Synergistically Boosted Degradation of Organic Dyes by CeO₂ Nanoparticles with Fluoride at Low pH

Catalysts that can work without the need of light and additional oxidants such as H2O2 to degrade organic pollutants have been long sought. In this work, we report that at acidic condition, CeO2 nanoparticles can effectively degrade various organic dyes such as rhodamine B, fluorescein, xylene cyanol FF, brilliant blue G-250, and coomassie brilliant blue R-250 in the presence of fluoride in dark. The degradation kinetics are fast, and F– accelerates the reaction by at least 89-fold. Each gram of CeO2 can degrade 0.47 g of rhodamine B before the need of regeneration. Therefore, the synergistic effect of fluoride and acid drastically boosted degradation of organic dyes by CeO2 under ambient temperature. No other chemicals like H2O2, UV light, or ultrasonic treatment are required. By using UV–vis spectrometry and chemical oxygen demand analysis, the removal of rhodamine B proceeded by an initial fast partial degradation followed by a slower full degradation. In addition, the removal capacity, reusability, the effect of CeO2, acid and F– were studied in detail. The mechanism of fluoride was attributed to the increased oxygen vacancy on CeO2, and a strong acidic environment further boosted this effect.