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。
By determining the polarization cureve, the discharge potentials of Sb (Ⅲ), Sn (Ⅳ), As (Ⅲ) and H~+ ions were obtain edas -0.92, -1.04, -0.81 and -1.12V respectively, which were checked with the thermodynamic calculation. Their dynamic parameters were estimated by the Tafel lines which resulted after modification of their concentration polarization. At 50℃, the rate constant was found to be 1.54×10~(-4) cm/s, the exchange current density 10~(-2) A/cm~2 and the activation energy 9100 cal/mole.The cathodic discharge mechanism of SbS_3~(3-) and SbS_4~(3-) has been investigated with the help of the chronopotentiometric method. It was shown that before charge transfer, the SbS_3~(3-) ions should be subjected to a prior chemical reaction, i. e. SbS_3~(3-)=SbS~++2S~(2-). The SbS~+ ions formed are then reduced to metallic Sb at the cathode. The discharge of SbS_4~(3-) ions at the cathode takes place in two steps: First, SbS_4~(3-) ions are directly discharged into SbS_3~(3-) and then further reduced into metallic Sb.
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