Aerobic and anaerobic TiO2-photocatalysed purifications of waters containing organic pollutants

Abstract Developments reported by European research groups in removal of dilute organic pollutants from water under the combined action of TiO 2 particles and solar-illumination are briefly outlined. Instances are given of poor correlation between trends actually observed for selected TiO 2 *-photocatalysed conversion in aerobic conditions and trends expected within the context of two-parameter Langmuir–Hinshelwood-type rate expressions. The necessity of recognising important kinetic roles of several parameters is emphasised not only for aerobic, but also for anaerobic conditions, e.g. TiO 2 *-photocatalysed conversions of chloromethane pollutants in deoxygenated aqueous solutions. Comparisons between initial TiO 2 -sensitized photocatalytic degradation (TiO 2 *-PCD) rates versus dark-equilibrated [ C ] eq profiles for one strongly-adsorbed and one weakly-adsorbed pollutant in aerated TiO 2 suspensions at concentrations − groups; (ii) adsorbate-enhanced hole–electron recombinations on the TiO 2 * surfaces (iii) mass transport limitations within the TiO 2 particle aggregates. Insights into the nature of strongly chemisorbing pollutants (e.g. hydroxybenzoic acids or catechol) onto TiO 2 (P25) were obtained by DRIFTS measurements upon freeze-dried TiO 2 powder samples after their dark-equilibration with 3–100 ppm solutions.