Taguchi optimization approach for metronidazole removal from aqueous solutions by using graphene oxide functionalized β-cyclodextrin/Ag nanocomposite.

Metronidazole (MNZ) is a major threat to the ecosystems and human health, due to its toxicity and carcinogenic nature. The main aim of this study was to evaluate the efficiency of graphene oxide functionalized β-cyclodextrin/Ag nanocomposite (GO/β-CD/Ag) for MNZ removal from aqueous solution. The effect of operational parameters such as solution pH (2-5), adsorbent dosages (0.2-1 g/L), contact time (10-80 min), initial MNZ concentrations (0.25-10 mg/L) and ionic strength (0.001-0.1 mol/L) was studied using Taguchi experimental design. The maximum removal efficiency of 93.5% was observed for optimum conditions. The optimum values of contact time, the initial MNZ concentration, the ionic strength, the adsorbent dosage and solution pH were found to be 20 min, 0.25 ppm, 0.01 mol/L, 0.4 g/L and 2, respectively. Freundlich and Dubinin-Radushkevich isotherm models were best-fitted with experimental data. Pseudo-first order and type 1 pseudo-second order kinetic models showed the maximum correlation with the experimental data. Adsorption experiments with real samples indicated that the adsorptive removal of MNZ from a hospital wastewater was 72%. Desorption studies showed maximum recovery of GO/β-CD/Ag nanocomposite during three cycles. According to the obtained results, it can be concluded that the application of carbon adsorbents such as GO/β-CD/Ag can be considered an efficient method for final treatment of effluents containing antibiotics.