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题名	镍硫化物阳极溶解的电化学研究
作者	方兆珩
学位类别	博士
答辩日期	1985-06-30
授予单位	中国科学院研究生院
导师	陈家镛
中文摘要	研究了合成镍硫化物Ni_8S_2、β-NiS，α-Ni_7S_6及NiS_2在酸性溶液中的阳极行为。镍硫化物电极达到稳定开路电位Er的过程，最缓慢的电化学过程。实验获得硫酸溶液中稳态Er与[H~+]关系：对Ni_3S_2，(partial deriv Er)/(partial deriv pH) = 0.027v/dec，对Nis，(partial derivEr)/(partial derivpH) = -0.049 v/dec(25 ℃)。溶液中Fe~(3+)、Cu~(2+)、Ag~+等金属阳离子影响镍硫化物的稳态Er值；阴离子对Ni_3S_2的稳态Er值几乎无影响，但影响NiS、Ni_7S_6的稳态Er值。动电位扫描极化实验表明，镍硫化物的阳极过程由性质不同的两大区段组成。按其不同的电化学特征，分别称为吸附一解吸反应及扩散控制区（简称扩散区）和活性溶解区。两大区段间过渡电位，因硫化物不同及溶液成分，温度等过程变量的变化而异。Ni_aS_z、Ni_7S_6、NiS的活性，溶解区显示二个平行反应的i-E曲线特征。循环电位扫描伏安图及电位阶跃瞬态i-t关系。显示第一平行反应伴随电化学结晶过程衣电化学反应控制。活性溶解伴随着表面形成固态生成物，讨论了三种不同类型产物层生成规律，并探讨了Ni_2S_2在H_2SO_4溶液中钝化过程的成因。活性溶解时镍硫化物的阳极行为似不受溶液中金属阳离子影响；溶液中阴离子对其二个平行反应有不同程度的抑制和促进作用，尤以Cl~-的影响最明显。温度低于75 ℃时，对活性溶解区阳极i-E行为的影响不明显，高于75 ℃时，则显示某种机理上改变。测定了镍硫化物在H_2SO_4和HCl溶液中阳极溶解时镍溶出表现电子数z及溶出速率。应用扫描电镜、X射线能谱分析及X射线晶体粉末衍射，确定H_2SO_4和HCl溶液中不同电位阳极溶解时表面产物层的形态、晶体成分及结构。在综合实验结果的基础上，推测镍硫化物阳极溶解存在三组平行反应：镍逐步溶出并形成不同硫化物中间体的反应，与形成元素硫的反应平行进行，并部分重叠；形成HSO_4~-或SO_4~(2-)的反应似在整个活性溶解区平行发生。本文还根据实验结果，讨论了镍锍氧化浸取速率及镍锍电解的阳极溶解电流效率问题。
英文摘要	The anodic dissolution of the synthetic nickel sulfides Ni_3S_2, Ni_7S_6, NiS & NiS_2 were studied in the acidic solutions. The electrode rest potentials of nickel sulfides were measured. A long period was allowed for reaching equilibrium. The experimental results obtained are reported as a function of hydrogen ion concentration. The relation between the steady state rest potential Er and the hydrogen ion concentration can be expressed as (partial deriv Er)/(partial deriv pH) = 0.027v dec. for Ni_3S_2 and (partial deriv Er)/(partial deriv pH) = -0.049 v dec. for NiS at 25 C and under N_2 atmosphere. The presence of metallic cations in solution, such as Fe~(3+), Cu~(2+) & Ag~+, has significant influence on the steady rest potential of nickel sulfides. The anions in solution had same influence on the steady rest potential of Ni_7S_6 & NiS, but not on Ni_3S_2. Experiments on the anodic process of the nickel sulfides by linear sweep voltammetry indicated that the voltammograms can be divided into two sections with different electrochemical behaviors. The first section can be considered as an adsorption-desorption reaction, controlled by diffusion, and the second is the section of active dissolution. The transfer potential between these two sections depend on the nature of sulfides, solution composition and temperature. The voltammograms of Ni_3S_2, Ni_7S_6 & NiS electrodes in the section of active dissolution indicated the characterictics of the presence of two parallel reactions. The cyclic voltammograms and the i-t transients of the potential step for Ni_3S_2 electrode show that the first parallel reaction is accompanied with an electrochemical cryctallization process and controlled by an electrochemical reaction. A solid product layer is formed on the electrode surface when the anode is dissolved. The mechanism of formation of three types of solid product layer and the passivation of Ni_3S_2 anode in H_2SO_4 solution are also discussed. The anodic behaviors of the nickel sulfides electrodes are not influenced by the metallic ions in solution. The anions in solution, however, have either depressive or promotive effects on the two parallel reactions. Among them, the Cl~- ions have the strongest effect. The temperature has a small influence of the behaviors below 75 C. The mechanism of reaction appears to the changed for temperature above 75 C. The apperent number of electron transfered and the rate of dissolution were measured in both H_2SO_4 and HCl solutions. The appearance, composition and the structure of the crystals of the products formea on the surface during the anodic dissolution at different electric potentials were identified with the scanning electron microscope, energy dispersive X-ray analysis spectrometer and X-ray powder diffraction. Based on the results of using different experimental techniques, three parallel reactions can be considering to occur at the anodic dissolution of the nickel sulfides. These rre (1) reaction of the dissolution of Ni~(2+) from the sulfides step by step with the formation of sulfides intermediates, (2) reaction of forming elemental S and (3) reaction of forming SO_4~(2-) or HSO_4~- ions. The first and the second reactions occur predominantly in the different range of potentials respectively and with some overlapping. The third reaction occurs probably within the total range of active dissolution. Based on the present experimental results, both the rate of oxidation leaching and current efficiency of electrorefining of nickel mattes were also discussed
语种	中文
公开日期	2013-09-27
页码	167
内容类型	学位论文
源URL	[http://ir.ipe.ac.cn/handle/122111/2073]
专题	过程工程研究所_研究所（批量导入）
推荐引用方式 GB/T 7714	方兆珩. 镍硫化物阳极溶解的电化学研究[D]. 中国科学院研究生院. 1985.

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