赤泥-钛白废酸综合回收中钪的萃取工艺

Technology of extracting scandium in comprehensive recovery of red mud-titanium white waste acid

针对赤泥-钛白废酸浸出液中钪及主要杂质的特点,采用先除杂后萃取的工艺对溶液中钪进行萃取分离.首先,将一定量的活性炭加入赤泥-钛白废酸浸出液中,吸附去除浸出液中的硅,硅的去除率可达96.70%,而钪的去除率仅为1.25%,这表明活性炭吸附除杂可在保证浸出液中钪含量基本不损失的情况下除去绝大部分的硅.除硅有效控制了浸出液的胶凝现象,有利于下一步的钪萃取工艺.在萃取工艺过程中,具体研究了除杂后液的酸度、相比、萃取时间、萃取剂体积分数对钪萃取率的影响.结果表明,除杂后液酸度以1.81 mol/L较优,既避免有机相乳化,又保证钪的高萃取率;相比在1/10~1/30之间时,钪萃取率达到平衡,但当相比为1/30时,发生乳化,难于分离,因此,相比1/25较优;萃取时间为15 min时,钪的萃取率达到平衡;萃取剂体积分数为15%P204+6%TBP时,钪的萃取率达到最大值.在较优的萃取工艺条件下,钪的萃取率达98.80%.

In this paper, the extraction technology of scandiumis studied by the process of extraction after removal of impurities according to the property of the leaching solution of red mud-titanium white waste acid.Firstly, a certain amount of activated carbon was added into the leaching solution to remove silicon dioxide（SiO2）. The removal rate of SiO2 was 96.70 % and the removal rate of scandium was 1.25 %. It shows that, most of the SiO2 is removed while the Sc^（3＋） content is almost constant after the addition of activated carbon. The removal of SiO2 caneffectively control the gelatinization of leaching solution and facilitate the subsequent extraction process.The effect of acidity of leach solution, extractant volume fraction, phase ratio and extraction time on scandium extraction rate were examined. The results show that the optimal acidity of leaching solution after purification at 1.81 mol/L which can avoid the emulsification of organic phase and ensure high extraction rate of scandium; the extraction rate of scandium reaches equilibrium when the phase ratio is between 1/10~1/30, and the phase ratio of 1/25 is the optimal because the leaching solution is emulsificated when the phase ratio was at 1/30; the extraction rate of scandium reaches equilibrium when the extraction time is 15 min, and reaches the maximum when the extractant volume fraction is 15 % P204 ＋ 6 % TBP. It＇s found that the extraction rate of scandium is 98.80 % under the optimum extraction conditions.