拜耳法赤泥中钪的两步盐酸浸出工艺

通过计算赤泥中所含金属氧化物与盐酸反应的吉布斯自由能，论证了两步盐酸酸浸提钪工艺的可行性。为使钪离子有高浸出率，同时与其他金属有较高的分离率，在二次酸浸中采用2.5 mol/L左右的低浓度盐酸开展了正交实验。使用Design-Expert 8.0软件对试验数据进行了分析，讨论了温度、时间、液固比、盐酸浓度对赤泥中各主要金属离子浸出的影响，建立了相应的多项式关联模型。确定的二次酸浸的最佳操作条件组合为:浸出温度为70℃，浸出时间为70 min，液固比为6，盐酸浓度为2.5 mol/L，在此条件下钪浸出率超过80%，铁、锆、钛等主要杂质离子浸出率维持在较低水平。

TWO-STEP HYDROCHLORIC ACID LEACHING OF SCANDIUM FROM RED MUD FROM BAYER PROCESS

The Gibbs free energy of reaction between various metal oxides and hydrochloric acid, was calculated to explore the feasibility of two-step hydrochloric acid leaching for scandium recovery from red mud produced in Bayer process. In order to achieve a high leaching rate of scandium ion and a high selectivity of scandium against other metals, orthogonal experiments of secondary acid leaching with low-concentration hydrochloric acid of about 2.5 mol/L were conducted. Design-Expert 8.0 software was utilized to analyze the experimental data, and the impacts of key factors, i.e. temperature, time duration, liquid-solid ratio, hydrochloric acid concentration on the leaching rate of various metal ions were discussed. The corresponding polynomial models were also established. Finally, the optimum operating conditions were determined as follows:leaching temperature of 70℃, duration of 70 min, liquid solid ratio of 6 and HCl concentration of 2.5 mol/L. A high leaching rate of more than 80% was achieved for scandium under such condition, while the leaching rates for the key impurities, i.e. Fe, Zr and Ti kept low.