PTFE-Enhanced Tribocatalytic Degradation of High-Concentration (100–500 mg/L) Rhodamine B Solutions Using TiO2 Nanoparticles

Dye wastewaters are produced in huge amounts every year world-widely and they pose serious threats to ecosystems and human health if not treated properly. High-concentration organic dye wastewaters are usually treated through multiple steps including pretreatment and advanced treatment. In this work, TiO2 nanoparticles suspended in high-concentration rhodamine B (Rh B) solutions up to 500 mg/L have been subjected to magnetic stirring to initiate tribocatalytic degradation of Rh B. While 100 and 200 mg/L Rh B solutions can be rather thoroughly degraded in beakers with four kinds of bottom/coatings (glass, Al2O3, Ti, and PTFE), 300 mg/L Rh B solutions can only be degraded effectively in a beaker with PTFE coating. Even 400 and 500 mg/L Rh B solutions can also be degraded rather thoroughly by TiO2 nanoparticles in a PTFE-coated beaker. EPR analyses revealed that PTFE coating enhanced the formation of both hydroxyl radicals and superoxide radicals by magnetic stirring-stimulated TiO2 nanoparticles. These findings highlight the importance of the synergism between materials in friction pairs for tribocatalysis and demonstrate a one-step tribocatalytic degradation of Rh B solutions with concentrations of real Rh B wastewaters.