材料期刊网

同一萃取剂不同机理萃取金属时的盐析规律应不相同。本文研究胺类在不同条件下萃取过渡金属W,Mo,V,Cr时的盐析效应,亦即胺类在按照溶剂化历程和阴离子交换历程萃取时的盐折效应及其机理。 胺类按照溶剂化历程萃取中性分子时,胺类首先与过渡元素含氧酸生成具有很大亲水性的水合络合物。水合络合物的形成与水的活度有关,盐析剂加入将直接降低水溶液中水的活度,从而降低金属分配比。而胺类在交换萃取时的盐析效应,主要决定于在萃取过程中主、副反应进行的程度及二者间的竞争能力。加入盐析剂可阻止副反应发生,从而有利于交换萃取。 关于溶剂萃取中的盐析效应,结合所研究的体系,提出了一些新的看法及观点。

The effect of the presence of inorganic salts in aqueous phase on solvent extraction of metals by an extractant could be different during extraction with different mechanisms. The salting-out effect of the extraction of W(Ⅵ), MoⅥ),V(Ⅴ) and Cr(Ⅵ) by amines under anion-exchange and solvation mechanisms respectively was studied. During solvation extraction of oxyacids of transition metals by amines, hydrophilic complexes were formed first between them. The formation of these complexes depends greatly on the activity of water molecules in the aqueous phase. The addition of inorganic salts to the aqueous phase will decrease the activity of water molecules and thus decrease the extraction of metals into the organic phase. However, during extraction of metals by amine salts with anion-exchange mechanism, the presence of inorganic salts will diminish or prevent the formation of hydrophilic complexes in the simultaneous side reaction and thus increase the percent of metals extracted by the main anion-exchange reaction. Therefore, the extraction of transition metals by amines can be increased or decreased by the addition, of inorganic salts to the aqueous phase with anion-exchange and solvation extraction mechanisms respectively. Some new viewpoints about salting-out effect in solvent extraction were proposed.