阅读说明：本技术 一种超支化木质素基阳离子淀粉多功能复合型絮凝剂及其制备与应用 (Hyperbranched lignin-based cationic starch multifunctional composite flocculant and preparation and application thereof ) 是由 刘伟峰 曾佳 邱学青 黄锦浩 杨东杰 张冬桥 楼宏铭 于 2021-07-16 设计创作，主要内容包括：本发明公开了一种超支化木质素基阳离子淀粉多功能复合型絮凝剂及其制备与应用。本发明首先通过烷烃桥联反应提高木质素的分子量,然后对高分子量木质素进行羧甲基化改性,最后使用工业级阳离子淀粉为原料,通过交联剂,与改性的木质素进行接枝反应,合成具有优良絮凝性能的超支化木质素基阳离子淀粉多功能复合型絮凝剂。本发明方法有效地克服了木质素基絮凝剂的合成步骤繁琐、成本高、不可完全降解、产物分子量低、絮凝效率低以及絮凝范围单一的问题。(The invention discloses a hyperbranched lignin-based cationic starch multifunctional composite flocculant and preparation and application thereof. According to the invention, firstly, the molecular weight of lignin is improved through alkane bridging reaction, then carboxymethylation modification is carried out on the high molecular weight lignin, and finally, industrial cationic starch is used as a raw material and is subjected to grafting reaction with the modified lignin through a cross-linking agent, so that the hyperbranched lignin-based cationic starch multifunctional compound flocculant with excellent flocculation performance is synthesized. The method effectively solves the problems of complicated synthetic steps, high cost, incomplete degradation, low product molecular weight, low flocculation efficiency and single flocculation range of the lignin-based flocculant.)

1. A preparation method of a hyperbranched lignin-based cationic starch multifunctional composite flocculant is characterized by comprising the following steps:

(1) preparing lignin into an alkali solution with the pH value of 11-13, heating to 50-110 ℃, adding a cross-linking agent, reacting for 2-4 hours, and obtaining high molecular weight lignin after the reaction is finished;

(2) preparing high molecular weight lignin into an alkali solution, heating to 40-80 ℃, adding a carboxylation modifier, reacting for 2-4 hours, and finally performing rotary evaporation and drying to obtain the high molecular weight lignin with high carboxymethyl content;

(3) adding ultrapure water into cationic starch, heating for gelatinization, then adding a cross-linking agent, reacting for 1-3 h, adding an alkalizing agent after the reaction is finished, adjusting the pH of the solution to 11-13, adding the high-molecular-weight lignin with high carboxymethyl content in the step (2), reacting for 1-3 h at 50-80 ℃, and purifying after the reaction is finished to obtain the hyperbranched lignin-based cationic starch multifunctional composite flocculant.

2. The preparation method of the hyperbranched lignin-based cationic starch multifunctional composite flocculant according to claim 1, wherein the mass ratio of the lignin to the crosslinking agent in the step (1) is 10: 1-10: 3;

the cross-linking agent in the step (1) is at least one of 1, 6-dibromohexane, epichlorohydrin and formaldehyde.

3. The preparation method of the hyperbranched lignin-based cationic starch multifunctional composite flocculant according to claim 1, wherein the mass ratio of the high molecular weight lignin and the carboxylated modifier in the step (2) is 10: 12.3-10: 18.2;

and (3) the carboxylation modifier in the step (2) is at least one of sodium monochloroacetate, sodium bromoacetate and itaconic acid.

4. The preparation method of the hyperbranched lignin-based cationic starch multifunctional composite flocculant according to claim 1, wherein the mass ratio of the cationic starch, the crosslinking agent and the high-molecular-weight lignin with high carboxymethyl content in the step (3) is (1-3): (0.5-3): 1;

the cross-linking agent in the step (3) is at least one of 1, 6-dibromohexane, epichlorohydrin and formaldehyde;

the cationic starch in the step (3) is at least one of corn cationic starch, cassava cationic starch, waxy starch and potato cationic starch, and the substitution degree is 0.02-0.1.

5. The preparation method of the hyperbranched lignin-based cationic starch multifunctional composite flocculant according to claim 1, wherein the lignin in the step (1) is at least one of byproduct alkali lignin obtained by alkali pulping in paper industry, enzymatic hydrolysis lignin extracted from ethanol prepared by fermentation of lignocellulose, organic solvent lignin extracted from lignocellulose by an organic solvent method and byproduct lignosulfonate prepared by sulfite method; wherein the byproduct lignosulfonate of the sulfite pulping is at least one of calcium lignosulfonate, sodium lignosulfonate and lignosulfonic acid.

6. The preparation method of the hyperbranched lignin-based cationic starch multifunctional composite flocculant according to claim 1, wherein the mass concentration of lignin in the alkali solution in the step (1) is 10-33%;

the mass concentration of the high molecular weight lignin in the alkali solution in the step (2) is 10-30%;

the mass concentration of the cationic starch in the ultrapure water in the step (3) is 1-10%;

and (3) adding the high-molecular-weight lignin with high carboxymethyl content in an alkali solution form, wherein the mass concentration of the high-molecular-weight lignin with high carboxymethyl content in the alkali solution is 5-10%, and the alkali solution is 2.0-5.0 mol/L of sodium hydroxide and/or potassium hydroxide aqueous solution.

7. The preparation method of the hyperbranched lignin-based cationic starch multifunctional composite flocculant according to claim 1, wherein the gelatinization temperature in the step (3) is 50-80 ℃ and the time is 30-60 min.

8. The preparation method of the hyperbranched lignin-based cationic starch multifunctional composite flocculant according to claim 1, wherein the alkali used in the alkali solution in the steps (1) and (2) and the alkalizing agent in the step (3) are both sodium hydroxide and/or potassium hydroxide, the alkalizing agent in the step (3) is added in the form of an aqueous solution, and the concentrations of the alkali solution in the steps (1) and (2) and the alkalizing agent aqueous solution in the step (3) are both 2.0-5.0 mol/L.

9. The hyperbranched lignin-based cationic starch multifunctional composite flocculant prepared by the method of any one of claims 1 to 8.

10. The use of the hyperbranched lignin-based cationic starch multifunctional composite flocculant of claim 9 in wastewater treatment.

Technical Field

The invention belongs to the technical field of flocculants, and particularly relates to a hyperbranched lignin-based cationic starch multifunctional composite flocculant and preparation and application thereof.

Background

In recent years, with the rapid development of industries, a large amount of industrial wastewater and domestic wastewater are generated in the industries of smelting, electroplating, mining, papermaking, electronics and the like, and the wastewater not only contains various inorganic and organic pollutants, but also contains various heavy metal pollutants. As the key of wastewater treatment, the most common method for improving the water quality treatment efficiency at home and abroad is flocculation sedimentation, and the common flocculant is acrylamide polymer PAM [ ACS Sustainable chem. Eng.3(2015)3253-3261 ]. At present, the linear ultrahigh molecular weight cationic polyacrylamide flocculant is most widely applied, but the flocculant has high viscosity and long dissolution time when in use, ionic monomers are randomly distributed on a polymer chain, the effective utilization rate of charges is low, and the flocculant has the problems of high production cost, high technical difficulty, nondegradable property and the like. Therefore, the development of novel degradable cationic flocculant is one of the keys for improving the sewage treatment technology, and also meets the requirement of high value of the traditional product.

The biomass raw material is green, nontoxic and degradable, and the environment pollution can be reduced by preparing the green flocculant from the biomass raw material. Wang et al graft-polymerize kraft lignin with 2-methacryloyloxyethyl trimethyl ammonium chloride (METAC) under acidic conditions to synthesize a cationic lignin polymer, and use the polymer to flocculate a 0.25 wt% kaolin suspension with a higher treatment efficiency than unmodified lignin or METAC homopolymer [ Ind.Eng.chem.Res.2018,57(19) 6595-. Plum et al prepared lignosulfonate from papermaking waste water, reacted with acrylamide and potassium persulfate at certain temperature to obtain graft copolymerization product for treating chromium-containing electroplating waste water [ industrial water treatment 200929 (11)28-31 ]. From the existing literature reports, the application of lignin-based flocculant prepared by using lignin as a raw material is more and more concerned. However, the lignin-based flocculant adopts a Grafting strategy of Grafting from, so that the Grafting efficiency is low, the product structure is uncontrollable, and the flocculation efficiency is low.

Patent CN109280174B discloses a hyperbranched lignin grafted cationic polyacrylamide flocculant and a preparation method thereof. In the method, acrylamide and cationic monomer are copolymerized to obtain a cationic polyacrylamide prepolymer with halogen atoms at the tail end; and then, Grafting and modifying the pre-synthesized cationic polyacrylamide prepolymer and lignin by adopting a Grafting to Grafting process to synthesize the hyperbranched lignin-grafted cationic polyacrylamide flocculant with excellent flocculation performance. The invention overcomes the problems of low activity, low molecular weight, uncontrollable structure and the like in the traditional in-situ grafting free radical polymerization reaction on lignin, and the flocculation efficiency of the obtained hyperbranched lignin-grafted cationic polyacrylamide flocculant is greatly improved. However, the lignin-based flocculant prepared by the method still needs to use acrylamide and an expensive cationic reagent to perform free radical polymerization reaction and then perform grafting reaction, the synthetic process requirement is high, the steps are complicated, and especially the raw materials cannot be completely degradable. In addition, the molecular weight of the lignin is low, and the obtained grafted product only has a single flocculation function and cannot synchronously flocculate and remove pollutants such as inorganic colloidal particles, heavy metal ions and the like.

Wu et al prepared three starch-based flocculants with different chain structures and charge properties by cationic monomer graft copolymerization, and used for flocculation of Humic Acid (HA), found that the starch-based flocculants with branched structures have better flocculation effects than linear starch-based flocculants [ Water Res.96(2016)126-135 ]. However, the branched grafting has low efficiency, uncontrollable structure, low overall flocculation efficiency and high cost. At present, cationic starch serving as a flocculating agent generally has the problems of poor solubility, difficulty in realizing a branched structure, low effective charge utilization rate, low flocculation efficiency and the like, and simultaneously, the active functional group of the starch-based flocculating agent is single, so that the starch-based flocculating agent only has single flocculation capacity and cannot synchronously flocculate and remove pollutants such as inorganic colloidal particles, heavy metal ions and the like.

Disclosure of Invention

In order to overcome the defects and shortcomings in the prior art, the invention mainly aims to provide a preparation method of a hyperbranched lignin-based cationic starch multifunctional composite flocculant.

The invention firstly improves the molecular weight of lignin by alkane bridging reaction, and then utilizes a plurality of active functional groups of the lignin such as hydroxyl, carboxyl, methoxyl and the like to Cu²⁺Has good adsorption capacity, further performs carboxymethylation modification on lignin, introduces more carboxyl groups on lignin molecules, and improves the Cu content of grafted products²⁺The adsorption flocculation capacity of (1); then directly using industrial cationic starch as a raw material, and performing graft reaction with modified lignin through a cross-linking agent to synthesize the hyperbranched lignin-based cationic starch multifunctional composite flocculant with excellent flocculation performance. The method effectively solves the problems of complicated synthetic steps, high cost, incomplete degradation, low product molecular weight, low flocculation efficiency and single flocculation range of the lignin-based flocculant.

The invention also aims to provide the hyperbranched lignin-based cationic starch multifunctional composite flocculant prepared by the method.

The invention further aims to provide application of the hyperbranched lignin-based cationic starch multifunctional composite flocculant.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a hyperbranched lignin-based cationic starch multifunctional composite flocculant comprises the following steps:

(1) preparing lignin into an alkali solution with the pH value of 11-13, heating to 50-110 ℃, adding a cross-linking agent, reacting for 2-4 hours, and obtaining high molecular weight lignin (LEL) after the reaction is finished;

(2) preparing high molecular weight lignin into an alkali solution, heating to 40-80 ℃, adding a carboxylation modifier, reacting for 2-4 hours, and finally performing rotary evaporation and drying to obtain high molecular weight lignin (CLEL) with high carboxymethyl content;

(3) adding ultrapure water into cationic starch CS, heating to 50-80 ℃ for gelatinization for 30-60 min, then adding a cross-linking agent, reacting for 1-3 h, adding an alkalizing agent after the reaction is finished, adjusting the pH value of the solution to 11-13, adding high-molecular-weight lignin with high carboxymethyl content in the step (2), reacting for 1-3 h at 50-80 ℃, and after the reaction is finished, purifying to obtain the hyperbranched lignin-based cationic starch multifunctional composite flocculant.

Preferably, the lignin in the step (1) is at least one of byproduct alkali lignin obtained by alkali pulping in paper industry, enzymatic hydrolysis lignin extracted from ethanol prepared by fermentation of lignocellulose, organic solvent lignin extracted from lignocellulose by an organic solvent method and byproduct lignosulfonate prepared by sulfite pulping; wherein the byproduct lignosulfonate of the sulfite pulping is at least one of calcium lignosulfonate, sodium lignosulfonate and lignosulfonic acid.

Preferably, the mass ratio of the lignin to the cross-linking agent in the step (1) is 10: 1-10: 3.

Preferably, the crosslinking agent in the step (1) is at least one of 1, 6-dibromohexane, epichlorohydrin and formaldehyde.

Preferably, the mass concentration of lignin in the alkali solution in the step (1) is 10-33%.

Preferably, the mass ratio of the high molecular weight lignin and the carboxylation modifier in the step (2) is 10: 12.3-10: 18.2.

Preferably, the carboxylation modifier in the step (2) is at least one of sodium monochloroacetate, sodium bromoacetate and itaconic acid.

Preferably, the mass concentration of the high molecular weight lignin in the alkali solution in the step (2) is 10-30%.

Preferably, the cationic starch in the step (3) is at least one of corn cationic starch, cassava cationic starch, waxy starch and potato cationic starch, and the substitution degree is 0.02-0.1.

Preferably, the mass concentration of the cationic starch in the ultrapure water in the step (3) is 1-10%.

Preferably, the crosslinking agent in the step (3) is at least one of epichlorohydrin, 1, 6-dibromohexane and formaldehyde.

Preferably, the mass ratio of the cationic starch, the cross-linking agent and the high-molecular-weight lignin with high carboxymethyl content in the step (3) is (1-3): (0.5-3): 1.

preferably, the alkali used in the alkali solution in the steps (1) and (2) and the alkalizing agent in the step (3) are both sodium hydroxide and/or potassium hydroxide, more preferably sodium hydroxide, the alkalizing agent in the step (3) is added in the form of an aqueous solution, and the concentrations of the alkali solution in the steps (1) and (2) and the aqueous solution of the alkalizing agent in the step (3) are both 2.0-5.0 mol/L.

Preferably, the high molecular weight lignin with high carboxymethyl content in the step (3) is added in the form of an alkali solution, the mass concentration of the high molecular weight lignin with high carboxymethyl content in the alkali solution is 5-10%, and the alkali solution is a 2.0-5.0 mol/L sodium hydroxide and/or potassium hydroxide aqueous solution.

Preferably, the purification method in step (3) is: extracting the product mixture obtained by the reaction with acetone, dialyzing and drying.

The invention provides a hyperbranched lignin-based cationic starch multifunctional composite flocculant prepared by the method.

The invention provides an application of the hyperbranched lignin-based cationic starch multifunctional composite flocculant in wastewater treatment.

According to the method, firstly, lignin with high molecular weight is obtained through alkyl bridging reaction, and the molecular weight of the lignin can be adjusted by changing the feeding ratio of the lignin to a cross-linking agent; then carrying out carboxylation modification, and preparing lignin with different carboxylation degrees by changing the feeding ratio of the lignin to a carboxylation modifier; secondly, a cross-linking agent is used, and the modified lignin and industrial cationic starch are subjected to grafting reaction by controlling reaction conditions to prepare the hyperbranched lignin-based cationic starch multifunctional composite flocculant with excellent flocculation performance; by changing the charge ratio of the modified lignin and the cationic starch, the macromolecular structure of the grafted product, including the grafting degree, the grafting efficiency, the cationic degree and the like, can be regulated, so that the branched structure of the hyperbranched lignin grafted polyacrylamide can be regulated. The method has the advantages of simple process, low cost, complete degradation of main raw materials, easy industrial production, effective overcoming of the defects of uncontrollable structure, difficult realization of branched structure and low effective utilization rate of charges of the starch-based flocculant product, and effectively overcoming of the problems of single function of the lignin-based flocculant and poor effect of removing heavy metal ions.

The invention effectively utilizes the lignin which contains a plurality of active functional groups, improves the molecular weight of the lignin and the removal capability of heavy metal ions by modification; the three-dimensional network structure of lignin is effectively utilized, and the modified hyperbranched structure flocculant has good flocculation performance. The method can be used for synchronous treatment of papermaking waste liquid, industrial waste water, waste water containing heavy metal ions and the like, the preparation process is simple, efficient, green and environment-friendly, the raw materials are cheap and easily available, and the lignin and the starch are natural, non-toxic and completely degradable, so that the production cost of the conventional polymeric flocculant can be greatly reduced, and the pollution to the environment is greatly reduced.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. the lignin and starch have wide raw material sources, are renewable, have environment-friendly and biodegradable properties, and are low in cost.

2. According to the invention, a plurality of active functional groups of lignin such as hydroxyl, carboxyl, methoxyl and the like are utilized to carry out alkylation and carboxylation modification on the lignin, so that the molecular weight of the lignin is improved, and more carboxyl groups are introduced into lignin molecules, so that the adsorption removal capacity of a grafting product on heavy metal ions is improved.

3. The method utilizes the three-dimensional network structure and numerous hydroxyl functional groups of the lignin, provides more active sites for the grafting reaction of the cationic starch, has simple and efficient grafting reaction, and improves the effective charge utilization rate of the cationic starch.

4. The invention adopts industrial lignin and cationic starch, has low production cost and environmental protection, abandons the use of expensive and non-degradable acrylamide monomer and cationic reagent in the traditional polymeric flocculant, and can completely degrade the prepared hyperbranched lignin-based cationic starch flocculant.

5. The hyperbranched lignin-based cationic starch multifunctional composite flocculant prepared by the invention can synchronously flocculate and remove inorganic colloidal particles, heavy metal ions and other pollutants.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.

Those who do not specify specific conditions in the examples of the present invention follow conventional conditions or conditions recommended by the manufacturer. The raw materials, reagents and the like which are not indicated for manufacturers are all conventional products which can be obtained by commercial purchase.

The flocculation experiment process comprises the following steps:

(1) flocculation of inorganic colloidal particles: preparing 1L of kaolin suspension with the mass fraction of 0.15-0.50%, adding 10-15 mg of polyaluminium chloride, stirring at 200rpm for 2 minutes at room temperature, adding 3-5 mg of flocculant, stirring at 200rpm for 2 minutes at room temperature, stirring at 40rpm for 10 minutes, standing and observing the flocculation process.

(2) Copper ion flocculation experimental process: preparing Cu from anhydrous copper sulfate²⁺Simulated sewage with concentration of 50mg/L, Cu in 1000mL²⁺6-14 mg of flocculant was added to the solution, immediately stirred rapidly at 200rpm for 2 minutes and then at a slower speed of 40rpm for 10 minutes.

(3) The mixed flocculation experiment process comprises the following steps: cu in 50mg/L²⁺And (3) taking a mixed solution of the solution and 150mg/L kaolin solution as simulated wastewater, adjusting the rotating speed of a flocculation settler to 200rpm, stirring for 2min, then adding 6-14 mg of flocculant into the mixed solution, and stirring at 200rpm and 2min quickly and then at 40rpm and 10min slowly.

And (3) testing flocculation performance:

(1) after the flocculation stirring experiment, standing for 1 minute, taking 20mL of liquid at a position 3cm away from the liquid level, putting the liquid into a sample bottle, carrying out turbidity analysis, judging the quality of flocculation performance by comparing the turbidity, wherein the lower the turbidity is, the better the flocculation performance is.

(2) Flocculation stirring experimentThen, the supernatant was filtered through a 0.22 μm organic phase pin filter (nylon) and diluted with 1% HNO₃Diluting, digesting in a digestion tank, and testing residual Cu by ICP-OES²⁺Concentration, and calculating Cu²⁺And (4) removing rate.

(3) After the flocculation stirring experiment, according to flocculation performance tests (1) and (2), taking supernate to respectively test the turbidity and the residual Cu of the supernate along with the change of time²⁺And (4) concentration.

In examples and comparative examples, 1 part by mass was 1g, and 1 part by volume was 1 mL.

Example 1

(1) Adding 10 parts by mass of enzymatic hydrolysis lignin into a three-mouth reaction bottle in a reactor with a stirring paddle, adding water for dissolving, adjusting the pH value to 11 by using 100 parts by volume of 0.50mol/L sodium hydroxide solution, heating to 50 ℃, adding 1 part by volume of epoxy chloropropane into the reaction bottle, controlling the pH value of a reaction solution to be about 11 in the reaction process, and taking out after reacting for 2 hours to obtain the high molecular weight lignin LEL.

(2) In a reactor equipped with a stirring paddle, 10 parts by mass of alkylated enzymatic lignin (LEL) is dissolved into 100 parts by volume of 0.50mol/L sodium hydroxide solution, and the solution is poured into a 500ml three-neck flask, the temperature is raised to 40 ℃, 12.3 parts by mass of sodium chloroacetate is dissolved by 10 parts by volume of 0.50mol/L sodium hydroxide solution, and then the sodium chloroacetate is dropped into the reaction solution, and the reaction time is controlled to be 2 hours. After the reaction, the mixture was cooled to room temperature and dialyzed 72 against a dialysis bag to remove the salts in the mixture. Finally, carboxymethylated alkylated lignin product CLAL is obtained by rotary evaporation and freeze drying.

(3) Dissolving 1.0 part by mass of industrial grade cationic Corn Starch (CS) with the substitution degree of 0.1 in 30 parts by volume of ultrapure water in a reactor provided with a stirring paddle, pouring the solution into a 250ml three-neck flask, heating the solution to 50 ℃, stirring the solution at 350rpm for 30min to gelatinize the cationic starch, adding 0.5 part by volume of Epoxy Chloropropane (ECH) as a cross-linking agent after the reaction is finished, keeping the reaction temperature unchanged, stirring the solution at 350rpm for 1h, adding 3 parts by volume of sodium hydroxide aqueous solution (1mol/L) to perform ring closure reaction on the epoxy chloropropane, keeping the reaction temperature unchanged, stirring the solution at 300rpm for 10min, finally dissolving 1 part by mass of the carboxymethylated alkylated lignin CLAL in the step (2) in 20 parts by volume of sodium hydroxide solution (1mol/L), pouring the solution into a reaction bottle, keeping the reaction temperature unchanged, stirring the solution at 350rpm for 1h, a solution with the final product is obtained. The product was precipitated with acetone and washed repeatedly 3 times with acetone, then dialyzed 72 and rotary evaporated to dryness to give the final product (flocculant).

6.8mg of the flocculant was added thereto, and after flocculating sewage containing 500ppm of kaolin, the turbidity removal rate was 91.6%.

14.0mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 89.2%.

14.0mg of the flocculant was added to flocculate 150ppm kaolin and 50ppm Cu²⁺After mixing the sewage, the turbidity removal rate is 90.1%, Cu²⁺The removal rate was 87.3%.

Example 2

(1) Adding 10 parts by mass of enzymatic hydrolysis lignin into a three-mouth reaction bottle in a reactor with a stirring paddle, adding water for dissolving, adjusting the pH value to 11 by using 50 parts by volume of 1.0mol/L sodium hydroxide solution, heating to 60 ℃, adding 2 parts by volume of epoxy chloropropane into the reaction bottle, controlling the pH value of a reaction solution to be about 11 in the reaction process, and taking out after reacting for 3 hours to obtain the high molecular weight lignin LEL.

In the step (2), the mass concentration of the alkylated enzymatic hydrolysis lignin (LEL) in the sodium hydroxide aqueous solution is adjusted to 20% as in example 1.

Step (3) was the same as in example 1.

6.8mg of the flocculant was added thereto, and after flocculating sewage containing 500ppm of kaolin, the turbidity removal rate was 93.5%.

14.0mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 91.3%.

14.0mg of the flocculant was added to flocculate 150ppm kaolin and 50ppm Cu²⁺After mixing the sewage, the turbidity removal rate is 91.4 percent, and Cu is removed²⁺The removal rate was 89.6%.

Example 3

(1) Adding 10 parts by mass of enzymatic hydrolysis lignin into a three-mouth reaction bottle in a reactor with a stirring paddle, adding water for dissolving, adjusting the pH value to 11 by using 30 parts by volume of 1.0mol/L sodium hydroxide solution, heating to 80 ℃, adding 3 parts by volume of epoxy chloropropane into the reaction bottle, controlling the pH value of reaction liquid to be about 11 in the reaction process, and taking out after reacting for 4 hours to obtain the high molecular weight lignin LEL.

In step (2), the mass concentration of alkylated enzymatic hydrolysis lignin (LEL) in the sodium hydroxide aqueous solution was adjusted to 30% as in example 1.

Step (3) was the same as in example 1.

6.8mg of the flocculant was added thereto, and after flocculating sewage containing 500ppm of kaolin, the turbidity removal rate was 96.1%.

14.0mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 90.2%.

14.0mg of the flocculant was added to flocculate 150ppm kaolin and 50ppm Cu²⁺After mixing the sewage, the turbidity removal rate is 94.3 percent, and Cu is removed²⁺The removal rate was 86.5%.

Example 4

Step (1) was the same as in example 2.

Step (2) the amount of sodium chloroacetate added was adjusted to 16.8 parts by mass as in example 2.

Step (3) was the same as in example 2.

7.4mg of the flocculant was added thereto, and after flocculating sewage containing 500ppm of kaolin, the turbidity removal rate was 93.1%.

14mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 93.5%.

14mg of the flocculant was added thereto to flocculate a mixture containing 150ppm of kaolin and 50ppm of Cu²⁺After mixing the sewage, the turbidity removal rate is 91.8 percent, and Cu is removed²⁺The removal rate was 90.5%.

Example 5

Step (1) was the same as in example 2.

In step (2), the amount of sodium chloroacetate added was adjusted to 18.2 parts by mass and the reaction temperature was adjusted to 110 ℃ as in example 2.

Step (3) was the same as in example 2.

7.2mg of the flocculant was added thereto, and after flocculating sewage containing 500ppm of kaolin, the turbidity removal rate was 94.2%.

14mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 97.8%.

14mg of the flocculant was added thereto to flocculate a mixture containing 150ppm of kaolin and 50ppm of Cu²⁺After mixing the sewage, the turbidity removal rate is 92.6 percent, and Cu is removed²⁺The removal rate was 95.9%.

Example 6

In the step (1), the mass concentration of the enzymatic hydrolysis lignin in the sodium hydroxide solution is adjusted to 30% as in example 5.

In step (2), the reaction time was adjusted to 3 hours as in example 5.

Step (3) dissolving 1.5 parts by mass of industrial cationic Corn Starch (CS) with a substitution degree of 0.1 in 30 parts by volume of ultrapure water in a reactor provided with a stirring paddle, pouring the solution into a 250ml three-neck flask, heating the solution to 60 ℃, stirring the solution at 350rpm for 40min to gelatinize the cationic starch, adding 1 part by volume of Epichlorohydrin (ECH) as a cross-linking agent after the reaction is finished, stirring the solution at 350rpm for 2h, adding 4 parts by volume of sodium hydroxide solution (4mol/L) to perform a ring-closing reaction on the epichlorohydrin, stirring the solution at 300rpm for 10min, finally dissolving 1 part by mass of the carboxymethylated alkylated lignin CLAL in the step (2) in 13 parts by volume of sodium hydroxide solution (1mol/L), pouring the solution into a reaction bottle, stirring the solution at 350rpm for 2h, a solution with the final product is obtained. The product was precipitated with acetone and washed repeatedly 3 times with acetone, then dialyzed 72 and rotary evaporated to dryness to give the final product (flocculant).

7.0mg of the flocculant was added to flocculate 500ppm kaolin-containing sewage, and the turbidity removal rate was 95.7%.

14mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 95.4%.

14mg of the flocculant was added thereto to flocculate a mixture containing 150ppm of kaolin and 50ppm of Cu²⁺Turbidity removal rate after mixing sewage94.2% of Cu²⁺The removal rate was 93.8%.

Example 7

Step (1) was the same as in example 6.

Step (2) was the same as in example 6.

(3) Dissolving 2.0 parts by mass of industrial grade cationic Corn Starch (CS) with the substitution degree of 0.1 in 30 parts by volume of ultrapure water in a reactor with a stirring paddle, pouring the solution into a 250ml three-neck flask, heating the solution to 70 ℃, stirring the solution at 350rpm for 50min to gelatinize the cationic starch, adding 1 part by volume of Epichlorohydrin (ECH) as a cross-linking agent after the reaction is finished, keeping the reaction temperature unchanged, stirring the solution at 350rpm for 2h, adding 4 parts by volume of sodium hydroxide solution (4mol/L) to perform ring-closure reaction on the epichlorohydrin, keeping the reaction temperature unchanged, stirring the solution at 300rpm for 20min, finally dissolving 1 part by mass of carboxymethylated alkylated lignin CLAL in the step (2) in 12 parts by volume of sodium hydroxide solution (1mol/L), pouring the solution into a reaction flask, keeping the reaction temperature unchanged, stirring the solution at 350rpm for 3h, a solution with the final product is obtained. The product was precipitated with acetone and washed repeatedly 3 times with acetone, then dialyzed 72 and rotary evaporated to dryness to give the final product (flocculant).

6.6mg of the flocculant was added to flocculate 500ppm kaolin-containing sewage, and the turbidity removal rate was 98.2%.

14.0mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 94.8%.

14.0mg of the flocculant was added to flocculate 150ppm kaolin and 50ppm Cu²⁺After mixing the sewage, the turbidity removal rate was 97.1%, Cu²⁺The removal rate was 91.6%.

Example 8

Step (1) was the same as in example 6.

Step (2) was the same as in example 6.

(3) Dissolving 2.5 parts by mass of industrial grade cationic Corn Starch (CS) with the substitution degree of 0.1 into 30 parts by volume of ultrapure water in a reactor provided with a stirring paddle, pouring the solution into a 250ml three-neck flask, heating the solution to 80 ℃, stirring the solution at 350rpm for 80min to gelatinize the cationic starch, adding 1 part by volume of Epichlorohydrin (ECH) as a cross-linking agent after the reaction is finished, keeping the reaction temperature unchanged, stirring the solution at 350rpm for 3h, adding 6 parts by volume of sodium hydroxide solution (4mol/L) to perform ring-closure reaction on the epichlorohydrin, keeping the reaction temperature unchanged, stirring the solution at 300rpm for 30min, finally dissolving 1 part by mass of carboxymethylated alkylated lignin CLAL in the step (2) into 11 parts by volume of sodium hydroxide solution (1mol/L), pouring the solution into a reaction flask, keeping the reaction temperature unchanged, stirring the solution at 350rpm for 3h, a solution with the final product is obtained. The product was precipitated with acetone and washed repeatedly 3 times with acetone, then dialyzed 72 and rotary evaporated to dryness to give the final product (flocculant).

6.4mg of the flocculant was added to flocculate 500ppm kaolin-containing sewage, and the turbidity removal rate was 99.6%.

14.0mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 93.1%.

14.0mg of the flocculant was added to flocculate 150ppm kaolin and 50ppm Cu²⁺After mixing the sewage, the turbidity removal rate is 98.8 percent, and Cu is removed²⁺The removal rate was 91.7%.

Example 9

Step (1) was the same as in example 6.

Step (2) was the same as in example 6.

(3) Dissolving 3.0 parts by mass of industrial grade cationic Corn Starch (CS) with the substitution degree of 0.1 in 30 parts by volume of ultrapure water in a reactor with a stirring paddle, pouring the solution into a 250ml three-neck flask, heating to 80 ℃, stirring at 350rpm for 30min for reaction to gelatinize the cationic starch, adding 1 part by volume of Epichlorohydrin (ECH) as a cross-linking agent after the reaction is finished, keeping the reaction temperature unchanged, stirring at 350rpm for reaction for 2h, adding 8 parts by volume of sodium hydroxide solution (4mol/L) for ring-closure reaction of the epichlorohydrin, keeping the reaction temperature unchanged, stirring at 300rpm for reaction for 30min, finally dissolving 1 part by mass of carboxymethylated alkylated lignin CLAL in the step (2) in 10 parts by volume of sodium hydroxide solution (1mol/L), pouring into a reaction bottle, keeping the reaction temperature unchanged, stirring at 350rpm for reaction for 3h, a solution with the final product is obtained. The product was precipitated with acetone and washed repeatedly 3 times with acetone, then dialyzed 72 and rotary evaporated to dryness to give the final product (flocculant).

6.2mg of the flocculant was added to flocculate 500ppm kaolin-containing sewage, and the turbidity removal rate was 90.7%.

14.0mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 87.6%.

14.0mg of the flocculant was added to flocculate 150ppm kaolin and 50ppm Cu²⁺After mixing the sewage, the turbidity removal rate is 88.5 percent, and Cu is removed²⁺The removal rate was 85.1%.

Example 10

Step (1) was the same as in example 6.

Step (2) was the same as in example 6.

(3) Dissolving 1.0 part by mass of industrial grade cationic Corn Starch (CS) with the substitution degree of 0.1 in 30 parts by volume of ultrapure water in a reactor provided with a stirring paddle, pouring the solution into a 250ml three-neck flask, heating the solution to 80 ℃, stirring the solution at 350rpm for reaction for 30min to gelatinize the cationic starch, adding 2 parts by volume of Epichlorohydrin (ECH) as a cross-linking agent after the reaction is finished, keeping the reaction temperature unchanged, stirring the solution at 350rpm for reaction for 2h, adding 6 parts by volume of sodium hydroxide solution (4mol/L) to perform ring-closure reaction on the epichlorohydrin, keeping the reaction temperature unchanged, stirring the solution at 300rpm for reaction for 20min, finally dissolving 1 part by mass of carboxymethylated alkylated lignin CLAL in the step (2) in 20 parts by volume of sodium hydroxide solution (1mol/L), pouring the solution into a reaction bottle, keeping the reaction temperature unchanged, stirring the solution at 350rpm for reaction for 2h, a solution with the final product is obtained. The product was precipitated with acetone and washed repeatedly 3 times with acetone, then dialyzed 72 and rotary evaporated to dryness to give the final product (flocculant).

7.6mg of the flocculant was added thereto, and after flocculation of 500ppm kaolin-containing sewage, the turbidity removal rate was 91.5%.

14.0mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 93.8%.

14.0mg of the flocculant was added thereto to flocculate kaolin containing 150ppmAnd 50ppm of Cu²⁺After mixing the sewage, the turbidity removal rate is 88.4 percent, and Cu is removed²⁺The removal rate was 91.5%.

Example 11

Step (1) was the same as in example 10.

Step (2) was the same as in example 10.

Step (3) as in example 10, the amount of epichlorohydrin added was adjusted to 3 parts by volume.

7.4mg of the flocculant was added thereto, and after flocculating sewage containing 500ppm of kaolin, the turbidity removal rate was 85.3%.

14.0mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 85.9%.

14.0mg of the flocculant was added to flocculate 150ppm kaolin and 50ppm Cu²⁺After mixing the sewage, the turbidity removal rate was 81.1%, Cu²⁺The removal rate was 83.0%.

Comparative example 1

The difference from example 10 is that: and (2) no crosslinking agent epichlorohydrin is added in the step (1).

7.2mg of the flocculant was added thereto, and after flocculating sewage containing 500ppm of kaolin, the turbidity removal rate was 98.5%.

14.0mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 80.3%.

8.0mg of the flocculant was added thereto to flocculate a mixture containing 150ppm of kaolin and 50ppm of Cu²⁺After mixing the sewage, the turbidity removal rate is 96.3 percent, and Cu is removed²⁺The removal rate was 78.6%.

Comparative example 2

The difference from example 2 is that: sodium chloroacetate in the step (2) without adding a carboxymethylation reagent.

7.2mg of the flocculant was added thereto, and after flocculating sewage containing 500ppm of kaolin, the turbidity removal rate was 99.1%.

14.0mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 15.3%.

14.0mg of the flocculant was added to flocculate 150ppm kaolin and 50ppm Cu²⁺After the sewage is mixed,turbidity removal rate was 98.6%, Cu²⁺The removal rate was 10.6%.

Comparative example 3

Flocculation experiments were performed using commercial cationic starch flocculants of technical grade with a cationicity of 0.1.

10.0mg of the flocculant was added to flocculate 500ppm kaolin-containing sewage, and the turbidity removal rate was 35.9%.

14.0mg of the flocculant was added thereto to flocculate Cu in an amount of 50ppm²⁺After the sewage, Cu²⁺The removal rate was 4.6%.

14.0mg of the flocculant was added to flocculate 150ppm kaolin and 50ppm Cu²⁺After mixing the sewage, the turbidity removal rate is 29.5 percent, and Cu is removed²⁺The removal rate was 3.8%.

Comparative example 4

Flocculation experiments were performed using commercial flocculants with a molecular weight of 1000 ten thousand and a cationicity of 10%.

3.2mg of the flocculant is added, and after the sewage containing 500ppm of kaolin is flocculated, the turbidity removal rate is 82.6%, and the flocculant has no copper ion removal capacity.

By comparing example 1 with example 3 and comparative example 1, it can be seen that the high molecular weight lignin obtained by the reaction of alkylated cross-linked lignin according to the present invention can improve the flocculation removal capability of the lignin-based flocculant on inorganic colloidal particles and copper ions.

The comparison of the example 2 with the example 5 and the comparative example 2 shows that the lignin with high carboxyl content can be obtained by adopting the carboxylation modified lignin reaction of the invention, and the hyperbranched lignin-based cationic starch multifunctional composite flocculant prepared by the cationic starch grafting process has better flocculation effect compared with the hyperbranched lignin-grafted cationic polyacrylamide flocculant disclosed in the patent CN109280174B, and most importantly, the invention successfully completes the flocculation on inorganic colloid particles and Cu²⁺Synchronous flocculation removal. The results of the other examples also demonstrate that the alkylation and carboxylation process of the present invention effectively enhances the simultaneous flocculation effect of lignin-based flocculants.

Through comparison between the example 10 and the comparative examples 3 and 4, the hyperbranched lignin-based cationic starch multifunctional composite flocculant prepared by the invention has better flocculation effect than industrial commercial cationic starch flocculants and commercial cationic polyacrylamide flocculants, and the flocculation performance is far better than that of other lignin graft flocculants.

The hyperbranched lignin-based cationic starch multifunctional composite flocculant prepared by the invention has the advantages of low cost, simple synthesis steps, complete biomass completely-degradable and environment-friendly flocculant, controllable hyperbranched macromolecular structure of the obtained lignin graft flocculant, high flocculation efficiency and multifunctional synchronous flocculation capacity.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.