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

Abstract

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 6.79nm. 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 2.0eV. 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 0.3mL H2O2, photocatalyst dosage of only 0.06 gL-1, and 15ppm initial RB concentration within 80min, and 94.5% for the removal of MB dye with 0.5mL of H2O2, 0.08 gL-1 of the fabricated photocatalyst and 6ppm of initial MB concentration within 120min. The photodegradation pathway followed the pseudo-first-order reaction kinetics with a rate constant of 0.00268min-1 and 0.00163min-1 for RB and MB respectively. The photocatalyst can be reused up to the 4th cycle with 80% efficiency.