In theory, the direct use of sunlight for the photocatalytic generation of highly oxidative radicals provides a giant, technological leap forward towards effective, cheap, and sustainable water treatment. In practice, however, the amount of interaction time that target contaminants spend with the generated radicals is a critical limiting factor. Dissolved organic matter can interfere significantly with the process by reacting competitively with the radicals, reducing their lifetimes. Given the complexity of natural organic matter (NOM), consisting of a wide range of molecules, little is known about which molecules exert the strongest quenching effects. A critical next step towards applying photocatalysis to environmental systems is the characterization of the intermolecular interactions between photocatalysts, target contaminants (i.e., pharmaceuticals or viruses), and NOM constituents. Here, the inhibition of TiO2-driven photooxidation processes is examined for three distinct fractions of organic matter collected from an operational Membrane Bioreactor (MBR) treatment facility in La Grande Motte, France. Organic matter was fractionated with XAD resins and concentrated via reverse osmosis. Additional samples were taken at different times during the membrane operational cycle (i.e., immediately before or after chemical cleaning and mid-cycle) to assess the practical implications of membrane operation and fouling on photocatalytic processes. The various fractions and samples of organic matter were characterized using fluorescence excitation emission matrix analysis. Photodegradation kinetics of probe compound, para-chlorobenzoic acid (pCBA) were measured as a function of organic matter concentration. Pseudo-first order kinetic models were sufficient to describe the hydroxyl radical production and reaction with pCBA in pure water cases but insufficient for complex waters. The implications of higher order photodegradation kinetics will be discussed. In addition to pCBA, MS2 bacteriophage inactivation kinetics were also examined for the various organic matter samples to compare inhibition of chemical oxidation (pCBA) compared to disinfection reactions.

Differentiating the inhibitory effects of natural organic matter constituents on photocatalytic treatment processes

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.