摘要
废旧稀土荧光粉经"酸浸-碱焙烧-水洗-酸浸"处理可浸出回收其中的Y, Eu, Tb, Ce等稀土。本文根据酸浸过程中的各组分的吉布斯自由能Δ_fG分别计算出各酸浸过程中各化学反应的吉布斯自由能Δ_rG,由能斯特公式计算出反应的电位与pH关系,进而绘制出两段酸浸过程中的电位-pH图,即不同活度的Al^(3+)与Y-Eu-H_2O系的电位-pH图和Tb-Ce-H_2O系电位-pH图,并分析了各组分的稳定区域。结果表明:废旧稀土荧光粉直接酸浸时,从25～100℃,在pH<6的酸性条件下,红粉中的Y_2O_3, Eu_2O_3以Y^(3+), Eu^(3+)的形式稳定存在水溶液中, Al(OH)_3稳定区域在pH为4.8～8.3之间,为防止Al ^(3+)水解,酸浸出液终点pH值应控制在3.5～4.0之间;从25～100℃,在酸性条件下,经碱焙烧水洗除铝后得到的TbO_2, CeO_2很难被酸直接浸出,同时Tb^(4+), Ce^(4+)在水溶液中不能稳定存在,但通过加入适当的还原剂,可将Tb^(4+), Ce^(4+)还原成Tb^(3+), Ce^(3+),便可存在于水溶液中。
Rare earths, e.g. Y, Eu, Tb and Ce in the waste rare earth phosphor powders could be recovered via the process of 'acid leaching-alkali roasting-water washing-acid leaching'. In this paper, the reaction Gibbs energy(ΔrG) in the acid leaching process was calculated according to the Gibbs energies(ΔfG) of each compound. The relationship between the potential and pH in each reaction was calculated by Nernst formula, and then the potential-pH plot was drawn in the two-stage acid leaching process. The potential-pH diagrams were drawn for the relationship between the different Al3+ ionic activity and Y-Eu-H2O(Tb-Ce-H2O) systems, and then the stable regions of each component were analyzed according to the diagrams. The results showed that in the direct acid leaching process, Y2O3 and Eu2O3 in red powder existed stably as the state of Y3+ and Eu3+ in the aqueous solution under condition of pH<6 and T=25~100 ℃. On the condition of pH=3.5~4.0, the hydrolysis of Al3+ could be prevented because the stable region of Al(OH)3 was in the range of pH 4.8 to 8.3. TbO2 and CeO2 obtained from the process of removing aluminum were difficult to be directly leached by acid under acidic condition and at the same time Tb4+ and Ce4+ could not stably exist in aqueous solution. However, Tb4+ could be reduced to Tb3+(Ce4+ to Ce3+) in an aqueous solution by addition of a suitable reducing agent.
作者
廖春发
钟立钦
曾颜亮
朱尚萍
黎振源
Liao Chunfa;Zhong Liqin;Zeng Yanliang;Zhu Shangping;Li Zhenyuan(Metallurgical and Chemical Engineering Institute,Jiangxi University of Science and Technology,Ganzhou 341000,China)
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2019年第2期179-185,共7页
Chinese Journal of Rare Metals
基金
国家自然科学基金项目(51464012)资助
关键词
废旧稀土荧光粉
“酸浸-碱焙烧-水洗-酸浸”工艺
酸浸
电位-PH图
waste rare earth phosphor powder
acid leaching-alkali roasting-water washing-acid leaching process
acid leaching
potential-pH diagram
作者简介
廖春发(1965-),男,江西吉安人,博士,教授,研究方向:有色金属分离及材料制备,电话:0797-8312061,E-mail:liaochfa@163.com
