title: The impact of background organic matter and alkalinity on the degradation of the pesticide metaldehyde by two advanced oxidation processes: UV/H₂O₂ and UV/TiO₂.
abstract: The impact of background constituents on the degradation of trace levels of micropollutants by two advanced oxidation processes: UV/H₂O₂ and UV/TiO₂ was studied. Experimental results demonstrated that the background scavenging rate rather than the concentration of micropollutant controls the required UV irradiation dose. The character of the natural organic matter had a limited impact on scavenging when the water source remains unchanged, however, a periodic bleed of hydrophobic material may substantially increase the minimum UV dose required to reach the desired micropollutant concentration. Moreover, in the case of UV/TiO₂, high concentrations of background organic matter do not only act as scavengers but also saturate the TiO₂ surface. Alkalinity inhibits the efficacy of UV/TiO₂ photocatalysis due to the formation of large TiO₂ aggregates. The study also demonstrated that the use of synthetic waters for treatability test purposes was an acceptable approach as long as both the background organic matter and the alkalinity were matched to that of the projected application. Finally spiking micropollutants at higher concentrations does not alter the significance of the findings as long as the background constituents represent more than 85% of the total scavenging rate.
authors: Cranfield University, Bedfordshire MK43 0AL, UK.
authors: Olivier
authors: O
authors: Autin
authors: Julie
authors: J
authors: Hart
authors: Peter
authors: P
authors: Jarvis
authors: Jitka
authors: J
authors: MacAdam
authors: Simon A
authors: SA
authors: Parsons
authors: Bruce
authors: B
authors: Jefferson
mesh_terms: D000079:Acetaldehyde / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry; D016166:Free Radical Scavengers / Q000032:analysis / Q000737:chemistry; D005618:Fresh Water / Q000737:chemistry; D006812:Humic Substances / Q000032:analysis*; D006861:Hydrogen Peroxide / Q000032:analysis / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D009994:Osmolar Concentration; D016877:Oxidants / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010316:Particle Size; D010575:Pesticides / Q000032:analysis / Q000737:chemistry*; D010782:Photolysis; D014025:Titanium / Q000032:analysis / Q000737:chemistry*; D014466:Ultraviolet Rays; D006113:United Kingdom; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry; D018508:Water Purification / Q000379:methods*
chemical_list: D016166:Free Radical Scavengers; D006812:Humic Substances; D016877:Oxidants; D010575:Pesticides; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; C002935:metaldehyde; D006861:Hydrogen Peroxide; D014025:Titanium; D000079:Acetaldehyde