Greatly enhanced tribocatalytic purification of concentrated dye wastewater by TiO2 nanoparticles through Ti and Al2O3 coatings

TiO₂ nanoparticles with high chemical stability, low cost and non-toxicity are attractive for large-scale catalytic applications. Non-piezoelectric amorphous TiO₂ nanoparticles were experimentally developed for the efficient degradation of dyes under mechanical friction induced by low-speed stirring at 400 rpm. The friction between the catalyst surface and the rotating disk promotes the transition of valence-band electrons in TiO₂, generating electron-hole pairs. These pairs subsequently react with hydroxide ions and dissolved oxygen in the dye solution to produce superoxide radicals and hydroxyl radicals, enabling the degradation of organic dyes under tribo-catalytic conditions. Al₂O₃ substrates were optimized compared to glass substrates. Non-piezoelectric amorphous TiO₂ nanoparticles were mechanically stirred at 400 rpm for 2 h and 2.5 h. Under these conditions, high-concentration methyl orange (30 mg/L) and methylene blue (20 mg/L) degraded by 99 % and 100 %, respectively. The tribocatalytic performance achieved for TiO₂ nanoparticles in this study is highly competitive for environmental remediation.