摘要
针对硅酸钠分解白钨矿的问题,对Ca-Si-W-H2O体系进行了热力学平衡分析,获得了一系列平衡关系图。理论分析表明,白钨矿可被硅酸钠分解,随着pH值升高,分解固相产物依次为CaSiO3和Ca3Si2O7。在低pH值的CaSiO3稳定区,白钨矿被硅酸钠分解,但溶液中钨浓度较低;在高pH值的Ca3Si2O7稳定区,氢氧化钠也参与了分解反应,钨浓度随pH值上升迅速增加。因此,硅酸钠分解白钨矿时可添加适量的氢氧化钠,以提高钨矿分解效果。分解实验验证了理论分析结果,实际分解效果变化的趋势与热力学分析一致。硅酸钠用量是影响浸出总体水平的重要因素,提高试剂浓度或添加氢氧化钠,能进一步提高钨的浸出率。对于WO3质量分数为55.0%白钨矿,在分解温度为180℃,分解时间为4 h,体系中硅与钨、氢氧根与钨、水与钨的摩尔比分别为2.0、0.5、35.3的条件下,钨的浸出率为96.9%。
In order to evaluate the feasibility of decomposing scheelite with sodium silicate, thermodynamics of Ca-Si-W-H2O system was studied and a series of equilibrium diagrams were obtained. Theoretical analysis shows that scheelite can be decomposed by sodium silicate under certain conditions and the solid reaction products are CaSiO3 and Ca3Si2O7. At lower pH values, scheelite is decomposed to CaSiO3 by sodium silicate, but W concentration in solution is lower. At higher pH values, it is jointly decomposed to Ca3Si2O7 by sodium silicate and sodium hydroxide, thus the W concentration increases greatly with increasing the pH value. Therefore, it is beneficial to add sufficient sodium hydroxide to the system. Besides, several tests are performed to verify the feasibility of such decomposition, and the experimental results are consistent in trend with the thermodynamic analysis. The dosage of sodium silicate has a remarkable effect on the reaction. Increasing reagent concentration and adding sodium hydroxide can improve the decomposition efficiency. When the WO3 mass fraction in scheelite is 55.0% and the molar ratios of Si to W, OH- to W and H2O to W in the system are 2.0, 0.5 and 35.3, respectively, the W leaching rate reaches 96.9% at 180 ℃ for 4 h.
出处
《中国有色金属学报》
EI
CAS
CSCD
北大核心
2012年第9期2636-2641,共6页
The Chinese Journal of Nonferrous Metals
基金
国家重点基础研究发展计划资助项目(2007CB613603)
关键词
硅酸钠
白钨矿
热力学
分解
sodium silicate
scheelite
thermodynamics
decomposition
