Optimization of Photocatalytic Degradation of Tetracycline Using Titania Based on Natural Zeolite by Response Surface Approach

Tetracycline (TC) is one of the most commonly applied antibiotic and due to the risk posed by antibiotic-resistant pathogens, the need for treating these wastewater is beyond question. Photocatalytic degradation of TC in aqueous solution was studied using TiO2 based on natural zeolite (clinoptilolite, CP) under UV irradiation in a batch reactor. For the first time, in order to propose an accurate model for the photocatalytic degradation of TC under UV light, central composite design based on response surface methodology was employed to assess the individual and interactive effects of several classic parameters on both TC degradation and TOC removal (mineralization). In order to analyze the process, three significant variables pH, catalyst concentration, and tetracycline concentration and tetracycline degradation as the process response were studied. The results of the experiments were fitted to quadratic polynomial models. A maximum degradation of TC of more than 77% was achieved at the optimum conditions (pH 5.9, catalyst concentration of 0.30 g L-1 and TC concentration of 8 mg L-1) within 60 of irradiation. The mineralization or oxidation profile, represented as the total organic carbon, was decreased significantly during the optimum conditions, achieving value near 54% after 4 h. The experimental values agreed with the predicted ones, indicating suitability of the model employed and the success of model in optimizing the conditions of photocatalysis. The quadratic model had high R-2 coefficient (0.980) and high F-value, confirming that the model was valid to predict the experimental results. Moreover, the adjusted R-2 is very close to the R-2 value as another evidence for goodness of the model fit. Initial TC concentration and catalyst dosage are the major factors affecting the photocatalytic degradation of TC using TiO2/CP.