七水硫酸锌热解过程的吉布斯自由能最小原理及TG-DTA分析

Gibbs free energy minimization and TG-DTA analysis for thermal decomposition of zinc sulfate heptahydrate

利用吉布斯自由能最小原理计算了七水硫酸锌在25～1100℃下的平衡组成，并结合TG—DTA研究了其热分解过程。七水硫酸锌的热解大致可以分为脱结晶水和无水物热分解两个阶段。脱水发生在室温～311℃时，无水物热分解则发生在687—1050℃时。脱水段固相含有ZnSO4·6H2O、ZnSO4·H2O、ZnSO4·xH2O[x∈（0．8，0．9）]等，无水物分解段中间产物有ZnO2·ZnSO4，最终固相产物为ZnO。结果表明，吉布斯自由能最小原理和TG—DTA具有内在一致性。

The chemical equilibriums of zinc sulfate heptahydrate at 25-1 100℃have been calculated by the method of Gibbs free energy minimization, meanwhile the thermal decomposition of the hydrates was investigated by TG-DTA.There were two stages approximately in the thermal decomposition of zinc sulfate heptahydrate：one was the dehydration of the hydrates, and another one was the thermolysis of the anhydrous salt.The dehydration occured at range of room temperature to 311 ℃,while the thermolysis at 687-1050 ℃.The solid phase dehydration products containedZnSO4·6H2O,ZnSO4·H2O,ZnSO4·xH2O[x∈（0.8,0.9）], and so on.The solid thermolysis products contained the intermediates ZnO2· ZnSO4 and the final solid phase product was ZnO.The results showed that there was internal consistency between Gibbs free energy minimization and TG-DTA.