Solar-powered degradation of malachite green dye via α-MnO2 nanorods with CTAB-mediated electron trapping

Malachite green (MG) dye is a highly toxic, non-biodegradable and environmentally persistent organic pollutant, posing a serious threat to aquatic ecosystems and human health. Therefore, its effective removal from wastewater is of great environmental significance. Among various approaches, photocatalytic degradation has emerged as a promising technique, owing to its efficiency, cost-effectiveness, and environmental sustainability. In this study, α-MnO 2 nanorods stabilized with cetyltrimethylammonium bromide (CTAB) (α-MnO 2 @CTAB) were synthesized at low temperature and employed for the photocatalytic degradation of MG dye under solar light. The morphology and structure of the materials were extensively characterized using various techniques. X-ray diffraction reveals the formation of a pure α-MnO 2 and α-MnO 2 @CTAB with crystallite sizes of 18 and 16 nm respectively. SEM and TEM images revealed the formation of rods with a thickness of 5–9 nm. α-MnO 2 @CTAB showed decreased band gap (1.52 V) and arc radius compared to α-MnO 2. Under solar illumination, the degradation of MG dye by α-MnO 2 @CTAB (0.02 min −1 ) exhibited a kinetic rate constant twice that of pure α-MnO 2 (0.01 min −1 ) reaching 98 % efficiency at pH 2 within 120 min. Radical trapping experiments revealed that holes (h + ) and hydroxyl radicals (·OH) are the primary reactive species responsible for MG degradation. Overall, the α-MnO 2 @CTAB nanocomposite demonstrates excellent photocatalytic activity, stability, and reusability, offering a simple and cost-effective strategy for efficient wastewater treatment and environmental remediation.