Composite polyaluminium chloride water treatment agent and preparation method thereof

Abstract

The present invention discloses a composite polyaluminum chloride water treatment agent and a preparation method thereof, belonging to the technical field of water treatment agents. The water treatment agent comprises the following raw materials by weight: 100 parts of polyaluminum chloride, 30-50 parts of modified sepiolite fibers, 10-20 parts of an auxiliary flocculant, and 15-25 parts of polyvinyl alcohol. The modified sepiolite fibers are loaded with multi-stage anions; the multi-stage anions include one or a combination of phosphate ions, silicate ions, and carbonate ions. The composite modified sepiolite fibers can greatly increase the structural stability and chemical stability of the polyaluminum chloride. Furthermore, the multi-stage anions loaded on the surface of the sepiolite fibers can further enhance the charge neutralization and adsorption bridging effects of the water treatment agent, thereby increasing the flocculation volume, and improving the flocculation effect and stability.

Description

Technical Field

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

[0002] With the development of industry and the improvement of people's living standards, water consumption is constantly increasing, and water pollution is becoming increasingly serious. Flocculation sedimentation is a simple and efficient method for solid-liquid separation of non-settling particles in the water treatment industry. The properties of the flocculant also directly affect the final flocculation effect, which in turn affects the subsequent process and the effluent quality.

[0003] Among them, polyaluminum chloride is a new type of high-efficiency inorganic polymer flocculant. Compared with traditional inorganic flocculants, polyaluminum chloride has more superior performance, greatly reduced dosage, shorter sedimentation time, and a wider range of suitable water addition. It is now widely used in raw water treatment as a water treatment agent.

[0004] However, there are still some problems with polyaluminium chloride as a water treatment agent. For example, its unstable chemical properties will affect its use effect; excessive addition of polyaluminium chloride will lead to an increase in the amount of sludge generated in the water treatment system, posing a challenge to the treatment capacity of the sludge dewatering system; the flocs formed are small and the turbidity removal effect is not ideal.

[0005] Therefore, some studies have been conducted to combine organic flocculants with polyaluminum chloride to enhance its flocculation effect and improve its existing problems. However, the resulting water treatment agent still suffers from unstable flocculation, weak ability to remove metal impurities from wastewater, and structural instability. Summary of the Invention

[0006] The present invention aims to provide a composite polyaluminium chloride water treatment agent and a preparation method thereof, so as to solve the problems of unstable chemical properties, unstable flocculation effect and poor removal of metal impurity ions of polyaluminium chloride water treatment agents.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides a composite polyaluminum chloride water treatment agent comprising the following raw materials in parts by weight:

[0009] 100 parts of polyaluminium chloride;

[0010] 30-50 parts of modified sepiolite fiber;

[0011] 10-20 parts of auxiliary flocculant;

[0012] 15-25 parts of polyvinyl alcohol;

[0013] The modified sepiolite fiber is loaded with multi-stage anions; the multi-stage anions include one or a combination of phosphate ions, silicate ions and carbonate ions.

[0014] By adopting technique scheme, modified sepiolite fiber is added in the composite polyaluminium chloride water treatment agent of the present invention, sepiolite fiber is a kind of natural mineral fiber, has unique lamellar and chain transition structure, compared to general sepiolite, the sepiolite of fibrous structure has larger specific surface area, adsorption capacity and ion exchange capacity.When compounded with polyaluminium chloride, there are a large amount of active sites in modified sepiolite fiber layered structure unit, such as silanol, also possess more complicated pore structure, can physical adsorption polyaluminium chloride molecule, prevent premature aggregation or precipitation of polyaluminium chloride, and the linear structure of sepiolite fiber itself can help bridging polyaluminium chloride molecule, forms larger network structure, contributes to maintaining the morphological integrity of polyaluminium chloride, thus promotes structural stability and chemical stability of polyaluminium chloride.And can also be used as heterogeneous nucleation center, promote aluminum hydroxide colloidal particles to form and deposit on its surface, improve the floc volume formed, accelerate sedimentation velocity, improve turbidity removal rate, improve stability.

[0015] Modified sepiolite fibers also possess strong adsorption and ion exchange capabilities. The presence of numerous acidic and alkaline centers on their surfaces helps absorb pollutants from water. Ion exchange also alters their interlayer spacing and surface properties, enhancing their adsorption capacity and improving the flocculation effect of the resulting water treatment agent. Furthermore, modified sepiolite fibers can compensate for the performance shortcomings of polyaluminum chloride (PAC), utilizing its exchange and adsorption capabilities to remove some impure metal ions from wastewater without affecting the properties of PAC itself, thereby enhancing the resulting water treatment agent's ability to remove metallic impurities.

[0016] The polyaluminum chloride compounded with modified sepiolite fiber can maintain a relatively stable crystal structure even under harsh conditions, which can broaden the application scope of the composite polyaluminum chloride water treatment agent and improve the chemical stability of polyaluminum chloride.

[0017] The modified sepiolite fibers are also loaded with multi-stage anions, which enhance the fibers' adsorption capacity and structural stability by forming more complex complexes with the chloride ions in polyaluminum chloride (PAC). The addition of anions also prevents further hydrolysis of PAC, helping to maintain its stability. Furthermore, the introduction of multi-stage anions reduces the PAC's positive charge density, thereby weakening the electrostatic repulsion between particles. This acts as a charge neutralizer and adsorption bridge, allowing the flocculated particles to aggregate more easily to form larger flocs. This improves the stability of the flocculation effect and facilitates the solid-liquid separation step in post-processing.

[0018] Preferably, the multi-stage anion is a combination of phosphate ion, silicate ion and carbonate ion in a molar ratio of (0.4-0.6): (0.3-0.5): (0-0.2).

[0019] More preferably, the multi-stage anion is a combination of phosphate ion, silicate ion and carbonate ion in a molar ratio of 0.5:0.4:0.1.

[0020] By adopting the above technical solution, the multi-stage anions loaded in the modified sepiolite fiber of the present invention are a combination of phosphate ions, silicate ions, and carbonate ions. Phosphate ions combined with silicate ions can avoid further hydrolysis of polyaluminium chloride, reduce the formation of high degree of polymerization or gelled aluminium hydroxide, thereby avoiding unnecessary precipitation formation and improving the stability of the modified sepiolite fiber composite polyaluminium chloride structure. At the same time, phosphate ions can regulate the pH value together with carbonate ions to maintain a good flocculation environment and can play a certain buffering role to avoid environmental impact. Silicate ions can help maintain good deturbidity ability under the stable pH range maintained by phosphate ions and carbonate ions, thereby improving the sewage treatment effect of the water treatment agent.

[0021] At the same time, the composite multi-stage anions can enhance the adsorption bridging effect by increasing the coordination and complexing ability. Among them, the phosphate ion has a strong coordination ability and can form a stable complex with the hydrolysis product of polyaluminum chloride. The silicate ion can establish a hydrogen bond with it, which can expand the spatial size of the flocs, thereby increasing the sedimentation rate and further improving the purification ability of the composite polyaluminum chloride water treatment agent.

[0022] Preferably, the raw materials of the modified sepiolite fiber include sepiolite fiber, tannic acid and water-soluble salt in a mass ratio of 1:(3.5-4):(0.3-0.4).

[0023] Preferably, the water-soluble salt includes a combination of one or more of water-soluble phosphates, water-soluble silicates and water-soluble carbonates.

[0024] More preferably, the water-soluble phosphate includes a combination of one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate and sodium hexametaphosphate.

[0025] More preferably, the water-soluble silicate includes a combination of one or more of sodium silicate, potassium silicate and lithium silicate.

[0026] More preferably, the water-soluble carbonate includes a combination of one or more of sodium carbonate, potassium carbonate, ammonium carbonate and ammonium bicarbonate.

[0027] Preferably, the modified sepiolite fiber is prepared according to the following method:

[0028] A water-soluble salt and tannic acid are prepared into a reaction aqueous solution, sepiolite fiber is added to the reaction aqueous solution, stirred and mixed for 10 to 30 minutes, the pH value of the solution is adjusted to 7.5 to 8.0, the temperature is increased to 60 to 65° C., stirred and reacted for 2 to 3 hours, and finally dried, calcined and ground to obtain the modified sepiolite fiber.

[0029] By adopting the above technical solution, a large number of silanol groups in the sepiolite fiber can form hydrogen bonds or covalent bonds with the phenolic hydroxyl groups or carboxyl groups in the tannic acid molecules. The tannic acid is fixed on the surface of the sepiolite fiber, thereby modifying the surface of the sepiolite fiber. The additional functional groups provided by the tannic acid can increase the number of active sites on the surface of the sepiolite fiber, help load multi-stage anions, and can react to obtain a more stable complex, maintain a high adsorption efficiency, and will not easily detach from the surface of the sepiolite fiber during use of the water treatment agent. In addition, the sepiolite fiber modified with tannic acid has higher structural integrity and stability, so that the obtained composite polyaluminum chloride has better physical properties.

[0030] Tannic acid can also participate in the coagulation process of polyaluminium chloride, promoting floc formation through adsorption and bridging, helping to form a more compact and stable floc structure. Furthermore, because the tannic acid is fixed to the modified sepiolite fibers, it can significantly reduce the interaction between the tannic acid and the polyaluminium chloride and the colloidal particles, reducing the adverse effects on coagulation efficiency. Tannic acid can also form relatively stable complexes with metal ions, improving the water treatment agent's ability to remove impurity metal ions.

[0031] Preferably, the sepiolite fiber is pretreated; the pretreatment process includes: adding the sepiolite fiber to a strong acid solution, stirring and shaking for 4 to 6 hours, then raising the temperature to 90 to 100° C. to activate for 2 to 3 hours, and finally calcining at 550 to 600° C. for 2 to 3 hours.

[0032] Preferably, the strong acid solution includes a hydrochloric acid aqueous solution and a sulfuric acid aqueous solution with a mass fraction of 15 to 25%.

[0033] Preferably, the solid-liquid ratio of sepiolite fiber to strong acid solution is 1:(8-10).

[0034] By adopting the above technical solution, the sepiolite fiber is also pretreated with strong acid before modification. The pretreatment can effectively remove impurities on the surface and internal pores of the sepiolite fiber, improve the adsorption capacity of the sepiolite fiber, and expose more active sites, thereby enhancing the interaction between tannic acid and sepiolite fiber and enhancing adsorption efficiency.

[0035] Preferably, the auxiliary flocculant includes any one of chitosan, sodium carboxymethyl starch and pectin.

[0036] More preferably, the auxiliary flocculant is pectin.

[0037] By adopting the above technical solution, in order to stabilize the flocculation properties of polyaluminium chloride, the addition of auxiliary flocculants can strengthen the flocculation process, connect the fine colloidal particles into larger flocs through bridging, increase the floc volume, improve the solid-liquid separation efficiency, and also improve the ability of the water treatment agent to remove color and turbidity.

[0038] Furthermore, the auxiliary flocculant of the present invention is pectin. Compared with other auxiliary flocculants, pectin has a longer molecular weight, and the active groups contained in the molecular chain can establish stronger bridge connections, forming a more stable and solid floc structure. Moreover, because pectin has both hydrophilic groups and hydrophobic segments, it can promote the flocculation process while adsorbing organic pollutants, thereby achieving a better flocculation effect.

[0039] Preferably, the molecular weight of polyvinyl alcohol is 5.0×10 4 ~7.0×10 4 .

[0040] By adopting the above-mentioned technical scheme, by carrying the modified sepiolite fiber with multi-stage anions and compounding polyaluminium chloride under the action of auxiliary flocculants, it is possible to achieve good flocculation effect and water treatment effect. However, in the face of extreme water quality or under the action of long-term stirring, stability will decrease, and the composite polyaluminium chloride and auxiliary flocculants have a trend of breaking away from the modified sepiolite fiber. Therefore, polyvinyl alcohol is also added in the process of compounding polyaluminium chloride. Polyvinyl alcohol itself has good film-forming property and adhesion, can react with the multiple active groups on the modified sepiolite fiber, strengthen the structural strength of the composite material obtained, play a certain protective effect, avoid the breakaway of polyaluminium chloride and also block the adverse effects of the outside world on the water treatment agent. And the large amount of polar groups and adhesion contained in polyvinyl alcohol also make it possible to fix organic pollutants by physical adsorption or chemical crosslinking in the water treatment process, improve the attractiveness of the water treatment agent to pollutants, thereby improving the flocculation efficiency and water treatment efficiency of the water treatment agent.

[0041] In a second aspect, the present invention provides a method for preparing a composite polyaluminum chloride water treatment agent, comprising the following process steps:

[0042] S1. The polyaluminum chloride and modified sepiolite fiber were mixed, an auxiliary flocculant was added, stirring and mixing were continued, wet ball milling was performed, and the premix was obtained after drying;

[0043] S2. Add polyvinyl alcohol and water to the premix, raise the temperature to 35-45° C., stir and mix for 2-3 hours, and finally dry to obtain a composite polyaluminum chloride water treatment agent.

[0044] Preferably, the solid-liquid ratio of wet ball milling is 1:(5-6); and the wet ball milling time is 1-2 hours.

[0045] Preferably, the mass ratio of water to polyvinyl alcohol is (0.9-1.2):1.

[0046] Beneficial effects of the present invention:

[0047] 1. The composite polyaluminum chloride water treatment agent of the present invention mainly comprises polyaluminum chloride and modified sepiolite fiber. The fiber structure of the sepiolite fiber can provide sufficient adsorption sites and bridging structure for polyaluminum chloride, thereby improving the structural stability of polyaluminum chloride and enhancing the adsorption capacity for pollutants. The modified sepiolite fiber of the present invention is also loaded with multi-stage anions, which can enhance the structural stability by forming more complex complexes with the chloride ions in polyaluminum chloride. The combination of multiple anions can enhance the charge neutralization and adsorption bridging effects, making it easier for the flocculated particles to aggregate together to obtain larger flocs, thereby improving the stability of the flocculation effect.

[0048] 2. Tannic acid is also fixed on the surface of the modified sepiolite fiber of the present invention, which can improve the adsorption rate of multi-stage anions on the one hand, and on the other hand can cooperate with polyaluminum chloride to help form a tighter and more stable floc structure, and can also complex metal ions to improve the ability of the composite water treatment agent to remove metal impurities.

[0049] 3. The composite polyaluminum chloride water treatment agent of the present invention also contains an auxiliary flocculant, which can enhance the flocculation process, improve the solid-liquid separation efficiency and the ability to remove turbidity; and polyvinyl alcohol is also added to protect the composite polyaluminum chloride water treatment agent from being easily decomposed and separated during the water treatment process, and can also enhance the attractiveness of the obtained water treatment agent to organic pollutants and improve the flocculation efficiency. DETAILED DESCRIPTION

[0050] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0051] Preparation Example

[0052] Preparation Example 1: A modified sepiolite fiber was prepared according to the following method:

[0053] 10 g of sepiolite fiber was passed through a 200-mesh sieve and added to 100 mL of a 20% hydrochloric acid aqueous solution. The mixture was stirred and shaken for 5 h, then the temperature was raised to 95 ° C for activation for 2 h, and finally calcined at 600 ° C for 2 h to obtain the pretreated sepiolite fiber.

[0054] 3 g of water-soluble salt and 38 g of tannic acid were prepared into a reaction aqueous solution with a mass fraction of 50%. 10 g of the sepiolite fiber obtained above was added to the reaction aqueous solution, stirred and mixed for 20 minutes, and then the pH value of the solution was adjusted to 7.5. The temperature was increased to 65°C and stirred for 2 hours. Finally, the modified sepiolite fiber was obtained by drying, calcining and grinding.

[0055] The water-soluble salt is a combination of sodium dihydrogen phosphate, sodium silicate and sodium carbonate in a molar ratio of 0.5:0.4:0.1.

[0056] Preparation Example 2, a modified sepiolite fiber, differs from Preparation Example 1 only in that the amount of water-soluble salt added is 3 g and the amount of tannic acid added is 35 g.

[0057] Preparation Example 3, a modified sepiolite fiber, is different from Preparation Example 1 only in that the amount of water-soluble salt added is 4 g, and the amount of tannic acid added is 45 g.

[0058] Preparation Example 4, a modified sepiolite fiber, differs from Preparation Example 1 only in that the water-soluble salt is a combination of sodium dihydrogen phosphate and sodium silicate in a molar ratio of 0.6:0.4.

[0059] Preparation Example 5, a modified sepiolite fiber, differs from Preparation Example 1 only in that the water-soluble salt is a combination of sodium dihydrogen phosphate, sodium silicate and sodium carbonate in a molar ratio of 0.4:0.4:0.2.

[0060] Preparation Example 6, a modified sepiolite fiber, differs from Preparation Example 1 only in that the water-soluble salt is a combination of sodium silicate and sodium carbonate in a molar ratio of 0.8:0.2.

[0061] Preparation Example 7, a modified sepiolite fiber, differs from Preparation Example 1 only in that the water-soluble salt is a combination of sodium dihydrogen phosphate and sodium carbonate in a molar ratio of 0.8:0.2.

[0062] Preparation Example 8, a modified sepiolite fiber, differs from Preparation Example 1 only in that the water-soluble salt is sodium dihydrogen phosphate.

[0063] Preparation Example 9, a modified sepiolite fiber, differs from Preparation Example 1 only in that the water-soluble salt is sodium silicate.

[0064] Preparation Example 10, a modified sepiolite fiber, is different from Preparation Example 1 only in that the water-soluble salt is sodium carbonate.

[0065] Preparation Example 11, a modified sepiolite fiber, is different from Preparation Example 1 only in that the amount of water-soluble salt added is 2 g.

[0066] Preparation Example 12, a modified sepiolite fiber, is different from Preparation Example 1 only in that the amount of water-soluble salt added is 5 g.

[0067] Preparation Example 13, a modified sepiolite fiber, is different from Preparation Example 1 only in that the amount of tannic acid added is 30 g.

[0068] Preparation Example 14, a modified sepiolite fiber, is different from Preparation Example 1 only in that the amount of tannic acid added is 50 g.

[0069] Preparation Example 15, a modified sepiolite fiber, differs from Preparation Example 1 only in that tannic acid is not added.

[0070] Preparation Example 16: A modified sepiolite fiber was prepared according to the following method:

[0071] 3 g of water-soluble salt and 38 g of tannic acid were prepared into a reaction aqueous solution with a mass fraction of 50%. 10 g of sepiolite fiber (passed through a 200-mesh sieve) was added to the reaction aqueous solution and stirred for 20 minutes. The pH value of the solution was adjusted to 7.5, the temperature was increased to 65°C, and the reaction was stirred for 2 hours. Finally, the modified sepiolite fiber was obtained by drying, calcining and grinding.

[0072] Preparation Example 17, a modified sepiolite fiber, differs from Preparation Example 1 only in that no water-soluble salt is added.

[0073] Preparation Example 18, a modified sepiolite fiber, differs from Preparation Example 1 only in that an equal amount of sepiolite powder is used to replace the sepiolite fiber.

[0074] Example

[0075] Example 1, a composite polyaluminum chloride water treatment agent, is prepared according to the following process steps:

[0076] S1. 100 g of polyaluminum chloride (Al2O3 ≥ 30%) and 40 g of the modified sepiolite fiber prepared in Preparation Example 1 were mixed uniformly, 15 g of pectin was added, and the mixture was stirred and wet-milled, wherein the solid-liquid ratio of the wet milling was 1:5; the wet milling time was 1.5 h, and the premix was dried to obtain a premix;

[0077] S2. Add 20g of polyvinyl alcohol (average molecular weight 6.0×10 4 ) and 20g water, raise the temperature to 40°C, stir and mix for 2h, and finally dry to obtain a composite polyaluminum chloride water treatment agent.

[0078] Example 2, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the amount of modified sepiolite fiber prepared in Preparation Example 1 added is 30 g; the amount of pectin added is 20 g; and the amount of polyvinyl alcohol added is 15 g.

[0079] Example 3, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the added amount of the modified sepiolite fiber prepared in Preparation Example 1 is 50 g; the added amount of pectin is 10 g; and the added amount of polyvinyl alcohol is 25 g.

[0080] Example 4, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 2 is used in place of the modified sepiolite fiber prepared in Preparation Example 1.

[0081] Example 5, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 3.

[0082] Example 6, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 4.

[0083] Example 7, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 5.

[0084] Example 8, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 6.

[0085] Example 9, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 7.

[0086] Example 10, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 8 is used in place of the modified sepiolite fiber prepared in Preparation Example 1.

[0087] Example 11, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 9 is used in place of the modified sepiolite fiber prepared in Preparation Example 1.

[0088] Example 12, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 10.

[0089] Example 13, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 11.

[0090] Example 14, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 12.

[0091] Example 15, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 13.

[0092] Example 16, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 14.

[0093] Example 17, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 16.

[0094] Example 18, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that an equal amount of chitosan is used to replace pectin.

[0095] Comparative Example

[0096] Comparative Example 1, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the added amount of the modified sepiolite fiber prepared in Preparation Example 1 is 20 g.

[0097] Comparative Example 2, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the added amount of the modified sepiolite fiber prepared in Preparation Example 1 is 60 g.

[0098] Comparative Example 3, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 15.

[0099] Comparative Example 4, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 17.

[0100] Comparative Example 5, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that the modified sepiolite fiber prepared in Preparation Example 1 is replaced by an equal amount of the modified sepiolite fiber prepared in Preparation Example 18.

[0101] Comparative Example 6, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that an equal amount of sepiolite fibers is used to replace the modified sepiolite fibers prepared in Preparation Example 1.

[0102] Comparative Example 7, a composite polyaluminum chloride water treatment agent, differs from Example 1 only in that no pectin is added.

[0103] Comparative Example 8, a composite polyaluminum chloride water treatment agent, was prepared according to the following process steps:

[0104] 100 g of polyaluminum chloride (Al2O3 ≥ 30%) and 40 g of the modified sepiolite fiber prepared in Preparation Example 1 were evenly mixed, 15 g of pectin was added, and the mixture was stirred and mixed, followed by wet ball milling. The solid-liquid ratio of the wet ball milling was 1:5; the wet ball milling time was 1.5 h, and the composite polyaluminum chloride water treatment agent was obtained after drying.

[0105] Performance testing

[0106] Sample preparation: organic sewage from urban rivers was collected, with an influent COD content of 330 mg / L and containing Cu 2+ 43.2 mg / L, take 500 mL of the above sewage, add the composite polyaluminum chloride water treatment agent obtained in the examples and comparative examples, the dosage is 25 mg / L, stir for 15 minutes, let it stand and settle for 15 minutes, take the supernatant as a sample for testing:

[0107] 1. COD test: According to the relevant records in HJ 828-2017 "Determination of Chemical Oxygen Demand in Water - Dichromate Method", the COD of the sample is tested and the CDO removal rate is calculated;

[0108] 2. Turbidity test: Test the turbidity of the sample according to the relevant records in GB / T 13200-1991 "Determination of Turbidity of Water Quality";

[0109] 3. Cu 2+ Test: Determination of Cu in samples 2+ Content, calculate Cu 2+ Removal rate.

[0110] The above test results are shown in Table 1:

[0111] Table 1 Performance test results

[0112]

[0113] According to Table 1, in combination with Example 1, Example 13, Example 14 and Comparative Example 4, it can be seen that the COD removal rate and Cu 2+Compared to Example 1, the removal rate decreased, the turbidity increased, and the performance of Comparative Example 4 decreased significantly. This is because, in Example 13, the content of multistage anions carried by the modified sepiolite fibers was reduced, which reduced the structural stability of the polyaluminum chloride. Furthermore, the charge neutralization and adsorption bridging effects of the water treatment agent decreased, resulting in a decreased removal efficiency and poor flocculation effect. This resulted in a decreased removal rate for the resulting composite polyaluminum chloride water treatment agent. In Comparative Example 4, the sepiolite fibers were not loaded with multistage anions, resulting in an even more significant performance decrease. In Example 14, the increased content of loaded multistage anions led to charge imbalance, which was detrimental to flocculation.

[0114] Combining Example 1, Example 15, Example 16 and Comparative Example 3, it can be seen that the COD removal rate and Cu 2+ The removal rate decreased compared with Example 1, and the turbidity increased, especially Cu 2+ Removal rate and turbidity change are more obvious.The reason is that, in embodiment 15, the tannic acid addition of modified sepiolite fiber in the preparation process is reduced, which can affect the stability of the multi-stage anion of load on the one hand, on the other hand, lacking the complexation and interaction of tannic acid, the removal rate of flocculation effect and impurity metal ions also decreases, and tannic acid is not added in comparative example 3, and the multi-stage anion is easy to break away from the modified sepiolite fiber surface in the water treatment process, reducing the synergistic enhancement effect to the composite polyaluminium chloride water treatment agent, and also greatly reducing the attraction and complexation between the metal ions, and the water treatment capacity declines more obviously.In embodiment 16, the addition of tannic acid is increased, and the active sites on the modified sepiolite fiber are occupied in a large number, which is unfavorable for the compound between polyaluminium chloride and the auxiliary flocculant on the contrary.

[0115] Combining Example 1 and Comparative Example 6, it can be seen that the COD removal rate and Cu 2+ The removal rate is significantly lower than that of Example 1, and the turbidity is significantly increased. The reason is that the sepiolite fiber in Comparative Example 6 has not undergone any modification treatment. Combined with the test results of Comparative Examples 3 and 4, it can be seen that the enhancing effects of tannic acid and multi-stage anions synergize with each other, which can greatly improve the removal ability of the water treatment agent.

[0116] Combining Example 1 and Comparative Example 5, it can be seen that the COD removal rate and Cu 2+ The removal rate decreased and the turbidity increased compared with Example 1. The reason is that in Comparative Example 5, sepiolite fiber was replaced by sepiolite powder. The sepiolite powder does not have the unique fiber structure of the original sepiolite fiber, resulting in a decrease in the binding force between the powder and the polyaluminum chloride, making it difficult to form a larger floc volume during the water treatment process, and the removal ability of the obtained water treatment agent is reduced.

[0117] Combining Example 1, Comparative Example 7 and Comparative Example 8, it can be seen that the COD removal rate and Cu 2+ The removal rate decreased compared with Example 1, and the turbidity increased significantly. The reason is that no auxiliary flocculant was added in Comparative Example 7, the flocculation effect decreased, and the ability to treat turbidity in sewage also decreased; no polyvinyl alcohol was added in Comparative Example 8, which lacked the protective effect on the modified sepiolite fiber composite polyaluminum chloride structure, and reduced the attraction of the composite polyaluminum chloride water treatment agent to organic pollutants and metal ions in sewage, resulting in a decrease in the flocculation effect.

[0118] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0119] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A composite polyaluminium chloride water treatment agent, characterized in that, Including the following raw materials in parts by weight: 100 parts of polyaluminium chloride; 30-50 parts of modified sepiolite fiber; 10-20 parts of auxiliary flocculant; 15-25 parts of polyvinyl alcohol; The modified sepiolite fiber is loaded with multi-stage anions; The multi-stage anions are a combination of phosphate ions, silicate ions and carbonate ions in a molar ratio of (0.4-0.6): (0.3-0.5): (0.1-0.2); The raw materials of the modified sepiolite fiber include sepiolite fiber, tannic acid and water-soluble salt in a mass ratio of 1: (3.5-4): (0.3-0.4); The water-soluble salts include water-soluble phosphates, water-soluble silicates and water-soluble carbonates; The modified sepiolite fiber is prepared according to the following method: A water-soluble salt and tannic acid are prepared into a reaction aqueous solution, sepiolite fibers are added to the reaction aqueous solution, stirred and mixed for 10 to 30 minutes, the pH value of the solution is adjusted to 7.5 to 8.0, the temperature is increased to 60 to 65° C., the reaction is stirred for 2 to 3 hours, and finally the modified sepiolite fibers are obtained through drying, calcining and grinding. The auxiliary flocculant includes any one of chitosan, sodium carboxymethyl starch and pectin.

2. The composite polyaluminium chloride water treatment agent according to claim 1, characterized in that: The sepiolite fibers are pretreated; The pretreatment process comprises: adding sepiolite fiber into a strong acid solution, stirring and shaking for 4-6 hours, then raising the temperature to 90-100° C. to activate for 2-3 hours, and finally calcining at 550-600° C. for 2-3 hours to obtain the obtained fiber.

3. The composite polyaluminium chloride water treatment agent according to claim 1, characterized in that: The molecular weight of the polyvinyl alcohol is 5.0×10 4 ~7.0×10 4 .

4. A method for preparing a composite polyaluminium chloride water treatment agent according to any one of claims 1 to 3, characterized in that: The process steps include: S1. The polyaluminum chloride and modified sepiolite fiber were mixed, an auxiliary flocculant was added, stirring and mixing were continued, wet ball milling was performed, and the premix was obtained after drying; S2. Add polyvinyl alcohol and water to the premix, raise the temperature to 35-45° C., stir and mix for 2-3 hours, and finally dry to obtain a composite polyaluminum chloride water treatment agent.

5. The preparation method of the composite polyaluminium chloride water treatment agent according to claim 4, wherein The solid-liquid ratio of the wet ball milling is 1:(5-6); and the wet ball milling time is 1-2 hours.

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