重金属盐溶解-沉淀反应的吉布斯自由能变的定量估算.pdf

第24卷第1期
化学研究
中国科技核心期刊
2013年1月
CHEMICAL RESEARCH
hxy@henu.edu.cn
重金属盐溶解-沉淀反应的吉布斯自由能变的定量估算
郭亚平,谢练武
(中南林业科技大学,湖南长沙410004
摘要:对重金属盐溶解-沉淀反应的吉布斯自由能变(△G)进行了定量估算;在不加缓冲剂和pH调节剂的纯水
体系中,观测了重金属离子Pb1、NP+及Zn2“的沉淀-溶解反应,计算了反应的表观平衡常数K及表观溶度积
常数K;与此同时,对相关计算结果进行了实验验证.结果表明,重金属盐溶解-沉淀反应的△G只与反应物的
初始浓度和平衡浓度有关,通过测定反应物的平衡浓度即可求得反应的△G;重金属离子Pb、N2+及Zn2的沉
淀溶解反应表观平衡常数K及表观溶度积常数K'皆随重金属盐的起始表观浓度Q的增大而发生规律性变
化:K先增大后减小,K趋于最大恒定值,并接近于K;而三种体系的△G均为负值,△G的绝对值先随Q。的
增大而増大,然后趋于相对恒定.实验结果表明,不能用K而只能用K。描述重金属盐的沉淀溶解平衡,△G绝
对值与真正参与反应的反应物的量呈正相关;△G<0说明纯水中重金属盐的溶解反应是自发进行的.类似地,
通过计算溶解-沉淀反应的△G,可以判断沉淀法处理重金属污染废水在热力学上的可行性
关键词:重金属离子;溶解-沉淀反应;吉布斯自由能变;定量估算
中图分类号:X703
文献标志码:A
文章编号:1008-1011(2013)01-0015-05
Quantitative calculation of the change of Gibbs free energy in
dissolution and precipitation reactions of heavy metal ions
GUO Ya-ping, XIE Lian-wu
(Central South University of Forestry Technology, Changsha410004, Junan, China)
Abstract: The change in the Gibbs'free energy(4G) of the dissolution-precipitation reaction of
heavy metal salts was quantitatively estimated. The dissolution-precipitation reactions of heavy
metal ions Pbit, Ni2+ and Zn*in pure water without buffer and ph-adjusting agent were in
vestigated, while the apparent equilibrium constant(K) and the apparent solubility product
constant(K p of the dissolution-precipitation reactions were calculated In the meantime,
relevant calculation results were verified by experiments. Results indicate that the AG of the
dissolution-precipitation reaction of heavy metal salts is only dependent on the initial concentra-
tion and equilibrium concentration of reactants, and it can be calculated by dctermining the
equilibrium concentration of the reactants. The K and Ks, of the precipitation-dissolution re
actions of heavy metal ions Pb"t, Niand Znt in aqueous system vary with increasing appar-
ent initial concentration (Q)of the heavy metals in a regular manner. Namely, K; tends to rise
initially but then stabilize with increasing Q, and Ks, tends to reach the maximum constant
and become close to K,, therewith. Besides, the calculated AG of the three systems is negative
and the absolute value of AG rises with increasing Q and tends to reach a constant. Relevant
experimental results indicate that the precipitation and dissolution reactions of heavy metal salts
收稿日期:2012-1ー4
金项目:国家环保部公益性行业科研专项资助项目(200909066),校青年基金资助项目(2008017B)
作者简介:郭亚平(1971一),女,副教授,硕士,研究方向为应用化学和环境科学.E-mail:gypcsfu@126.com