The dissolving process of rare earth tailings in the dilute sulphuric acid and then in the dilute hydrochloric acid was studied. The undissolved rare earths in the tailings and calcium sulfate were concentrated in acid-insoluble residues. After solid-liquid separation, calcium sulfates were dissolved in dilute hydrochloric acid by dissolving the sulfuric acid insoluble in dilute hydrochloric acid. The grade of RE in the dilute hydrochloric acid insoluble residues is 43.60% and basically reaches the grade of rare earth concentrate. Calcium sulfate whiskers were prepared by means of ethanol crystallization and its optimum processing parameters were determined: At room temperature, the initial concentration of calcium sulfate is 0.009 mol/L, pH=1.0-1.5, the volume ratio of solution to ethanol is 1:2, and stalling time is 2 h. Under the optimal conditions, the recovery rate of calcium is more than 85% in rare earth tailings. The purity of calcium sulfate whiskers is more than 98% and the mean diameter of whiskers is 1 μm. The aspect ratio of calcium sulfate whiskers may come up to 80.%本研究采用稀硫酸溶解稀土尾矿,稀土尾矿中难溶的稀土矿物和钙的溶解产物硫酸钙存在于硫酸不溶物中,固液分离后用稀盐酸进一步溶解硫酸不溶物,使固态的硫酸钙溶解在稀盐酸中.尾矿中的稀土富集于盐酸不溶物中,盐酸不溶物中稀土氧化物质量分数为43.60％.采用乙醇结晶的方法制备硫酸钙晶须,确定结晶制备的最佳条件为:室温下,硫酸钙的初始浓度为0.009 mol/L左右,pH为1.0～1.5,溶液与乙醇的体积比为1:2,静置时间为2h.在此最佳条件下,稀土尾矿中钙的回收率大于85％,产品硫酸钙晶须纯度达98％以上,晶须平均直径为1 μm,平均长径比达80.
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