Optimization and kinetics of rhodamine B photodegradation with a novel nitrogen-doped CeO2/ZnO nanocatalyst

The study addresses the severe threat caused by wastewater containing toxic and non-biodegradable organic dyes like rhodamine B (RhB) to the biota, by fabricating a novel and efficient nanocatalyst, N-CeO 2 /ZnO, with tremendous removal of RhB through doping nitrogen onto CeO 2 mixed with ZnO using the hydrothermal method. The characterization of the nanocatalyst is explored by TEM, SEM, EDX, XRD, BET, DRS and FTIR. Box Behnken design (BBD) in response surface methods was used to evaluate the operational parameters impacting the process, including pH, initial RhB dye concentration, time, and dosage. The fabricated N-CeO 2 /ZnO nanocatalyst possesses band gap of lower energy 3.04 eV in comparison with that of the precursors, as well as a better BET-surface area of 41.78 m 2 /g, and was found to be mesoporous. The XRD analysis of N-CeO 2 /ZnO revealed its nano-crystallinity having a particle and crystallite size of 56.74 nm and 58.30 nm respectively. The photodegradation efficiency of N-CeO 2 /ZnO nanocatalyst (93.21%) was more effective on RhB dye than CeO 2 /ZnO (76.7%), CeO 2 (48.8%), and ZnO (44.65%) alone. The photodegradation process is influenced by all the process parameters. The quadratic model of BBD-RSM efficiently predicts the optimum conditions (pH 4, C o = 20 mg/L, 90 and 0.3 g nanocatalyst dosage) for the degradation process. The first-order rate constant for photocatalytic degradation is 0.008 min −1 and fit best for the kinetic modeling. Investigation into scavengers identified hydroxyl radicals (OH • ) as the fundamental active species for the degradation process. N-CeO 2 /ZnO nanocatalyst has shown a promising capability for removing RhB dye from wastewater.