Photocatalytic Degradation and Mineralization of Ciprofloxacin: Optimization of Operating Parameters Using Box–Behnken Experimental Design

In this paper, the photocatalytic degradation and mineralization of the ciprofloxacin antibiotic (CPF) have been performed with anatase TiO₂ catalyst, supported on cellulosic paper, under UV light, using lamps Philips (wavelength of 365 nm), and at various initial CPF concentrations, concentrations of hydrogen peroxide, pH, and reaction times. The CPF removal efficiencies and the total organic carbon (TOC) removal efficiencies have been studied using the experimental responses obtained by a four-factor-three-level Box–Behnken design under response surface methodology (BBD-RSM). This provided 27 experiments for CPF initial concentration ranging from 10 to 40 mg/L, the concentration of hydrogen peroxide ranging from 50 to 300 mg/L, the solution pH ranging from 2 to 10, and the contact time ranging from 1 to 5 h, which were respectively coded as X₁, X₂, X₃, and X₄ at three levels (− 1; 0; and 1). The significances of the factors and their interactions were determined using analysis of variance (ANOVA) tests. The optimum experimental conditions of the tested variables were determined by graphical optimization, and the experimental conditions were found to reach maximum degradation (100%) and maximum mineralization (81.50%), at a CPF initial concentration of 10 mg/L, hydrogen peroxide concentration of 175 mg/L, pH 8, and reaction time of 4 h. The BBD resulted in a good-technique to study and optimize the effects of various factors on CPF degradation. Fourier-transform infrared spectroscopy was performed to define the chemical compositions of the catalyst before and after the degradation of the antibiotic. The surface morphologies of the catalyst before and after the treatment were also characterized using scanning electron microscopy. The degradation mechanism was also discussed. The use of hydrogen peroxide in the presence of TiO₂ catalyst and under UV light could be adopted as an efficient method for CPF degradation and mineralization.