A polymeric aluminum iron silicate and its preparation method

Abstract

This invention discloses a polymeric aluminum iron silicate and its preparation method, belonging to the field of water treatment technology. The method utilizes the mother liquor generated during the production of sodium fluorosilicate from fluorine-containing waste acid, comprising the following steps: S1: Adding acid to the mother liquor, stirring to produce a precipitate, filtering, washing, and drying the precipitate to obtain silicic acid, then adding alkali to react with the silicic acid for 1.8-2.2 hours to obtain a sodium silicate solution; S2: Adding an oxidant to steel pickling waste liquid containing ferrous ions and free acid, stirring to obtain polyferric chloride; S3: Mixing the sodium silicate solution obtained in step S1, the polyferric chloride obtained in step S2, polyaluminum chloride, and a stabilizer, and aging to form polymeric aluminum iron silicate. This invention utilizes waste materials, and the resulting polymeric aluminum iron silicate exhibits good stability.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and particularly relates to a polymerized aluminum iron silicate and its preparation method. Background Technology

[0002] Polymeric aluminum iron silicate is a high-quality flocculant for water treatment, exhibiting excellent bridging and flocculation capabilities, and demonstrating good removal effects on COD, phosphorus, and heavy metals. However, polymeric aluminum iron silicate is extremely unstable and easily hydrolyzes into a gel. Furthermore, the mother liquor generated during the production of sodium fluorosilicate from fluorinated waste acid is mostly directly treated and purified, failing to achieve effective recycling. Similarly, there is a lack of effective utilization of steel pickling waste liquid.

[0003] Therefore, there is an urgent need for a method to prepare polyferric aluminum silicate that can utilize the mother liquor and steel pickling waste liquid generated in the production of sodium fluorosilicate from existing fluorine-containing waste acid, and to produce polyferric aluminum silicate with good stability. Summary of the Invention

[0004] The purpose of this invention is to provide a polymerized aluminum iron silicate and its preparation method, so as to overcome at least one of the above-mentioned defects in the prior art.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing polyferric aluminum silicate, which utilizes the mother liquor generated during the production of sodium fluorosilicate from fluorine-containing waste acid. The method includes the following steps: S1: Add acid to the mother liquor, stir to produce a precipitate, filter, wash and dry the precipitate to obtain silicic acid, then add alkali to react with the silicic acid for 1.8-2.2 hours to obtain a sodium silicate solution; S2: Add an oxidant to steel pickling waste liquid containing ferrous ions and free acid and stir to obtain polyferric chloride; S3: Mix the sodium silicate solution obtained in step S1, the polyferric chloride obtained in step S2, the polyaluminum chloride, and the stabilizer, and mature to form polyferric aluminum silicate.

[0007] Preferably, the mass ratio of the stabilizer to the polymerized aluminum iron silicate in step S3 is ≥1:25.

[0008] Preferably, the stabilizer in step S3 is sodium hexametaphosphate.

[0009] Preferably, the mother liquor generated during the production of sodium fluorosilicate from fluorine-containing waste acid includes 14-16 wt / % H2SiF6, 0.8-1.0 wt / % Na2SiF6, 0.005-0.02 wt / % HCl, and 19.2-21.3 wt / % NaCl.

[0010] Preferably, in step S1, the acid solution is hydrochloric acid, with an HCl content of 28-34 wt%, the alkali solution is sodium hydroxide, with a NaOH content of 29-35 wt%, and the stirring conditions are: room temperature, vacuum degree 0.06-0.10 MPa, stirring speed 55-65 r / min, the mass ratio of mother liquor to hydrochloric acid is 100:1-2.5, and the reaction conditions of silicic acid and alkali solution are room temperature and atmospheric pressure, with a mass ratio of silicic acid to alkali solution of 1:3-3.5.

[0011] Preferably, in step S2, before adding the oxidant, iron oxide powder is added to the steel pickling waste liquid containing ferrous ions and free acid and heated to dissolve, resulting in a mixed liquid. The mixed liquid is sampled and tested for the content of total ferrous ions, ferrous ions, and free acid. The amount of stabilizer to be added is calculated based on the test results of the total ferrous ion content. Then, the stabilizer is added to the mixed liquid and stirred evenly at room temperature. The amount of oxidant to be added is calculated based on the test results of the ferrous ion and free acid content. After the stabilizer and the mixed liquid are stirred evenly at room temperature, the oxidant is slowly added to the mixed liquid according to the calculated amount of oxidant to be added. After the oxidant is added, stirring is continued at room temperature for 0.9-1.1 hours.

[0012] Preferably, the ferrous chloride content in the steel pickling waste liquid is 23-25 ​​wt%, the free acid content (calculated as HCl) is 2-4 wt%, the phosphoric acid content in the stabilizer of step S2 is 65-75 wt%, the sulfuric acid content is 5-7 wt%, the mass ratio of phosphoric acid in the stabilizer to the total iron in the mixture of step S1 is 0.35-0.50, and the oxidant is sodium chlorate with a purity ≥99%.

[0013] Preferably, in step S3, the sodium silicate solution contains 35-40 wt% silicic acid, the polyferric chloride contains 11-13 wt% total iron, and the polyaluminum chloride contains 9-11 wt% alumina and 0.05-0.15 wt% iron oxide.

[0014] Preferably, in step S3, the mass ratio of sodium silicate solution to polymerized aluminum iron silicate is 1:116.52-119.56.

[0015] The present invention also provides a polymeric iron aluminum silicate, which is prepared by the above-described method for preparing polymeric iron aluminum silicate, and has a basicity ≥25.0%.

[0016] The beneficial effects of this invention are as follows:

[0017] This invention utilizes the mother liquor generated during the production of sodium fluorosilicate from fluorine-containing waste acid, steel pickling waste liquid, sodium hexametaphosphate, and polyaluminum chloride to synthesize polyferric aluminum silicate, achieving the effect of treating waste with waste, utilizing waste, and turning waste into treasure. Traditional polyferric aluminum silicate has very poor stability, and finding a suitable stabilizer and its ratio is extremely difficult, a problem in the industry. This invention not only found a suitable stabilizer but also, through repeated experimental design and corrections, finally selected an appropriate stabilizer ratio: sodium hexametaphosphate as the stabilizer, with a stabilizer-to-polyferric aluminum silicate mass ratio ≥ 1:25. This solves the problem of traditional polyferric aluminum silicate being extremely unstable and prone to hydrolysis and gelation, exhibiting good stability. Detailed Implementation

[0018] The present invention will now be further described in conjunction with specific embodiments.

[0019] This embodiment provides a method for preparing polymeric aluminum iron silicate, utilizing the mother liquor generated during the production of sodium fluorosilicate from fluorine-containing waste acid in the chip industry. The mother liquor includes fluorosilicic acid (H₂SiF₆ 15.2 wt / %), sodium fluorosilicate (Na₂SiF₆ 0.9 wt / %), hydrochloric acid (HCl 0.01 wt / %), and sodium chloride (NaCl 20.1 wt / %), and includes the following steps:

[0020] S1: Add hydrochloric acid (HCl content 31 wt%) to the mother liquor, stir to produce a precipitate, filter, wash, and dry the precipitate to obtain silicic acid. Then add alkaline solution to react with the silicic acid for 1.8-2.2 hours to obtain sodium silicate solution. The alkaline solution is sodium hydroxide (NaOH content 32 wt%). The stirring conditions are: room temperature, vacuum degree 0.08 MPa, stirring speed 60 r / min, mass ratio of mother liquor to hydrochloric acid 100:2, reaction conditions of silicic acid and alkaline solution at room temperature and pressure, and mass ratio of silicic acid to alkaline solution 1:3.205.

[0021] S2: Iron oxide powder is heated and dissolved in steel pickling waste liquid containing ferrous ions (24.1 wt / %) and free acid (3.0 wt / %, calculated as HCl) to obtain a mixed solution. The mixed solution is sampled and tested for total ferric ions, ferrous ions, and free acid content. Based on the total ferric ion content test results, the amount of stabilizer to be added is calculated. Then, stabilizer (phosphoric acid content 70 wt / %, sulfuric acid content 6 wt / %) is added to the mixed solution and stirred evenly at room temperature. Next, based on the ferrous ion and free acid content test results, the amount of oxidant to be added (sodium chlorate purity = 99%) is calculated. After the stabilizer and mixed solution are stirred evenly at room temperature, the oxidant is slowly added to the mixed solution according to the calculated amount. After the oxidant is added, stirring is continued at room temperature for 1 hour to obtain polyferric chloride. The mass ratio of phosphoric acid in the stabilizer to total ferric ions in the mixed solution of step S1 is 0.4.

[0022] S3: The sodium silicate solution obtained in step S1 (silicic acid content of 37.2 wt / %), the polyferric chloride obtained in step S2 (total iron content of 12.8 wt / %), the polyaluminum chloride (alumina 10.1 wt / %), and the stabilizer (sodium hexametaphosphate) are mixed and aged to form polyferric aluminum silicate. The mass ratio of stabilizer to polyferric aluminum silicate is ≥1:25, and the mass ratio of sodium silicate solution to polyferric aluminum silicate is 1:117.08.

[0023] This embodiment also provides a polymeric iron aluminum silicate, which is prepared by the above-described method for preparing polymeric iron aluminum silicate, with a basicity of 25.0% and a stability period of >30 days.

[0024] The following experiments investigated the factors affecting the stability of polymeric aluminum iron silicate:

[0025] 1. Preparation of sodium silicate solution

[0026] 1.1 Experimental Principle

[0027] The mother liquor produced during the production of sodium fluorosilicate from fluorine-containing waste acid mainly consists of fluorosilicic acid, sodium fluorosilicate, hydrochloric acid, and sodium chloride. We utilize the principle that sodium fluorosilicate reacts with hydrochloric acid to form fluorosilicic acid, and that fluorosilicic acid hydrolyzes under acidic conditions to precipitate silicic acid. An appropriate amount of hydrochloric acid is added to the mother liquor to precipitate silicic acid, while the generated hydrogen fluoride is extracted under vacuum and absorbed with water to form hydrofluoric acid. The precipitate is filtered and washed to obtain relatively pure silicic acid, which is then reacted with caustic soda to synthesize soluble sodium silicate.

[0028] The chemical equations involved are as follows:

[0029] Na₂SiF₆ + 2HCl = 2NaCl + H₂SiF₆

[0030] H₂SiF₆ + H₂O = H₂SiO₃ + 6HF

[0031] H₂SiO₃ + 2NaOH = Na₂SiO₃ + H₂O

[0032] 1.2 Detection Method

[0033] 1.2.1 Industrial sodium fluorosilicate testing standard GB-T23936-2018.

[0034] 1.2.2 Industrial sodium silicate testing standard GB / T4209-2008.

[0035] 1.3 Experimental Procedure

[0036] Experimental materials: Mother liquor generated during the production of sodium fluorosilicate from fluorine-containing waste acid in the chip industry.

[0037] H2SiF6 15.2wt / %

[0038] Na2SiF6 0.9wt / %

[0039] HCl 0.01wt / %

[0040] NaCl 20.1 wt / %

[0041] Hydrochloric acid (HCl) content 31.0 wt / % Industrial grade

[0042] Industrial grade liquid alkali (NaOH) with a content of 32.0 wt / %

[0043] Silver nitrate, analytical grade

[0044] Experimental equipment

[0045] Two 500ml 24# ground glass three-necked bottles

[0046] 1 vacuum pump

[0047] One set of filtration equipment

[0048] 1 drying oven

[0049] 1.3.1 Preparation of Silicic Acid

[0050] 1.3.1.1 Experimental Procedure

[0051] After setting up the reaction and absorption apparatus, add 100g of mother liquor produced during the production of sodium fluorosilicate from fluorinated waste acid to a 500ml three-necked flask and start stirring. Then add varying amounts of hydrochloric acid and turn on the vacuum pump. Precipitation forms rapidly. After reacting for a period of time, observe until no more precipitate forms, then stop stirring and the vacuum pump. Filter the material, and after filtration, wash it multiple times with tap water. Test the filtrate with silver nitrate solution; stop washing when no chloride ions are found in the filtrate. Remove the filter residue and dry it in an oven at 105℃ until constant weight. After cooling, weigh it.

[0052] The experimental data and detection results for the preparation of silicic acid are shown in Table 1:

[0053] Table 1. Experimental data and test results for the preparation of silicic acid.

[0054]

[0055] 1.3.1.2 Experimental Results and Discussion

[0056] Under experimental conditions of room temperature, vacuum of 0.08 MPa, and stirring speed of 60.0 r / min, the optimal mass ratio of mother liquor to hydrochloric acid for preparing silicic acid from the mother liquor generated during the production of sodium fluorosilicate using fluorine-containing waste acid is 100:2, considering yield, purity, and cost. Repeating the experiment under the conditions specified in #3 yielded the same results.

[0057] 1.4 Preparation of Sodium Silicate

[0058] 1.4.1 Experimental Procedure

[0059] Silicic acid was added to a beaker at room temperature and pressure, followed by the addition of a suitable amount of 32.0 wt% liquid alkali. The reaction proceeded for 2 hours until all the silicic acid dissolved. The reaction product was a sodium silicate solution. Samples were then taken for testing.

[0060] The experimental data and test results for the preparation of sodium silicate are shown in Table 2:

[0061] Table 2 Experimental data and test results for the preparation of sodium silicate

[0062] Project / Number 5# 6# 7# Silicic acid g 20.0 20.0 20.0 liquid alkali g 64.1 65.0 66.0 Stirring speed r / min 60.0 60.0 60.0 Sodium silicate solution g 84.0 85.0 86.0 Sodium silicate content % 37.2 36.8 36.3

[0063] Experimental Results and Analysis: The experimental results show that the optimal mass ratio of silicic acid to liquid alkali is 20:64.1.

[0064] 1.5 Experimental Conclusions

[0065] A reasonable process was adopted to synthesize sodium silicate solution using mother liquor, hydrochloric acid, and liquid alkali generated during the production of sodium fluorosilicate from fluorine-containing waste acid. The experimentally usable sodium silicate solution was successfully produced.

[0066] 2. Preparation of polyferric chloride

[0067] 2.1 Principle of Polyferric Chloride Preparation

[0068] The synthesis principle of polyferric chloride is as follows:

[0069] 6Fe 2+ +ClO3 - +6H + =6Fe 3+ +3H₂O+Cl -

[0070] 6HCl + Fe₂O₃ == 2FeCl₃ + 3H₂O

[0071] Fe 3+ +OH - →Fe(OH) 2+

[0072] Fe 3+ +2OH - →Fe(OH)2 +

[0073] Fe 3+ +3OH - →Fe(OH)3↓ (This precipitate is easily formed if the reaction is not properly controlled)

[0074] 2Fe3+ +2OH - →Fe2(OH)2 4+

[0075] 3Fe 3+ +4OH - →Fe3(OH)4 5+

[0076] Overall polymerization reaction: m[Fe2(OH)] n Cl 6-n ]==[Fe2(OH) n Cl 6-n ] m

[0077] 1) Synthesis route of polyferric chloride (PFC)

[0078] 1.1) Pretreatment of steel pickling waste liquid: Weigh an appropriate amount of steel pickling waste liquid into a 500ml glass beaker, add an appropriate amount of iron oxide powder, and heat to dissolve. Take samples and test according to the method in HG / T4672-2014 "Water Treatment Agent Polyferric Chloride": total iron, ferrous ion and free acid content.

[0079] 1.2) PFC synthesis: Add an appropriate amount of stabilizer, stir evenly, and then slowly add an appropriate amount of sodium chlorate to oxidize ferrous chloride. After the sodium chlorate is added, continue stirring for 1 hour. Take samples and test them according to the method of HG / T4672-2014 "Water Treatment Agent Polyferric Chloride": total iron, ferrous ions and basicity.

[0080] 2.1.3 Instruments and Reagents

[0081] 1) Instruments: Intelligent magnetic electric heating stirrer, 250ml beaker, 25ml alkaline burette.

[0082] 2) Raw materials and reagents

[0083] (1) Steel pickling waste liquid: ferrous chloride 24.1 wt / %, free acid (calculated as HCl) 3.0 wt / %.

[0084] (3) Other reagents and materials: 99wt / % sodium chlorate.

[0085] (4) Analytical reagents: according to HG / T4672-2014 "Water Treatment Agents - Polyferric Chloride"

[0086] 2.1.2 Synthesis process of polyferric chloride

[0087] The experimental data and test results for the preparation of polyferric chloride are shown in Table 3:

[0088] Table 3 Experimental data and test results for the preparation of polyferric chloride.

[0089]

[0090]

[0091] Experimental Results and Analysis

[0092] Experimental results show that it is feasible to produce PFC (Potentially Fertilizer) water treatment agent using stabilizer and steel pickling waste liquid as raw materials and auxiliary oxidant, which can also maximize the utilization of waste resources. The optimal process ratio is: stabilizer phosphoric acid (H3PO4) / Fe mass ratio of about 0.4, and the optimal reaction time is 1 hour at room temperature.

[0093] 3. Preparation and Stability Selection of Polymeric Ferroaluminum Silicate

[0094] 3.1 Quality Indicators of Polymeric Aluminum Iron Silicate

[0095] The quality indicators of polymeric aluminum iron silicate are shown in Table 4:

[0096] Table 4 Quality Indicators of Polyaluminum Ferrisilicate

[0097] Indicator Name index Total iron content % ≥ 11.0 <![CDATA[Percentage content of alumina (Al2O3) ≥]]> 6.0 <![CDATA[Relative density / (20 °C, g / cm 3 ) ≥]]> 1.200 pH value (1% aqueous solution) 1.5-4.0 Insoluble matter content % ≤ 0.5

[0098] 3.2 Experimental Principle

[0099] At room temperature and pressure, appropriate amounts of polyaluminum chloride, stabilizer, and synthesized polyferric chloride and sodium silicate are mixed and aged to form a polyaluminum iron silicate solution.

[0100] The chemical formulas involved are as follows:

[0101] 1 / 2mNa2SiO3+FeCl3+Al(OH)nCl m =FeAl(OH)n(SiO3) 1 / 2m +mNaCl

[0102] 3.3 Experiment

[0103] 3.3.1 Synthesis of Polymeric Aluminum Iron Silicate

[0104] Experimental instruments

[0105] One HJ-6 magnetic stirrer heater

[0106] 5 250ml beakers

[0107] 500ml beakers

[0108] 100 sample vials (100ml each)

[0109] Experimental materials

[0110] Sodium silicate solution 37.2 wt / %

[0111] Polyferric chloride total iron 12.8 wt / %

[0112] Polyaluminum chloride, alumina 10.1 wt / %, iron oxide 0.1 wt / %

[0113] The testing method adopted is the water treatment polyaluminum ferric chloride industry standard HG / T-2018.

[0114] The experimental data and test results for the preparation of polyaluminum ferric chloride are shown in Table 5:

[0115] Table 5. Experimental data and test results for the preparation of polyaluminum ferric chloride.

[0116]

[0117] Experimental analysis: In the absence of a stabilizer, the polymeric aluminum iron silicate is relatively stable when the amount of sodium silicate is 1 / 113 = 0.88%.

[0118] 3.3.2 Selection of Polymeric Aluminum Iron Silicate Stabilizer

[0119] Different types of stabilizers were added to the newly prepared polymeric aluminum iron silicate according to formula 1# at room temperature and pressure, and after stirring evenly, a sample was retained to observe its stability.

[0120] 3.3.2.1 Effects of various stabilizers on polyaluminum iron silicate

[0121] Experimental raw materials

[0122] Freshly prepared polyferroaluminosilicate

[0123] Stabilizers: Sodium carbonate, sodium nitrite, trisodium phosphate, sodium hexametaphosphate.

[0124] Experimental instruments

[0125] 5 conical flasks of 250

[0126] 1 / 100 electronic balance

[0127] Magnetic stirrer.

[0128] The experimental data and observation results of the effects of various stabilizers on polymeric aluminum iron silicate are shown in Table 6:

[0129] Table 6. Experimental data and observation results on the effects of various stabilizers on polyaluminum iron silicate.

[0130]

[0131] Results and Discussion: The experimental results show that sodium carbonate, sodium nitrite, and trisodium phosphate have no stabilizing effect on polyferric aluminum silicate, while sodium hexametaphosphate has a stabilizing effect on polyferric aluminum silicate.

[0132] 3.3.2.2 Experiment on the optimal ratio of stabilizer D to polyaluminum iron silicate

[0133] Experimental raw materials

[0134] Freshly prepared polyferroaluminosilicate

[0135] Stabilizer: Sodium hexametaphosphate.

[0136] Experimental instruments

[0137] 5 conical flasks of 250

[0138] 1 / 100 electronic balance

[0139] Magnetic stirrer.

[0140] The experimental data and observation results of the optimal ratio of sodium hexametaphosphate to polyaluminum iron silicate are shown in Table 7:

[0141] Table 7. Experimental data and observation results of the optimal ratio of sodium hexametaphosphate and polyaluminum iron silicate.

[0142]

[0143] Results and Discussion: Polyaluminum iron silicate only maintains stable gelation over a long period of time when the ratio of sodium hexametaphosphate to polyaluminum iron silicate is greater than 4 / 100.

[0144] 4. Conclusion

[0145] 4.1 It is feasible to use the mother liquor generated during the production of sodium fluorosilicate from the multi-component fluorine-containing waste acid in the chip industry and hydrochloric acid to produce silicic acid, and then use liquid alkali and silicic acid to produce sodium silicate.

[0146] 4.2 It is feasible to produce polyferric chloride using steel pickling waste liquid with the addition of a suitable stabilizer.

[0147] 4.3 It is feasible to prepare polymerized aluminum iron silicate from sodium silicate solution, polyferric chloride, and polyaluminum chloride, but it must be under the protection of sodium hexametaphosphate to be stable.

[0148] 4.4 In summary, it is feasible to produce polymeric aluminum iron silicate from the mother liquor generated during the production of sodium fluorosilicate from multi-component fluorine-containing waste acid, steel pickling waste liquid, and polyaluminum chloride. Polymeric aluminum iron silicate is stable under the protection of an appropriate amount of sodium hexametaphosphate, therefore this experiment was successful.

[0149] This invention utilizes the mother liquor generated during the production of sodium fluorosilicate from fluorine-containing waste acid, steel pickling waste liquid, sodium hexametaphosphate, and polyaluminum chloride to synthesize polyferric silicate, achieving the effect of treating waste with waste, utilizing waste, and turning waste into treasure. Traditional polyferric silicate has very poor stability, and finding a suitable stabilizer and its ratio is extremely difficult, a problem in the industry. This invention not only found a suitable stabilizer but also, through repeated experimental design and corrections, finally selected a suitable stabilizer ratio: sodium hexametaphosphate as the stabilizer, with a stabilizer-to-polyferric silicate mass ratio ≥1:25. This solves the problem of traditional polyferric silicate being extremely unstable and prone to hydrolysis and gelation, exhibiting good stability.

[0150] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing polymeric aluminum iron silicate, characterized in that, The production process utilizes the mother liquor generated during the production of sodium fluorosilicate from fluorine-containing waste acid, including the following steps: S1: Add acid to the mother liquor, stir to produce a precipitate, filter, wash and dry the precipitate to obtain silicic acid, then add alkali to react with the silicic acid for 1.8-2.2 hours to obtain sodium silicate solution; S2: Add iron oxide powder to the steel pickling waste liquid containing ferrous ions and free acid and heat to dissolve it to obtain a mixed liquid. Take a sample of the mixed liquid to test the content of total ferrous ions, ferrous ions and free acid. Calculate the amount of stabilizer to be added based on the test results of the total ferrous ion content. Then add the stabilizer to the mixed liquid and stir evenly at room temperature. Calculate the amount of oxidant to be added based on the test results of the ferrous ion and free acid content. After the stabilizer and the mixture are stirred evenly at room temperature, the oxidant is slowly added to the mixture according to the calculated amount of oxidant to be added. After the oxidant is added, stirring is continued at room temperature for 0.9-1.1 h to obtain polyferric chloride. In step S2, the stabilizer contains 65-75 wt% phosphoric acid and 5-7 wt% sulfuric acid, and the mass ratio of phosphoric acid in the stabilizer to total iron in the mixture is 0.35-0.

50. The oxidant is sodium chlorate with a purity of ≥99%; S3: Mix the sodium silicate solution obtained in step S1, the polyferric chloride and polyaluminum chloride obtained in step S2, and the stabilizer, and mature them into polyaluminum ferric silicate. In step S3, the mass ratio of the stabilizer to the polymerized aluminum iron silicate is ≥1:25, and the stabilizer is sodium hexametaphosphate.

2. The method for preparing polymeric aluminum iron silicate according to claim 1, characterized in that: The mother liquor generated during the production of sodium fluorosilicate from fluorine-containing waste acid includes 14-16 wt / % H2SiF6, 0.8-1.0 wt / % Na2SiF6, 0.005-0.02 wt / % HCl, and 19.2-21.3 wt / % NaCl.

3. The method for preparing polymeric aluminum iron silicate according to claim 1, characterized in that: In step S1, the acid solution is hydrochloric acid, with an HCl content of 28-34 wt%, and the alkaline solution is sodium hydroxide, with a NaOH content of 29-35 wt%. The stirring conditions are: room temperature, vacuum degree 0.06-0.10 MPa, stirring speed 55-65 r / min; The mass ratio of mother liquor to hydrochloric acid is 100:1-2.5; The reaction conditions between silicic acid and alkaline solution are normal temperature and pressure; The mass ratio of silicic acid to alkaline solution is 1:3-3.

5.

4. The method for preparing polymeric aluminum iron silicate according to claim 1, characterized in that: The ferrous chloride content in the steel pickling waste liquid is 23-25 ​​wt%, and the free acid content (calculated as HCl) is 2-4 wt%.

5. The method for preparing polymeric aluminum iron silicate according to claim 1, characterized in that: In step S3, the silicic acid content in the sodium silicate solution is 35-40 wt%; The total iron content in polyferric chloride is 11-13 wt%; Polyaluminum chloride comprises 9-11 wt / % alumina and 0.05-0.15 wt / % iron oxide.

6. The method for preparing polymeric aluminum iron silicate according to claim 1, characterized in that: In step S3, the mass ratio of sodium silicate solution to polymerized aluminum iron silicate is 1:116.52-119.

56.

7. Polymeric aluminum iron silicate, characterized in that: It is prepared by the method of any one of claims 1-6, and has a basicity ≥25.0%.

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