(中南大学 冶金与环境学院,长沙 410083)
摘 要: 利用双氧水易与钨形成可溶性过氧钨酸的特性,提出了双氧水(H2O2)协同盐酸分解人造白钨(CaWO4)的新工艺,使CaWO4以氯化钙(CaCl2)和过氧钨酸(H4[WO3(O2)2])的形式溶解到浸出体系中,大幅提高了人造白钨的分解率。研究盐酸和双氧水浓度、反应温度、液固比及反应时间等因素对人造白钨分解效果的影响。结果表明:在H2O2存在的情况下,盐酸用量可大幅降低,所用的盐酸初始浓度很低故挥发损失很少;H2O2浓度的增加有利于反应的进行;当温度低于30 ℃时,升高温度对人造白钨的分解浸出有明显的促进作用,超过40 ℃后H2O2会逐渐分解且产物过氧钨酸变得不稳定反而不利于浸出。得到的较优条件如下:H2O2浓度2.4 mol/L,盐酸浓度1.5 mol/L,温度30 ℃,液固比10:1(mL/g),反应时间40 min。在此条件下,人造白钨实现了完全分解。
关键字: 人造白钨;盐酸;双氧水;过氧钨酸
(School of Metallurgy and Environment, Central South University, Changsha 410083, China)
Abstract:A new process was proposed for the digestion of synthetic scheelite (CaWO4) in hydrochloric acid solution using hydrogen peroxide (H2O2) as complexing agent. H2O2 as a chelating agent, can readily react with H2WO4 to form water-soluble peroxotungstic acid H4[WO3(O2)2], and the conversion rate of WO3 was raised substantially. The effects of relevant parameters, such as the concentrations of HCl and H2O2, reaction temperature, liquid-to-solid ratio and reaction time, were studied. The results show that increasing the concentration of H2O2 benefits the process and both the concentrate and consumption of HCl drastically drop and the volatility loss of HCl reduces noticeably. Elevating the temperature promotes the decomposition of CaWO4 below 30 ℃ while becomes unfavorable above 40 ℃ because the stability of H2O2 and peroxotungstic acid gradually decreases. The optimum process conditions are as follows: the concentrations of H2O2 and HCl are 2.4 and 1.5 mol/L, respectively, the temperature is 30 ℃, the liquid-to-solid ratio is 10:1 (mL/g), and the reaction time is 40 min. Under these conditions the synthetic scheelite can be completely decomposed.
Key words: synthetic scheelite; hydrochloric acid; hydrogen peroxide; peroxotungstic acid