叔胺TOA从含钒钢渣直接酸浸液中萃钒除铁的研究

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

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[(C_(8)H_(17))_(3)NH]_(2)SO_(4),可通过阴离子交换反应完成萃取过程;水相中的V(Ⅳ)经H_(2)O_(2)氧化后转化为V(Ⅴ),利用氨水中和将水相pH值提高,VO_(2)^(+)则转化为多种形式的阴离子;当钒以特定形式[H_(2)V_(10)O_(28)]^(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[H_(2)V_(10)O_(28)]^(4-)的形式存在,而且在此范围内增大pH值,[H_(2)V_(10)O_(28)]^(4-)浓度以及HSO_(4)^(-)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Fe^(3+)形式存在,难以被TOA共萃,从而可达到萃钒除铁的目的。

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 H_(2)SO_(4) to convert to[(C_(8)H_(17))_(3)NH]_(2)SO_(4),can achieve extraction through anion-exchange reaction.Through oxidation by H_(2)O_(2),V(Ⅳ)in aqueous phasewas oxidized to V(Ⅴ).Through neutralization by NH_(3)·H_(2)O to increase aqueous phase pH,VO^(2)+was converted to various forms of anions.When vanadium was in the specific form of[H_(2)V_(10)O_(28)]^(4-),a higher extraction rate could be obtained.Vanadium could exist in form of[H_(2)V_(10)O_(28)]^(4-)within a wide pH range of 1.2~2.4.As the pH increased within this pH range,the concentration of[H_(2)V_(10)O_(28)]^(4-)and the dissociation of HSO_(4)^(-)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.