Photocatalytic mediated destruction of 2-chlorobiphenyl by a ZnO-[10%]BiOI p-n heterojunction: effect of some process parameters
Darlington C. Ashiegbu, J.H. Potgieter
Abstract
Abstract This study involved the synthesis, characterization, and application of various photocatalysts and heterojunctions using zinc oxide (ZnO), tungsten trioxide (WO 3 ), and bismuth oxyiodide (BiOI) for the photo-abatement of 2-chlorobiphenyl (2CBP). Scanning electron microscopy revealed a variety of morphologies for all composites, while energy-dispersive X-ray spectroscopy only identified reference elements and X-ray diffraction patterns displayed crystalline patterns with no impurity peaks. The absorbance of the heterostructures exhibited slight red shifts as WO 3 and BiOI were etched into ZnO. Except for ZnO-[10%]WO 3 , the band gaps of all composites decreased/narrowed as the doping of WO 3 and BiOI into ZnO increased. Nitrogen sorption isotherms revealed that almost all the prepared materials had a Type IV isotherm, and the heterostructures showed higher surface area measurements compared to the undoped composites. The ZnO-[10%]BiOI heterojunction, which displayed the best photoactivity, was further investigated to analyze the influence of some operating conditions. Results revealed that the initial pollutant concentration influenced the degree of photodegradation, which decreased with increased initial 2CBP concentration. The optimum photocatalytic performance was detected at neutral pH. The pseudo-first order kinetic model showed that doubling the heterojunction’s weight increased the rate constant from 0.0054 to 0.0089 min −1 , while increasing the pH to 11.3 resulted in an 18-fold reduction. Overall, the study demonstrated the potential application of ZnO-[10%]BiOI heterostructure as a highly effective photocatalyst for recalcitrant contaminants in water.