optimization of photocatalytic reduction of cr(vi) in water with nano zno/todorokite as a catalyst: using taguchi experimental design

In the present work, the solid state dispersion method has been used to stabilize zno on todorokite (td). zno/td catalysts have been characterized by sem and xrd. optimum process conditions were determined for the removal of cr(vi) from water using the taguchi fractional design method. four controllable factors containing ph, photocatalyst amount, irradiation intensity and initial concentration of cr(vi) at three levels were identified for each factor. the optimum conditions were found to be as follows ph= 2, photocatalyst amount= 100 mg/l, irradiation intensity= 7.63 w/m^2 and cr(vi) concentrations= 15 ppm. in optimum conditions a first order reaction to k= 0.1492 min^−1 was observed in the photocatalytic reduction of cr(vi) in water by uv/zno/td.