硫化沉镍条件的热力学分析

THERMODYNAMIC STUDY ON SULPHIDIZING PRECIPITATION OF NICKEL

研究了在不同条件（如硫化物试剂、温度、ｐＨ值）下生成的镍硫化合物的组成及结构类型。在非氧化还原反应条件下，硫化沉镍产物为ＮｉＳ。当温度较高（＞８０℃）、反应速度较快时，产物ＮｉＳ为属于ＮｉＡｓ结构的αＮｉＳ；当温度较低（＜６０℃）、反应较缓慢时，产物为针硫镍型的βＮｉＳ。在有电子得失的硫化沉镍过程中，沉淀产物的组成依沉镍试剂及溶液ｐＨ值的变化而变化。用硫代硫酸盐沉镍，在任何ｐＨ条件下，其产物均为ＮｉＳ２。在有元素硫存在并参与的沉镍反应中，ＮｉＳ２总比ＮｉＳ优先生成。用连二亚硫酸盐（Ｓ２Ｏ２－４）沉镍时，若ｐＨ值大于７．０９，其产物为Ｎｉ３Ｓ２，若小于７０９，则产物为ＮｉＳ２。

Structures and compositions of nickel sulfides formed under different conditions (for example, sulfide agents, temperature and acidity) have been studied. Under neutral condition, the products of nickel sulfide precipitation is NiS with two types of structure, α NiS and β NiS. When the temperature is more than 80℃ and the concentration of the reactant is higher, the product formed is α NiS(NiAs structure);inversely, it is β NiS (millerite). Under the condition of sulphidizing precipitation of nickel with oxido reduction, the compositions of the precipitates are dependent on the sulfide agents and pH value. In the whole range of pH value, if thiosulphate is used to precipitate nickel, the precipitate is NiS 2. In the presence of element sulfur, NiS 2 can be formed selectively. When the precipitation agent is dithionite, the precipitate is Ni 3S 2(alkaline condition) and NiS 2(acid condition), respectively.