盐酸液中钇(Ⅲ)和铕(Ⅲ)的P507溶剂萃取平衡分析

摘要

为了精确预测非理想条件下稀土金属溶剂萃取的平衡分配比,研究了溶于Shellsol D70中的P507溶剂对盐酸液中钇(Ⅲ)和铕(Ⅲ)的萃取平衡,建立化学基模型,并通过非线性最小二乘法确定萃取平衡常数.所建模型涉及了在低酸度区的离子交换反应和高酸度区的溶剂化萃取反应；模型还考虑了稀土金属与Cl-的配位反应,并用萃取剂的有效浓度代替[(HR)2],进而分别对水相和有机相(HR2)的非理想性加以修正.对稀土单元体系,在较宽的初始浓度范围内(稀土浓度最高至0.1 mol/L,盐酸浓度0.07-3.00 mol/L,萃取剂浓度0.25-1.00 mol/L),由模型计算的稀土分配比与实验测得的数据吻合良好,验证了模型的有效性.对于稀土二元体系,该模型能以良好的精度对平衡分配比进行工程预测.%For the accurate prediction of equilibrium distribution ratios of rare earth metals during solvent extraction under non-ideal conditions,the extraction equilibria of yttrium(Ⅲ)and europium(Ⅲ)from the hydrochloric acid solutions with P507 in Shellsoi D70 were studied.A chemically-based model was established and the extraction equilibrium constants were determined by the nonlinear least squares method.The proposed model involves the cation exchange reaction and the solvation extraction in the low and high acidity regions,respectively.In the model,the nonideality of the aqueous phase and(HR)2 was corrected by considering the complexation of the metals with(Cl-)and by replacing[(HR)2]with its effective concentration,respectively.This model was verified by fair agreement between the calculated metal distribution ratios and those experimentally obtained in the single metal systems.The feed concentrations for the systems are in wide ranges of the metal(up to 0.1 mol/L),hydrochloric acid(0.07-3.00 mol/L)and the extractant(0.25-1.00 mol/L).The model enables the engineering prediction of the equilibrium distribution ratios with good accuracy in a binary metal system.