Efficient photocatalytic degradation of metronidazole in wastewater under simulated sunlight using surfactant- and CuS-activated zeolite nanoparticles.

Hexadecyltrimethylammonium-bromide-activated zeolite nanoparticles coated with copper sulfide (ZEO/HDTMA-Br/CuS) was evaluated as a photocatalyst under sunlight for the degradation of metronidazole (MET). The surface and structural characteristics of ZEO/HDTMA-Br/CuS and other materials used in this study were analyzed using field emission-scanning electron microscopy, Fourier transform infrared and ultraviolet-visible diffuse reflectance spectroscopies, X-ray diffraction, Brunauer-Emmett-Teller surface area and Barrett-Joyner-Halenda pore size and volume analyses, and pH of zero charge test. ZEO/HDTMA-Br/CuS exhibited excellent surface and structural catalytic properties. For a comprehensive study of the degradation process, several parameters, such as the pH (3-11), MET concentration (10-30 mg/L), ZEO/HDTMA-Br/CuS dose (0.005-0.1 g/L), reaction time (5-200 min), and HO concentration (50-200 mg/L), were optimized. ZEO/HDTMA-Br/CuS achieved 100% degradation efficiency when 10 mg/L MET was used under the optimum conditions: pH = 7, ZEO/HDTMA-Br/CuS dose = 0.01 g/L, and reaction time = 180 min. The degradation efficiency increased when the concentration of HO was increased from 50 to 150 mg/L and decreased with further increase to 200 mg/L, indicating that the efficiency of MET degradation highly depends on the concentration of HO in an aqueous solution. The degradation kinetics analysis revealed that the degradation is of the pseudo first-order. Thus, ZEO/HDTMA-Br/CuS proved to be an exceptional catalyst for the photodegradation of MET in aqueous media.