Abstract
The optimization processes of photo degradation are complicated and expensive when it is performed with traditional methods such as one variable at a time. In this research, the condition of ortho-cresol (o-cresol) photo degradation was optimized by using a semi empirical method. First of all, the experiments were designed with four effective factors including irradiation time, pH, photo catalyst’s amount, o-cresol concentration and photo degradation % as response by response surface methodology (RSM). The RSM used central composite design (CCD) method consists of 30 runs to obtain the actual responses. The actual responses were fitted with the second order algebraic polynomial equation to select a model (suggested model). The suggested model was validated by a few numbers of excellent statistical evidences in analysis of variance (ANOVA). The used evidences include high F-value (143.12), very low P-value (<0.0001), non-significant lack of fit, the determination coefficient (R2 = 0.99) and the adequate precision (47.067). To visualize the optimum, the validated model simulated the condition of variables and response (photo degradation %) be using a few number of three dimensional plots (3D). To confirm the model, the optimums were performed in laboratory. The results of performed experiments were quite close to the predicted values. In conclusion, the study indicated that the model is successful to simulate the optimum condition of o-cresol photo degradation under visible-light irradiation by manganese doped ZnO nanoparticles.
Highlights
Advanced oxidation processes (AOPs) are physicochemical procedures, which are designed to remove environmental organic and inorganic pollutions
Statistical methods To find the optimum conditions of the photo degradation, the experiments were designed by response surface methodology (RSM) and central composite design (CCD) (Table 1 the design is in code)
No study has been conducted on application of the RSM that have been reported on the photo degradation of ortho-cresol (o-cresol) by manganese-doped zinc oxide (Mn-doped Zinc oxide (ZnO)) nanoparticles as photo catalyst
Summary
Advanced oxidation processes (AOPs) are physicochemical procedures, which are designed to remove environmental organic and inorganic pollutions. The significance and adequacy of the model was determined by a few numbers of statistical evidences that appear in analysis of variance (ANOVA) as output of the CCD method These evidences include Fisher variation ratio (F-value), probability value (P-value), Lack of Fit, coefficient of determination R-squared (Rd2), adjusted R-squared (R2Adj), predicted R-squared (RP2red) and adequate precision of Predicted Residual Error of Sum of Squares (PRESS). The local optimums in terms of the actual variables can be determined by differentiating Eq 3 for irradiation time (Eq 4), pH (Eq 5), amount of photo catalyst (Eq 6), and o-cresol concentration (Eq 7). The effect of pH, photo catalyst amount and o-cresol concentration on photo degradation was investigated during the irradiation time while two variables in each case held constant (e.g. Figure 2a). The experimental values were reasonably close to the simulated values that indicated the high validity and adequacy of the model
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