工业磷酸中As(Ⅲ)的电化学沉积

Electrodeposition of As(Ⅲ) in technical grade phosphoric acid

运用恒电流法在铜柱电极上研究了工业磷酸中毒性较大的As(Ⅲ)还原为无毒单质砷的电化学行为。实验表明,当电流密度控制在-0.044 mA/cm2以内时可以很好地将As(Ⅲ)转化为单质砷并抑制砷化氢析出。由塔费尔拟合推算得到As(Ⅲ)转化为单质砷的交换电流密度为-6.324×10-7mA/cm2,此过程为不可逆过程。采用表面积为15.8 cm2的铜柱电极,在电流密度为-0.038 mA/cm2,温度为80℃条件下,将磷酸中As(Ⅲ)含量由10.92×10-6降到0.47×10-6,电流效率达7.55%。

Electrodeposition of As（ Ⅲ ） in the technical grade phosphoric acid was studied on copper cylinder electrode by the constant current method and the aim was to remove the arsenic in phosphoric acid. In this process, the oxidation state and toxic As（Ⅲ） was reduced to nontoxic element arsenic. The results showed that As（Ⅲ ）was reduced to As efficiently without releasing toxic AsH3 under the condition of current density i = - 0.044 mA/cm^2. The Tafel plot analyses reveal that the eleetrodeposition of arsenic is a totally irreversible electrode reaction and the exchange current density is i0 = -6. 324×10^-7 mA/cm^2. The concentration of As（Ⅲ） in phosphoric acid was reduced to 0.47×10^-6 from 10.92×10^-6 at current density j = -0.038 mA/cm^2 and temperature T = 80℃. The current efficiency for arsenic was 7.55%.