磷酸钠－氢氧化钠浸出氟化钙动力学研究

针对现行主流氢氧化钠和碳酸钠浸出低品位白钨矿存在浸出剂用量大，浸出率低的弊端，提出磷酸钠－氢氧化钠－氟化钙协同高效浸出低品位白钨矿的新工艺。氟化钙作为固体氟源，在浸出过程中首先发生溶解并释放出游离的氟离子，再参与白钨矿的浸出反应生成氟磷酸钙沉淀。因此，氟化钙的溶解速率对白钨矿浸出速率有较大影响。文章使用等浸出率法，对磷酸钠－氢氧化钠分解氟化钙的动力学进行了研究。考查了浸出温度及磷酸钠浓度对氟化钙浸出速率的影响。结果表明:氟化钙浸出速率受浸出温度影响很大，而受磷酸钠浓度影响相对较小，浸出反应表观活化能为134.57 kJ/mol，表观反应级数为0.92，氟化钙浸出过程受化学反应控制。研究结果对低品位白钨矿浸出过程强化具有一定的理论指导作用。 

Kinetics study of leaching calcium fluoride with sodium phosphate and sodium hydroxide

Since the disadvantages of the current prevailing method that sodium hydroxide and sodium carbonate have been used to leach low-grade scheelite with a large amount of leaching agent and low leaching rate,a new process for synergistically efficiently leaching low-grade scheelite with sodium phosphate-sodium hydroxide-calcium fluoride is proposed.During the leaching process,calcium fluoride used as a solid source of fluorine,first dissolves and releases free fluoride ions,and then participates in the leaching reaction of scheelite to generate calcium fluorophosphate precipitation.Therefore,its dissolution rate has a greater influence on the leaching rate of scheelite.In this paper,the kinetics of calcium fluoride leaching by sodium phosphate sodium hydroxide was studied by the method of equal leaching rate.The effects of leaching temperature and sodium phosphate concentration on the leaching rate of calcium fluoride were investigated.The results showed that the leaching rate of calcium fluoride was greatly affected by leaching temperature,but less affected by the concentration of sodium phosphate.The apparent activation energy of leaching reaction was 134.57 kJ/mol with the apparent reaction order 0.92.The leaching process of calcium fluoride was controlled by chemical reaction.This study has a theoretical guidance for strengthening the leaching process of low-grade scheelite.