Electrochemical Oxidation of Cyanide Complexes with Copper at Carbon Fibre

Abstract

The oxidative degradation of cyanide wastes is very important in industrial waste management and for wastewater treatment. Electrochemical methods of waste treatment enable minimization of the need for chemical additives and sludge disposal. Anodic oxidation of cyanides can lead to formation of non toxic products such as N₂ and CO₂ or NO₃ ⁻ and CO₃ ²⁻. A consideration of possible oxidation products in alkaline media, based on standard reduction potentials given below indicates that at low values of the applied potential, formation of the cyanates (CNO⁻) is thermodynamically preferred¹.

$$CN{O^ - } + {H_2}O + 2e \to C{N^ - } + 2O{H^ - }{\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} E^\circ = - 0.97V$$

(1)

$$C{O_2} + 0.5{N_2} + 2{H^ + } + 5e \to C{N^ - } + 2O{H^ - }{\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} E^\circ = - 0.49V$$

(2)

$$CO_3^{2 - } + NO_3^ - + 6{H^ + } + 10e \to C{N^ - } + 6O{H^ - }{\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} E^\circ = + 0.14V$$

(3)

However, cyanates are 1000 time less toxic than cyanides.