A kaolinite/ $$\hbox {TiO}_{2}$$TiO2 /ZnO-based novel ternary composite for photocatalytic degradation of anionic azo dyes

Solar-assisted photocatalytic degradation of organic pollutants has emerged as efficient technology for the effective treatment of industrial wastewater. Here, we report a simple technique for the fabrication of a novel ternary photocatalyst from kaolinite (K), $$\hbox {TiO}_{2}$$ (T) and ZnO (Z). The most efficient catalyst was prepared at a calcination temperature of $$600{^{\circ }}\hbox {C}$$. The fabricated ternary composite was characterized using different analytical techniques including Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, field emission-scanning electron microscopy and energy dispersive X-ray spectroscopy. The photocatalytic degradation was performed at room temperature ($$25{^{\circ }}\hbox {C}$$) using Remazol Red (RR), an anionic azo dye, as the model compound. A maximum of 98% degradation of RR was found with the ternary catalyst $$\hbox {K}_{0.50}\hbox {T}_{0.45}\hbox {Z}_{0.05}$$, which was prepared from 50% kaolinite (w/w), 45% $$\hbox {TiO}_{2}$$ (w/w) and 5% ZnO (w/w). The catalyst was found to be suitable for long-term repeated applications. Mechanistic investigation through radical trapping experiments confirmed hydroxyl radicals as the potential contributor to the photocatalytic degradation of RR. It is highly expected that a novel photocatalyst design such as this will pave way towards further development of materials capable of hazardous dye removal from industrial effluents.