Development and application of a first order rate equation for modelling the dissolution of gold in cyanide solution

A first order rate equation has been shown to accurately model the rate of gold extraction by cyanidation. The equation has the following form: E = EI(1 − e^−kt)where E is the gold extraction (%) at time t (hours), EI is the ultimate gold extraction (%) and k is the rate constant (h⁻). Cyanidation of four distinct ore samples indicated that the equation predicted the gold extraction as a function of time with a mean error of less than 3%.An algorithm has been developed so that the rate constant and ultimate fold extraction can be estimated from only four data points collected within the initial 28 hours of the leach. The model equation can also be used to statiscally quantify the effect of process variables on the rate of gold extraction and ultimate recovery. An example of the effect of dissolved oxygen concentration on the rate of gold extraction using Casa Berardi East zone ore is included in the report. The precision with which the extraction can be predicted could be increased by an improved sampling technique to minimize the error at leach times from 0 – 8 hours.