叔胺TOA从含钒钢渣直接酸浸液中萃钒除铁的研究

用叔胺TOA对含钒钢渣直接酸浸液进行溶剂萃取，考查了主要因素对萃钒除铁的影响，并分析了TOA的构效关系及其萃钒除铁的溶液化学行为。结果表明:在TOA体积浓度15%、初始水相pH 1.8~1.9、相比A/O为3、萃取时间3 min的最佳条件下，经4级逆流萃取，较好地实现了萃钒除铁，钒萃取率达98%，而铁则很少被共萃。TOA的N原子具有较强给电子性的弧对电子，经硫酸酸化，转化为（C₈H₁₇）₃NH]₂SO₄，可通过阴离子交换反应完成萃取过程；水相中的V（Ⅳ）经H₂O₂氧化后转化为V（Ⅴ），利用氨水中和将水相pH值提高，VO₂+则转化为多种形式的阴离子；当钒以特定形式H₂V₁₀O₂₈]4-存在时，可获得较高的萃取率；在pH 1.2~2.4较宽范围内，钒均可以H₂V₁₀O₂₈]4-的形式存在，而且在此范围内增大pH值，H₂V₁₀O₂₈]4-浓度以及HSO₄-解离度增加，钒萃取率因而提高；但当pH>1.9时，Fe（Ⅲ）会发生水解沉淀，阻碍两相分离并引起钒的共沉淀损失，对萃取极为不利；当pH < 2.0时，Fe（Ⅲ）以Fe3+形式存在，难以被TOA共萃，从而可达到萃钒除铁的目的。 

Extracting Vanadium over Iron from Direct Acid Leaching Solution of V-bear-ing Steel Slag by Solvent Extraction with Tertiary Amine TOA

Solvent extraction of direct acid leaching solution of vanadium-bearing steel slag with tertiary amine TOA, was carried out, and the effects of the main factors on extraction of vanadium over iron were investigated. Meanwhile, the structure-activity relationship of TOA and the solution chemical behavior of extracting vanadiumover iron were analyzed. Through a 4-stage countercurrent extraction under the following optimum conditions: TOA concentration of 15 vol.%, initial aqueous phase pH of 1.8~1.9, phase ratio (A/O) of 3, and extraction time of 3 min, the extraction of vanadium over iron was well achieved, and vanadium extraction rate reached 98% whereas iron was barely extracted. N atom of TOA has a lone pair of electrons and can be an electron contributor, TOA acidified by H₂SO₄ to convert to (C₈H₁₇)₃NH]₂SO₄, can achieve extraction through anion-exchange reaction.Through oxidation by H₂O₂, V(Ⅳ) in aqueous phasewas oxidized to V(Ⅴ). Through neutralization by NH₃·H₂O to increase aqueous phase pH, VO₂+ was converted to various forms of anions. When vanadium was in the specific form of H₂V₁₀O₂₈]4-, a higher extraction rate could be obtained. Vanadium could exist in form of H₂V₁₀O₂₈]4- within a wide pH range of 1.2~2.4. As the pH increased within this pH range, the concentration of H₂V₁₀O₂₈]4- and the dissociation of HSO₄- also increased, which improved extraction rate. However, Fe(III) would be precipitated by hydrolysis at pH > 1.9, which would prevent the two phases from separating and cause a coprecipitation loss of vanadium.When pH < 2.0, Fe (Ⅲ) existed in the form of Fe3+ and could not be extracted by TOA, so the purpose of extracting vanadium over iron was realized.