Method for removing impurity iron from hydrochloric acid raw phosphoric acid by solvent extraction process

Abstract

The invention discloses a method used for removing ferrum impurities out of hydrochloric acid and rough phosphate by using a solvent extraction method: 1). organic matters is removed: rough phosphate produced by a hydrochloric acid method is added with activated carbon at a mass ratio of 100: 0.5 to 5, so as to absorb and remove the organic impurities in the rough phosphate acid; 2). extraction of ferrum is extracted: tributyl phosphite (TBP) is added to the rough phosphate acid in an organic phase / water phase volume ratio of 1: 3 to 8, and the two phase solution is mixed after being preheated for 5 to 30 minutes in water bath measured 25 to 85 DEG C, and then the mixture is shaken for 5 to 20 minutes, then settled and stratified so as to separate the extraction phase containing ferrum with 3 consecutive extraction stages, ferrum impurities out of the rough phosphate produced by the hydrochloric acid method is removed, finally the phosphorous acid without ferrum is acquired. The invention has the advantages that: firstly, the proportion for phosphorous acid to be extracted by organic phase in 3 stages is less than 15 percent, whereas, the ferrum impurities have the high extraction rate, so that the ferrum impurities can be completely separated from the phosphorous acid, and after purification the ferrum content in the phosphorous acid reaches a first-class production quality standard for industrial phosphorous acid; secondly, the method is suitable for extraction of ferrum impurities in case of a low concentration of the rough phosphorous acid, with advantages of low operation cost and expedience for exploitation of depleted phosphorous acid resources; thirdly, the TBP extraction agent adopted has low solubility in water, and the extraction agent after being extracted can be recycled after an acid-stripping treatment.

Description

technical field [0001] The invention relates to a technology for purifying iron impurities in wet-process phosphoric acid, in particular to a method for removing impurity iron from wet-process crude phosphoric acid produced from poor phosphate rock by hydrochloric acid method. Background technique [0002] At present, the world's energy demand is becoming increasingly tense, and the price of thermal phosphoric acid continues to rise. The production of wet process phosphoric acid is likely to replace the production of thermal phosphoric acid. However, the proportion of lean phosphate rock in phosphate rock resources is increasing, and the impurity content in wet-process phosphoric acid is high, especially impurities such as iron, aluminum and magnesium will lead to the formation of insoluble sludge and the increase of phosphoric acid viscosity, and the presence of iron will change. The color of the product is seriously affected, which seriously affects the quality and use of ...

AI Technical Summary

Problems solved by technology

However, the proportion of lean phosphate rock in phosphate rock resources is increasing, and the impurity content in wet-process phosphoric acid is high, especially impurities such as iron, aluminum and magnesium will lead to the formation of insoluble sludge and the increase of phosphoric acid viscosity, and the presence of iron will change. The color of the product is seriously affected, which seriously affects the quality and use of phosphoric acid

[0003] Although there are many ways to purify iron, in crude phosphoric acid prepared by hydrochloric acid method, Fe 3+ with Cl - Coordination to form FeCl 3 molecule or FeCl 4 - In the form of anions, and each species associates with the surrounding phosphoric acid molecules, it is difficult to achieve the purpose of effective separation by means of ion exchange and activated carbon adsorption.

EDTA complexation-adsorption method has strong ability to purify iron, but its cost is high

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