CuO-CO2-NH3-H2O体系孔雀石浸出的热力学分析

针对氨浸出孔雀石的问题,对CuO-CO2-NH3-H2O体系进行了热力学分析,获得了一系列平衡关系图.结果表明,随着pH值升高,OH^-取代CO3^2-参与形成沉淀,使稳定存在的固体按蓝铜矿、孔雀石、氢氧化铜的顺序转变.pH值对铜的溶解起决定性作用.pH值较低时,H^＋和Cu^2＋竞争与NH3的结合,溶液中铜氨配合物浓度低;pH值较高时,OH-和NH3竞争与Cu^2＋的结合,使铜转化为氢氧化铜沉淀;pH值8-11时,H^＋和OH^-的竞争作用较弱,大部分NH3与Cu^2＋形成配合物,其中Cu（NH3）2＋4为优势物种.氨浸出孔雀石的理论最佳pH值在9.3-9.4之间,该条件时总铜和总氮平衡浓度大体呈直线关系.

Thermodynamic analysis of leaching malachite in CuO-CO2-NH3-H2O system

In or der to investigate issues of leaching malachite with ammoniacal solution, thermodynamic equilibriums of CuO-CO2-NH3-H2 O system is studied, obtaining a series of equilibrium diagrams. The results show that OH-replaces gradually to form precipitate when pH is increased. The order of stable solids from low to high pH value is as follows： azurite, malachite and copper hydroxide. PH plays a decisive role in copper leaching. At low pH, H＋competes with Cu2＋to combine with NH3, which leads to a low concentration of copperammonia complex in solution; at high pH, OH-competes with NH3 to combine with Cu2＋, which makes copper in solution convert to copper hydroxide precipitate. When the pH value is between 8 and 11, the competitive effects of H＋and OH-are relatively weak. Most ammonia form complex with copper, and is the predominant species. Besides, the calculated theoretical optimal pH for leaching malachite is between 9.3 and 9.4. There is a roughly linear relationship between the total concentration of copper and nitrogen under this condition.