SU1465419A1 - Method of treating effluents of extraction phosphoric acid production - Google Patents

Abstract

The invention relates to the disposal of waste production of mineral fertilizers and materials. The aim of the invention is to increase the efficiency of the method by obtaining an additional fertilizer and reclamation means of improved quality. The wastewater produced by extraction phosphoric acid is subjected to electrodialysis treatment in a three-chamber electrodialyzer with water supplied to all chambers and when 95-150% carbonized phosphate is introduced into the anode chamber. When the pH of the suspension in the cathode chamber is 6.0-6.5, phosphogypsum is added to it at a mass ratio of the suspension and phosphogypsum (16-80): and the process of electrodialysis continues until the pH of the suspension in the cathode chamber reaches 7.0-7, five. After completion of the process, the purified water and sediment from the cathode chamber are separated, and the precipitate is dried. The resulting product is a fertilizer and ameliorative with a capacity of up to 160% and a RaO3 content of up to 20%. 2 tab. (Ls

Description

one

This invention relates to the disposal of waste products from the production of mineral fertilizers and ameliorants.

The purpose of the invention is to increase the efficiency of the method by obtaining an additional fertilizer and ameliorative medium of improved quality.

Example. Sewage water produced by EPA, containing 5000 mg /% P2O5 and 2500 mg /% CaO, in an amount of 12 kg is subjected to electrodialysis treatment in a three-chamber electrodialyzer with the supply of waste water to all its chambers and with constant mixing.

Carbonized phosphorite is introduced into the anode chamber in the amount of 95-150% based on the fluorine content of the wastewater. In the process of conducting electrodialysis of waste water with the imposition of a constant

electric field is observed migration of cations and anions through the electrodialysis chambers. Due to the electrochemical processes, the solution in the anode chamber becomes acidic, and in the cathode - alkaline. A change in pH through the electrodialysis chambers creates the necessary condition for decarbonating phosphate in the anode chamber and purifying water in the cathode. At the same time (at pH 5) in the cathode chamber, phosphates and phosphates are formed and precipitate, containing 1-2% fluorine and more than 30% Rho3. When the pH of the catalit reaches a value of 6.2, 125 g of phosphogypsum is introduced into the cathode chamber with 100% moisture capacity, containing 1% P2O5. The mass ratio of the suspension — phosphogypsum is 32. Electrodialysis is continued until the pH of the catholyte is 7.2 and then the resulting pulp is fed

4 O5 01

WITH

in the sludge separator, where the separation of the pulp into clarified catholyte and condensed product. The rate of clarification of the catholyte is 0.48 m / h. The degree of purification of catholyte from P2O5 is 98%. After filtration and drying, 45 g of a fertilizer mixture with a 150% moisture capacity containing 15.5% P2O5 total are obtained. and 14.9% P2O5 citrate, plant.

With the introduction of phosphogypsum in the cathode chamber in an amount of 250 and 50 g, which corresponds to a suspension-phosphogypsum ratio of 16 and 80, 270 and 65 g of fertilizer composition containing 6.3 and 20.0% of P2O5 total are obtained.

The feasibility of the selected parameters is illustrated in Table. .

The limiting ratios and suspensions of α-phosphogypsum were not chosen randomly, since the process was not economically feasible for less than 16 times and because the moisture capacity of the resulting mixture and the concentration of P205 increased slightly compared to the initial phosphohisis. The introduction of phosphogypsum in a ratio of more than 80 leads to a decrease in the rate of clarification of the suspension and a deterioration in the quality of clarified water (due to an increase in the amount of suspended particles in it).

With the introduction of phosphogypsum into the cathode chamber of the electrodialyzer, the neutralization of phosphogypsum occurs, the pH of the suspension decreases to 5.8-5.5, which is accompanied by the dissolution of part of the phosphogypsum in the resulting suspension. The process is wrapped up when the pH of the cathode chamber reaches 7.0-7.5. Neutralization of unwashed P2O5 impurities improves the physicomechanical properties of phosphogypsum. The feasibility of administering phosphogypsum in a given m. PH range (6.0-6.5) is necessitated by the need to neutralize P2O5 impurities and transfer them to the citrated area of the form (Ca (НРО4) 22Н2О without loss. ) 2 leads to losses due to the migration of phosphate ions (H2PO4) to the anodic chamber of the electrodialyzer.The limiting value in relation to the pH of the introduction of phosphogypsum is chosen based on the fact that water-soluble phosphates are formed in the system at A. Sr6,4 - acid-soluble forms, which p) leads to y less digestible phosphate content. Thus, the content of digestible phosphates depends on the pH of the phosphogypsum.

The resulting fertilizer composition should be dried at 55-60 ° C to avoid the conversion of calcium sulfate dihydrate (CaSO, 2H20) to the hemihydrate {CaSO.c 5Н2О). Phosphogypsum can be used immediately after its removal from the process at which it is formed (taking into account its moisture content, i.e., to calculate

air-dry matter), but it can also be taken from dumps and used without any pretreatment.

The product obtained in the proposed method has improved properties as a fertilizer composition for chemical soil amelioration, which results in an increase in the moisture content of the composition up to 160% and a P2O5 content of up to 20%. The combination of the reclamation properties of the composition with the fertilizer increases its agrochemical efficiency. An agrochemical evaluation of the proposed fertilizer composition was carried out under the conditions of a vegetative experiment on perennial grasses. In the experiments, the efficiency of using phosphogypsum itself, phosphogypsum mixed with lime, phosphogypsum mixed with phosphates obtained by the prototype and the proposed method was compared.

The results of the experiments are presented in table. 2

As can be seen from the presented data, the greatest increase in yield per mowing was obtained when applying the proposed fertilizer composition. In experiment 4, a mixture obtained by mechanical mixing of foosgips with phosphates formed in the cathodic chamber of the electrodialysis apparatus during wastewater treatment according to the prototype is used. As can be seen from the presented data, the mixture obtained by simple addition of phosphate gives a smaller agrochemical effect, because the proposed composition. Consequently, the increased agrochemical effect does not stem from the composition of the mixture, but from the method of its preparation and is due to an increase in the capacity of the composition. The increase in moisture content of the composition occurs due to the processing of phosphogypsum in the cathode chamber of the electrodialyzer as follows. When phosphogypsum is introduced into the cathode chamber of an electrodialyzer, recrystallization of the dissolved part of phosphogypsum occurs with the formation and precipitation of calcium sulfate dihydrate (CaSO4-2H20). Recrystallization of phosphogypsum occurs due to the fact that as the electrodialysis purification proceeds, the calcium ions of the same name concentrate in the cathode chamber, which shift the equilibrium towards the formation of a precipitate, and with an excess of calcium ions, small crystals are observed; Thus, two processes proceed simultaneously in the cathode chamber: on the one hand dissolution, and on the other hand precipitation of calcium sulfate. Seed analysis showed that calcium sulfate crystals with a size of 80–40 µm were formed, while the initial phosphogypsum was in the range of 200 × X80 µm, and the precipitate formed had a high specific surface area and moisture capacity. When this occurs, the uniform mutual distribution of the philosophic 1ca

with phosphate, which also leads to an increase in agrochemical efficiency improver.

Claims (1)

Invention Formula The wastewater treatment method of producing phosphoric acid from fluorine by electrodialysis in a three-dimensional electrodialyzer when the source water is supplied to all chambers and carbonium sediment from the cathode chamber, characterized in that, in order to increase the efficiency of the method by obtaining an additional fertilizer and meliorative means of improved quality, when reaching the cathode chamber in the process. electrodialysis, the pH of the suspension is 6.0-6.5, phosphogypsum is additionally introduced into it at a mass ratio of 16-80: 1 and the process is continued until the pH of the suspension is reached in the cathode chamber ..V ... ... m. “V. About ... and c, j.uuHiiMt.uAep-pH pH of the suspension in the cathode chamber phosphorite in the anode chamber with a pH of 7.0–7.5, and the precipitate from the cathode chamber after the next separation of purified water from purified water is dried. and sediment from the cathode chamber, characterized in that, in order to increase the efficiency of the method by obtaining an additional fertilizer and ameliorative means of improved quality, when reaching the cathode chamber in the process. electrodialysis, the pH of the suspension is 6.0-6.5, phosphogypsum is additionally introduced into it at a mass ratio of 16-80: 1 and the process is continued until the pH of the suspension is reached in the cathode chamber the pH of the suspension in the cathode chamber 7.0-7.5, and the precipitate from the cathode chamber is dried after separation from the purified water. Without phosphogypsum Phosphogypsum100 Phosphogypsum-lime (1: 1) 70 The mixture of phosphogypsum with phosphates (the mixture contains 15.5% Pi 05) 85 Fertilizer composition obtained by the proposed method contains 15.5%) 150 Table 1 table 2 - - 85.6 1.6 15 0.15 89.5 1.3 15 0.07 92.3  15 0.82 126.0 4.5 15 0.82 140.5