Efficient degradation of pharmaceutical micropollutants in water and wastewater by FeIII-NTA-catalyzed neutral photo-Fenton process.

Ferric-nitrilotriacetate complex (FeIII-NTA) has been adopted to catalyze the photo-Fenton degradation of emerging pharmaceutical micropollutants in water and wastewater at neutral pH. The generation of hydroxyl radicals (HO) in UVA/FeIII-NTA/H2O2 was identified by using electron spin resonance (ESR) trapping technique. The effects of critical parameters (e.g., NTA:FeIII molar ratio, FeIII-NTA and H2O2 dosages) on the steady-state HO concentrations were studied in terms of the degradation of carbamazepine (CBZ, as a model compound) in Milli-Q water. In addition, the degradation of pharmaceuticals mixtures (including CBZ, crotamiton (CRMT) and ibuprofen (IBP)) in wastewater effluents from a biological aerated filter (BAF) by UVA/FeIII-NTA/H2O2 was studied in continuous-flow mode. The results showed that the efficacies of FeIII-NTA in catalyzing photo-Fenton degradation of pharmaceuticals in wastewater effluents were comparable to those obtained by FeIII-ethylenediamine-N,N'-disuccinic acid (FeIII-EDDS), and far exceeded other FeIII-L complex (e.g., citric acid, malonic acid, oxalic acid and tartaric acid). More than 92% degradation efficiencies of CBZ, CRMT and IBP were obtained in continuous-flow mode under the given conditions of 0.178 mM FeIII-NTA (1:1), 4.54 mM H2O2, UVA intensity 4.05 mW cm-2, hydraulic retention time (HRT) 2 h, influent pH 7.6 (±0.2) and temperature 20 °C. The results presented herein suggest that FeIII-NTA-catalyzed neutral photo-Fenton reaction can be an alternative tertiary process for the treatment of pharmaceutical micropollutants in secondary wastewater effluents.