硫磷混酸分解白钨矿过程中伴生稀土的行为

摘要

The thermodynamic equilibrium diagrams for the distribution of species of accompanying rare earth(REE) at different pH values, sulfuric and phosphorous acid concentrations were drawn at 25 ℃. Using these diagrams, the technical methods for extracting rare earth and tungsten were found theoretically and tested by experiments. It appears that rare earth ions can be coordinated by phosphorous acid, sulfate anion or hereopolytungstate anion at different pH values. When the pH value is less than 1, rare earth ions coordinate with phosphorous acid or sulfate anion preferentially and transform to cation cluster. At the pH range of 1-3, rare earth ions coordinate with hereopolytungstate anion and transform to lanthanide containing anion cluster. These complexations are favorable to decompose rare earth minerals. The heteropoly acid can promote the decomposition of rare earth. When the mass fraction of WO3and rare earths in scheelite are 26.11% and 0.13%, and the concentration of sulfuric and phosphoric acid are 2.5 and 1 mol/L, respectively, the leaching rates of La, Ce, Nd reach 85.61%,45.68% and 47.03% at 90 ℃ for 5 h. Besides, rare earth and tungsten also can be extracted separately or simultaneously as the species of complexations difference.%通过热力学计算绘制25 ℃时硫磷混酸分解白钨矿过程中伴生稀土物种随pH值以及混酸浓度变化的热力学平衡图,利用这些分析从理论上寻找稀土与钨综合提取的技术,并通过实验验证此技术的可行性.结果表明:稀土离子可与磷酸、硫酸根以及杂多酸形成络合物而富集在溶液中,不同的pH条件下稀土被络合成阳离子或阴离子.当pH<1时,稀土优先与磷酸、硫酸根络合形成阳离子;而当pH约为1~3时,稀土与杂多酸络合成稀土磷钨杂多阴离子,这些配位可促进稀土矿物的分解.实验还表明了杂多酸对稀土分解有促进作用,对于WO3、伴生稀土质量分数分别为26.11%和0.13%的白钨矿,在温度90 ℃、反应时间5 h、磷酸浓度1 mol/L、硫酸浓度2.5 mol/L条件下,稀土La、Ce、Nd浸出率可达85.61%、45.68%和47.03%.此外,根据稀土与钨络合物种形态的差异可设计稀土与钨分步或同步提取工艺.