P204-P507-HCl体系回收废FCC催化剂中稀土的优化

针对废流化催化裂化(FCC)催化剂的资源化利用问题，采用溶剂萃取法从废FCC催化剂中高效回收稀土。对无机酸浸出过程、二(2-乙基己基)磷酸(P204)和2-乙基己基膦酸单2-乙基己基酯(P507)单独萃取稀土过程以及P204-P507复合萃取稀土过程分别进行了研究。结果表明，盐酸为最佳浸出剂，在最佳浸出条件(4 mol·L⁻¹盐酸溶液、浸出时间为4 h、60 ℃、固液比为1∶15)下，Ce和La的浸出率分别为99.7%和97.7%。萃取过程的最佳条件为萃取剂浓度1.5 mol·L⁻¹、浸出液初始pH=2.5，P204和P507对Ce和La的萃取率均较高，而P507对杂质铝的萃取率远低于P204。P204-P507复合萃取体系中P507体积比为0.2时，Ce和La的回收率分别达到80.4%和75.3%，略低于纯P204萃取体系，而杂质铝的回收率小于10.0%。P204-P507复合萃取体系能有效降低回收稀土中杂质铝的萃取量。本研究可为从废FCC催化剂中回收高纯度稀土提供参考。

Recovery of rare earth elements from spent FCC catalysts in P204-P507-HCl system

Aiming at the problem of resource utilization of spent fluidized catalytic cracking (FCC) catalysts, the solvent extraction method is used to efficiently recover rare earths from spent FCC catalysts. The process of inorganic acid leaching, single extraction of bis (2-ethylhexyl) phosphoric acid (P204) and single 2-ethylhexyl phosphonate (P507) and composite extraction of rare earth by P204-P507 were studied. The results showed that hydrochloric acid was the best leaching agent. Under the optimal leaching conditions (4 mol·L−1 hydrochloric acid solution, leaching time of 4 h, 60 ℃, solid-liquid ratio of 1:15), the leaching rates of Ce and La were 99.7% and 97.7%, respectively. The optimal extraction conditions were as follows: the concentration of extractant was 1.5 mol·L−1, the initial pH of leaching solution was 2.5, and the extraction rates of Ce and La were both higher for P204 and P507, while the extraction rates of aluminum for P507 were much lower than that for P204. When the volume ratio of P507 in P204-P507 was 0.2, the recovery of Ce and La reached 80.4% and 75.3%, respectively, slightly lower than that of pure P204, while the recovery of aluminum was less than 10.0%. The P204-P507 composite extraction system can effectively reduce the content of aluminum impurities in the recycled rare earth, providing a useful reference for the recovery of high purity rare earth from the waste FCC catalyst.