Effects of process variables and their interactions on solubility of metal ions from crude kaolin particles: results of a statistical design of experiments

Solubility of metal ions from kaolin particles was investigated in the presence of three different anionic dispersing agents [sodium salt of polyacrylic acid (NaPAA), sodium hexametaphosphate (NaHMP), and sodium silicate (Na-silicate)] by conducting statistically designed experiments based on Box Behnken method. Quadratic response model was used to: (1) study the relationship between the concentration of metal ions as the measured response to the input variables, which consist of wt.% solids, pH, time (aging), and dispersant dosage; and (2) find predictive models for the concentration of metal ions as a function of the above-mentioned input variables. Results indicate that both pH of the slurry and the dosage of the dispersing agent used to prepare the suspension significantly affect the concentration of metal ions in supernatant. When dispersing agents were added to the system, there was a significant increase in the concentration of metal ions in supernatant particularly in the presence of NaPAA and NaHMP. Results are presented and discussed.