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

Conversion of carbon-rich waste biomass into valuable products is an environmentally sustainable method. This study accentuates the synthesis of novel SnO QDs@g-CN/biochar using low-cost sawdust by applying the pyrolysis method. Morphology, structure, and composition of the synthesized SnO QDs@g-CN/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 SnO QDs was measured from TEM and found to be 6.79 nm. Optical properties of the as-synthesized SnO QDs@g-CN/biochar were characterized using UV-visible spectroscopy. The direct band gap of synthesized SnO QDs@g-CN/biochar nanocomposite was calculated from Tauc's plot and found to be 2.0 eV. The fabricated SnO QDs@g-CN/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 HO, photocatalyst dosage of only 0.06 gL, and 15 ppm initial RB concentration within 80 min, and 94.5% for the removal of MB dye with 0.5 mL of HO, 0.08 gL 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 and 0.00163 min for RB and MB respectively. The photocatalyst can be reused up to the 4 cycle with 80% efficiency.