Enhanced photocatalytic degradation of hazardous dyes using a novel ternary Co₃O₄-CuO-SnO₂ heterojunction: experimental and RSM-based process optimization

Hazardous dyes, such as Eosin Yellow and Malachite Green are widely applied in textile and paper industries. These dyes are highly dangerous to the environment and human health because they are chemically stable and toxic. In this study a ternary Co₃O₄-CuO-SnO₂ was prepared through co-precipitation and ultrasonic-assisted, to incorporate the optical and electronic characteristics of the constituent metal oxides to facilitate visible-light-driven photocatalysis. Structural, morphological, and elemental composition of the composite, single-phase purity, and reduced band gap of 2.28 eV were confirm using through the X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR) and UV–Vis spectroscopy. Experiments for photocatalytic degradation showed that the removal of dye is highly depends on time of irradiation, dosage of catalyst, initial concentration of dye and the pH of the solution. The One-Factor-at-a-Time (OFAT) and Response Surface Methodology (RSM) with Central Composite Design (CCD) was used to optimize the maximum removal efficiencies of 99.15% for EY dye (40 min, pH 3, 0.01 g catalyst) and 99.31% for MG dye(50 min, pH 11). Individual and interactive parameters were statistically analyzed using ANOVA to confirm significance of the parameters. Diagnostic plots were used to verify model reliability. The improved photocatalytic activity is attributed to synergistic interfacial, effective charge separation, inhibited electron-hole recombination, and high chemical stability. The outcomes reveal that Co₃O₄-CuO-SnO₂ composite is a highly active, and stable, which can be used a viable and sustainable solution for the cleaning of dye polluted wastewater.