选择性还原浸出废旧稀土绿色荧光粉及热力学分析

Selective Reduction Leaching of Rare Earth from Waste Green Phosphor and Thermodynamic Analysis

针对废旧绿粉中铝酸盐结构的稀土元素浸出率低,且四价铈难以浸出等问题,通过对绿粉经焙烧进行物相重构后所得的物料作为浸出原料,采用盐酸浸出并添加H_2O_2作为还原剂,考察了H_2O_2添加量、浸出温度、盐酸浓度、液固比、浸出时间等因素对稀土浸出率的影响,并对焙烧产物添加H_2O_2时的浸出热力学进行了分析。研究结果表明,在添加体积分数5%的H_2O_2,浸出温度75℃,盐酸浓度2 mol·L^(-1),液固比14∶1,浸出时间1 h的条件下,稀土的浸出率可达93.4%。热力学分析可知浸出体系的pH须小于3.79,并须添加还原电位小于CeO_2-Ce^(3+)线的还原剂。

Aiming at low leaching rate of rare earth, especially tetravalent cerium, from waste aluminate green phosphor,it was pretreated by roasting and then used as the raw material. H202 was used to reduce tetravalent cerium to trivalent cerium in hydrochloric acid solution. Effects of leaching temperature, hydrochloric acid concentration, amount of H2 02, liquid - solid ra- tio and leach time on. leaching rate of rare earth were investigated. Thermodynamic analysis for leaching process was conduc- ted. The results show that, under the conditions of H2 02 5 % , leaching temperature 75 ℃, concentration of hydrochloric acid 2 tool · L-l , liquid - solid ratio 14：1 and leaching time 1 h, the leaching ratio of rare earth is 93.4% . Thermodynamic analy- sis shows the leaching system pH should he less than 3.79, and reduction potential of reduetant should be lower than CeO2 - Ce3 ＋ line.