A method for back-extracting iron-loaded p204 organic phase and back-extraction solution for removing iron

Abstract

The invention discloses a method for stripping an iron-loaded P2O4 organic phase and removing iron from strip liquor, and belongs to the technical field of hydrometallurgy. The method comprises the following steps: (1) mixing an oxalic acid solution serving as a stripping agent with the iron-loaded P2O4 organic phase, and performing reverse-flow stripping at the temperature of 20-40 DEG C to obtain iron-rich strip liquor and a blank P2O4 organic phase; (2) performing photodecomposition on the iron-rich strip liquor by means of solar radiation to precipitate and remove iron, or adding iron powder into the iron-rich strip liquor under heating and stirring conditions to remove iron by means of reductive precipitation; (3) filtering precipitated and iron-removed materials to separate a solid phase and a liquid phase out; (4) replenishing oxalic acid into the separated liquid phase, namely, an iron-poor oxalic acid solution, returning to the step (1) for recycling, and recycling the solid phase in the form of a ferrous oxalate product. The method is free from acid mist pollution in the operating environment, and has the advantages of simple process, no discharge of waste residues or waste liquor, high efficiency, environmental friendliness and high practicability.

Description

technical field [0001] The invention belongs to the technical field of hydrometallurgy, and in particular relates to a method for back-extracting an iron-loaded P204 organic phase and a back-extraction solution for removing iron. Background technique [0002] P204 is an acidic phosphorus-type extractant, the Chinese name is two (2-ethylhexyl) phosphoric acid, which is widely used in the hydrometallurgy of non-ferrous metals, such as the separation of nickel and cobalt, extraction of zinc, extraction of indium, nickel, cobalt Extraction and removal of impurities and rare earth extraction and grouping in the refining process. [0003] In the process of using P204 for extraction, separation of metals, or extraction and removal of impurities, some iron ion impurities are unavoidable in the aqueous phase feed liquid, and P204 has a strong ability to extract Fe(III). Fe(III) in the organic phase is difficult to be completely back-extracted under certain conditions. Therefore, dur...

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Problems solved by technology

[0003] In the process of using P204 for extraction, separation of metals, or extraction and removal of impurities, some iron ion impurities are unavoidable in the aqueous phase feed liquid, and P204 has a strong ability to extract Fe(III). Fe(III) in the organic phase is difficult to be completely back-extracted under certain conditions. Therefore, during the recycling of the P204 organic phase, Fe(III) will be enriched in the organic phase, and then the P204 organic phase will be extracted and separated. Decreased capacity; in industrial applications, some people call it "poisoning" of the P204 organic phase; for this reason, how to strip and remove iron from the Fe(III)-loaded P204 organic phase has always been concerned

[0004] Due to the strong stability of Fe(III) in the P204 organic phase, it cannot be effectively stripped even with high-concentration sulfuric acid. At present, the most commonly used stripping agent in industry is hydrochloric acid solution with a concentration of about 6mol / L, and it is also available in The industrial application of adding alkali metal or alkaline earth metal chloride to the hydrochloric acid solution to strip iron; the main disadvantage of using a hydrochloric acid solution of about 6mol / L or a mixed solution of hydrochloric acid and chloride for stripping is that the stripping agent has a large acid mist and the operating conditions Poor; in addition, the hydrochloric acid in the stripping agent is generally far excessive. During the recycling process, the iron ion concentration in the stripping solution gradually increases, and the free acidity decreases. When the free hydrochloric acid concentration drops to about 5mol / L, the effect of stripping iron It can only be discharged as waste acid and replaced with a new stripping agent; in this case, the consumption of stripping agent is large, and a large amount of free hydrochloric acid in the waste acid is not fully utilized, and the neutralization of the waste acid is difficult. It will bring a large amount of neutralized waste residue, which is easy to pollute the environment

[0005] In view of this, the application number is that the patent application of 200610152788.3 proposes to add NaOH solution in the P204 after hydrochloric acid regeneration, makes the Fe in P204 organic 3+ Form Fe(OH) 3 , after precipitation, discard the sediment Fe(OH) 3 , to regenerate iron-containing P204; this method still uses high-concentration hydrochloric acid for regeneration, and then uses sodium hydroxide for deep regeneration, and Fe(OH) 3 Precipitation, prone to emulsification and three-phase matter, difficult to separate the two phases, do not use regeneration operation

[0006] The patent application with the application number 201210036114.2 proposes that the P204 organic phase is first regenerated by back extraction with 6mol / L hydrochloric acid, and then undergoes alkaline washing with aqueous solution of sodium hydroxide + ammonium bicarbonate, and pickling with aqueous solution of oxalic acid + sulfuric acid. The whole process still cannot get rid of the 6mol / L With the use of L hydrochloric acid stripping agent, it is difficult to treat the iron-containing hydrochloric acid waste liquid, and after the 6mol / L hydrochloric acid stripping treatment, an additional stage of alkali washing and a stage of pickling are added. The overall process consumes a lot of acid and alkali, and the cost of waste acid and alkali Follow-up difficult

[0007] The patent No. 93111639.2 uses 2~4mol / L NH 4 F is made stripping agent, the (NH 4 ) 3 FeF 6 Add ammonia water to adjust the pH to 7~9 to convert it into Fe(OH) 3 Precipitate while making NH 4 F regeneration is returned to use; One of its disadvantages is that (NH 4 ) 3 FeF 6 Precipitation brings inconvenience to the stripping operation; in addition, the use of F-containing reagents in the process is likely to cause fluorine hazards to the environment, such as Fe(OH) 3 Precipitation entrained fluorine-containing solution is easy to pollute the environment

[0008] The patent application whose application number is 201210164356.X discloses a method for eluting Fe in P204 extractant 3+ method; this method is based on Fe 2+ The stability of the complex formed by the reaction with P204 extractant is lower than that of Fe 3+ According to this principle, by adding a reducing agent, the Fe in the poisoned extractant can be eluted. 3+ The purpose of the process is essentially reduction and stripping; the reduction and stripping temperature is 60~90°C, the reducing agent used is sodium borohydride, phosphorous acid, hydroxylamine hydrochloride or oxalic acid, and the reduction and stripping time is 0.5~2 Hours; due to the limitation of the reduction and stripping method itself, a higher stripping temperature must be used, which will inevitably cause the volatilization loss of the organic phase, and the treatment method of the iron-containing waste acid is not given.

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