Abstract
Cadmium leaching experiments from hazardous waste containing 16.5 wt% CdO were conducted using H2SO4. Dominant
experimental and process parameters were determined by factorial design. Six controlling factors were considered, i.e. solidliquid
ratio, acid concentration, reaction time, particle size, stirring speed and temperature. Analysis of variance (ANOVA) was
used to identify main effects and their interactions. An empirical model, based upon experimental results, was developed to
optimize the cadmium extraction by the process. The optimisation study showed that leaching time, solid-liquid ratio and acid
concentration were the main factors affecting cadmium extraction. It was found that 91% of cadmium could be extracted under
the optimum conditions. Verification experiments showed that the predicted values were in good agreement with the
experimental values.