A water treatment agent based on the comprehensive utilization of red mud and its preparation method

Abstract

This invention belongs to the field of water treatment agent technology, specifically relating to a water treatment agent based on the comprehensive utilization of red mud and its preparation method. The raw materials for preparing the water treatment agent based on the comprehensive utilization of red mud, by weight, include 95-105 parts red mud, 25-35 parts dolomite, 10-20 parts diatomite, and 5-10 parts sodium polyacrylate. This invention aims to overcome the technical bottlenecks of red mud-based water treatment agents through component design and process optimization. By introducing dolomite to regulate the alkalinity of the system to activate the adsorption activity of red mud, utilizing the high specific surface area of ​​diatomite to enhance mass transfer and dispersibility, and supplementing with sodium polyacrylate to achieve rapid flocculation and separation of adsorbed pollutants. Through pH regulation, multi-level adsorption, co-precipitation, and flocculation coupling, the components form a synergistic removal mechanism for COD, ammonia nitrogen, and total phosphorus, significantly improving treatment efficiency and economy, and providing a new approach for the high-value utilization of red mud.

Description

Technical Field

[0001] This invention belongs to the field of water treatment agent technology, specifically relating to a water treatment agent based on the comprehensive utilization of red mud and its preparation method. Background Technology

[0002] With increasingly stringent industrial wastewater discharge standards, the development of efficient and low-cost water treatment agents has become a research hotspot in the field of environmental engineering. Although traditional water treatment materials have a certain ability to remove pollutants, they suffer from problems such as high raw material costs, limited functionality, and the risk of secondary pollution, making it difficult to meet the advanced treatment needs of complex wastewater from industrial parks with high COD, high ammonia nitrogen, and high phosphorus.

[0003] Red mud, an alkaline solid waste generated during alumina production, has an annual discharge exceeding 150 million tons, with global stockpiles exceeding 4 billion tons. Its main components are metal oxides such as SiO2, Al2O3, Fe2O3, and CaO, which theoretically can be used as adsorbents or catalyst carriers for wastewater treatment. However, the high alkalinity (pH 10-13), low specific surface area (typically <20 m² / g), and potential leaching risk of heavy metals severely limit its direct application. Existing red mud resource utilization technologies are mostly focused on the building materials sector, and their application in water treatment generally suffers from incomplete dealkalization, low utilization rate of active components, and unstable pollutant removal effects.

[0004] Existing red mud-based water treatment materials are mostly designed using single modification methods, which can partially improve adsorption performance but fail to address the lack of functional synergy. Furthermore, the combination of red mud with auxiliary components such as dolomite and diatomaceous earth lacks systematic pretreatment, resulting in weak interfacial bonding and severe shielding of active sites, making it difficult to achieve synergistic effects.

[0005] To address the aforementioned issues, there is an urgent need to develop a red mud-based multi-effect water treatment agent. Through optimized raw material pretreatment and synergistic design of multi-component functions, this agent can overcome the technical bottlenecks of low adsorption capacity and narrow pollutant removal range of traditional materials, while simultaneously enabling the large-scale, high-value utilization of red mud. Summary of the Invention

[0006] The purpose of this invention is to provide a water treatment agent based on the comprehensive utilization of red mud and its preparation method, which can improve the removal rate of COD, ammonia nitrogen and total phosphorus.

[0007] A water treatment agent based on the comprehensive utilization of red mud, the raw materials for its preparation, by weight, include 95-105 parts of pretreated red mud, 25-35 parts of pretreated dolomite, 10-20 parts of pretreated diatomite, and 5-10 parts of sodium polyacrylate.

[0008] The red mud mainly consists of SiO2, Al2O3, CaO, Fe2O3, etc.

[0009] Preferably, the dolomite has a moisture content of 1.4%-1.45% and a bulk density of 1600-1700 kg / m³. 3 The mud content is ≤0.15%.

[0010] In some preferred embodiments, the dolomite comes from Chenming Yuhua Stone Processing Plant in Liuhe District, Nanjing City, and is a raw dolomite ore.

[0011] The diatomaceous earth is mainly composed of SiO2, Al2O3, Fe2O3, etc.

[0012] Preferably, the sodium polyacrylate has a relative molecular mass of 5 million to 7 million.

[0013] In some preferred embodiments, the sodium polyacrylate is sourced from Shanghai Maclean Biochemical Technology Co., Ltd.

[0014] By adding appropriate amounts of dolomite, diatomaceous earth, and sodium polyacrylate to red mud, a water treatment agent was prepared that can achieve highly efficient synergistic removal of pollutants such as COD, ammonia nitrogen, and total phosphorus from water. This is likely because the addition of dolomite can dynamically adjust the pH of the system, not only promoting the conversion of some ammonia nitrogen into ammonia gas for volatilization, but also optimizing the adsorption activity of hydroxyl complexes of iron and aluminum ions in the red mud, thereby promoting the adsorption of phosphate ions. Simultaneously, the calcium and magnesium ions in the dolomite, after being activated, can also react with phosphate and ammonium ions, simultaneously removing nitrogen and phosphorus. Through the synergistic effect of red mud and diatomaceous earth, the high specific surface area and mesoporous structure of diatomaceous earth can not only disperse red mud particles, preventing agglomeration and increasing the adsorption area, but also allow the silanol groups on the surface to adsorb low molecular weight organic matter through hydrogen bonds, achieving a synergistic effect in removing COD. Sodium polyacrylate (SPA) bridging red mud, dolomite, and diatomaceous earth particles into a porous composite, preventing the loss of active components and stabilizing the removal efficiency of each effective component for pollutants. It also exhibits some flocculation effect, aggregating precipitated particles into larger ones and improving sedimentation efficiency. However, red mud is a solid waste with high alkali content, complex mineral composition, and poor dispersibility; dolomite is a mineral, with magnesium and calcium ions both contained in magnesium-calcium carbonate; and natural diatomaceous earth contains certain impurities that limit its adsorption performance. Without pretreatment of these raw materials, the performance of the prepared water treatment agent will be significantly affected.

[0015] The method for preparing the water treatment agent based on the comprehensive utilization of red mud includes the following steps:

[0016] S1. Red mud, dolomite and diatomite are pretreated to obtain pretreated red mud, pretreated dolomite and pretreated diatomite; sodium polyacrylate is prepared into an 8% sodium polyacrylate aqueous solution.

[0017] S2. Mix the pretreated red mud, pretreated dolomite and pretreated diatomite evenly to obtain a mixed dry material;

[0018] S3. Spray sodium polyacrylate aqueous solution onto the surface of the mixed dry material, and make it into particles with a diameter of 2-4 mm in a disc granulator. Spray dry until the moisture content is ≤1% to obtain the water treatment agent.

[0019] The method for preparing the pretreated red mud includes the following steps:

[0020] A1. Dealkali removal: Red mud is subjected to three-stage pressure filtration and then microwave dried to obtain dealkali-removed red mud;

[0021] A2. Acid etching: The dealkalized red mud and mixed acid solution are mixed, ultrasonically reacted, washed with deionized water until neutral, and vacuum dried at 60°C until the water content is ≤3% to obtain acid-etched red mud.

[0022] A3. Loading: The acid-etched red mud is immersed in a ferrate solution, shaken at room temperature for 1.5-2.5 hours, and then coated. After filtration at 60°C, it is vacuum dried until the moisture content is ≤1% to obtain the pretreated red mud.

[0023] Preferably, in step A1, the three-stage pressure filtration includes a first-stage pressure filtration, a second-stage pressure filtration, and a third-stage pressure filtration.

[0024] Preferably, the first stage of pressure filtration is plate and frame pressure filtration, with the following specific conditions: pressure 0.6-0.8 MPa, pressure maintained until the pH of the filtrate is ≤13.5.

[0025] Preferably, the second stage of pressure filtration is vacuum pressure filtration, with the following specific conditions: vacuum degree of -0.08MPa and moisture content reduced to 45% or below.

[0026] Preferably, the third-stage pressure filtration is a high-pressure diaphragm pressure filtration, specifically under the following conditions: pressure 2.5-3.0 MPa, and diaphragm compression to pH ≤ 9.

[0027] Preferably, in step A1, microwave drying includes a first stage of microwave drying and a second stage of microwave drying.

[0028] Preferably, the conditions for microwave drying in the first stage are: power 400-600W, time 5min, and temperature 75-85℃.

[0029] Preferably, the conditions for microwave drying in the second stage are: power 200-350W, time 10-20min, and temperature 100-110℃.

[0030] Preferably, in step A2, the solid-liquid ratio of the dealkalized red mud and the mixed acid solution is 1g:(5-10)mL.

[0031] Preferably, the concentration of the mixed acid in the mixed acid solution is 0.4-0.6 mol / L.

[0032] Preferably, the mixed acid comprises citric acid and hydrochloric acid.

[0033] Preferably, the molar ratio of citric acid to hydrochloric acid is (2-6):1; more preferably, it is 4:1.

[0034] Preferably, the specific conditions for the ultrasonic response are: frequency of 35-45kHz, power of 150-250W, temperature of 58-62℃, and time of 1.5-2.5h.

[0035] Preferably, in step A3, the solid-liquid ratio of acid-etched red mud and ferrate solution is 1g:(10-20)mL.

[0036] Preferably, the concentration of ferrate in the ferrate solution is 1.8-2.2 g / L, and the solvent is a 4% sodium hydroxide aqueous solution.

[0037] Preferably, the ferrate includes either potassium ferrate or sodium ferrate.

[0038] Preferably, the specific steps of the coating treatment are as follows: add an aqueous solution of sodium alginate with a mass fraction of 2.5%-3.5% and stir for 30-40 minutes.

[0039] Preferably, the solid-liquid ratio of the acid-etched red mud and the sodium alginate aqueous solution with a mass fraction of 2.5%-3.5% is 1g:(30-40)mL.

[0040] Pretreatment of red mud can increase its specific surface area while releasing active metal oxides and improving the removal efficiency of organic matter, thus comprehensively enhancing its beneficial effects on wastewater treatment. This is likely because a three-stage pressure filtration dealkali removal process is first employed to remove free alkali and bound sodium step by step, avoiding excessive acid consumption during subsequent acid etching. Then, microwave pulse drying induces the transformation of iron and aluminum oxides in the red mud from amorphous to goethite, thereby increasing the specific surface area and promoting the adsorption of phosphate and organic pollutants. Next, a mixed acid selectively dissolves amorphous silicates in the red mud, forming a mesoporous structure, while simultaneously grafting carboxylic acid groups to enhance ion exchange capacity and chelate heavy metal ions. Optimizing the mixed acid ratio also prevents the destruction of the red mud's framework structure by a single strong acid. Finally, loading with ferrate and coating with sodium alginate not only promotes the degradation of organic matter but also prevents the rapid decomposition of ferrate ions, extending their action cycle and thus improving the effectiveness of the water treatment agent.

[0041] Preferably, the preparation method of the pretreated dolomite includes the following steps: crushing the dolomite to a particle size of 5-10 mm, calcining it at 650-700℃ for 1.5-2.5 h, and then ball milling it through a 400-mesh sieve to obtain the pretreated dolomite.

[0042] The method for preparing the pretreated diatomaceous earth includes the following steps:

[0043] B1. Purification: After calcining diatomaceous earth at 500-600℃ for 1-2 hours, soak it in a 10% (v / v) acid solution, ultrasonically clean it for 30-50 minutes, wash it with water until neutral, and then dry it to obtain purified diatomaceous earth.

[0044] B2. Modification: After mixing purified diatomaceous earth and the modifier, adjust the pH to 4-5, age at 58-62℃ for 10-15 hours, and wash with water until no Cl is present. - Calcination at 500-600℃ for 1-3 hours yields modified diatomaceous earth;

[0045] B3. Compound preparation: Mix modified diatomaceous earth, mineral powder and fly ash to obtain a solid mixture, add pore-forming agent and deionized water and stir evenly, dry at 100-110℃ and calcine at 700-750℃ for 1-2 hours to obtain the final product.

[0046] Preferably, in step B2, the solid-liquid ratio of purified diatomaceous earth to modifier is 1g:(15-20)mL.

[0047] Preferably, the modifier includes aluminum chloride solution and ferric chloride solution.

[0048] Preferably, the molar ratio of aluminum to iron in the modifier is 0.2-0.4.

[0049] Preferably, the concentration of the aluminum chloride solution is 0.2-0.4 mol / L; and the concentration of the ferric chloride solution is 0.1-0.3 mol / L.

[0050] Preferably, in step B3, the mass ratio of modified diatomaceous earth, mineral powder, and fly ash is (2-3):(1-2):1; more preferably, it is 5:3:2.

[0051] Preferably, the pore-forming agent includes one or more of sodium bicarbonate, polyethylene glycol, and starch.

[0052] Preferably, the amount of pore-forming agent added is 5%-10% of the mass of the solid mixture.

[0053] Preferably, the solid-liquid ratio of the solid mixture and deionized water is 1 g: (0.8-1.2) mL.

[0054] Pretreatment of diatomaceous earth can increase its specific surface area and total pore volume without damaging its structure, thereby significantly improving its adsorption capacity and thus enhancing its ability to adsorb COD, ammonia nitrogen, and other pollutants from water. This is likely because the diatomaceous earth is first purified through calcination followed by acid washing, which not only removes organic impurities and Ca / Fe oxides, increasing the purity of silica, but also increases the specific surface area. Then, by selecting specific modifiers and controlling their molar ratio, stable pillared ions are generated, increasing the interlayer spacing. The bimetallic pillars enhance the surface acidic sites and ion exchange capacity, greatly improving the adsorption capacity. Finally, by compounding mineral powder and fly ash and using polyethylene glycol as a pore-forming agent, nanoscale permeable channels are constructed, optimizing mass transfer efficiency and active site distribution, further improving the adsorption capacity. In practice, it is necessary to control the order of calcination and acid washing during purification. Calcination before acid washing can prevent organic matter from carbonizing and clogging the pores, affecting the pore structure and adsorption effect.

[0055] This invention successfully prepared a water treatment agent by adding auxiliary components and compounding it with red mud, while simultaneously optimizing the pretreatment of red mud and other raw materials. This agent not only efficiently removes COD but also deeply removes ammonia nitrogen and enhances phosphorus removal. It overcomes the technical bottlenecks of traditional red mud-based materials, which suffer from single-function limitations and low efficiency. It is particularly suitable for the deep treatment of complex wastewater in industrial parks, combining high efficiency, low cost, and environmental friendliness. Furthermore, by converting industrial solid waste red mud into a high-quality water treatment agent, waste resource utilization aligns with environmental protection trends.

[0056] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0057] 1. The water treatment agent prepared in this invention, based on the comprehensive utilization of red mud, activates the adsorption activity of red mud by introducing dolomite to regulate the alkalinity of the system, enhances mass transfer and dispersibility by utilizing the high specific surface area of ​​diatomaceous earth, and achieves rapid flocculation and separation of adsorbed pollutants by supplementing with sodium polyacrylate. Through pH regulation, multi-level adsorption, co-precipitation, and flocculation coupling, the components form a synergistic removal mechanism for COD, ammonia nitrogen, and total phosphorus, significantly improving treatment efficiency and economy, and providing a new approach for the high-value utilization of red mud.

[0058] 2. By pretreating red mud, this invention can increase the specific surface area of ​​red mud, release active metal oxides, and improve the removal effect of organic matter, thereby comprehensively improving the beneficial effect of red mud on wastewater treatment.

[0059] 3. This invention employs a three-stage pressure filtration dealkali removal process to remove free alkali and bound sodium step by step, avoiding excessive acid consumption during subsequent acid etching. Microwave pulse drying can induce the transformation of iron and aluminum oxides in red mud from amorphous to goethite, thereby increasing the specific surface area of ​​red mud and promoting the adsorption of phosphate and organic pollutants.

[0060] 4. This invention improves the specific surface area and total pore volume of diatomaceous earth by pretreating it without damaging its structure, thereby greatly increasing the adsorption capacity of diatomaceous earth and thus improving its adsorption capacity for COD, ammonia nitrogen, etc. in water.

[0061] 5. By selecting specific modifiers and controlling the molar ratio of the modifiers, this invention generates stable pillared ions, increases the interlayer spacing of diatomaceous earth, and enhances the surface acidic sites and ion exchange capacity through bimetallic pillars, thereby greatly improving the adsorption capacity of diatomaceous earth. Detailed Implementation

[0062] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] All raw materials used in this invention are commercially available, specifically:

[0064] Red mud, main components (w / %): iron oxide, 15.9; aluminum oxide, 22.7; silicon dioxide, 14.3; titanium dioxide, 4.6; calcium oxide, 4.5; magnesium oxide, 2; sodium oxide, 4.2; other substances, balance. From the aluminum plant of Henan Branch of Aluminum Corporation of China.

[0065] Dolomite, with a moisture content of 1.4%-1.45% and a bulk density of 1600-1700 kg / m³. 3 The mud content is ≤0.15%, and it comes from Chenming Yuhua Stone Processing Plant in Liuhe District, Nanjing City. It is a raw dolomite ore.

[0066] Diatomaceous earth, main components (w / %) are: silicon dioxide, 89.01%; iron oxide, 3.31%; aluminum oxide, 3.1%; sodium oxide, 1.87%; calcium oxide, 1.07%; other substances, balance. Sourced from Sinopharm Chemical Reagent Co., Ltd.

[0067] Sodium polyacrylate has a relative molecular mass of 5 million to 7 million and is sourced from Shanghai Maclean Biochemical Technology Co., Ltd.

[0068] Mineral powder, S105 grade; fly ash, Grade 1 fly ash; both from Lingshou County Yehui Mineral Products Co., Ltd.

[0069] Example 1

[0070] This embodiment provides a water treatment agent based on the comprehensive utilization of red mud. The raw materials for its preparation, by weight, include 100 parts of pretreated red mud, 30 parts of pretreated dolomite, 15 parts of pretreated diatomite, and 8 parts of sodium polyacrylate.

[0071] The preparation method of the water treatment agent based on the comprehensive utilization of red mud includes the following steps:

[0072] S1. Prepare an 8% sodium polyacrylate aqueous solution by mass fraction;

[0073] S2. Mix the pretreated red mud, pretreated dolomite and pretreated diatomite evenly to obtain a mixed dry material;

[0074] S3. Spray an aqueous solution of sodium polyacrylate onto the surface of the mixed dry material, and form it into granules with a diameter of 2-4 mm in a disc granulator. Spray dry the granules until the moisture content is 0.5% to obtain the water treatment agent.

[0075] The method for preparing the pretreated red mud includes the following steps:

[0076] A1. Dealkali removal: Red mud is subjected to three-stage pressure filtration and then microwave dried to obtain dealkali-removed red mud;

[0077] A2. Acid etching: The dealkalized red mud and mixed acid solution are mixed, ultrasonically reacted, washed with deionized water until neutral, and vacuum dried at 60°C until the water content is 2.5% to obtain acid-etched red mud;

[0078] A3. Loading: The acid-etched red mud is immersed in a ferrate solution, shaken at room temperature for 2 hours, and then coated. After filtration at 60°C, it is vacuum dried to a moisture content of 0.5% to obtain the pretreated red mud.

[0079] In step A1, the three-stage pressure filtration consists of a first-stage pressure filtration, a second-stage pressure filtration, and a third-stage pressure filtration.

[0080] The first stage of pressure filtration is plate and frame pressure filtration, with the following specific conditions: pressure 0.7 MPa, maintained until the pH of the filtrate is 13.

[0081] The second stage of pressure filtration is vacuum pressure filtration, with the following specific conditions: vacuum degree of -0.08MPa and moisture content reduced to 45%.

[0082] The third stage of pressure filtration is high-pressure diaphragm pressure filtration, with the following specific conditions: pressure 2.8 MPa, and diaphragm compression to pH 9.

[0083] In step A1, microwave drying consists of a first-stage microwave drying and a second-stage microwave drying.

[0084] The conditions for the first stage of microwave drying are: power 500W, time 5min, and temperature 80℃.

[0085] The conditions for the second stage of microwave drying are: power 300W, time 15min, and temperature 105℃.

[0086] In step A2, the solid-liquid ratio of the dealkalized red mud and the mixed acid solution is 1g:8mL.

[0087] The concentration of the mixed acid in the mixed acid solution is 0.5 mol / L.

[0088] The mixed acid is citric acid and hydrochloric acid in a molar ratio of 4:1.

[0089] The specific conditions for the ultrasonic response are: frequency of 40kHz, power of 200W, temperature of 60℃, and time of 2h.

[0090] In step A3, the solid-liquid ratio of the acid-etched red mud and the ferrate solution is 1g:15mL.

[0091] The ferrate solution contains 2 g / L of ferrate, and the solvent is a 4% (w / w) sodium hydroxide aqueous solution.

[0092] The ferrate is potassium ferrate.

[0093] The specific steps of the coating treatment are as follows: add a 3% sodium alginate aqueous solution and stir for 35 minutes.

[0094] The solid-liquid ratio of the acid-etched red mud and the 3% sodium alginate aqueous solution is 1g:35mL.

[0095] The method for preparing the pretreated dolomite includes the following steps: crushing the dolomite to a particle size of 5-10 mm, calcining it at 680°C for 2 hours, and then ball-milling it through a 400-mesh sieve to obtain the pretreated dolomite.

[0096] The method for preparing the pretreated diatomaceous earth comprises the following steps:

[0097] B1. Purification: After calcining diatomaceous earth at 550℃ for 1.5h, it is soaked in a 10% (v / v) acid solution, ultrasonically cleaned for 40min, washed with water until neutral, and then dried to obtain purified diatomaceous earth.

[0098] B2. Modification: After mixing purified diatomaceous earth and the modifier, the pH is adjusted to 4.5, and the mixture is aged at 60℃ for 12 hours. It is then washed with water until no Cl- is present. - Calcination at 550℃ for 2 hours yields modified diatomaceous earth;

[0099] B3. Compound preparation: Modified diatomaceous earth, mineral powder and fly ash are mixed to obtain a solid mixture. After adding pore-forming agent and deionized water and stirring evenly, the mixture is dried at 105℃ and calcined at 730℃ for 1.5h to obtain the final product.

[0100] In step B2, the solid-liquid ratio of purified diatomaceous earth and modifier is 1g:15mL.

[0101] The modifier is an aluminum chloride solution or an iron chloride solution.

[0102] In the modifier, the molar ratio of aluminum to iron is 0.3.

[0103] The concentration of the aluminum chloride solution is 0.3 mol / L; the concentration of the ferric chloride solution is 0.2 mol / L.

[0104] In step B3, the mass ratio of modified diatomaceous earth, mineral powder, and fly ash is 5:3:2.

[0105] The pore-forming agent is sodium bicarbonate.

[0106] The amount of pore-forming agent added is 8% of the mass of the solid mixture.

[0107] The solid-liquid ratio of the solid mixture and deionized water is 1 g: 1 mL.

[0108] Example 2

[0109] The difference between this embodiment and Embodiment 1 is that the raw materials for the preparation of the water treatment agent based on the comprehensive utilization of red mud, by weight, include 105 parts of pretreated red mud, 25 parts of pretreated dolomite, 10 parts of pretreated diatomite, and 5 parts of sodium polyacrylate.

[0110] Comparative Example 1

[0111] The difference between this comparative example and Example 1 is that the raw materials for the water treatment agent based on the comprehensive utilization of red mud, by weight, include 100 parts of red mud, 30 parts of pretreated dolomite, 15 parts of pretreated diatomite, and 8 parts of sodium polyacrylate.

[0112] Comparative Example 2

[0113] The difference between this comparative example and Example 1 is as follows: A1, dealkalization: the red mud was subjected to primary pressure filtration and then microwave dried to obtain dealkalized red mud; the primary pressure filtration was plate and frame filtration, and the specific conditions were: pressure 0.7 MPa, holding time 1 h.

[0114] Comparative Example 3

[0115] The difference between this comparative example and Example 1 is as follows: A1, dealkali removal: the red mud was subjected to three-stage pressure filtration and then dried to constant weight to obtain dealkali-removed red mud.

[0116] Comparative Example 4

[0117] The difference between this comparative example and Example 1 is as follows: A2, acid etching: Dealkalized red mud and hydrochloric acid solution were mixed, ultrasonically reacted, washed with deionized water until neutral, and vacuum dried at 60°C until the water content was 2.5% to obtain acid-etched red mud. The concentration of the hydrochloric acid solution was 0.5 mol / L.

[0118] Comparative Example 5

[0119] The difference between this comparative example and Example 1 is that the preparation method of the pretreated red mud includes the following steps:

[0120] A1. Dealkali removal: Red mud is subjected to three-stage pressure filtration and then microwave dried to obtain dealkali-removed red mud;

[0121] A2. Acid etching: Mix the dealkalized red mud with a mixed acid solution, react with ultrasound, wash with deionized water until neutral, and vacuum dry at 60°C until the water content is 0.5% to obtain the pretreated red mud.

[0122] Comparative Example 6

[0123] The difference between this comparative example and Example 1 is as follows: B1. Purification: Soak in a 10% (v / v) acid solution, ultrasonically clean for 40 min, wash with water until neutral, dry, and then calcine at 550°C for 1.5 h to obtain purified diatomaceous earth.

[0124] Comparative Example 7

[0125] The difference between this comparative example and Example 1 is that the preparation method of the pretreated diatomaceous earth includes the following steps:

[0126] B1. Purification: After calcining diatomaceous earth at 550℃ for 1.5h, it is soaked in a 10% (v / v) acid solution, ultrasonically cleaned for 40min, washed with water until neutral, and then dried to obtain purified diatomaceous earth.

[0127] B2. Compound preparation: The purified diatomaceous earth, mineral powder and fly ash are mixed to obtain a solid mixture. After adding the pore-forming agent and deionized water and stirring evenly, the mixture is dried at 105℃ and calcined at 730℃ for 1.5h to obtain the final product.

[0128] The mass ratio of the purified diatomaceous earth, mineral powder, and fly ash is 5:3:2.

[0129] Performance testing

[0130] 800 mL of domestic wastewater from the waterworks was collected, and its initial COD, initial ammonia nitrogen, and initial total phosphorus content were determined. A 20% (w / w) solution of water treatment agent was prepared, and 4 mL of this solution was added to 800 mL of domestic wastewater. The mixture was rapidly mixed for 30 seconds, then slowly mixed for 3 minutes, and allowed to settle for 10 minutes. The supernatant was then collected, and the COD, ammonia nitrogen, and total phosphorus content were determined. The removal rates of these three substances were calculated using the formula (initial value - treated value) / initial value × 100%. COD, ammonia nitrogen, and total phosphorus measurements were performed according to GB3838-2002 "Water Quality Classification and Limits". The results are shown in Table 1.

[0131] Table 1 Measurement Results

[0132]

[0133] According to statistics, the water treatment agents based on the comprehensive utilization of red mud prepared in Examples 1-2 of this invention

[0134] The COD degradation rate, ammonia nitrogen removal rate, and total phosphorus removal rate were all high. Comparative Example 1 did not pretreat the red mud; Comparative Example 2 only used single-stage pressure filtration; Comparative Example 3 did not undergo microwave drying after three-stage pressure filtration, only ordinary drying; Comparative Example 4 only used hydrochloric acid during acid etching, not citric acid; Comparative Example 5 did not undergo the loading treatment in step A3; Comparative Example 6 first acid-leached and then calcined the diatomaceous earth; Comparative Example 7 did not undergo the modification treatment in step B2 with the diatomaceous earth. The resulting water treatment agents all had insufficient COD degradation rate, ammonia nitrogen removal rate, and total phosphorus removal rate. Therefore, the water treatment agent prepared using the raw materials and methods described in this application not only improves the pollutant removal range and can simultaneously degrade COD and remove ammonia nitrogen and phosphorus, but also exhibits excellent degradation and removal rates.

[0135] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A water treatment agent based on comprehensive utilization of red mud, characterized in that, The preparation raw material, by weight parts, includes pretreated red mud 95-105 parts, pretreated dolomite 25-35 parts, pretreated diatomite 10-20 parts, and sodium polyacrylate 5-10 parts. The preparation method of the pretreated red mud comprises the following steps: A1, alkali removal: the red mud is sequentially subjected to first-stage, second-stage and third-stage pressure filtration, and then subjected to first-stage and second-stage microwave drying, to obtain alkali-removed red mud; the first-stage pressure filtration is plate-frame pressure filtration, with specific conditions being: pressure 0.6-0.8 MPa, pressure maintaining until the pH of the filtrate is ≤13.5; the second-stage pressure filtration is vacuum pressure filtration, with specific conditions being: vacuum degree -0.08 MPa, water content being reduced to 45% or below; the third-stage pressure filtration is high-pressure diaphragm pressure filtration, with specific conditions being: pressure 2.5-3.0 MPa, diaphragm extrusion until the pH is ≤9; the first-stage microwave drying has conditions being: power 400-600 W, time 5 min, and temperature 75-85℃; the second-stage microwave drying has conditions being: power 200-350 W, time 10-20 min, and temperature 100-110℃; A2, acid etching: the alkali-removed red mud is mixed with a mixed acid solution, and then subjected to ultrasonic reaction, washed with deionized water until neutral, and vacuum dried, to obtain acid-etched red mud; A3, loading: the acid-etched red mud is immersed in a high ferrate solution, oscillated, and then subjected to coating treatment, and vacuum dried, to obtain the product. The preparation method of the pretreated diatomite comprises the following steps: B1, purification: the diatomite is calcined, immersed in an acid solution, ultrasonically cleaned, washed with water until neutral, and dried, to obtain purified diatomite; B2, modification: after mixing the purified diatomite and modifier, adjust the pH to 4-5, age at 58-62°C for 10-15h, wash with water until no Cl - , calcine to obtain modified diatomite; B3, compounding: the modified diatomite, mineral powder and fly ash are mixed in a mass ratio of (2-3):(1-2):1 to obtain a solid mixture, a pore-forming agent and deionized water are added, stirred uniformly, dried, and calcined, to obtain the product.

2. The water treatment agent based on comprehensive utilization of red mud according to claim 1, characterized in that, The modifier comprises an aluminum chloride solution and a ferric chloride solution.

3. The water treatment agent based on comprehensive utilization of red mud according to claim 2, characterized in that, In the modifier, the molar ratio of aluminum to iron is 0.2-0.

4.

4. The water treatment agent based on comprehensive utilization of red mud according to claim 1, characterized by, The preparation method of the pretreated dolomite comprises the following steps: the dolomite is crushed to a particle size of 5-10 mm, calcined at 650-700℃ for 1.5-2.5 h, and then ground through a 400-mesh sieve, to obtain the pretreated dolomite.

5. A method for preparing the water treatment agent based on comprehensive utilization of red mud according to any one of claims 1-4, characterized in that, The method comprises the following steps: S1, the sodium polyacrylate is configured into a sodium polyacrylate aqueous solution with a mass fraction of 8%; S2, the pretreated red mud, pretreated dolomite and pretreated diatomite are mixed uniformly to obtain a mixed dry material; S3, the sodium polyacrylate aqueous solution is sprayed on the surface of the mixed dry material, and the particles with a diameter of 2-4 mm are prepared in a disc granulator, and then spray-dried until the water content is ≤1%, to obtain the water treatment agent.

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