Plant-based green fabrication of CuO-CdO-bentonite S-scheme heterojunction with enhanced photocatalytic performance for the degradation of levofloxacin.

In this research, for the first time, CuO and CdO nanoparticles (NPs) were synthesized using Ferula persica and anchored on layered bentonite as a novel S-scheme nano-heterojunction (denoted as CuO-CdO-BT). Ferula persica acted as a naturally-sourced reducing agent and stabilizer for the synthesis of NPs. The performance of CuO-CdO-BT was evaluated for the degradation of levofloxacin from an aqueous solution under sunlight. The characterization results clarified that the bentonite as a support not only reduced the agglomeration of CuO and CdO NPs but also decreased the size of biosynthesized NPs, which increased the active surface of NPs and the photodegardation efficiency. The effect of operational reaction system variables was examined to optimize the photocatalytic capability of CuO-CdO-BT. Under optimum conditions (catalyst dosage = 0.4 g/L, LVF concentration = 10 mg/L and pH = 8), 96.11% of levofloxacin was degraded using CuO-CdO-BT after 30 min with degradation kinetic of 0.108 min-1, which was about 2.4 and 4.2 times higher than those of bare CuO and CdO NPs, respectively. The improvement of the photocatalytic degradation efficiency of CuO-CdO-BT compared to CuO and CdO NPs was due to preventing the recombination of charge carriers in the S-scheme system. The radical quenching experiments ascertained the generation of [Formula: see text]·OH, and [Formula: see text] species in the CuO-CdO-BT system, indicating that ·OH radicals have a more prominent role than [Formula: see text] and [Formula: see text] in the photocatalytic reaction. The six possible levofloxacin pathways of LVF degradation were suggested based on HPLC-MS analysis. Over 88.5% LVF was removed using CuO-CdO-BT after three catalyst reuse cycles, indicating a cost-effectiveness potential of the biosynthesized photocatalyst reusability. Almost complete mineralization of LVF was obtained by the CuO-CdO-BT photocatalyst after 180 min of reaction. Based on findings, the S-scheme mechanism of photo-generated electron-hole pairs transfer in the CuO-CdO-BT system was found. The unique structural features of the new generation of S-scheme heterojunction and green synthesis of NPs using plants provide promising photocatalysts to improve wastewater treatment.

A green approach to synthesis of ZnO nanoparticles using jujube fruit extract and their application in photocatalytic degradation of organic dyes.

Zinc oxide nanoparticles (NPs) were synthesized using a green method in the presence of jujube fruit extract as a reducing agent and a stabilizer. The characteristics of the NPs were determined by various analyses, including transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The results suggest that high quality ZnO NPs in terms of size distribution and morphology were synthesized. The obtained NPs were then used as photocatalyst to degrade two organic dyes, methylene blue (MB) and eriochrome black-T (ECBT) in a model wastewater under direct sunlight. The kinetics of photodegradation of the aforesaid organic dyes was also studied. ZnO NPs exhibited a great photocatalytic performance, which resulted in degradation efficiencies of about 92% and 86% within 5 h at the rate constants of 8.7 × 10-3 min-1 and 6.7 × 10-3 min-1 for MB and ECBT, respectively. Moreover, the NPs demonstrated stable photocatalytic activity after sequential degradation experiments.