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.

SnO2 and CuO anchored on zeolite as an efficient heterojunction photocatalyst for sunlight-assisted degradation of cefixime.

The fabrication of heterojunction nanocomposites has been proven as a highly efficient strategy to achieve promising photocatalysts. In this study, tin oxide (SnO2) and copper oxide (CuO) nanoparticles (NPs) were synthesized in situ using Rosmarinus officinalis and simultaneously anchored on zeolite for the fabrication of zeolite/SnO2/CuO as a novel heterojunction photocatalyst. The performance of zeolite/SnO2/CuO was assessed against photodegradation of cefixime as a model pharmaceutical contaminant. A good catalytic potential and synergistic effect was obtained for zeolite/SnO2/CuO compared to pure SnO2 and CuO NPs. Under optimum conditions, 89.65% of cefixime was degraded after 2.5 h under natural sunlight. Based on radical quenching experiments, the importance of involved oxidizing species in the photodegradation of cefixime using zeolite/SnO2/CuO was in order of h+ > •OH > [Formula: see text]. Among studied anions, the highest inhibitory effect was observed for nitrate ion. Also, the main intermediates of the photodegradation process of cefixime in zeolite/SnO2/CuO system were determined by HPLC-MS and the possible pathways were suggested. More than 83% cefixime was removed after three catalyst reuse cycles, indicating a cost-effectiveness potential in the reusability of zeolite/SnO2/CuO. Also, the toxicity and plant growth tests revealed the feasibility of discharging the treated cefixime solutions to irrigate agricultural crops. Overall, the obtained results provide a promising technique with a synergistic feature for the efficient removal of organic pollutants.

Synthesis and characterization of SnO2 NPs for photodegradation of eriochrome black-T using response surface methodology.

The domestic and industrial sewage contains an extensive range of various organic compounds. Due to the toxicity of these materials, their degradation is considered one of the great environmental challenges. To address this problem, SnO2 nanoparticles (NPs) were synthesized via a green route, and they were used as an efficient catalyst for the degradation of an organic dye. In the stage of synthesis of nanoparticles, Thymus vulgaris L. extract acted as an efficient capping agent and renewable reducing agent, and SnO2 NPs were synthesized without addition of any hazardous surfactants. The successful synthesis of SnO2 NPs was confirmed by XRD, FT-IR, SEM, EDX, and TEM. The photocatalytic performance of SnO2 NPs was examined for the degradation of eriochrome black-T (ECBT) as a toxic organic dye in aqueous medium under ultraviolet irradiation. Furthermore, the response surface methodology (RSM) with central composite design (CCD) model was carried out to study of the effects of three different operational parameters on degradation of ECBT. In this design, initial pH of solution (3-11), reaction time (0.5-4 h), and the catalyst loading (0.05-0.12 g) were selected as three factors, whereas the degradation efficiency was chosen as the response. The results of the experimental design indicated that initial pH and catalyst loading were highly significant factors, whereas the reaction time was less important than other factors. Also, recyclability of catalyst was investigated, and the obtained results showed that SnO2 NPs could be easily recovered and reused for at least 4 cycles without any significant decrease in their activity.

Green synthesis of SnO2-ZnO-eggshell nanocomposites and study of their application in removal of mercury (II) ions from aqueous solution.

BACKGROUND: Mercury (Hg) in dental amalgam is the world's hidden source of mercury contamination. The development of more eco-friendly and cost-effective adsorbents to reduce mercury pollutants in wastewater is highly desirable and is still a major challenge. In this study, a novel nanocomposite was synthesized and used as an efficient adsorbent for the removal of Hg(II) ions from aqueous solution. METHODS: A green and cost-effective method was described to the synthesis of SnO2-ZnO-eggshell nanocomposites using teucrium polium extract as a renewable reductant and mild stabilizer. The biosynthesized nanocomposites were characterized by various techniques. The novel SnO2-ZnO-eggshell nanocomposites were used as an effective adsorbent in the removal of mercury (II) ions. To achieve the maximum absorption efficiency of Hg(II) ions, the effect of operating factors such as pH value, the dose of catalyst, the initial metal concentration of Hg(II) ions, and catalyst type were evaluated. RESULTS: The removal percentage and adsorption capacity of Hg(II) were obtained 99.15% and 396.6 mg.g-1, respectively, under optimal conditions after 5 minutes. The selectivity of SnO2-ZnO-eggshell nanocomposites for the adsorption of metal ions was studied, and the highest selectivity was obtained for adsorption of Hg (II) ions. Furthermore, the SnO2- ZnO-eggshell nanocomposites could be recovered and reused at least three times without considerable loss of their efficiency. CONCLUSIONS: The present approach has advantages such as rapidity, simplicity, selectivity, low cost and, most importantly, the use of nanocomposites containing a bio-waste material of eggshell for removal of Hg(II) ions from aqueous solution.

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.

Ultrasonic assisted fabrication of first MoO3/copper complex bio-nanocomposite based on Sesbania sesban plant for green oxidation of alcohols.

MoO3 nanoparticles were obtained using Sesbania sesban. Novel Schiff base ligand and its nanocomplex of copper were synthesized under ultrasonic irradiation. First MoO3/Copper Schiff base complex nanocomposite (NMCS) based on this natural plant was prepared and characterized by TEM, SEM, AFM, FT-IR, TGA, EDAX and elemental analysis. Then atom-efficient and selective oxidation of alcohols using hydrogen peroxide catalyzed by NMCS bio-nanocomposite under ultrasonic irradiation was reported. Structurally diverse set of alcohols was transformed into desired aldehyde and ketone products with high conversion and excellent selectivity under solvent free conditions. Products were isolated easily from green media, and the catalyst could be reused six times without any appreciable decrease in catalytic activity and selectivity.