RU2375334C1 - Method of extracting phosphorus from iron-containing waste products of vyatsko-kamsk phosphorites - Google Patents

Abstract

FIELD: construction industry.

SUBSTANCE: method of utilising phosphorus from iron-containing wastes formed during nitric-acid processing of Vyatsko-Kamsk phosphorites to fertilisers as per nitric-acid technology involves processing of wastes with mixture of nitric and sulphuric acids, separation of the obtained calcium sulphate by filtering, introduction of NaOH solution to the rest solution, bringing pH value to values not less than 12, sediment detachment of ironic hydroxide (III) by filtering and return of the rest solution containing sodium phosphate to the process of obtaining fertilisers. The obtained solution includes sodium phosphate without iron compounds, and sediment is iron hydroxide containing phosphorus compounds in quantity of 1-1.5% of the one taken for being processed.

EFFECT: method allows extracting phosphorus from wastes of nitric-acid processing of Vyatsko-Kamsk phosphorites thus obtaining useful product for being used in fertiliser producing methods.

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Description

The invention relates to the disposal of waste generated during the processing of phosphorites by nitric acid technology, namely, the allocation of phosphorus from waste generated during the processing of Vyatka-Kama phosphorites into fertilizers.

Currently, the task of expanding the raw material base for the production of phosphorus-containing fertilizers is urgent, but the phosphorites of explored deposits and, in particular, the phosphorites of the Vyatka-Kama deposit contain many harmful impurities, especially iron and aluminum oxides, so they are not suitable for processing. The chemical composition of the Vyatka-Kama phosphorites: P ₂ O ₅ - 23.5-25.0; CaO - 36.1-39.5; Fe ₂ O ₃ - 3.8-5.5; Al ₂ O ₃ - 2.8-3.5; CO ₂ - 4.4-5.0; MgO - 0.8; fluorine - 2.5-3.0; insoluble residue - 15.6 (M. Pozin. Technology of mineral salts. 4.2, L., Chemistry, 1974, p. 811).

A known method of producing a nitric acid extract from Vyatka-Kama phosphorites, in which the phosphate rock of the Vyatka-Kama field is treated with nitric acid at a temperature of 20 ° C. The method allows to reduce the content of iron and aluminum in a nitric acid extract. (Pat. RF №2288906, С05В 11/06, publ. 10.12.2006).

The disadvantage of this method is the incomplete extraction of phosphorus from phosphate rock, because up to 28% of phosphorus compounds in terms of P ₂ O ₅ go into waste in the form of an insoluble precipitate together with iron and aluminum oxides. Methods for the extraction of phosphorus from the waste of nitric acid processing of Vyatka-Kama phosphorites are not described in the literature.

An object of the present invention is to recover phosphorus from the above precipitate.

The stated technical problem is solved in that according to the invention, the waste of nitric acid processing of Vyatka-Kama phosphorites is treated with a mixture of nitric and sulfuric acids to transfer all components into a solution, the obtained calcium sulfate is separated by filtration, then the alkali solution is added, the pH is adjusted to at least 12, the precipitate is separated iron (III) hydroxides by filtration, and the remaining solution containing sodium phosphate is returned to the fertilizer production process.

The method was tested in laboratory conditions.

Example

The insoluble precipitate obtained by ammonizing the nitric phosphate solution with ammonia to pH = 0.9 is separated from the solution by filtration. The precipitate has the following composition,%:

P ₂ O ₅ - 28.0 Fe - 5.5 Sa - 14.0 Al - 1.2 Insoluble precipitate - 40

For experiments take 16 g of iron-containing precipitate, treated with a mixture of HNO ₃ (20%) and H ₃ SO ₄ (20%). The amount of sulfuric acid is taken from the stoichiometric calculation of the conversion of calcium to calcium sulfate, and the amount of nitric acid from the calculation of the conversion of iron and aluminum phosphates into the solution with an excess of up to 10%. The precipitate is treated with a mixture of acids at t = 60 ° C for 30 minutes. The suspension is filtered under vacuum. The precipitate was washed with 130 ml of H ₂ O (t = 60 ° C).

The resulting solution was treated with 40% NaOH in an amount of 10.5 g (4.2 g of NaOH 100%). In this treatment, the total amount of alkali added was such that the solution reached a pH of 12. The resulting suspension was heated to t = 90 ° C and held at this temperature for 30 minutes, after which it was filtered under vacuum. The precipitate was washed with 180 ml of H ₂ O (t = 90 ° C).

The results of the experiments are summarized in table 1.

Table 1
Processing iron sludge. No. op. pH The content of P ₂ O ₅ , Fe, Al in the sediment,% of taken for experiments The content of P ₂ O ₅ , Fe, Al in solution,% of taken for experiments P ₂ O ₅ Fe Al P ₂ O ₅ Fe Al one 12.0 5.5 - - 94.5 no - 2 12,2 3.0 98.7 2.2 97.0 no - 3 12.5 6.2 99.3 2.2 93.8 no 97.8 four 11.0 17.0 99.0 - 83.0 1,0 - 5 9.0 40,0 98.0 80.0 60.0 2.0 20,0 6 7.0 40,0 97.0 48.0 60.0 3.0 52.0 7 5.3 45.0 94.0 one hundred 55.0 6.0 no

In all experiments where the pH value was not less than 12, no iron compounds were found in the phosphorus-containing solution, and with the precipitate, which was iron (III) hydroxide, the losses of P ₂ O ₅ amounted to about 5% of its content in the processed sample.

Claims (1)

A method of extracting phosphorus from iron-containing wastes of nitric acid processing of Vyatka-Kama phosphorites, including treating iron-containing wastes with a mixture of nitric and sulfuric acids, separating the resulting calcium sulfate by filtration, introducing NaOH solution into the remaining solution, adjusting the pH to at least 12, separating the precipitate of iron hydroxide (III ) filtering and returning the remaining solution containing sodium phosphate to the fertilizer production process.