TiO2–MgO/Kaolinite Hybrid Catalysts: Synthesis, Characterization, and Photocatalytic Activity for the Degradation of Crystal Violet Dye and Toxic Volatile Butyraldehyde

This work reports the synthesis and photocatalytic performance of TiO2–MgO/kaolinite nanocomposites for the degradation of crystal violet (CV) and butyraldehyde under UV irradiation. MgO incorporation enhanced charge separation by limiting electron–hole recombination, while the halloysite-type kaolinite support increased surface area and improved dispersion of the active phases. The materials exhibited strong synergy between adsorption and photocatalysis, as the clay support pre-concentrated pollutants and facilitated their rapid degradation. The composite containing 10 wt% MgO (TK10) showed the highest efficiency, achieving 99.8% CV removal and outperforming commercial P25. The catalyst also demonstrated efficient degradation of gaseous butyraldehyde, highlighting its dual applicability for water and air purification. Kinetic analysis indicated a pseud-second-order adsorption mechanism, and isothermal data fitted the Langmuir model, suggesting monolayer adsorption. The TK10 composite showed excellent stability and reusability over multiple cycles, underscoring its potential as a cost-effective and environmentally benign photocatalyst for integrated environmental remediation.