废旧荧光粉中稀土元素浸出的电位-pH图
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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(Δ_rG) in the acid leaching process was calculated according to the Gibbs energies(Δ_fG) 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 Al~(3+) ionic activity and Y-Eu-H_2O(Tb-Ce-H_2O) 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, Y_2O_3 and Eu_2O_3 in red powder existed stably as the state of Y~(3+) and Eu~(3+) 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 Al~(3+) could be prevented because the stable region of Al(OH)_3 was in the range of pH 4.8 to 8.3. TbO_2 and CeO_2 obtained from the process of removing aluminum were difficult to be directly leached by acid under acidic condition and at the same time Tb~(4+) and Ce~(4+) could not stably exist in aqueous solution. However, Tb~(4+) could be reduced to Tb~(3+)(Ce~(4+) to Ce~(3+)) in an aqueous solution by addition of a suitable reducing agent.
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(Δ_rG) in the acid leaching process was calculated according to the Gibbs energies(Δ_fG) 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 Al~(3+) ionic activity and Y-Eu-H_2O(Tb-Ce-H_2O) 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, Y_2O_3 and Eu_2O_3 in red powder existed stably as the state of Y~(3+) and Eu~(3+) 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 Al~(3+) could be prevented because the stable region of Al(OH)_3 was in the range of pH 4.8 to 8.3. TbO_2 and CeO_2 obtained from the process of removing aluminum were difficult to be directly leached by acid under acidic condition and at the same time Tb~(4+) and Ce~(4+) could not stably exist in aqueous solution. However, Tb~(4+) could be reduced to Tb~(3+)(Ce~(4+) to Ce~(3+)) in an aqueous solution by addition of a suitable reducing agent.
引文
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[7] Xiao C, Xiao L S, Zeng L, Gao C J. Therodynamic study on removal of magnesium from lithium chloride solutions using phosphate precipitation method [J]. Chinese Journal of Rare Metals, 2016, 40(2): 149.(肖超, 肖连生, 曾理, 高从堦. 氯化锂溶液磷酸盐沉淀法除镁的热力学分析 [J]. 稀有金属, 2016, 40(2): 149.)
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[11] Tunsu C, Ekberg C, Retegan T. Characterization and leaching of real fluorescent lamp waste for the recovery of rare earth metals and mercury [J]. Hydrometallurgy, 2014, 144-145: 91.
[12] Zhang S G, Yang M, Liu H, Pan D A, Tian J J. Recovery of waste rare earth fluorescent powders by two steps acid leaching [J]. Rare Metals, 2013, 32(6): 609.
[13] Liao C F, Chen J Y, Zeng Y L, Li A l. Selective reduction leaching of waste rare earth green phosphor and thermodynamic analysis [J]. Chinese Rare Earth, 2015, 36(6): 7. (廖春发, 陈静远, 曾颜亮, 李阿林. 选择性还原浸出废旧稀土绿色荧光粉及热力学分析 [J]. 稀土, 2015, 36(6): 7.)
[14] Wang D J. Phase Diagram and Thermochemical Database Principle and Application [M]. Kunming: Yunnan Science and Technology Press, 2001. 119.(王达健. 相图和热化学数据库原理与应用 [M]. 昆明: 云南科学技术出版社, 2001. 119.)
[15] Liu H. Recycling of Rare Earth Elements from Waste Phosphor and the Alkaline Fusion Mechanism [D]. University of Science and Technology Beijing, 2015. 50.(刘虎. 废旧稀土荧光粉的回收及其碱熔机理研究 [D]. 北京科技大学, 2015. 50.)
[16] Li Z Y. Research on Process and Mechanism of Recovery of Rare Earth From Waste Rare Earth Fluorescent Powders Using Alkaline Roasting-Two Steps of Acid Leaching Process [D]. Jiangxi University of Science and Technology, 2017. 18.(黎振源. 碱焙烧—两步酸浸法从废旧稀土荧光粉回收稀土工艺及机理的研究 [D]. 江西理工大学, 2017. 18.)
[17] Wu W Y. Rare Earth Metallurgy [M]. Beijing: Chemical Industry Press, 2005. 6.(吴文远. 稀土冶金学 [M]. 北京: 化学工业出版社, 2005. 6.)
[18] Chi R A, Tian J. Weathering Shell Leached Rare Earth Mining Chemical Metallurgy [M]. Beijing: Science Press, 2006. 186.(池汝安, 田君. 风化壳淋积型稀土矿化工冶金. 北京: 科学出版社, 2006. 186.)
[19] Svehla G; Gao L Z. Automatic Potential Titration [M]. Beijing: Atomic Energy Press, 1985. 38.((美)斯维拉(Svehla G); 高立译. 自动电位滴定 [M]. 北京: 原子能出版社, 1985. 38.)
[20] Zhang Z X. Process Research on Recovery of Rare Earth of Waste Rare Earth Fluorescent Powders by Alkali fusion-Washing-Reduction Acid Leaching [D]. Jiangxi University of Science and Technology, 2016. 44.(张兆雪. 稀土荧光粉废料碱熔—水浸—还原酸浸回收稀土工艺研究 [D]. 江西理工大学, 2016. 44.)
[2] Yin Z X, Zhou H J, Ma J. Application of electric potentia-pH diagran in hydrametallurgy [J]. Journal of Guizhou University of Technology (Natural Science Edition), 2008, 37(5): 24.(尹卓湘, 周红娟, 马婕. 电位-pH图在湿法冶金中的应用 [J]. 贵州工业大学学报(自然科学版), 2008, 37(5): 24.)
[3] Wu J H, Su T, Liu G, Zhang W H, Wei T, Luo M M. Controlled potential for selectively dissolving nickel-based superalloy wastes containing rhenium element [J]. Chinese Journal of Rare Metals, 2016, 40(7): 737.(邬建辉, 苏涛, 刘刚, 张文宏, 魏涛, 罗妹妹. 镍基含铼废合金控制电位选择性溶解工艺研究 [J]. 稀有金属, 2016, 40(7): 737.)
[4] Zhong Z Q, Mei G G. Application of electric potentia-pH diagran in hydrametallurgy [J]. Nonferrous Metals (Extractive Metallurgy), 1979, 3: 28.(钟竹前, 梅光贵. 电位—pH图在湿法冶金中的应用 [J]. 有色金属(冶分), 1979, 3: 28.)
[5] You H X, Xu H B, Zhang Y, et al. Potential-pH diagrams of Cr-H2O system at elevated temperatures [J]. Transactions of Nonferrous Metals Society of China, 2010, 20(S1): 26.
[6] Zhang J L, Zhang L F. Thermodynamic equilibrium of Mo(VI)-V(V)-H2O system and its application for deep removal of vanadium from molybdate solution [J]. Chinese Journal of Rare Metals, 2016, 40(7): 701.(张家靓, 张立峰. Mo(VI)-V(V)-H2O系的热力学平衡与钼酸盐深度除钒工艺的理论分析 [J]. 稀有金属, 2016, 40(7): 701.)
[7] Xiao C, Xiao L S, Zeng L, Gao C J. Therodynamic study on removal of magnesium from lithium chloride solutions using phosphate precipitation method [J]. Chinese Journal of Rare Metals, 2016, 40(2): 149.(肖超, 肖连生, 曾理, 高从堦. 氯化锂溶液磷酸盐沉淀法除镁的热力学分析 [J]. 稀有金属, 2016, 40(2): 149.)
[8] Ge B G. The innovative development of traditional fluorescent lamp technology promotes the new generation of rare earth trichromatic phosphors [J]. Rare Earth Information, 2017, (2): 28.(葛葆珪. 传统荧光灯技术的创新发展促进稀土三基色荧光粉新生 [J]. 稀土信息, 2017, (2): 28.)
[9] Zhang B, Wang W, Gao Z G. Comprehensive recycling of the abandoned rare earth functional materials [J]. Conservation and Utilization of Mineral Resources, 2014, (6): 46.(张博, 王威, 高照国. 废弃稀土功能材料的综合回收利用 [J]. 矿产保护与利用, 2014, (6): 46.)
[10] Zhao Z, Xu G L. Present situation and development trend of technology of rare earth elements in waste phosphor [J]. Journal of the Chinese Society of Rare Earths, 2015, 33(6): 641. (赵卓, 徐桂丽. 废弃荧光粉中稀土元素的回收技术现状与发展趋势 [J]. 中国稀土学报, 2015, 33(6): 641.)
[11] Tunsu C, Ekberg C, Retegan T. Characterization and leaching of real fluorescent lamp waste for the recovery of rare earth metals and mercury [J]. Hydrometallurgy, 2014, 144-145: 91.
[12] Zhang S G, Yang M, Liu H, Pan D A, Tian J J. Recovery of waste rare earth fluorescent powders by two steps acid leaching [J]. Rare Metals, 2013, 32(6): 609.
[13] Liao C F, Chen J Y, Zeng Y L, Li A l. Selective reduction leaching of waste rare earth green phosphor and thermodynamic analysis [J]. Chinese Rare Earth, 2015, 36(6): 7. (廖春发, 陈静远, 曾颜亮, 李阿林. 选择性还原浸出废旧稀土绿色荧光粉及热力学分析 [J]. 稀土, 2015, 36(6): 7.)
[14] Wang D J. Phase Diagram and Thermochemical Database Principle and Application [M]. Kunming: Yunnan Science and Technology Press, 2001. 119.(王达健. 相图和热化学数据库原理与应用 [M]. 昆明: 云南科学技术出版社, 2001. 119.)
[15] Liu H. Recycling of Rare Earth Elements from Waste Phosphor and the Alkaline Fusion Mechanism [D]. University of Science and Technology Beijing, 2015. 50.(刘虎. 废旧稀土荧光粉的回收及其碱熔机理研究 [D]. 北京科技大学, 2015. 50.)
[16] Li Z Y. Research on Process and Mechanism of Recovery of Rare Earth From Waste Rare Earth Fluorescent Powders Using Alkaline Roasting-Two Steps of Acid Leaching Process [D]. Jiangxi University of Science and Technology, 2017. 18.(黎振源. 碱焙烧—两步酸浸法从废旧稀土荧光粉回收稀土工艺及机理的研究 [D]. 江西理工大学, 2017. 18.)
[17] Wu W Y. Rare Earth Metallurgy [M]. Beijing: Chemical Industry Press, 2005. 6.(吴文远. 稀土冶金学 [M]. 北京: 化学工业出版社, 2005. 6.)
[18] Chi R A, Tian J. Weathering Shell Leached Rare Earth Mining Chemical Metallurgy [M]. Beijing: Science Press, 2006. 186.(池汝安, 田君. 风化壳淋积型稀土矿化工冶金. 北京: 科学出版社, 2006. 186.)
[19] Svehla G; Gao L Z. Automatic Potential Titration [M]. Beijing: Atomic Energy Press, 1985. 38.((美)斯维拉(Svehla G); 高立译. 自动电位滴定 [M]. 北京: 原子能出版社, 1985. 38.)
[20] Zhang Z X. Process Research on Recovery of Rare Earth of Waste Rare Earth Fluorescent Powders by Alkali fusion-Washing-Reduction Acid Leaching [D]. Jiangxi University of Science and Technology, 2016. 44.(张兆雪. 稀土荧光粉废料碱熔—水浸—还原酸浸回收稀土工艺研究 [D]. 江西理工大学, 2016. 44.)
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