Visible-light-driven photocatalytic degradation of Rose Bengal and Methylene Blue using low-cost sawdust derived SnO2 QDs@g-C3N4/biochar nanocomposite.

Conversion of carbon-rich waste biomass into valuable products is an environmentally sustainable method. This study accentuates the synthesis of novel SnO2 QDs@g-C3N4/biochar using low-cost sawdust by applying the pyrolysis method. Morphology, structure, and composition of the synthesized SnO2 QDs@g-C3N4/biochar nanocomposite were characterized using SEM (scanning electron microscope), TEM (transmission electron microscope), XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), FT-IR (infrared spectroscopy) and PL (photoluminescence) spectroscopy. The average diameter of the SnO2 QDs was measured from TEM and found to be 6.79 nm. Optical properties of the as-synthesized SnO2 QDs@g-C3N4/biochar were characterized using UV-visible spectroscopy. The direct band gap of synthesized SnO2 QDs@g-C3N4/biochar nanocomposite was calculated from Tauc's plot and found to be 2.0 eV. The fabricated SnO2 QDs@g-C3N4/biochar photocatalyst exhibited outstanding photocatalytic degradation efficiency for the removal of Rose Bengal (RB) and Methylene Blue (MB) dye through the Advanced Oxidation Process (AOP). The synthesized photocatalyst showed a degradation efficiency of 95.67% for the removal of RB under optimum conditions of 0.3 mL H2O2, photocatalyst dosage of only 0.06 gL-1, and 15 ppm initial RB concentration within 80 min, and 94.5% for the removal of MB dye with 0.5 mL of H2O2, 0.08 gL-1 of the fabricated photocatalyst and 6 ppm of initial MB concentration within 120 min. The photodegradation pathway followed the pseudo-first-order reaction kinetics with a rate constant of 0.00268 min-1 and 0.00163 min-1 for RB and MB respectively. The photocatalyst can be reused up to the 4th cycle with 80% efficiency.

ZnO-based Cu metal-organic framework (MOF) nanocomposite for boosting and tuning the photocatalytic degradation performance.

Although metal-organic frameworks (MOFs) are a viable choice for photocatalysts with large surface area and tunable pore structure, the rapid recombination of excited photogenerated charges results in low activity towards photodegradation. Aiming at improving the photocatalytic activities of MOFs, different strategies to incorporate MOF with light-harvesting semiconductors have been developed. In this research, we report an effective photocatalyst designed by incorporating Cu-MOF with ZnO for the photocatalytic degradation of Rose Bengal exhibiting excellent degradation efficiency of 97.4% in 45 min under natural sunlight with catalyst dosage of 320 mg/L. The optical, morphology and surface characteristics of the prepared nanocomposite were studied using scanning electron microscopy (SEM-EDX), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (PXRD), Brunauer-Emmett-Teller (BET) analysis, thermogravimetric (TGA) analysis, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and ultraviolet diffused reflectance spectroscopy (UV-DRS) techniques. Further studies showed that the degradation followed first-order kinetics with a rate constant of 0.077869 min-1. The degradation mechanism was investigated by photoluminescence (PL) study, XPS, zeta potential and quenching experiment in presence of different scavengers. Meanwhile, the fabricated composite displayed good recovery and reuse properties up to 5 cycles as revealed by XRD analysis proving itself a potential MOF-based photocatalyst towards environmental remediation process.

Magnetic nanocomposite adsorbents for abatement of arsenic species from water and wastewater.

The presence of high concentrations of arsenic species in drinking water and other water bodies has become one of the most critical environmental concerns. Therefore, decontamination of arsenic-containing water is essential for improved health and environmental concern. In recent years, nano-adsorbents have been widely used for the adsorptive removal of arsenic from water. Separating existing nano-adsorbents from treated waters, on the other hand, is a critical issue for their potential applications in natural water treatment. To address these issues and to effectively remove arsenic from water, researchers looked at iron oxide-based magnetic nanocomposite adsorbents. The magnetic nanoadsorbents have the benefit of surface functionalization, making it easier to target a specific pollutant for adsorption, and magnetic separation. In addition, magnetic nanoparticles have a large surface area, high chemical inertness, superparamagnetic, high magnetic susceptibility, small particle size, and large specific surface area, and are especially easily separated in a magnetic field. Magnetic nano-adsorbents have been discovered to have a lot of potential for eliminating arsenic from water. The recent advances in magnetic nano-absorbents for the cleanup of arsenic species from water are summarized in this paper. Future perspectives and directions were also discussed in this article. This will help budding researchers for the further advancement of magnetic nanocomposites for the treatment of water and wastewater contaminated with arsenic.