SU975570A1 - Process for purifying phosphoric acid from iron - Google Patents

Description

one

This invention relates to a process for the purification of phosphoric acid from impurities, in particular iron, and can be used in the chemical industry.

A known method of purification of phosphoric acid from impurities, in particular iron, by extracting it with sulfonic acids in a diluent. Extraction is carried out at 29--65 ° C and the ratio of the organic phase to the aqueous, is 1: 1-100: 1. The iron recovery rate is 60%.

However, in this method, the degree of iron extraction is not high enough.

A known method of purifying thermal phosphoric acid (650/0 PjOs) from iron by introducing hydrobromic acid into it and extracting iron with trialkylphosphate in benzene, the ratio of organic phase to water being 0.5: 1. The concentration of trialkyl phosphate in benzene is 50 vol%. The concentration of iron in the purified phosphoric acid solution is 0.001 / oPe2O3, which contributes to less than 80% of the extraction of iron from phosphoric acid 2.

However, according to a known method, the degree of extraction of iron from phosphoric acid is not high enough.

The aim of the invention is to increase the degree of extraction of iron from phosphoric acid.

The goal is achieved by the fact that according to the method of purification of phosphoric acid from iron, a mixture of di-2-ethylhexyldithiophosphoric acid and 2-ethylhexanol in a diluent is taken as an extractant and extraction is carried out with respect to the organic phase to the aqueous one, equal to (0.5-1): one.

The concentration of di-2-ethylhexyldithiophosphoric acid in the mixture is 1-1.25 mol / l, and 2-ethylhexol - 15-20-25 vol.%

The method allows to increase the degree of iron extraction from concentrated phosphoric acid solutions (8-12 M) up to 80-97.9%.

The dependence of the degree of iron extraction on the ratio of organic and aqueous phases is given in Table. one.

From the data table. 1 it follows that with a Vo: VB ratio of less than 0.5: 1 and more than 1: 1, the degree of iron recovery is not high enough. The optimum phase ratio is (0.5-1): 1 At concentrations of di-2-ethylhexyldithiophosphoric acid less than 1 and more than 1.25 mol / l, the degree of iron recovery is less. When the concentration of 2-ethylhexanol in the mixture is less than 20% by volume, the degree of iron recovery is less than SGP / o, and at a concentration of more than 25% by volume, the degree of iron recovery increases by 1.5% with increasing concentration from 25 to 500/0. Limit hydrocarbons are taken as diluents: hexane, heptane, retan, decane Extraction is carried out at 22 + 2 ° C. Iron was extracted from the organic phase with a F / O-HNM solution of sulfosalicylic acid in 6-7 N, ammonia solution. Example 1. In a separating funnel, 20 ml of 12 M phosphoric acid containing 0.112 g / l of iron and 20 ml of the organic phase containing 1.25 mol / l of di-2-ethylhexyldithiophosphoric acid (D2 EHDTPA) and 25 v / v are mixed 2-ethylhexanol in hexane. The phase mixing time is 3 min.

The ratio of organic and aqueous phases, PP: VB

The degree of iron extraction,% After separation and separation of the phases, the residual iron content in phosphoric acid is determined, which is 0.014 g / l. The iron recovery is 87 ,. Example 2. In a separating funnel, 30 ml of phosphoric acid (Example 1) and an organic phase containing 1.25 mol / l of E2 EHDTPA, 20 v / v 2-ethylhexanol in hexane are mixed for 3 minutes. The degree of iron extraction into the organic phase is 80P / o. Example 3. The extraction of iron are from 12 M phosphoric acid extractant (example 1) in several stages. The dependence of the degree of extraction and residual iron content in the solution is given in Table. 2. From the data table. 2 it follows that three extraction steps are sufficient. The proposed method allows to improve the quality of phosphoric acid and products based on it by extracting iron impurities from it. table 1

1 2 3

0.157

0.0236

0,0071

table 2

85.0

95.50

97.90

Claims (2)

Invention Formula . The method of purification of phosphoric acid from iron, including the extraction of iron with an organic extractant, followed by phase separation, characterized in that, in order to increase the degree of iron extraction, a mixture of di-2-ethylhexyl dithiophosphoric acid and 2-ethylhexanol in the diluent is taken as the extractant and the extraction is carried out organic phase to water, equal to (0.5-1): 1. Continued tabl, 2 2. A method according to claim 1, characterized in that the concentration of di-2-ethylhexyldithiophosphoric acid in the mixture is 1 -1.25 mol / l and the concentration of 2-ethylhexanol is 20-25% by volume. Sources of information taken into account in the examination 1. US patent number 4082836, class. 423-3215, published. 1978 2. Patent of the GDR No. 57025, cl. 12-i 25/16, published 1967.