钨酸钠溶液氢氧化钙苛化-沉淀白钨的研究

钨酸钠溶液氢氧化钙苛化-沉淀白钨工艺是实现钨矿NaOH分解试剂回收,以至黑钨和黑白钨混合矿绿色冶炼的技术途径;研究了不同温度下钨酸钠溶液氢氧化钙苛化-沉淀白钨反应的平衡常数和标准自由能变化,分析了氢氧化钠和钨酸钠的活度系数对反应平衡的影响;工艺研究表明:温度和钨酸钠溶液浓度对白钨沉淀率的影响非常显著.当氢氧化钙用量为1.4倍理论量,温度100℃,钨酸钠溶液钨浓度为105 g/L,保温时间为2 h,搅拌速度为350 r/min,白钨沉淀率可达96%以上.与传统工艺采用氯化钙作为沉淀剂相比,氢氧化钙沉淀白钨所需的理论量倍数较大、反应的时间较长、搅拌速度更快.

Causticizing-precipitating scheelite by calcium hydroxide from sodium tungstate solution

The process of causticizing-precipitating scheelite by calcium hydroxide from sodium tungstate solution is the technical way of the realization of recycling NaOH reagent for tungsten ore decomposition,and wolframite and scheelite and wolframite mixed ore green smelting. This paper studies equilibrium constant and standard free energy change of causticizing-precipitating scheelite by calcium hydroxide from sodium tungstate solution reaction at different temperatures, and analyzes the effect of the activity coefficient of sodium hydroxide and sodium tungstate on the reaction equilibrium. The research shows that the effect of temperature and sodium tungstate solution concentration on precipitation rate of scheelite is very significant.When the calcium hydroxide dosage is 1.4 times of the theoretical amount, temperature 100 ℃, tungsten concentration of sodium tungstate solution is 105 g/L, the holding time is 2 h, the stirring speed is 350 r/min,the precipitation rate of scheelite can reach above 96 %. Comparing with traditional process of calcium chloride used as a precipitating agent, calcium hydroxide precipitating scheelite requires larger times of the theoretical amount, longer reaction time and faster stirring speed.