifically comprises the steps:

(1) Dissolve 13.2g of commercially available crystalline aluminum chloride and 11g of calcium chloride (the molar ratio of aluminum chloride to calcium chloride is 1:1) in 130mL of deionized water, and react under heating and stirring at 84°C for 42min; the reaction is over Afterwards, take the upper layer solution and stir at 60°C for 4.5 hours to mature to obtain liquid polyaluminum chloride;

(2) After dissolving 5.5g of sodium silicate in 65mL of deionized water, adjust the pH value to 5.1 to obtain a polysilicic acid solution;

(3) Add 3.7g of polysilicate solution (molar ratio Al/Si=0.8) to 6.2g of liquid polyaluminum chloride, stir at room temperature for 1 hour for aging, dry after aging to prepare a solid, and obtain a secondary fiber for slowing down Modified polyaluminum chloride (PAC) for ultrafiltration treatment of membrane fouling in papermaking wastewater.

The prepared modified PAC is used to slow down the membrane pollution of secondary fiber papermaking wastewater ultrafiltration treatment, including the following steps:

(1) Measure 200mL of secondary fiber papermaking wastewater after biological treatment, adjust the water sample to pH 9, add 2mL of commercially available polyaluminum chloride PAC to dissolve and prepare 100mg/L solution and modified polyaluminum chloride PAC to dissolve and prepare The 100mg/L solution was stirred for 10 minutes at a speed of 300r/min, stirred for 20 minutes at a speed of 30r/min, and left to settle for 30 minutes before entering the ultrafiltration membrane treatment system and running for 10 minutes.

(2) After adding commercially available polyaluminum chloride PAC and modified polyaluminum chloride PAC, add 4 mL of 1 mg/L cationic polyacrylamide CPAM, and the rest of the conditions are the same as step (1).

Table 1 shows the effects of different treatment methods on the membrane fouling and effluent quality of the ultrafiltration system.

Table 1 Effect of different treatments on membrane fouling and effluent quality of ultrafiltration system

As can be seen from Table 1, the system flux decay of adding commercially available polyaluminum chloride PAC is 50.2%, the wastewater TSS is reduced from 246mg/L to 94mg/L, and the TSS removal rate is 61.79%; The system flux attenuation was 70.1%, the wastewater TSS was reduced from 246mg/L to 4mg/L, and the TSS removal rate was 98.37%. The turbidity of the wastewater slows down the degree of fouling of the membrane.

Example 3

The preparation of modified polyaluminum chloride specifically comprises the steps:

(1) Dissolve 20g of commercially available crystalline aluminum chloride and 20g of calcium chloride (the molar ratio of aluminum chloride to calcium chloride is 1:1.2) in 150mL of deionized water, and react under stirring at 85°C for 45min; , take the upper layer solution and stir at 65°C for 5 hours to mature to obtain liquid polyaluminum chloride;

(2) After dissolving 6g of sodium silicate in 75mL of deionized water, adjust the pH value to 6 to obtain a polysilicate solution;

(3) Add 4.6g of polysilicic acid solution (molar ratio Al/Si=1) to 7.8g of liquid polyaluminum chloride, stir at room temperature for 1.5h for aging, dry after aging to prepare a solid, and obtain a solution for slowing down the secondary Modified polyaluminum chloride (PAC) for ultrafiltration treatment of membrane fouling in fiber and papermaking wastewater.

In step (1), calcium nitrate and calcium oxide are respectively used instead of calcium chloride, and steps (2) and (3) are the same to prepare different modified polyaluminum chlorides.

The prepared modified PAC is used to slow down the membrane pollution of secondary fiber papermaking wastewater ultrafiltration treatment, including the following steps:

Measure 200mL of secondary fiber papermaking wastewater after biological treatment, adjust the water sample to pH 9, add 2mL of the 100mg/L solution prepared by dissolving the above-mentioned modified polyaluminum chloride, stir for 10 minutes at a speed of 300r/min, and then Add 4 mL of 1 mg/L cationic polyacrylamide CPAM, stir for 20 minutes at a speed of 30 r/min, let it settle for 30 minutes, enter the ultrafiltration membrane treatment system, and run for 10 minutes.

Table 2 shows the results of different modified polyaluminum chlorides prepared to slow down membrane fouling in ultrafiltration treatment of secondary fiber papermaking wastewater.

Table 2 Effects of different aluminum chloride polymerization methods on membrane fouling and effluent quality

It can be seen from Table 2 that compared with calcium nitrate and calcium oxide, the modified polyaluminum chloride obtained by the polymerization of crystalline aluminum chloride and calcium chloride has very significant turbidity removal performance.

Example 4

The preparation of modified polyaluminum chloride specifically comprises the steps:

(1) Dissolve commercially available crystalline aluminum chloride and calcium chloride in 130mL deionized water, and react under heating and stirring at 84°C for 42min; Aluminum;

(2) After dissolving 5.5g of sodium silicate in 65mL of deionized water, adjust the pH value to 5.1 to obtain a polysilicic acid solution;

(3) Add 3.7g of polysilicate solution (molar ratio Al/Si=0.8) to 6.2g of liquid polyaluminum chloride, stir at room temperature for 1 hour for aging, dry after aging to prepare a solid, and obtain a secondary fiber for slowing down Modified polyaluminum chloride (PAC) for ultrafiltration treatment of membrane fouling in papermaking wastewater.

In step (1), the molar ratios of aluminum chloride and calcium chloride are respectively 1:0.7, 1:0.9, 1:1, 1:1.1, 1:1.2, and the steps (2) and (3) are the same to obtain Different modified polyaluminum chlorides.

The prepared modified PAC is used to slow down the membrane pollution of secondary fiber papermaking wastewater ultrafiltration treatment, including the following steps:

Measure 200mL of secondary fiber papermaking wastewater after biological treatment, adjust the water sample to pH 9, add 2mL of the 100mg/L solution prepared by dissolving the above-mentioned modified polyaluminum chloride, stir for 10 minutes at a speed of 300r/min, and then Add 4 mL of 1 mg/L cationic polyacrylamide CPAM, stir for 20 minutes at a speed of 30 r/min, let it settle for 30 minutes, enter the ultrafiltration membrane treatment system, and run for 10 minutes.

Table 3 shows the results of prepared different modified polyaluminum chlorides for reducing membrane fouling in ultrafiltration treatment of secondary fiber papermaking wastewater.

Table 3 Effect of molar ratio of aluminum chloride to calcium chloride on membrane fouling and effluent quality

It can be seen from Table 3 that when the molar ratio of crystalline aluminum chloride to calcium chloride is 1:1, the modified polyaluminum chloride obtained by polymerization has very significant turbidity removal performance.

Example 5

The preparation of modified polyaluminum chloride specifically comprises the steps:

(1) Dissolve 13.2g of commercially available crystalline aluminum chloride and 11g of calcium chloride (the molar ratio of aluminum chloride to calcium chloride is 1:1) in 130mL of deionized water, and react under heating and stirring at 84°C for 42min; the reaction is over Afterwards, take the upper layer solution and stir at 60°C for 4.5 hours to mature to obtain liquid polyaluminum chloride;

(2) After dissolving 5.5g of sodium silicate in 65mL of deionized water, adjust the pH value to 5.1 to obtain a polysilicic acid solution;

(3) Add polysilicic acid solution to liquid polyaluminium chloride, stir at room temperature for 1 hour to ripen, dry after ripening to prepare a solid, and obtain a modified polysilicic acid solution for slowing down the fouling of the secondary fiber papermaking wastewater ultrafiltration treatment membrane. Aluminum (PAC).

In step (3), the addition amount of polyaluminum chloride and polysilicic acid is added respectively according to molar ratio Al/Si=0.7, Al/Si=0.8, Al/Si=0.9, Al/Si=1, step (1) , (2) are the same, and different modified polyaluminum chlorides are prepared.

The prepared modified PAC is used to slow down the membrane pollution of secondary fiber papermaking wastewater ultrafiltration treatment, including the following steps:

Measure 200mL of secondary fiber papermaking wastewater after biological treatment, adjust the water sample to pH 9, add 2mL of the 100mg/L solution prepared by dissolving the above-mentioned modified polyaluminum chloride, stir for 10 minutes at a speed of 300r/min, and then Add 4 mL of 1 mg/L cationic polyacrylamide CPAM, stir for 20 minutes at a speed of 30 r/min, let it settle for 30 minutes, enter the ultrafiltration membrane treatment system, and run for 10 minutes.

Table 4 shows the results of different modified polyaluminum chlorides prepared to slow down the membrane fouling of secondary fiber papermaking wastewater ultrafiltration treatment.

Table 4 Effect of molar ratio of polyaluminum chloride to polysilicate on membrane fouling and effluent quality

It can be seen from Table 4 that when the molar ratio of polyaluminum chloride to polysilicate is Al/Si=0.8, the modified polyaluminum chloride obtained by polymerization has a very significant turbidity removal performance.

Claims (9)

1. a kind of preparation method for being used to slow down the modified polyaluminium chloride of secondary fiber papermaking waste water hyperfiltration treatment fouling membrane, its It is characterised by, comprises the following steps：

（1）Aluminium chloride and calcium chloride are dissolved in deionized water, reacted under heating stirring；After reaction terminates, take upper strata molten Liquid is cured, and obtains liquid polymerization aluminium chloride；

（2）After sodium metasilicate is dissolved in into deionized water, pH value is adjusted, obtains polysilicon acid solution；

（3）Polysilicon acid solution is added into liquid polymerization aluminium chloride, is cured, is dried after curing at room temperature, obtains being used to subtract The modified polyaluminium chloride of slow secondary fiber papermaking waste water hyperfiltration treatment fouling membrane.

A kind of 2. modified poly for being used to slow down secondary fiber papermaking waste water hyperfiltration treatment fouling membrane according to claim 1 The preparation method of aluminium chloride, it is characterised in that step（1）In, the amount of the aluminium chloride and calcium chloride in molar ratio 1:0.7~1.2 Addition.

A kind of 3. modified poly for being used to slow down secondary fiber papermaking waste water hyperfiltration treatment fouling membrane according to claim 1 The preparation method of aluminium chloride, it is characterised in that step（1）In, the solid-to-liquid ratio of the aluminium chloride and deionized water is 10 ~ 20：100 ~150 g/mL。

A kind of 4. modified poly for being used to slow down secondary fiber papermaking waste water hyperfiltration treatment fouling membrane according to claim 1 The preparation method of aluminium chloride, it is characterised in that step（1）In, the reaction is to react 40 ~ 45min at 80 ~ 85 DEG C.

A kind of 5. modified poly for being used to slow down secondary fiber papermaking waste water hyperfiltration treatment fouling membrane according to claim 1 The preparation method of aluminium chloride, it is characterised in that step（1）In, the curing is 4 ~ 5h of stirring at 55 ~ 65 DEG C.

A kind of 6. modified poly for being used to slow down secondary fiber papermaking waste water hyperfiltration treatment fouling membrane according to claim 1 The preparation method of aluminium chloride, it is characterised in that step（2）In, the regulation pH value is to adjust pH value to 5 ~ 6.

A kind of 7. modified poly for being used to slow down secondary fiber papermaking waste water hyperfiltration treatment fouling membrane according to claim 1 The preparation method of aluminium chloride, it is characterised in that step（2）In, the solid-to-liquid ratio of the sodium metasilicate and deionized water is 5 ~ 6：50~75 g/mL。

A kind of 8. modified poly for being used to slow down secondary fiber papermaking waste water hyperfiltration treatment fouling membrane according to claim 1 The preparation method of aluminium chloride, it is characterised in that step（3）In, the amount of the liquid aluminium polychloride and polysilicon acid solution is massaged You add than Al/Si=0.7 ~ 1.

A kind of 9. modified poly for being used to slow down secondary fiber papermaking waste water hyperfiltration treatment fouling membrane according to claim 1 The preparation method of aluminium chloride, it is characterised in that step（3）In, the curing is that 1 ~ 1.5 h is stirred at room temperature.