Photodegradation of Molasses Wastewater Using TiO₂–ZnO Nanohybrid Photocatalyst Supported on Activated Carbon

Abstract

Molasses wastewater (MWW) is characterized by high organic loading and a recalcitrant dark brown color. A study was carried out to determine the photocatalytic efficiency of TiO2–ZnO nanohybrid supported onto activated carbon (AC) for the remediation of MWW. Immobilization of ZnO onto TiO2 formed TiO2–ZnO, which was then supported onto AC forming TiO2–ZnO–AC composite. X-ray diffraction (XRD), scanning electron (SEM), energy-dispersive X-ray (EDX) and Fourier transform infrared (FTIR) spectroscopies, and transmission electron (TEM) microscopy revealed the successful hybridization of TiO2 and ZnO, and the subsequent support of the hybrid onto AC. Photoluminescence (PL) spectroscopy further revealed a restrained electron-hole pair recombination resulting from both the successful formation of a heterojunction, and the introduction of electron accepting AC support. Photodegradation process was monitored by color and total organic carbon (TOC) reductions. It was observed that TiO2–ZnO (ratio 3:1) supported onto AC (30% loading) had a higher adsorptive capacity and catalytic activity than bare TiO2–ZnO resulting in a 14% increment in overall color reduction. UV-photodegradation was found to be very effective for color as compared to TOC reduction, with 96% and 9% reductions, respectively, after 1 hour of irradiation. A pH of 5 was found to be optimum for photodegradation.