Assessment of the principal factors influencing the silver cyanidation process by using Plackett-Burman experimental design

Abstract

For decades, the cyanidation process is frequently used for gold and silver extraction, as well as metal extraction as a sub-product of lead, zinc, and copper metallurgy. The present study focuses on the factors that influence silver extraction efficiency, which represents the rate of silver dissolution in a sodium cyanide solution. The screening design of Plackett and Burman has been performed to investigate the variables that have the most impact on the extraction of metal namely temperature, pH, free cyanide concentration, dissolved oxygen level, pulp density, lead nitrate ratio (Pb(NO3)2ratio), and setting time.To evaluate the meaning of the seven variables, twelve experiments were carried out and the result revealed that for a 95% confidence level, the chosen parameters for the model are meaningful in their whole. The following three factors were significant (P<0.05) when it comes to the silver cyanidation process including, setting time, pulp density, and free cyanide concentration. The variance analysis (ANOVA) using a Fisher test has shown that the setting time was considered to have the most significant effect for a significance level of 1% (Fstatistics=22.8328 > Fc=21.2). Likewise, for a 95% confidence level, both pulp density and free cyanide concentration have a major influence on the response. The Pareto diagram results clearly show that pulp density and setting time represent 20% of factors that have 80% effect on the silver extraction. Model validation verified that no statistically relevant distinction was made between the predicted and experimental results with the determination coefficient R2=0.93, this mean that the metal extraction is better fitted to the model and the predictability of the model is adequate to explain 93% of the variation in the dependent variable as a function of factor variation.