Removal of oxytetracycline hydrochloride from aqueous solutions using natural zeolite

Abstract

The toxicity of antibiotic residues in water resources adversely affects the environment. Recent studies have focused on the removal of organic pollutants such as antibiotics from aqueous solutions with cheap and environmentally compatible adsorbents. In this study, adsorption of oxytetracycline hydrochloride (OTC-HCL) on the natural Manisa-Gördes clinoptilolite was investigated in the batch system at 298-323 K. Effects of pH, initial concentration, adsorbent dosage, contact time, stirring speed and temperature on adsorption were examined and optimum parameters were determined. Isotherm models including Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin were applied to analyze the adsorption data. Kinetic constants were determined by pseudo-first order (PFO), pseudo-second order (PSO), intraparticle diffusion and Elovich models. Adsorption of OTC-HCL on natural zeolite fitted well to the Freundlich and pseudo-second order models. The maximum adsorption capacity of natural zeolite was determined as 60.97 mg/g at 323 K. Thermodynamic studies indicated that the adsorption of OTC-HCL on natural zeolite was spontaneous and endothermic. Physicochemical characterization of natural zeolite was conducted by N2 adsorption-desorption, XRD, FTIR, SEM-EDX analyses before and after adsorption. SBET, specific surface area of the natural zeolite decreased after adsorption process. Characterization results showed that OTC-HCL molecules were successfully adsorbed on the natural zeolite surface.