Phosphate removal from water by fly ash: Factorial experimental design

The influence of three variables (phophate concentration, initial pH of solution (pH 0) and the fly ash dosage) on the removal efficiency of phosphate (% E) and equilibrium pH of solution (pH eq) by using fly ash was studied by means of 2 3 full factorial experimental designs. The parameters coded as x 1, x 2 and x 3, consecutively , were used. The parameters were investigated at two levels (−1 and 1). The effects of these factors on dependent variables, namely, % E and pH eq were investigated. To determine the significance of effects, the analysis of variance with 95% confidence limits was used. It was shown that % E and pH eq 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 pH 0, respectively.