Polyaluminum chloride composite water treatment agent and preparation method thereof

Abstract

The invention relates to the technical field of water treatment, and particularly provides a polyaluminum chloride composite water treatment agent and a preparation method thereof, and the polyaluminum chloride composite water treatment agent comprises the following components in percentage by weight: 80-90% of polyaluminum chloride; 0.5%-2% of modified chitosan; 3%-8% of sodium lignosulphonate-Fe < 3 + > complex; 0.1%-0.5% of a pH regulator; wherein the modified chitosan is citric acid cross-linked chitosan, the deacetylation degree of the modified chitosan is not lower than 85%, and in the sodium lignosulphonate-Fe < 3 + > complex, the molar ratio of Fe < 3 + > to sodium lignosulphonate is 1: 3. Through the synergistic interaction of polyaluminum chloride and a natural polymer composite system, the design of an efficient, green and multifunctional water treatment agent is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a polyaluminum chloride composite water treatment agent and a preparation method thereof. Background Art

[0002] With the acceleration of the global industrialization process and the intensification of water resource shortage, water treatment technology has become the core means to ensure drinking water safety, industrial sustainable development and environmental protection. Traditional inorganic flocculants have defects such as large dosage, excessive residual metal ions, and loose flocs, and their effects are significantly reduced especially in scenarios with high turbidity, low temperature or complex pollutants. For example, aluminum salt flocculants are prone to cause secondary pollution of water bodies, while iron salt flocculants may cause color problems. In addition, although synthetic polymer flocculants are highly efficient, their problems of difficult degradation and toxic residues have been much criticized.

[0003] As the second-generation inorganic polymer flocculant, polyaluminum chloride has gradually replaced traditional aluminum salts since the 1960s due to its high-charge polymerization structure and strong electro-neutralization ability. To improve the performance of PAC, existing technologies mostly adopt the method of compounding with other materials, but there are still significant problems: for example, when compounded with polyacrylamide, although the flocculation efficiency is improved, the difficult degradation of PAM and the toxicity of acrylamide monomers limit its application in sensitive fields such as food and medicine. In some existing patent solutions, by introducing light absorbers, although they have both ultraviolet absorption and sterilization functions, the raw material preparation is complex, the cost is high, and some components have ecological toxicity risks. According to market forecasts.

[0004] Constructing an efficient, low-toxic and multifunctional composite water treatment system has become one of the technical problems to be solved urgently at present. Summary of the Invention

[0005] In view of this, the present invention proposes a polyaluminum chloride composite water treatment agent and a preparation method thereof.

[0006] The technical solution of the present invention is realized as follows: The present invention provides a polyaluminum chloride composite water treatment agent, calculated by weight percentage as 100%, including the following components:

[0007] Polyaluminum chloride 80%-90%;

[0008] Modified chitosan 0.5%-2%;

[0009] Sodium lignosulfonate-Fe 3+ Complex 3%-8%;

[0010] pH regulator 0.1%-0.5%;

[0011] The balance is water;

[0012] Among them, the modified chitosan is citric acid-crosslinked chitosan with a deacetylation degree of not less than 85%, and sodium lignosulfonate-Fe 3+ In the complex, Fe 3+ The molar ratio of to sodium lignosulfonate is 1:3.

[0013] Taking polyaluminum chloride as the main component, its Keggin structure quickly neutralizes the negative charges on the surface of colloidal particles through strong electro-neutralization ability, forms dense flocs and accelerates precipitation. Compared with traditional aluminum salts, PAC has a higher degree of polymerization, stronger adaptability to low-temperature and low-turbidity water, and lower residual aluminum ions, meeting the drinking water standard. Citric acid reacts with the amino and hydroxyl groups of chitosan through carboxyl groups to form a crosslinked network, improving the water solubility and charge density of chitosan. A deacetylation degree of ≥85% ensures that more active amino groups are exposed. After crosslinking, the natural antibacterial property of chitosan is retained, and at the same time, heavy metal ions are adsorbed through amino groups to achieve deep removal of pollutants. Fe 3+ Complexes with the sulfonic acid groups of sodium lignosulfonate to form a positively charged complex, enhancing the charge neutralization ability for colloidal particles. At the same time, the lignin skeleton provides a bridging effect to promote the growth of flocs. Fe 3+ The complex can inhibit metal corrosion in an acidic environment and extend the service life of water treatment equipment.

[0014] Using bio-based materials such as chitosan and sodium lignosulfonate to replace traditional polyacrylamide can avoid the residue of toxic monomers and improve the biodegradation rate.

[0015] In some embodiments, the preparation method of the modified chitosan includes: dissolving chitosan in a 1%-2% dilute acetic acid solution to obtain a 2%-4% chitosan-acetic acid solution, adding 5%-10% of the mass of chitosan of citric acid, heating to 55-65°C for heat preservation and stirring reaction for 1-3 h, and freeze-drying after dialysis to obtain the modified chitosan.

[0016] Low-concentration acetic acid can both protonate the amino groups of chitosan to enhance its water solubility and avoid excessive degradation of the chitosan molecular chain caused by strong acids. At a ratio of 5%-10%, the carboxyl groups of citric acid crosslink with the amino groups of chitosan through ionic and covalent bonds to form a three-dimensional network structure. Excessive citric acid will cause excessive crosslinking and reduce the flexibility of the material. Dialysis can use a dialysis membrane with a cut-off molecular weight of 8-10 kDa. Dialysis removes unreacted citric acid, acetic acid and small molecule by-products to prevent the residual acid from damaging the biocompatibility of the material. Citric acid crosslinking improves the dry-state breaking strength and wet-state breaking strength of chitosan.

[0017] In some embodiments, the preparation method of the sodium lignosulfonate-Fe 3+ complex includes: mixing a 5%-10% sodium lignosulfonate solution with an FeCl3 solution according to Fe 3+Mix at a molar ratio of 1:3 with sodium lignosulfonate, adjust the pH to 4.0 - 5.0, stir and react at 55 - 65 °C for 0.5 - 1.5 h, and then spray dry to obtain sodium lignosulfonate-Fe 3+ complex.

[0018] The sulfonic acid groups and phenolic hydroxyl groups of sodium lignosulfonate are the main coordination sites of Fe 3+ , and a stable complex is formed through ion exchange and chelation. A molar ratio of Fe 3+ to sodium lignosulfonate of 1:3 can ensure that each Fe 3+ binds to 3 sulfonic acid groups, avoiding hydrolysis caused by excessive Fe 3+ to form Fe(OH)3 precipitation. By controlling the pH at 4 - 5, the sulfonic acid groups of sodium lignosulfonate remain ionized, while the hydrolysis tendency of Fe 3+ is relatively low, ensuring that the chelation reaction dominates.

[0019] In some embodiments, it further includes 0.1% - 1% of a bacteriostatic synergist, and the bacteriostatic synergist is at least one of tea polyphenols and baicalein.

[0020] Tea polyphenols damage the integrity of the bacterial cell membrane through phenolic hydroxyl groups, resulting in the leakage of intracellular substances. At the same time, they inhibit the activities of DNA gyrase and RNA polymerase, blocking nucleic acid and protein synthesis. They inhibit the early adhesion of biofilms such as Pseudomonas aeruginosa and block the quorum sensing signal transmission. The strong antioxidant property of tea polyphenols can protect other active ingredients (such as chitosan, Fe 3+ complex) from oxidative inactivation and extend the stability of the system. Baicalein destroys the cell wall of Gram-positive bacteria by inhibiting peptidoglycan synthase and interferes with replication and transcription by embedding in the DNA base sequence. It has a significant early inhibitory effect on Pseudomonas aeruginosa biofilms, but requires combination with antibiotics for mature biofilms.

[0021] The hydroxyl radicals generated by the hydrolysis of PAC and the antioxidant property of tea polyphenols form a dynamic balance: tea polyphenols scavenge excessive free radicals to protect the activity of PAC, while the Fe 3+ complex enhances the oxidation ability through the Fenton reaction, accelerating the degradation of organic matter. Modified chitosan adsorbs the bacterial cell membrane through positive charges, while tea polyphenols / baicalein form a double bacteriostatic barrier by destroying the lipopolysaccharide layer of the cell wall. Chitosan inhibits the initial adhesion of bacteria, and tea polyphenols block the quorum sensing signal. The two work together to remove mature biofilms and prevent regeneration. The oxidation of Fe 3+ activates the antiviral activity of baicalein, and at the same time, the sulfonic acid groups of sodium lignosulfonate chelate heavy metal ions and cooperate with the phenolic hydroxyl groups of tea polyphenols to form heavy metal-phenol chelates. Tea polyphenols or baicalein as bacteriostatic synergists, through cooperation with PAC, modified chitosan, sodium lignosulfonate-Fe 3+Charge complementarity, oxidation synergy, and pH adaptation of components such as complexes are achieved to realize the multi-functional integration of "bacteriostasis - flocculation - adsorption - corrosion inhibition". This system combines high efficiency and environmental protection.

[0022] In some embodiments, the pH regulator is citric acid.

[0023] The second aspect of the present invention also provides a preparation method of the above polyaluminum chloride composite water treatment agent, including the following steps: Mix a polyaluminum chloride solution (Al2O3 10% - 30%) with modified chitosan and lignosulfonate - Fe 3+ complex, adjust the pH value to 5.0 - 6.0, stir at 100 - 200 rpm for 30 min at 40 °C to obtain the composite water treatment agent.

[0024] In some embodiments, it also includes adding a bacteriostasis synergist.

[0025] The present invention has the following beneficial effects compared with the prior art:

[0026] Through the synergistic effect of the polyaluminum chloride and natural polymer composite system, the present invention realizes the design of a highly efficient, green, and multi-functional water treatment agent. With citric acid cross-linked chitosan and lignosulfonate - Fe 3+ complex as the core, combined with tea polyphenols or baicalein bacteriostasis synergists, it significantly improves the turbidity removal rate, COD removal rate, and heavy metal adsorption capacity, and at the same time has broad-spectrum bacteriostasis and biodegradability. Compared with the traditional PAM system, this solution uses natural components to replace synthetic polymers, eliminates the risk of acrylamide residue, reduces the comprehensive cost, and expands to sensitive scenarios such as food processing wastewater and drinking water pretreatment, realizing the multi-functional integration of flocculation - bacteriostasis - adsorption - corrosion inhibition, and combining high efficiency and environmental friendliness. Specific Embodiments

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0028] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the embodiments of the present invention belong. If the definitions stated in this part are contrary to or inconsistent with the definitions stated in the patents, patent applications, published patent applications, and other publications incorporated herein by reference, the definitions listed in this part shall prevail over the definitions incorporated herein by reference.

[0029] Unless otherwise specified, the methods used in the following examples are conventional methods. The materials, reagents and instruments used, unless otherwise specified, are conventional materials, reagents and instruments in the art, and those skilled in the art can obtain them through commercial channels.

[0030] When an equivalent, concentration or other value or parameter is expressed as a range, a preferred range or a range defined by a series of upper preferred values and lower preferred values, it should be understood that all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value are specifically disclosed, regardless of whether the ranges are separately disclosed. For example, when the range "1 to 5" is disclosed, the described range should be interpreted as including the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range. In the specification and claims of this application, range limitations may be combined and / or interchanged, and these ranges include all sub-ranges contained therein if not otherwise stated.

[0031] Example 1

[0032] Raw materials:

[0033] Polyaluminum chloride (Al2O3 = 12%): 85 wt%.

[0034] Modified chitosan (degree of deacetylation = 85%): 1.5%

[0035] Sodium lignosulfonate-Fe 3+ Complex (Fe 3+ / lignin molar ratio 1:3): 5%

[0036] pH regulator (citric acid): 0.5%

[0037] The balance is water

[0038] Preparation of modified chitosan:

[0039] Dissolve chitosan in a 1.5% dilute acetic acid solution to prepare a 3% chitosan-acetic acid solution;

[0040] Add 8% of the mass of chitosan of citric acid and stir and react at 60 °C for 2 hours;

[0041] Dialyze for 48 hours (cut-off molecular weight 8 kDa), and freeze-dry to obtain porous modified chitosan

[0042] Sodium lignosulfonate-Fe 3+ Preparation of complex:

[0043] Mix an 8% sodium lignosulfonate solution with 0.1 mol / L FeCl3 in a molar ratio of 1:3;

[0044] Adjust the pH to 4.5 and stir the reaction at 60 °C for 1 hour;

[0045] Perform spray drying (inlet temperature 180 °C, outlet 80 °C) to obtain a brown powder.

[0046] Compound preparation:

[0047] Mix the PAC solution (concentration 10%) with modified chitosan and sodium lignosulfonate-Fe 3+ complex; add citric acid to adjust the pH to 5.5;

[0048] Stir at 40 °C and 150 rpm for 30 minutes.

[0049] Example 2

[0050] Raw materials:

[0051] Polyaluminum chloride (Al2O3 = 12%): 85 wt%

[0052] Modified chitosan (degree of deacetylation = 85%): 1.5%

[0053] Sodium lignosulfonate-Fe 3+ complex (Fe 3+ / lignin molar ratio 1:3): 5%

[0054] Bacteriostatic synergist (tea polyphenols): 0.3%

[0055] pH regulator (citric acid): 0.5%

[0056] The balance is water

[0057] Preparation of modified chitosan:

[0058] Dissolve chitosan in a 1.5% dilute acetic acid solution to prepare a 3% chitosan-acetic acid solution;

[0059] Add citric acid at 8% of the mass of chitosan and stir the reaction at 60 °C for 2 hours;

[0060] Dialyze for 48 hours (cut-off molecular weight 8 kDa) and freeze-dry to obtain porous modified chitosan Sodium lignosulfonate-Fe 3+ Preparation of complex:

[0061] Mix an 8% sodium lignosulfonate solution with 0.1 mol / L FeCl3 at a molar ratio of 1:3;

[0062] Adjust the pH to 4.5 and stir the reaction at 60 °C for 1 hour;

[0063] Perform spray drying (inlet temperature 180 °C, outlet 80 °C) to obtain a brown powder.

[0064] Compound preparation:

[0065] Mix the PAC solution (concentration 10%) with modified chitosan and sodium lignosulfonate-Fe 3+ complex; add tea polyphenols, and adjust the pH to 5.5 with citric acid;

[0066] Stir at 40 °C and 150 rpm for 30 minutes.

[0067] Example 3

[0068] Raw materials:

[0069] Polyaluminum chloride (Al2O3 = 12%): 90 wt%

[0070] Modified chitosan (degree of deacetylation = 85%): 2%

[0071] Sodium lignosulfonate-Fe 3+ complex (Fe 3+ / lignin molar ratio 1:3): 8%

[0072] pH regulator (citric acid): 0.5%

[0073] The balance is water

[0074] Preparation of modified chitosan:

[0075] Dissolve chitosan in 1.5% dilute acetic acid solution to prepare 3% chitosan-acetic acid solution;

[0076] Add 8% of the mass of chitosan of citric acid, stir and react at 60 °C for 2 hours;

[0077] Dialyze for 48 hours (cut-off molecular weight 8 kDa), and freeze-dry to obtain porous modified chitosan 3+ Preparation of sodium lignosulfonate-Fe complex:

[0078] Mix 8% sodium lignosulfonate solution with 0.1 mol / L FeCl3 at a molar ratio of 1:3;

[0079] Adjust the pH to 4.5, stir and react at 60 °C for 1 hour;

[0080] Spray dry (inlet temperature 180 °C, outlet 80 °C) to obtain a brown powder.

[0081] Compound preparation:

[0082] Mix the PAC solution (concentration 10%) with modified chitosan and sodium lignosulfonate-Fe 3+ complex; add citric acid to adjust the pH to 5.5;

[0083] Stir at 40 °C and 150 rpm for 30 minutes.

[0084] Comparative Example 1

[0085] Raw materials:

[0086] Polyaluminum chloride (Al2O3 = 28%) 85 wt%.

[0087] PAM: 0.2%

[0088] Ferrous sulfate: 10%

[0089] The balance is water

[0090] Compound preparation:

[0091] Mix the PAC solution (concentration 10%) with PAM and ferrous sulfate;

[0092] Stir at 40 °C and 150 rpm for 30 minutes.

[0093] Comparative Example 2

[0094] Raw materials:

[0095] Polyaluminum chloride (Al2O3 = 12%) 85 wt%.

[0096] Chitosan (degree of deacetylation = 85%): 1.5%

[0097] Sodium lignosulfonate: 5%

[0098] pH regulator (citric acid): 0.5%

[0099] The balance is water

[0100] Compound preparation:

[0101] Mix the PAC solution (concentration 10%) with chitosan and sodium lignosulfonate;

[0102] Add citric acid;

[0103] Stir at 40 °C and 150 rpm for 30 minutes.

[0104] Comparative Example 3

[0105] Raw materials:

[0106] Polyaluminum chloride (Al2O3 = 12%) 85 wt%.

[0107] Modified chitosan (degree of deacetylation = 85%): 1.5%

[0108] Sodium lignosulfonate-Fe 3+ Complex (Fe 3+ / lignin molar ratio 1:3): 5% pH regulator (citric acid): 0.5%

[0109] Surplus water

[0110] Preparation of modified chitosan:

[0111] Dissolve chitosan in 1.5% dilute acetic acid solution to prepare 3% chitosan - acetic acid solution; add 8% citric acid based on the mass of chitosan and stir - react at 60°C for 2 hours;

[0112] Dialyze for 48 hours (cut - off molecular weight 8 kDa), and freeze - dry to obtain porous modified chitosan - lignosulfonate - Fe 3+ Preparation of complex:

[0113] Mix 8% lignosulfonate solution and 0.1 mol / L FeCl3 in a molar ratio of 1:3;

[0114] Adjust the pH to 4.5 and stir - react at 60°C for 1 hour;

[0115] Spray - dry (inlet temperature 180°C, outlet 80°C) to obtain a brown powder.

[0116] Preparation of compound:

[0117] Mix the PAC solution (concentration 10%) with modified chitosan and lignosulfonate - Fe 3+ complex;

[0118] Add citric acid to adjust the pH to 5.5;

[0119] Stir at 40°C and 150 rpm for 30 minutes.

[0120] Respectively detect the turbidity removal rate, COD removal rate, sedimentation time, biodegradability, antibacterial rate and toxicity residue (acrylamide) of the composite water treatment agents prepared in the above - mentioned examples and comparative examples,

[0121] The detection results are as follows:

[0122]

[0123] Compared with Comparative Example 1, in Example 1, using natural polymers to replace PAM significantly improves biodegradability and has no toxic residues.

[0124] Compared with Comparative Example 2, the key to improving the flocculation efficiency in Example 1 is the complexation of citric acid - crosslinked chitosan with trivalent iron ions and lignosulfonate.

[0125] It can be seen from the comparison between Example 2 and Comparative Example 3 that tea polyphenols and chitosan have a synergistic antibacterial effect, significantly prolonging the storage stability of the agent.

[0126] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A polyaluminum chloride composite water treatment agent, characterized in that, Calculated on a weight percentage of 100%, it includes the following components: Polyaluminum chloride 80% - 90%; Modified chitosan 0.5% - 2%; Sodium lignosulfonate-Fe 3+ Complex 3%-8%; pH regulator 0.1% - 0.5%; The balance is water; Among them, the modified chitosan is citric acid cross-linked chitosan with a deacetylation degree of not less than 85%, and the molar ratio of Fe 3+ in the lignosulfonate-Fe 3+ complex to lignosulfonate is 1:

3.

2. The polyaluminum chloride composite water treatment agent according to claim 1, wherein The preparation method of the modified chitosan includes: dissolving chitosan in a 1% - 2% dilute acetic acid solution to obtain a chitosan - acetic acid solution with a concentration of 2% - 4%, adding 5% - 10% of citric acid based on the mass of chitosan, heating to 55 - 65 °C, keeping warm and stirring for reaction for 1 - 3 h, and freeze - drying after dialysis to obtain modified chitosan.

3. The polyaluminum chloride composite water treatment agent according to claim 1, wherein The sodium lignosulfonate-Fe 3+ complex preparation method includes: mixing a 5%-10% sodium lignosulfonate solution with an FeCl3 solution at a molar ratio of Fe 3+ to sodium lignosulfonate of 1:3, adjusting the pH to 4.0-5.0, stirring and reacting at 55-65°C for 0.5-1.5 h, and then spray-drying to obtain the sodium lignosulfonate-Fe 3+ complex.

4. The polyaluminum chloride composite water treatment agent according to claim 1, wherein It also includes 0.1% - 1% of an antibacterial synergist, and the antibacterial synergist is at least one of tea polyphenols and baicalein.

5. The polyaluminum chloride composite water treatment agent according to claim 1, characterized in that, The pH regulator is citric acid.

6. A preparation method of the polyaluminum chloride composite water treatment agent according to any one of claims 1-5, characterized in that, It includes: Mix the polyaluminum chloride solution (Al2O3 10%-30%) with the modified chitosan and sodium lignosulfonate-Fe 3+ complex, adjust the pH value to 5.0-6.0, stir at 40 °C at 100-200 rpm for 30 min to obtain the composite water treatment agent.

7. The preparation method according to claim 6, characterized in that, It also includes adding an antibacterial synergist.

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