Figure 3
The simultaneous behavior of the variables during p -cresol photodegradation in the quadratic model, (a) behavior irradiation time and pH, (b) behavior concentration of p-cresol and irradiation time, (c) behavior of pH and concentration of p-cresol. The red and black lines on the Figures 2 and 3 are the above and below axes as showed on the figures respectively which provided by the software (RSM).