Modeling and Optimization of Cefixime Removal from Aqueous Solutions by Poly(vinylidene fluoride)/Graphitic Carbon Nitride/Chitosan Membrane Using Response Surface Methodology

Hypothesis: Medicinal compounds, pharmaceutical substances and their metabolites enter the environment through hospital, domestic and pharmaceutical industries. Conventional technologies are not able to treat such wastewaters fully and therefore they are abundantly found in water. So far, various chemical, physical and biological methods have been used to remove medicinal compounds from aqueous solutions. In this research, PVDF/g-C3N4/Chitosan as a new and powerful membrane was prepared and removal of cefixime from aqueous solutions was investigated using response surface methodology (RSM).

PVDF/g-C3N4/Chitosan membrane was prepared by immersing the PVDF/g-C3N4 membrane in a solution containing different percentages of chitosan. To evaluate the efficiency of the PVDF/g-C3N4/chitosan membrane in removing cefixime, the response surface methodology was used based on the central composition design and four parameters, i.e., chitosan percentage, g-C3N4 value, pH of solution and cefixime concentration were selected as dependent variables. The quadratic model was used to calculate the four dependent variables.

The results showed that among the studied parameters, chitosan had a major effect on the structural properties of the PVDF/g-C3N4/chitosan membrane due to the conversion of polyvinylidene fluoride membrane to hydrophilic ones. According to the results, the maximum cefixime removal by the PVDF/g-C3N4/chitosan membrane was about 81.34% at a solution pH of 4.42, 3.19% chitosan, 0.11 g g-C3N4 and cefixime concentration of 42.51 mg/L. The numerical optimization results showed a slight difference between the predicted number (81.34%) and the experimentally obtained number (78.21%). Also, the high correlation coefficient (99.41%) showed that the response surface methodology has a high potential for predicting and optimizing the cefixime removal process by PVDF/g-C3N4/chitosan membrane with a small number of experiments.