Role of Clay Dispersion and Cation Transfer in Montmorillonite-Catalyzed Ozonation of Bisphenol A in Water Treatment and Induced Ecotoxicity

The effects of exchangeable cations on bisphenol A adsorption and degradation were investigated in montmorillonite-catalyzed ozonation and compared to the parent bentonite. Total BPA removal (100%) can be achieved after only 5 min adsorption on NaMt and by 15 min ozonation with all clay catalysts but without complete mineralization. The BPA degradation level was found to correlate to the ecotoxicity of the ozonized BPA mixtures, using the aquatic plant Lemna minor as a bioindicator species. Liquid chromatography revealed that BPA adsorption contributes to the ozonation process and that BPA degradation rates and ecotoxicity strongly depend on the exchangeable cation and the particle size of the clay catalyst. These factors also appear to govern the ozonation and adsorption process through catalyst dispersion in the liquid medium, with direct effects on the toxicity towards the living species. The results of the present work allow envisaging clay-based oxidative water treatments with advanced BPA removal that drastically reduce the amounts of persistent derivatives.