Phosphate removal from water by fly ash: Factorial experimental design

The influence of three variables (phophate concentration, initial pH of solution (pH0) and the fly ash dosage) on the removal efficiency of phosphate (% E) and equilibrium pH of solution (pHeq) by using fly ash was studied by means of 23 full factorial experimental designs. The parameters coded as x1, x2 and x3, consecutively, were used. The parameters were investigated at two levels (−1 and 1). The effects of these factors on dependent variables, namely, % E and pHeq were investigated. To determine the significance of effects, the analysis of variance with 95% confidence limits was used. It was shown that % E and pHeq obtained in this study were found to be 99.6% and 11.16, corresponding to the operating condition of 25 mg l−1, 2 g l−1 and 5.5 for the phosphate concentration, fly ash dosage and pH0, respectively.