Kinetic study on HCN volatilization in gold leaching tailing ponds


In this work, the detailed analysis of HCN volatilization, taking place in tailing storage facilities, was made. Volatilization experiments were performed at conditions typical of gold leaching industrial tailing ponds. The meticulous statistical analysis (including full factorial 33 experimental design) let to determine the variables and their interactions affecting the percentage of HCN volatilization. Volatilization tests were performed in an open, temperature-controlled, continuously-stirred batch reactor. The percentage of HCN volatilization was directly proportional to the temperature and temperature-pH interaction and inversely proportional to the pH, cyanide concentration, and pH-pH and temperature-cyanide concentration interactions. HCN volatilization was promoted at acidic conditions. A first order rate law was used to represent the volatilization rate. The specific rate constant (k) was found to be following function of temperature and pH: k(T,pH) = Ao.exp(-18760/T), where: In(A(0)) = (0.11 +/- 0.11)-pH + (58.08 +/- 0.16). The obtained kinetic model represented properly (R-2 = 0.90) experimental data in a wide range of industrial conditions: cyanide concentration (300-2000 mg.L-1), pH (3-9), and temperature (16-20 degrees C). The increase in temperature, from 16 to 20 C, let to the increase in k, by a factor of ca. 2.5 +/- 0.8. The increase in solution pH, from 3 to 9, provoked its decrease, by a factor of ca. 1.9 +/- 0.3.


Palabras clave

HCN volatilization, Kinetic study, Gold leaching tailing ponds