Liquid polyaluminum ferric sulfate flocculant, preparation process and application of liquid polyaluminum ferric sulfate flocculant in wastewater treatment

Abstract

The invention discloses a liquid polyaluminum ferric sulfate flocculant, a preparation process and application of the liquid polyaluminum ferric sulfate flocculant in wastewater treatment. The process comprises the following steps: (1) stirring and mixing gypsum and wastewater, adjusting the pH value, and carrying out filter pressing treatment; (2) stirring and mixing the filtrate and gypsum again, adjusting the pH value, and carrying out secondary filter pressing treatment; (3) carrying out oxidation treatment on the filtrate to prepare liquid polyaluminum ferric sulfate; and (4) adding a modifier into the liquid polyaluminum ferric sulfate for modification treatment to prepare the liquid polyaluminum ferric sulfate flocculant. The liquid polyaluminum ferric sulfate flocculant disclosed by the invention not only has higher economic value, but also realizes effective recovery and utilization of resources. In the production process, the process effectively reduces emission and reduces adverse effects on the environment. Meanwhile, the production cost is low, the production period is short, the comprehensive economic benefits of enterprises are remarkably improved, and positive contributions are made for promoting the development of circular economy.

Description

[Technical field]

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a liquid polyaluminium ferric sulfate flocculant, a preparation process and application thereof in treating wastewater. [Background technology]

[0002] Activated clay, as one of the core raw materials in the field of petrochemicals and daily chemicals, plays an irreplaceable role in the refining and decolorization of mineral oils, vegetable oils and even animal fats. This high-performance material is derived from natural bentonite and is transformed through a carefully designed wet acidification process. Each step of the production process contains the harmonious coexistence of technology and nature.

[0003] In the birth journey of activated clay, the first thing is to fully hydrate the bentonite to make its structure loose and facilitate the subsequent reaction. Then, add an appropriate amount of sulfuric acid for activation. This step is the key to activating the adsorption performance of bentonite, giving it stronger decolorization and purification capabilities through chemical reactions. But what comes with it is the high content of acidic substances in the product. In order to meet the strict industry standard HG / T2569-2007, multiple water washings must be implemented during the production process to ensure that the acidity drops below 0.2%. This step not only tests the patience and fine operation of technicians, but is also accompanied by the generation of a large amount of wastewater. The production of each ton of activated clay is usually accompanied by the birth of at least 30 to 40 tons of wastewater.

[0004] In these wastewaters, aluminum sulfate and incompletely reacted sulfuric acid dominate. If they are discharged directly without treatment, it will be tantamount to wasting precious resources and placing a heavy burden on the natural environment. Ecological problems such as water acidification and soil pollution will follow. Therefore, wastewater treatment and resource utilization have become an indispensable part of the activated clay production chain.

[0005] It is worth noting that the output of gypsum slag, a byproduct of the activated clay production process, is also considerable. The production of each ton of activated clay is accompanied by the output of about 1.6 tons of gypsum slag. The surface of gypsum slag is acidic, and if not handled properly, it can easily cause environmental pollution problems. Faced with this challenge, the industry is actively exploring ways to increase the value of gypsum slag, striving to maximize the use of resources while reducing environmental pollution.

[0006] In the construction field, gypsum slag has been tried as a cement retarder, filling material, etc., which effectively reduces the pressure on the exploitation of natural gypsum resources; in the agricultural field, its potential application value is also being gradually explored. However, the current utilization of gypsum slag is still mainly based on traditional brick making and stockpiling. Although these methods can alleviate environmental pollution to a certain extent, the degree of resource utilization is low and there is a risk of secondary pollution. Therefore, developing new ways to utilize gypsum slag at a high value has become a technical problem that needs to be solved urgently.

[0007] In this context, an innovative idea emerged: using the high-concentration sulfuric acid wastewater generated during the production of activated clay, dissolving iron and aluminum elements in gypsum slag through a specific process, and then preparing polyaluminum ferric sulfate flocculant. This solution can not only effectively reduce production costs, but also achieve in-depth treatment and resource utilization of wastewater, realize effective emission reduction during the production process, and reduce the negative impact on the environment. At the same time, the wide application of the flocculant will further promote the development of circular economy and build a more green and sustainable industrial ecosystem.

[0008] The Chinese patent application document (publication number: CN118745033A) discloses a method for producing polyaluminum ferric sulfate water purifying agent using red gypsum, including the following steps: (1) stirring and mixing red gypsum with the wastewater from the production of activated clay, adjusting the pH of the mixed solution, and performing pressure filtration to obtain a primary filtrate; (2) performing a second stirring and mixing of the primary filtrate with red gypsum, adjusting the pH of the mixed solution, adjusting the composition of iron oxide, aluminum oxide, and sulfur trioxide in the liquid, and then performing pressure filtration to obtain a secondary filtrate; (3) oxidizing the secondary filtrate to prepare liquid polyaluminum ferric sulfate; (4) adding a modifying material to the liquid polyaluminum ferric sulfate for modification treatment to prepare a polyaluminum ferric sulfate water purifying agent. This method can achieve the recycling of resources and effective emission reduction during production, but there are problems such as slow flocculation speed and incomplete flocculation, which cannot meet the application requirements.

Summary of the Invention

[0009] The present invention provides a liquid polyaluminum ferric sulfate flocculant, a preparation process thereof, and its application in treating wastewater, aiming to explore a solution to a technical problem: how to effectively utilize activated clay to dissolve the iron and aluminum elements carried by gypsum from wastewater containing high-concentration sulfuric acid, and further optimize the process flow to prepare an efficient flocculant. The application goal of this flocculant is to significantly improve the turbidity removal efficiency and the removal rate of chemical oxygen demand (COD) during the sewage treatment process.

[0010] To solve the above technical problems, the present invention adopts the following technical solutions:

[0011] A preparation process of a liquid polyaluminum ferric sulfate flocculant, including the following steps:

[0012] (1) Mix the wastewater from the production of activated clay with bentonite, control the temperature of the solution at 89 - 94 °C to dissolve aluminum sulfate in bentonite into the production wastewater, and then circulate the activated clay production wastewater with increased aluminum sulfate concentration and mix it with newly added bentonite to make the aluminum sulfate reach saturation;

[0013] (2) Control the temperature of the production wastewater saturated with aluminum sulfate prepared in step (1) at 90 - 93 °C, then adjust the pH value to 4.8 - 5.2, and then add potassium sulfate;

[0014] (3) Add polyaluminum sulfate to the solution prepared in step (2). After flocculating potassium alum, then filter to remove impurities. Cool the obtained clear liquid, and then press the potassium alum at a pressure of 0.83 - 0.92 MPa to a water content of 39% - 44% to obtain filter cake crude potassium alum, and collect all the filtrates of this step at the same time;

[0015] (4) Put the crude potassium alum prepared in step (3) into water with a weight of 112% - 123%, heat it to 92 - 96 °C and stir until the crude potassium alum is completely dissolved. Then add polyaluminum sulfate. After flocculating potassium alum, then remove impurities again. Cool the obtained clear liquid to below 5 °C, and then press-filter the potassium alum at a pressure of 0.85 - 0.91 MPa to obtain potassium alum, and collect all the filtrates of this step at the same time;

[0016] (5) Collect and mix the filtrates of step (3) and the filtrates in step (4). Add lime to the mixed filtrates to react to form iron hydroxide. After the filtrates are neutralized, press-filter them with a filter press at a pressure of 0.87 - 0.96 MPa to a water content of 40% - 45% to obtain filter cake gypsum;

[0017] (6) Dry the filter cake gypsum prepared in step (5) to obtain gypsum;

[0018] (7) Stir and mix the gypsum prepared in step (6) with the production wastewater of activated clay. Conditions: temperature is 32 - 36 °C, rotation speed is 200 - 400 r / min, adjust the pH of the mixed liquid to 0.9 - 1.7, and perform pressure filtration treatment to obtain primary filtrate;

[0019] (8) Perform a second stirring and mixing of the primary filtrate prepared in step (7) with newly added gypsum, adjust the acidity of the mixed liquid, adjust the pH of the mixed liquid to 1.8 - 2.6, adjust the composition of iron oxide, aluminum oxide, and sulfur trioxide in the liquid, and then perform pressure filtration treatment to obtain secondary filtrate;

[0020] (9) Treat the secondary filtrate prepared in step (8) with oxygen oxidation to obtain liquid polyaluminum ferric sulfate;

[0021] (10) Add a modifier to the liquid polyaluminum ferric sulfate prepared in step (9), and then stir at a temperature of 52 - 55 °C and a rotation speed of 300 - 500 r / min for 1.5 - 2 h to obtain a liquid polyaluminum ferric sulfate flocculant.

[0022] Preferably, in step (1), the activated clay production wastewater with increased aluminum sulfate concentration is recycled and mixed with newly added bentonite, and this method is cycled 3 - 4 times to saturate the aluminum sulfate.

[0023] Preferably, in step (2), the amount of potassium sulfate is such that the molar concentration ratio of K + :Al 3+ :SO4 2- in alum is 1 - 1.04:1:2 - 2.02.

[0024] Preferably, the clear liquid obtained in step (3) is cooled to below 6°C.

[0025] Preferably, in step (4), the potassium alum is filtered to a water content of 40% - 43%.

[0026] Preferably, in step (5), the filtrate is neutralized to a pH value of 7.1.

[0027] Preferably, in step (6), the filter cake gypsum is dried in the sun to a water content of ≤6.5%.

[0028] Preferably, during the treatment in step (9), the air pressure of the oxygen pressure gauge is maintained at 0.01 - 0.02 MPa.

[0029] Compared with the prior art, the present invention exhibits significant technical advantages. These advantages are not only reflected in the process innovation but also achieve a qualitative leap in the actual application effect and environmental protection benefits. Specifically, the technical advantages of the present invention can be elaborated in detail from the following aspects:

[0030] (1) Efficient conversion and utilization of by - products

[0031] During the production process of activated clay, traditional processes often generate a large amount of gypsum by - products. If these by - products are not properly treated, they will not only occupy land resources but also may impose a burden on the environment. However, the present invention ingeniously adopts the acid leaching method to deeply explore the gypsum component and successfully extracts the effective components therein, namely aluminum and iron. This innovative step not only realizes the resource utilization of by - products but also opens up a new way to produce flocculants using the solid gypsum of activated clay by - products.

[0032] In the process of producing polyaluminum ferric sulfate with gypsum, the present invention precisely controls the reaction conditions, including fine-tuning the reaction pH value, accurately grasping the degree of polymerization, strictly proportioning the main component content, and scientifically setting the dosage of the modifier. Finally, a liquid polyaluminum ferric sulfate flocculant with excellent performance is produced. The performance of this flocculant in practical applications is remarkable: when treating sewage, the turbidity removal rate of the sewage is as high as over 98.0%, and the COD (chemical oxygen demand) removal rate reaches over 98.8%. Moreover, large flocs can be rapidly formed within just 59 seconds. This series of data fully demonstrates that using the flocculant of the present invention to treat sewage can not only achieve a rapid and efficient flocculation effect, but also ensure that the turbidity of the supernatant after flocculation is extremely low, while meeting the strict national requirement that the COD removal rate in sewage discharge is higher than 93%, showing the significant progress of the present invention in the field of sewage treatment.

[0033] (2) Optimization of product physical and chemical indicators and improvement of economic benefits

[0034] The liquid polyaluminum ferric sulfate flocculant prepared by the present invention also performs excellently in terms of physical and chemical indicators. Specifically, the mass fraction of alumina in this product is not less than 7.9%, the mass fraction of total iron is not less than 1.4%, and the mass fraction of ferrous iron is strictly controlled below 0.2%. These excellent physical and chemical indicators not only ensure the stability and high efficiency of the product, but also endow it with high economic value.

[0035] More importantly, the implementation of the present invention not only realizes the recycling of resources, but also effectively reduces wastewater discharge, with the emission reduction ratio reaching over 12%. The realization of this environmental benefit not only reduces the negative impact on the environment, but also conforms to the current global concept of circular economy. In addition, the production cost of the present invention is relatively low, the production cycle is short, and it is easy to achieve large-scale production. These advantages enable enterprises to improve production efficiency and reduce operating costs while ensuring product quality, thereby achieving new production goals and enhancing the comprehensive economic benefits of enterprises.

[0036] In summary, the present invention not only achieves an innovative breakthrough at the technical level, but also makes remarkable progress in practical application effects and environmental benefits. Its successful implementation not only provides a new idea for the resource utilization of activated clay by-products, but also injects new vitality into the development of the sewage treatment and environmental protection industries.

Description of the Drawings

[0037] Figure 1 It is a diagram of the gypsum product prepared in Example 2.

[0038] Figure 2 It is a photo of the turbid sewage in a certain river in Long'an County, Nanning before flocculation.

[0039] Figure 3The photo after flocculation of the turbid sewage in a certain river in Long'an County, Nanning City, treated with the liquid polyaluminum ferric sulfate flocculant produced in Example 2.

Specific Embodiments

[0040] To better understand the present invention, it is illustrated by the following examples. These examples belong to the protection scope of the present invention, but do not limit the protection scope of the present invention.

[0041] In the embodiment of the present invention, a preparation process of a liquid polyaluminum ferric sulfate flocculant includes the following steps:

[0042] (1) Mix the activated clay production wastewater with bentonite, control the temperature of the solution at 89 - 94 °C to dissolve the aluminum sulfate in the bentonite into the production wastewater, and then circulate the activated clay production wastewater with increased aluminum sulfate concentration and mix it with the newly added bentonite. Circulate in this way for 3 - 4 times to make the aluminum sulfate reach saturation;

[0043] (2) Control the temperature of the production wastewater with saturated aluminum sulfate obtained in step (1) at 90 - 93 °C, then adjust the pH value to 4.8 - 5.2, and then add potassium sulfate. The amount of potassium sulfate is such that the molar concentration ratio of K + :Al 3+ :SO4 2- is 1 - 1.04:1:2 - 2.02;

[0044] (3) Add polyaluminum sulfate to the solution obtained in step (2). After coagulating potassium alum, then filter to remove impurities. Cool the obtained clear liquid to below 6 °C, and then under a pressure of 0.83 - 0.92 MPa, press the potassium alum to a moisture content of 39% - 44% to obtain a filter cake of crude potassium alum, and at the same time collect all the filtrates of this step;

[0045] (4) Put the crude potassium alum obtained in step (3) into water with a weight of 112% - 123%, heat it to 92 - 96 °C and stir until the crude potassium alum is completely dissolved. Add polyaluminum sulfate, coagulate potassium alum, then remove impurities again. Cool the obtained clear liquid to below 5 °C, and then under a pressure of 0.85 - 0.91 MPa, press the potassium alum to a moisture content of 40% - 43% to obtain potassium alum, and at the same time collect all the filtrates of this step;

[0046] (5) Collect and mix the filtrates of step (3) and step (4). Add lime to the mixed filtrate to react to generate iron hydroxide. After the filtrate is neutralized to a pH value of 7.1, filter it under a pressure of 0.87 - 0.96 MPa by a filter press to a moisture content of 40% - 45% to prepare a filter cake of gypsum;

[0047] (6) Dry the filter cake gypsum obtained in step (5) until the water content is ≤ 6.5% to obtain gypsum;

[0048] (7) Stir and mix the gypsum obtained in step (6) with the activated clay production wastewater under the conditions: temperature is 32 - 36 °C, rotation speed is 200 - 400 r / min, adjust the pH of the mixed solution to 0.9 - 1.7, and perform pressure filtration to obtain the primary filtrate;

[0049] (8) Conduct a second stirring and mixing of the primary filtrate obtained in step (7) with newly added gypsum, adjust the acidity of the mixed solution, adjust the pH of the mixed solution to 1.8 - 2.6, adjust the composition of iron oxide, aluminum oxide, and sulfur trioxide in the liquid, and then perform pressure filtration to obtain the secondary filtrate;

[0050] (9) Treat the secondary filtrate obtained in step (8) by oxidation with oxygen, and maintain the air pressure of the oxygen pressure gauge at 0.01 - 0.02 MPa during the treatment to obtain liquid polyaluminum ferric sulfate;

[0051] (10) Add a modifier to the liquid polyaluminum ferric sulfate obtained in step (9), the modifier includes potassium carboxymethyl cellulose, sodium hexametaphosphate, sodium persulfate, and an additive, and then stir at a temperature of 52 - 55 °C and a rotation speed of 300 - 500 r / min for 1.5 - 2 h to obtain a liquid polyaluminum ferric sulfate flocculant;

[0052] The additive includes acrylamide and acrylate - acrylate copolymer, the mass ratio of acrylamide to acrylate - acrylate copolymer is 1:1 - 1:3, the dosage of potassium carboxymethyl cellulose accounts for 5.2% - 8.7% of the mass of liquid polyaluminum ferric sulfate, the dosage of sodium hexametaphosphate accounts for 3.8% - 5.5% of the mass of liquid polyaluminum ferric sulfate, the dosage of sodium persulfate accounts for 1.3% - 2.4% of the mass of liquid polyaluminum ferric sulfate, and the dosage of the additive accounts for 0.2% - 0.4% of the mass of liquid polyaluminum ferric sulfate.

[0053] The technical principle of the present invention:

[0054] The preparation process of the high - efficiency liquid polyaluminum ferric sulfate flocculant of the present invention is ingenious in that through a series of finely controlled steps, it not only makes full use of resources but also significantly improves the performance of the product, reflecting significant technological progress. The following is a detailed analysis of this preparation process, focusing on the specific functions of each raw material, the necessity and importance of controlling the raw material dosage and optimizing the process parameters, as well as the achieved technical effects.

[0055] (1)Initial fusion of raw materials and saturation of aluminum sulfate: First, the wastewater from activated clay production is mixed with bentonite. The innovation of this step lies in using the waste (wastewater from activated clay production) as a solvent, which not only reduces environmental pollution but also saves water resources. The solution temperature is controlled at 89 - 94 °C. This temperature range can effectively promote the dissolution of aluminum sulfate in bentonite and accelerate the reaction process. By adding fresh bentonite to the wastewater from activated clay production in a cyclic manner and controlling the number of cycles at 3 - 4 times, the saturation of aluminum sulfate is ensured, which is the key to improving the efficiency of subsequent reactions and the purity of products.

[0056] (2)pH adjustment and preparation of potassium alum precursor: In the aluminum sulfate - saturated production wastewater, the temperature is further adjusted to 90 - 93 °C, and the pH value is precisely controlled at 4.8 - 5.2. This pH range is conducive to the formation of stable aluminum ion forms, laying the foundation for the subsequent synthesis of potassium alum. Potassium sulfate is added, and the precise control of its amount (so that the molar concentration ratio of K + :Al 3+ :SO4 2- is 1 - 1.04:1:2 - 2.02) is the key to forming an ideal potassium alum structure and directly affects the flocculation performance of the final product.

[0057] (3)Preliminary preparation of potassium alum and impurity removal: Poly aluminum sulfate is added to promote the coagulation of potassium alum, and then impurities are removed by filtration to ensure product purity. It is cooled to below 6 °C and filtered under a specific pressure (0.83 - 0.92 MPa) to obtain a filter cake of crude potassium alum with a moisture content of 39% - 44%. This step optimizes the moisture content and is conducive to subsequent dissolution and re - processing.

[0058] (4)Purification of potassium alum: The crude potassium alum is redissolved in an appropriate amount of water, and poly aluminum sulfate is added again for coagulation. The temperature, pH, and filtration conditions are strictly controlled to obtain potassium alum with higher purity and more stable structure. The fine regulation of this step significantly improves the flocculation efficiency of the product.

[0059] (5)Preparation of gypsum: The filtrate is collected and mixed, and lime is added to react to form iron hydroxide, which is neutralized to a pH value of 7.1, and gypsum is obtained by filtration. This process not only realizes waste utilization but also ensures the quality and moisture content of gypsum by precisely controlling the pH and filtration conditions, providing high - quality raw materials for subsequent steps.

[0060] (6)Drying of gypsum: The gypsum is dried in the sun until the water content ≤ 6.5%. This step ensures the stability and storability of gypsum and provides a reliable basis for subsequent mixing.

[0061] (7 - 8) Mixed solution preparation and composition adjustment: Mix the gypsum with the waste water from activated clay production. Optimize the conditions of the mixed solution by adjusting the temperature, rotation speed, and pH value. Then, through secondary stirring and mixing and acidity adjustment, precisely control the composition of iron oxide, aluminum oxide, and sulfur trioxide. This series of delicate operations is crucial for the formation of highly efficient polyaluminum ferric sulfate.

[0062] (9) Oxygen oxidation treatment: Use oxygen to oxidize the secondary filtrate while maintaining a low air pressure (0.01 - 0.02 MPa), which helps to form stable oxidized ions and provides favorable conditions for the polymerization reaction.

[0063] (10) Modifier addition and final product preparation: Add a modifier to the liquid polyaluminum ferric sulfate. The modifier includes potassium carboxymethyl cellulose, sodium hexametaphosphate, sodium persulfate, and an additive.

[0064] In the in - depth exploration of the modification preparation process of liquid polyaluminum ferric sulfate, by carefully selecting and proportioning potassium carboxymethyl cellulose, sodium hexametaphosphate, sodium persulfate, and a unique additive - acrylamide and acrylic acid - sodium acrylate copolymer, not only is its flocculation performance significantly improved, but also a leap in technical effects is achieved. This process is full of scientific fine control and wonderful chemical synergy.

[0065] 1) Analysis of the synergy mechanism:

[0066] a. The bridging effect of potassium carboxymethyl cellulose: With its excellent dispersion performance, potassium carboxymethyl cellulose forms a thin adsorption layer in the liquid polyaluminum ferric sulfate solution, effectively preventing direct contact and premature flocculation between particles, and providing a uniform dispersion environment for subsequent chemical modification. Its dosage is strictly controlled between 5.2% - 8.7% of the mass of liquid polyaluminum ferric sulfate. This ratio is the result of repeated experimental optimization, which can not only ensure good dispersion effects but also avoid the cost increase and possible negative impacts caused by excessive use.

[0067] b. The fine - tuning effect of sodium hexametaphosphate: The introduction of sodium hexametaphosphate, as a multifunctional phosphate compound, can not only adjust the structure of liquid polyaluminum ferric sulfate at the molecular level, enhance its stability, but also, through its unique chelating ability, form stable complexes with metal ions in the solution, further refine the particles, and improve the flocculation efficiency. Its dosage ratio of 3.8% - 5.5% takes into account the balance between ensuring the modification effect, economic benefits, and environmental protection requirements.

[0068] c. Enhancement effect of sodium persulfate: During the preparation of the flocculant, due to its strong oxidizing property, sodium persulfate promotes the chain growth reaction among the molecules of liquid polyaluminum ferric sulfate, forming larger and more stable polymers, thus significantly enhancing the flocculation ability. The dosage of 1.3%-2.4% precisely controls the "degree" of the chain extension reaction, which not only promotes chain growth but also avoids the polymer degradation that may be caused by overreaction.

[0069] d. Synergistic effect of additives: As the core component of the additive, the acrylic acid-sodium acrylate copolymer combines the hydrophobicity of acrylamide and the hydrophilicity of acrylic acid-sodium acrylate with its unique molecular structure. It can form a three-dimensional network structure with strong adsorption ability in water, quickly capture and bridge the suspended particles and colloidal substances in water, and form flocs that are easy to precipitate. Its mass ratio is set between 1:1 and 1:3, and the dosage of the additive accounts for 0.2%-0.4% of the mass of liquid polyaluminum ferric sulfate, which is the best ratio obtained through precise calculation and experimental verification, ensuring the maximization of the flocculation effect.

[0070] d. The synergy of the four components creates excellent results: During the modified preparation of liquid polyaluminum ferric sulfate, potassium carboxymethyl cellulose, sodium hexametaphosphate, sodium persulfate, and the additive do not exist in isolation but depend on each other and act synergistically. The dispersion effect of potassium carboxymethyl cellulose provides a good basis for the fine-tuning of sodium hexametaphosphate, and the chain growth effect of sodium persulfate further enhances the stability and flocculation ability of the whole system. Finally, the addition of the additive is like the finishing touch, perfectly integrating the functions of each component, jointly improving the flocculation effect of the liquid polyaluminum ferric sulfate flocculant, and achieving a qualitative leap from a single component to a composite system. This process not only demonstrates the wonderful charm of chemistry but also brings a more efficient and environmentally friendly solution to the water treatment field.

[0071] 2) Key control and optimization in the preparation process:

[0072] By optimizing the stirring temperature, rotation speed, and time, the product performance has been significantly improved. The addition of the modifier not only enhances the stability and adaptability of the flocculant but also improves its flocculation effect in complex water quality, which is the key technological innovation point of the present invention.

[0073] In summary, the preparation process of the liquid polyaluminum ferric sulfate flocculant of the present invention not only realizes the efficient utilization of resources but also significantly improves the flocculation performance of the product by precisely controlling the raw material dosage and optimizing the process parameters, achieving unexpected technical effects and demonstrating remarkable technological progress and environmental friendliness.

[0074] To make the disclosure of the present invention more complete, the present invention will be described below through more specific embodiments.

[0075] Example 1

[0076] In an embodiment of the present invention, a preparation process of a liquid polyaluminum ferric sulfate flocculant comprises the following steps:

[0077] (1) Mix the activated clay production wastewater with bentonite, control the temperature of the solution at 90 °C to dissolve the aluminum sulfate in the bentonite in the production wastewater, and then circulate the activated clay production wastewater with increased aluminum sulfate concentration and mix it with newly added bentonite. Repeat this method 3 times to saturate the aluminum sulfate.

[0078] (2) Control the temperature of the production wastewater with saturated aluminum sulfate obtained in step (1) at 90 °C, then adjust the pH value to 4.9, and then add potassium sulfate. The amount of potassium sulfate is such that the molar concentration ratio of K + :Al 3+ :SO4 2- is 1 - 1.01:1:2.

[0079] (3) Add polyaluminum sulfate to the solution obtained in step (2). After coagulating potassium alum, then filter to remove impurities. Cool the obtained clear liquid to 6 °C, and then press the potassium alum at a pressure of 0.85 MPa to a moisture content of 43% to obtain a filter cake of crude potassium alum. At the same time, collect all the filtrates from this step.

[0080] (4) Put the crude potassium alum obtained in step (3) into water with a weight of 115%, heat it to 93 °C and stir until the crude potassium alum is completely dissolved. Then add polyaluminum sulfate. After coagulating potassium alum, then remove impurities again. Cool the obtained clear liquid to 5 °C, and then press the potassium alum at a pressure of 0.85 MPa to a moisture content of 42% to obtain potassium alum. At the same time, collect all the filtrates from this step.

[0081] (5) Collect and mix the filtrates from step (3) and the filtrates from step (4). Add lime to the mixed filtrates to react and generate iron hydroxide. After the filtrates are neutralized to a pH value of 7.1, filter press at a pressure of 0.88 MPa to a moisture content of 44.2% to obtain a filter cake of gypsum.

[0082] (6) Dry the filter cake of gypsum obtained in step (5) until the water content is 6.3% to obtain gypsum. After the gypsum is dried, ground, and sieved, perform chemical composition analysis using an X-ray fluorescence spectrometer. Its main chemical composition is as follows: SO3 is 35.25%, CaO is 31.87%, Al2O3 is 8.91%, Fe2O3 is 6.46%, MgO is 2.58%, and SiO2 is 0.73%.

[0083] (7) Stir and mix the gypsum obtained in step (6) with the activated clay production wastewater under the conditions of a temperature of 35 °C, a rotation speed of 200 r / min, adjust the pH of the mixed solution to 1, and perform pressure filtration to obtain a primary filtrate;

[0084] (8) Conduct a second stirring and mixing of the primary filtrate obtained in step (7) with newly added gypsum, adjust the acidity of the mixed solution, adjust the pH of the mixed solution to 2.6, adjust the composition of iron oxide, aluminum oxide, and sulfur trioxide in the liquid, and then perform pressure filtration to obtain a secondary filtrate;

[0085] (9) Oxidize the secondary filtrate obtained in step (8) with oxygen, and maintain the air pressure of the oxygen pressure gauge at 0.02 MPa during the treatment to obtain liquid polyaluminum ferric sulfate;

[0086] (10) Add a modifier to the liquid polyaluminum ferric sulfate obtained in step (9). The modifier includes potassium carboxymethyl cellulose, sodium hexametaphosphate, sodium persulfate, and an additive. Then stir at a temperature of 52 °C and a rotation speed of 300 r / min for 2 h to obtain a liquid polyaluminum ferric sulfate flocculant;

[0087] The additive includes acrylamide and acrylate-acrylate copolymer. The mass ratio of acrylamide to acrylate-acrylate copolymer is 1:1.2. The dosage of potassium carboxymethyl cellulose accounts for 5.3% of the mass of the liquid polyaluminum ferric sulfate. The dosage of sodium hexametaphosphate accounts for 4.0% of the mass of the liquid polyaluminum ferric sulfate. The dosage of sodium persulfate accounts for 1.5% of the mass of the liquid polyaluminum ferric sulfate. The dosage of the additive accounts for 0.4% of the mass of the liquid polyaluminum ferric sulfate.

[0088] Example 2

[0089] In the embodiment of the present invention, a preparation process of a liquid polyaluminum ferric sulfate flocculant includes the following steps:

[0090] (1) Mix the activated clay production wastewater with bentonite, control the temperature of the solution at 92 °C to dissolve the aluminum sulfate in the bentonite in the production wastewater, and then circulate the activated clay production wastewater with increased aluminum sulfate concentration and mix it with newly added bentonite. Repeat this method 4 times to make the aluminum sulfate reach saturation;

[0091] (2) Control the temperature of the production wastewater with saturated aluminum sulfate obtained in step (1) at 92 °C, then adjust the pH value to 5, and then add potassium sulfate. The amount of potassium sulfate is such that the molar concentration ratio of K + :Al 3+ :SO4 2- is 1 - 1.01:1:2.01;

[0092] (3) Add polyaluminum sulfate to the solution obtained in step (2). After flocculating potassium alum, filter to remove impurities. Cool the resulting clear liquid to 4°C, and then press the potassium alum at a pressure of 0.91 MPa to a water content of 39% to obtain crude potassium alum filter cake. At the same time, collect all the filtrates from this step;

[0093] (4) Put the crude potassium alum obtained in step (3) into water with a weight of 116%. Heat to 95°C and stir until the crude potassium alum is completely dissolved. Add polyaluminum sulfate. After flocculating potassium alum, remove impurities again. Cool the resulting clear liquid to 4°C, and then press the potassium alum at a pressure of 0.9 MPa to a water content of 41% to obtain potassium alum. At the same time, collect all the filtrates from this step;

[0094] (5) Collect and mix the filtrates from step (3) and step (4). Add lime to the mixed filtrate to react to form iron hydroxide. After the filtrate is neutralized to a pH value of 7.1, filter press at a pressure of 0.95 MPa until the water content is 42% to obtain filter cake gypsum;

[0095] (6) Dry the filter cake gypsum obtained in step (5) until the water content is 5.8% to obtain gypsum (see Figure 1 ). After drying, grinding, and sieving this gypsum, use an X-ray fluorescence spectrometer for chemical composition analysis. Its main chemical composition is as follows: SO3 is 35.02%, CaO is 31.95%, Al2O3 is 9.06%, Fe2O3 is 6.44%, MgO is 2.46%, and SiO2 is 0.69%.

[0096] (7) Stir and mix the gypsum obtained in step (6) with the wastewater from the production of activated clay. Conditions: temperature is 34°C, rotation speed is 300 r / min. Adjust the pH of the mixed liquid to 1.2, and perform filter press treatment to obtain the primary filtrate;

[0097] (8) Conduct a second stirring and mixing of the primary filtrate obtained in step (7) with the newly added gypsum. Adjust the acidity of the mixed liquid, adjust the pH of the mixed liquid to 2.3, adjust the composition of iron oxide, aluminum oxide, and sulfur trioxide in the liquid, and then perform filter press treatment to obtain the secondary filtrate;

[0098] (9) Oxidize the secondary filtrate obtained in step (8) with oxygen. Keep the air pressure of the oxygen pressure gauge at 0.02 MPa during the treatment to obtain liquid polyaluminum ferric sulfate;

[0099] (10) Add a modifier to the liquid polyaluminum ferric sulfate obtained in step (9). The modifier includes potassium carboxymethyl cellulose, sodium hexametaphosphate, sodium persulfate, and an additive. Then stir at a temperature of 53°C and a rotation speed of 400 r / min for 1.8 h to obtain a liquid polyaluminum ferric sulfate flocculant;

[0100] The additive includes acrylamide and acrylic acid - sodium acrylate copolymer. The mass ratio of acrylamide to acrylic acid - sodium acrylate copolymer is 1:2. The dosage of potassium carboxymethyl cellulose accounts for 7.2% of the mass of liquid polyaluminum ferric sulfate. The dosage of sodium hexametaphosphate accounts for 4.6% of the mass of liquid polyaluminum ferric sulfate. The dosage of sodium persulfate accounts for 2% of the mass of liquid polyaluminum ferric sulfate. The dosage of the additive accounts for 0.3% of the mass of liquid polyaluminum ferric sulfate.

[0101] Example 3

[0102] In the embodiment of the present invention, a preparation process of a liquid polyaluminum ferric sulfate flocculant includes the following steps:

[0103] (1) Mix the activated clay production wastewater with bentonite, control the temperature of the solution at 90 °C to dissolve the aluminum sulfate in the bentonite into the production wastewater, and then circulate the activated clay production wastewater with increased aluminum sulfate concentration and mix it with newly added bentonite. Repeat this method 4 times to make the aluminum sulfate reach saturation.

[0104] (2) Control the temperature of the production wastewater with saturated aluminum sulfate obtained in step (1) at 90 °C, then adjust the pH value to 5.2, and then add potassium sulfate. The amount of potassium sulfate is such that the molar concentration ratio of K + :Al 3+ :SO4 2- is 1.04:1:2.02.

[0105] (3) Add polyaluminum sulfate to the solution obtained in step (2), coagulate potassium alum, then filter to remove impurities. Cool the obtained clear liquid to 6 °C, and then under a pressure of 0.88 MPa, press the potassium alum to a water content of 42% to obtain a filter cake of crude potassium alum. At the same time, collect all the filtrates of this step.

[0106] (4) Put the crude potassium alum obtained in step (3) into water with a weight of 117%, heat it to 93 °C and stir until the crude potassium alum is completely dissolved. Then add polyaluminum sulfate, coagulate potassium alum, and then remove impurities again. Cool the obtained clear liquid to 5 °C, and then under a pressure of 0.87 MPa, press the potassium alum to a water content of 42% to obtain potassium alum. At the same time, collect all the filtrates of this step.

[0107] (5) Collect and mix the filtrates of step (3) and the filtrates in step (4), add lime to the mixed filtrates to react to form iron hydroxide. After the filtrate is neutralized to a pH value of 7.1, filter it under a pressure of 0.91 MPa by a filter press to a water content of 42% to obtain a filter cake of gypsum.

[0108] (6) The filter cake gypsum obtained in step (5) is dried until the water content is 6.3%, and gypsum is obtained. After drying, grinding, and sieving, the chemical composition of the gypsum is analyzed by an X-ray fluorescence spectrometer. Its main chemical composition is as follows: SO3 is 36.11%, CaO is 32.03%, Al2O3 is 9.12%, Fe2O3 is 6.56%, MgO is 2.47%, and SiO2 is 0.71%.

[0109] (7) The gypsum obtained in step (6) is stirred and mixed with the activated clay production wastewater. Conditions: the temperature is 33 °C, the rotation speed is 200 r / min, the pH of the mixed solution is adjusted to 1.5, and pressure filtration is carried out to obtain a primary filtrate.

[0110] (8) The primary filtrate obtained in step (7) is stirred and mixed with newly added gypsum for the second time. The acidity of the mixed solution is adjusted, the pH of the mixed solution is adjusted to 1.9, and after adjusting the composition of iron oxide, aluminum oxide, and sulfur trioxide in the liquid, pressure filtration is carried out to obtain a secondary filtrate.

[0111] (9) The secondary filtrate obtained in step (8) is treated by oxidation with oxygen. During the treatment, the air pressure of the oxygen pressure gauge is maintained at 0.02 MPa to obtain liquid polyaluminum ferric sulfate.

[0112] (10) A modifier is added to the liquid polyaluminum ferric sulfate obtained in step (9). The modifier includes potassium carboxymethyl cellulose, sodium hexametaphosphate, sodium persulfate, and an additive. Then, it is stirred at a temperature of 55 °C and a rotation speed of 500 r / min for 1.5 h to obtain a liquid polyaluminum ferric sulfate flocculant.

[0113] The additive includes acrylamide and acrylate-acrylate copolymer. The mass ratio of acrylamide to acrylate-acrylate copolymer is 1:3. The dosage of potassium carboxymethyl cellulose accounts for 8.2% of the mass of liquid polyaluminum ferric sulfate. The dosage of sodium hexametaphosphate accounts for 5.1% of the mass of liquid polyaluminum ferric sulfate. The dosage of sodium persulfate accounts for 1.9% of the mass of liquid polyaluminum ferric sulfate. The dosage of the additive accounts for 0.2% of the mass of liquid polyaluminum ferric sulfate.

[0114] Example 4

[0115] In the embodiment of the present invention, a preparation process of a liquid polyaluminum ferric sulfate flocculant includes the following steps:

[0116] (1) The activated clay production wastewater is mixed with bentonite. The temperature of the solution is controlled at 93 °C to dissolve the aluminum sulfate in the bentonite in the production wastewater. Then, the activated clay production wastewater with increased aluminum sulfate concentration is circulated and mixed with newly added bentonite. According to this method, it is circulated 4 times to make the aluminum sulfate reach saturation.

[0117] (2) Control the temperature of the production wastewater saturated with aluminum sulfate obtained in step (1) at 92 °C, then adjust the pH value to 4.9, and then add potassium sulfate. The amount of potassium sulfate is such that the molar concentration ratio of K + :Al 3+ :SO4 2- is 1.03:1:2.01;

[0118] (3) Add polyaluminum sulfate to the solution obtained in step (2). After aggregating potassium alum, then filter to remove impurities. Cool the obtained clear liquid to 5 °C, and then press the potassium alum to a moisture content of 42% under a pressure of 0.85 MPa to obtain filter cake crude potassium alum, and at the same time collect all the filtrates of this step;

[0119] (4) Put the crude potassium alum obtained in step (3) into water with a weight of 117%, heat it to 92 °C and stir to completely dissolve the crude potassium alum, add polyaluminum sulfate, after aggregating potassium alum, then remove impurities again. Cool the obtained clear liquid to 5 °C, and then press the potassium alum to a moisture content of 45% under a pressure of 0.88 MPa to obtain potassium alum, and at the same time collect all the filtrates of this step;

[0120] (5) Collect and mix the filtrates of step (3) and the filtrates in step (4). Add lime to the mixed filtrates to react to form iron hydroxide. After the filtrates are neutralized to a pH value of 7.1, filter press under a pressure of 0.89 MPa until the moisture content is 40% to obtain filter cake gypsum;

[0121] (6) Dry the filter cake gypsum obtained in step (5) until the water content is 6.1% to obtain gypsum. After the gypsum is dried, ground, and sieved, its chemical composition is analyzed by an X-ray fluorescence spectrometer. Its main chemical composition is as follows: SO3 is 35.48%, CaO is 31.99%, Al2O3 is 8.87%, Fe2O3 is 6.76%, MgO is 2.23%, and SiO2 is 0.68%.

[0122] (7) Stir and mix the gypsum obtained in step (6) with the production wastewater of activated clay. Conditions: temperature is 32 °C, rotation speed is 200 r / min, adjust the pH of the mixed liquid to 1.7, and perform filter press treatment to obtain primary filtrate;

[0123] (8) Perform a second stirring and mixing of the primary filtrate obtained in step (7) with the newly added gypsum, adjust the acidity of the mixed liquid, adjust the pH of the mixed liquid to 1.9, adjust the composition of iron oxide, aluminum oxide, and sulfur trioxide in the liquid, and then perform filter press treatment to obtain secondary filtrate;

[0124] (9) Treat the secondary filtrate obtained in step (8) by oxidation with oxygen. During the treatment, maintain the air pressure of the oxygen pressure gauge at 0.01 MPa to obtain liquid polyaluminum ferric sulfate.

[0125] (10) Add a modifier to the liquid polyaluminum ferric sulfate obtained in step (9). The modifier includes potassium carboxymethyl cellulose, sodium hexametaphosphate, sodium persulfate, and an additive. Then, stir at a temperature of 52 °C and a rotation speed of 300 r / min for 2 h to obtain a liquid polyaluminum ferric sulfate flocculant.

[0126] The additive includes acrylamide and acrylic acid-sodium acrylate copolymer. The mass ratio of acrylamide to acrylic acid-sodium acrylate copolymer is 1:1. The dosage of potassium carboxymethyl cellulose accounts for 5.8% of the mass of the liquid polyaluminum ferric sulfate. The dosage of sodium hexametaphosphate accounts for 4.1% of the mass of the liquid polyaluminum ferric sulfate. The dosage of sodium persulfate accounts for 1.7% of the mass of the liquid polyaluminum ferric sulfate. The dosage of the additive accounts for 0.3% of the mass of the liquid polyaluminum ferric sulfate.

[0127] Example 5

[0128] In an embodiment of the present invention, a preparation process of a liquid polyaluminum ferric sulfate flocculant includes the following steps:

[0129] (1) Mix the activated clay production wastewater with bentonite, control the temperature of the solution at 93 °C to dissolve the aluminum sulfate in the bentonite in the production wastewater, and then circulate the activated clay production wastewater with increased aluminum sulfate concentration and mix it with newly added bentonite. Repeat this method 3 times to make the aluminum sulfate reach saturation.

[0130] (2) Control the temperature of the production wastewater with saturated aluminum sulfate obtained in step (1) at 92 °C, then adjust the pH value to 5.1, and then add potassium sulfate. The amount of potassium sulfate is such that the molar concentration ratio of K + :Al 3+ :SO4 2- is 1:1:2.02.

[0131] (3) Add polyaluminum sulfate to the solution obtained in step (2). After aggregating potassium alum, then filter to remove impurities. Cool the obtained clear liquid to 6 °C, and then press the potassium alum at a pressure of 0.9 MPa to a moisture content of 44% to obtain a filter cake of crude potassium alum, and at the same time collect all the filtrates of this step.

[0132] (4) Put the crude potassium alum obtained in step (3) into water with a weight of 122%, heat it to 95 °C and stir until the crude potassium alum is completely dissolved. Then add polyaluminum sulfate. After coagulating the potassium alum, remove impurities again. Cool the obtained clear liquid to 5 °C, and then press the potassium alum to a water content of 43% under a pressure of 0.9 MPa to obtain potassium alum. At the same time, collect all the filtrates from this step;

[0133] (5) Collect and mix the filtrates from step (3) and step (4). Add lime to the mixed filtrate to react and form iron hydroxide. After the filtrate is neutralized to a pH value of 7.1, filter it under a pressure of 0.91 MPa by a filter press until the water content is 42% to obtain filter cake gypsum;

[0134] (6) Dry the filter cake gypsum obtained in step (5) until the water content is 6.2% to obtain gypsum. After the gypsum is dried, ground, and sieved, use an X-ray fluorescence spectrometer to analyze its chemical composition. The main chemical compositions are as follows: SO3 is 36.19%, CaO is 32.24%, Al2O3 is 8.79%, Fe2O3 is 6.84%, MgO is 2.78%, and SiO2 is 0.82%.

[0135] (7) Stir and mix the gypsum obtained in step (6) with the production wastewater of activated clay. Conditions: temperature is 32 °C, rotation speed is 400 r / min, adjust the pH of the mixed liquid to 1.6, and perform filter press treatment to obtain the primary filtrate;

[0136] (8) Perform a second stirring and mixing of the primary filtrate obtained in step (7) with the newly added gypsum, adjust the acidity of the mixed liquid, adjust the pH of the mixed liquid to 2.5, adjust the composition of iron oxide, aluminum oxide, and sulfur trioxide in the liquid, and then perform filter press treatment to obtain the secondary filtrate;

[0137] (9) Perform oxygen oxidation treatment on the secondary filtrate obtained in step (8). During the treatment, keep the air pressure of the oxygen pressure gauge at 0.02 MPa to obtain liquid polyaluminum ferric sulfate;

[0138] (10) Add a modifier to the liquid polyaluminum ferric sulfate obtained in step (9). The modifier includes potassium carboxymethyl cellulose, sodium hexametaphosphate, sodium persulfate, and an additive. Then stir at a temperature of 55 °C and a rotation speed of 500 r / min for 1.5 h to obtain a liquid polyaluminum ferric sulfate flocculant;

[0139] The additive includes acrylamide and acrylic acid-sodium acrylate copolymer. The mass ratio of acrylamide to acrylic acid-sodium acrylate copolymer is 1:2. The dosage of potassium carboxymethyl cellulose accounts for 6.4% of the mass of liquid polyaluminum ferric sulfate. The dosage of sodium hexametaphosphate accounts for 5.2% of the mass of liquid polyaluminum ferric sulfate. The dosage of sodium persulfate accounts for 2.1% of the mass of liquid polyaluminum ferric sulfate. The dosage of the additive accounts for 0.3% of the mass of liquid polyaluminum ferric sulfate.

[0140] Comparative Example 1

[0141] The polyaluminum ferric sulfate water purifying agent (flocculant) was prepared by the method of Example 3 in the Chinese patent application document "A Method for Producing Polyaluminum Ferric Sulfate Water Purifying Agent Using Red Gypsum (Publication No.: CN118745033A)".

[0142] Take the turbid sewage (water temperature 25.2 °C) from a certain river in Long'an County, Nanning City for flocculation tests. Use the flocculants in Examples 1-5 and Comparative Example 1 for flocculation respectively, observe the flocculation phenomenon, and measure the turbidity of the turbid sewage before and after flocculation as well as the COD removal rate of the sewage. The test results are shown in the following table. The turbidity was detected by an XZ-0101B turbidity detector, and the COD determination method is as follows:

[0143] (1) Take 20.00 mL of sewage and place it in a 250 mL ground-glass reflux conical flask. Accurately add 10.00 mL of potassium dichromate standard solution and several small zeolites. Connect and shake the conical flask to mix the solution evenly, and heat and reflux for 2 h (starting from the time when boiling begins).

[0144] (2) After cooling, rinse the condenser tube wall with 90 mL of water and remove the conical flask. The total volume of the solution shall not be less than 140 mL, otherwise the titration end point is not obvious due to excessive acidity.

[0145] (3) After the solution cools down again, add 3 drops of ferroin indicator solution and titrate with ammonium ferrous sulfate standard solution. The color of the solution changes from yellow through blue-green to reddish-brown as the end point, and record the consumption of ammonium ferrous sulfate standard solution.

[0146] (4) While measuring the sewage, take 20.00 mL of double-distilled water and perform a blank test according to the same operation steps. Record the consumption of ammonium ferrous sulfate standard solution when titrating the blank.

[0147] (5) Calculate

[0148] CODCr(O2, mg / L) = (V0 - V1) × C × 8 × 1000 / V

[0149] Where: C - the concentration of ammonium ferrous sulfate standard solution, mol / L;

[0150] V0——the amount of ammonium ferrous sulfate standard solution used in the blank titration, mL;

[0151] V1——the amount of ammonium ferrous sulfate standard solution used in the titration of sewage, mL;

[0152] V——volume of sewage, ml;

[0153] 8——Molar mass of oxygen (1 / 2O), g / mol.

[0154]

[0155]

[0156] From the detailed data analysis in the above table, it can be seen that: (1) When comparing the experimental results of Examples 1 to 5, the present invention can clearly observe that the flocculants described in these examples are used to treat sewage, and the effect is extremely significant. Specifically, the turbidity removal rate of sewage has reached a high level of more than 98.0%, and the removal rate of chemical oxygen demand (COD) is as high as more than 98.8%, which fully demonstrates the high efficiency of the flocculants of the present invention. It is particularly worth mentioning that these flocculants can quickly generate large and structurally stable floccules in a very short time - only 59 seconds. This feature not only greatly improves the efficiency of sewage treatment, but also ensures that the treated water is clear and transparent, and the turbidity of the supernatant is extremely low, almost reaching the level of no impurities visible to the naked eye. In addition, after the sewage is treated with this flocculant, its high COD removal rate fully meets the strict national standards for the COD content in sewage discharge to be less than 7% (that is, the removal rate is greater than 93%), further proving the advanced nature and practicality of the technology of the present invention.

[0157] In Example 2, the present invention found the best flocculation effect and applied it to the treatment of an actual turbid river water in Nanning. Figure 2 (before treatment) and Figure 3 The sharp contrast between the original turbid river water and the treated river water (after treatment) shows intuitively that the originally turbid river water becomes clear and transparent after being treated with the flocculant of the present invention. The flocculation effect is very significant, the suspended matter in the water body is effectively removed, and the water quality is greatly improved.

[0158] (2) Further compare the experimental phenomena and data of Examples 1 to 5 with those of Comparative Example 1 (representing the prior art). The present invention finds that the flocculants provided by the present invention show obvious advantages in multiple key performance indicators. First, in terms of the flocculation speed, the flocculants prepared in Examples 1 to 5 are 18.1% to 36.1% faster than that of Comparative Example 1. This means that in practical applications, the flocculants of the present invention can complete the sewage purification process faster, thus effectively improving the efficiency of sewage treatment. Secondly, in terms of the removal rate of sewage turbidity, the flocculants in Examples 1 to 5 are 1.9% to 2.7% higher than that of Comparative Example 1. This means that the present invention can remove suspended solids and impurities in water more thoroughly, further improving the water quality. Finally, in terms of the COD removal rate, the flocculants in Examples 1 to 5 are also 0.7% to 1.2% higher than that of Comparative Example 1. This once again proves the excellent performance of the present invention in removing organic pollutants.

[0159] In summary, whether from the key indicators such as flocculation speed, turbidity removal rate or COD removal rate, the flocculants of the present invention show more superior performance than the prior art. These significant advantages are not only reflected in the laboratory tests, but also fully verified in practical applications. Therefore, it can be confidently said that the technology of the present invention has made significant progress and breakthroughs compared with the prior art, bringing new hopes and possibilities to the field of sewage treatment.

[0160] The above content does not determine that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should all be regarded as belonging to the patent protection scope determined by the claims submitted by the present invention.

Claims

1. A preparation process of a liquid polyaluminum ferric sulfate flocculant, characterized in that, It includes the following steps: (1) Mix the waste water from activated clay production with bentonite, control the temperature of the solution at 89 - 94 °C to dissolve aluminum sulfate in bentonite into the production waste water, and then recycle the activated clay production waste water with increased aluminum sulfate concentration and mix it with newly added bentonite to saturate the aluminum sulfate; (2) Control the temperature of the production waste water with saturated aluminum sulfate prepared in step (1) at 90 - 93 °C, then adjust the pH value to 4.8 - 5.2, and then add potassium sulfate; (3) Add polyaluminum sulfate to the solution prepared in step (2), coagulate potassium alum, then filter to remove impurities, cool the obtained clear liquid, and then press the potassium alum at a pressure of 0.83 - 0.92 MPa to a moisture content of 39% - 44% to obtain filter cake crude potassium alum, and collect all the filtrates of this step at the same time; (4) Put the crude potassium alum prepared in step (3) into water with a weight of 112% - 123%, heat it to 92 - 96 °C and stir to completely dissolve the crude potassium alum, add polyaluminum sulfate, coagulate potassium alum, then remove impurities again, cool the obtained clear liquid to below 5 °C, and then press filter the potassium alum at a pressure of 0.85 - 0.91 MPa to obtain potassium alum, and collect all the filtrates of this step at the same time; (5) Collect and mix the filtrates of step (3) and step (4), add lime to the mixed filtrate to react to generate iron hydroxide, after the filtrate is neutralized, filter press it at a pressure of 0.87 - 0.96 MPa to a moisture content of 40% - 45% to obtain filter cake gypsum; (6) Dry the filter cake gypsum prepared in step (5) to obtain gypsum; (7) Stir and mix the gypsum prepared in step (6) with the waste water from activated clay production, conditions: temperature is 32 - 36 °C, rotation speed is 200 - 400 r / min, adjust the pH of the mixed liquid to 0.9 - 1.7, and perform filter press treatment to obtain primary filtrate; (8) Conduct a second stirring and mixing of the primary filtrate prepared in step (7) with newly added gypsum, adjust the acidity of the mixed liquid, adjust the pH of the mixed liquid to 1.8 - 2.6, adjust the composition of iron oxide, aluminum oxide, and sulfur trioxide in the liquid, and then perform filter press treatment to obtain secondary filtrate; (9) Oxidize the secondary filtrate prepared in step (8) with oxygen to obtain liquid polyaluminum ferric sulfate; (10) Add a modifier to the liquid polyaluminum ferric sulfate prepared in step (9), and then stir at a temperature of 52 - 55 °C and a rotation speed of 300 - 500 r / min for 1.5 - 2 h to obtain a liquid polyaluminum ferric sulfate flocculant.

2. The preparation process of the liquid polyaluminum ferric sulfate flocculant according to claim 1, characterized in that, In step (1), recycle the activated clay production waste water with increased aluminum sulfate concentration and mix it with newly added bentonite, and cycle 3 - 4 times according to this method to saturate the aluminum sulfate.

3. The preparation process of the liquid polyaluminum ferric sulfate flocculant according to claim 1, characterized in that, The amount of potassium sulfate described in step (2) is such that the molar concentration ratio of K + :Al 3+ :SO4 2- is 1 - 1.04:1:2 - 2.

02.

4. The preparation process of the liquid polyaluminum ferric sulfate flocculant according to claim 1, characterized in that, Cool the obtained clear liquid in step (3) to below 6 °C.

5. The preparation process of the liquid polyaluminum ferric sulfate flocculant according to claim 1, characterized in that, In step (4), press filter the potassium alum to a moisture content of 40% - 43%.

6. The preparation process of the liquid polyaluminum ferric sulfate flocculant according to claim 1, characterized in that, Neutralize the filtrate in step (5) to a pH value of 7.

1.

7. The preparation process of the liquid polyaluminum ferric sulfate flocculant according to claim 1, characterized in that, Dry the filter cake gypsum in step (6) to a water content of ≤6.5%.

8. The preparation process of the liquid polyaluminum ferric sulfate flocculant according to claim 1, characterized in that, Keep the air pressure of the oxygen pressure gauge at 0.01 - 0.02 MPa during the treatment in step (9).

9. A liquid polyaluminum ferric sulfate flocculant prepared by the process according to any one of claims 1-8.

10. Use of the liquid polyaluminum ferric sulfate flocculant according to claim 9, characterized in that, Applied to the treatment of wastewater.

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