选择性沉淀法除钼后溶液中铜的行为研究

Behavior of Copper in Solution after Removing Molybdenum by Selective Precipitation

针对钨冶炼过程中采用选择性沉淀法除钼后溶液中铜浓度"反常"偏高的现象,利用同时平衡原理,对该溶液体系中的Cu-NH3-C l-S复杂络合平衡进行了热力学计算,并根据结果绘制了有关平衡图,同时结合生产实际进行了分析与解释。结果表明,选择性沉淀法除钼后溶液中的铜可与HS-,NH3,C l-和OH-等阴离子形成多种复杂络合离子,但大多数铜络合离子浓度非常低,对溶液中总铜浓度影响很小;造成铜的"反常"偏高的主要原因在于铜与HS-形成的Cu(HS)3-和CuS(HS)33-络离子,并且在计算条件下,该类络离子的浓度随pH值及溶液中[S]的增加而迅速增加。最后根据分析结果,提出了避免铜杂质超标的对策,主要方法如下:(1)在不造成大量钨损的前提下尽可能降低溶液硫化的pH值或在保证硫化深度的前提下尽可能降低硫化剂的用量,可使除钼后溶液中铜浓度降低;(2)可以在除钼后向溶液中加入氧化剂(如H2O2)将溶液中剩余的硫氧化成SO24-,使其无法与铜络合从而减少溶液中的铜浓度;(3)因铜络离子均以络阴离子的形式存在,可通过溶剂萃取或阴离子交换树脂吸附,将含铜络阴离子除去,从而降低溶液中的铜浓度。

During tungsten extraction,the solution showed extraordinarily high copper concentration after the molybdenum was removed by selective precipitation process.Aiming at this phenomenon,thermodynamic calculation for the complex equilibrium system of Cu-NH3-Cl-S was carried out according to the simultaneous equilibrium principle,and the related equilibrium diagrams were also drawn.The results indicated that,copper could form various complex ions with HS-,NH3,Cl-,OH-and other anions.But most of them had quite low concentration,which affected little on total copper concentration in the solution.The main reason causing unexpected high copper ion concentration was the formation of Cu（HS）-3 and CuS（HS）3-3 between copper ions and HS-.Moreover,under the conditions of calculation,the concentration of copper complex ions increased greatly with the increase of pH value and [S] in the solution.According to the analytical results,measures to avoid the unqualified copper concentration were put forward as follows：（1） Under the premise of no large amount of tungsten loss,the sulfurizing pH value of the solution or the dose of sulfurizing agent should be lowered as far as possible only if guaranteeing the depth of sulfurizing.（2） Oxidant（H2O2,for instance） could be added to oxidize sulfur left in the solution into SO2-4 so as to make it unable to form complex with copper ions.（3）Since all copper complex ions were in forms of complex anions,they could be adsorbed through the solvent extraction or anion exchange resin to be removed,and thereby the copper levels in the solution could be reduced.