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本文是湿法炼Sb的物理化学研究中的一部分。当用Na_2S-NaOH溶液浸出复杂的Pb-Sb精矿时,Sb以SbS_3~(3-)离子形态进入溶液。精矿中的Sn和As部分溶解,而Pb则留在残渣中与Sb分离,SbS_3~(3-)离子与空气接触时,部分氧化成SbS_4~(3-)离子。用稳态法测定了极化曲线,确定了在硫化碱溶液中Sb(Ⅲ).Sn(Ⅳ),As(Ⅲ),Sb(Ⅴ)和H~+离子的放电电位。其相应数值如下:-0.92,-1.04,-0.81,-0.68和-1.12V。这些数值分别用纯化学试剂配制的溶液和工业电解液进行了比较测定,并用热力学计算结果进行核对。Sb(Ⅴ)的放电电位还通过计时电位法核对。将所得极化曲线进行浓差极化修正后获得了Tafel直线,由此计算出有关的电极动力学参数。应用计时电位法,探讨了SbS_3~(3-)和SbS_4~(3-)离子的阴极放电机理。结果表明:SbS_3~(3-)离子放电前经历一个前置转化步骤,即: SbS_3~(3)→SbS~++2S~(2-) (1)生成的中间产物SbS~+按下列反应SbS~++3e→Sb+S~(2-) (2)还原为金属Sb。SbS_4~(3-)离子在阴极上放电过程分两步进行,首先,SbS_4~(3-)离子按下式还原为SbS_3~(3-)离子, SbS_4~(3-)+2e→SbS_3~(3-)+S~(2-) (3)生成的中间产物SbS_3~(3-)离子再按反应(1)和(2)式还原为金属Sb。
This article is part of the physicochemical study of wet-process Sb. When the complex Pb-Sb concentrate is leached with Na_2S-NaOH solution, Sb enters the solution in the form of SbS_3 ~ (3-) ions. In the concentrate, Sn and As are partly dissolved, while Pb is left in the residue to separate from Sb. When SbS_3 ~ (3-) ions are in contact with air, they are partially oxidized to SbS_4 ~ (3-) ions. The polarization curves were determined by the steady state method, and the discharge potentials of Sb (Ⅲ) .Sn (Ⅳ), As (Ⅲ), Sb (Ⅴ) and H ~ + ions in the alkali sulfide solution were determined. The corresponding values are as follows: -0.92, -1.04, -0.81, -0.68 and -1.12V. These values were compared with pure chemical reagent solution and industrial electrolyte were measured and compared with the results of thermodynamic calculations. The discharge potential of Sb (V) was also checked by chronopotentiometry. The obtained polarization curve was subjected to concentration polarization correction to obtain a Tafel line, thereby calculating the relevant electrode kinetic parameters. The cathodic discharge mechanism of SbS_3 ~ (3-) and SbS_4 ~ (3-) ions was discussed by using the chronopotentiometric method. The results show that SbS3 ~ (3-) ions undergo a pre-conversion step prior to discharge: SbS3 ~ (3) → SbS ~ ++ 2S ~ (2-) SbS ~ + 3e → Sb + S ~ (2-) (2) reduced to metal Sb. SbS_4 ~ (3-) ions are discharged in the cathode in two steps. Firstly, SbS_4 ~ (3-) ions are reduced to SbS_3 ~ (3-) ions and SbS_4 ~ (3 -) + 2e → SbS_3 ~ (3 -) + S ~ (2-) (3) generated intermediate SbS_3 ~ (3-) ions according to the reaction (1) and (2) reduced to metal Sb.