Removal of phosphate from aqueous solution by red mud using a factorial design.

The purpose of the work is to study the adsorption of phosphate on red mud from aqueous solutions using 2(3) full factorial designs. The important parameters, which affect the removal efficiency of phosphate and final pH of solution (pH(f)), such as phosphate concentration, initial pH of solution (pH(i)) and the red mud dosage were investigated. The effects of individual variables and their interaction effects for dependent variables, namely, phosphate removal efficiency and pH(f) were determined. The results of the study showed that phosphate removal efficiency and pH(f) were found to be 97.6% and 10.9 with optimal reaction conditions initial phosphate concentration 25 mg l(-1), red mud dosage 1.5 g l(-1), pH(i) 3.0, respectively. It was found that adequate amount of calcium ions and higher final pH than 9 are ideal conditions for maximum phosphate removal.