Titanium dioxide nanofibers integrated stainless steel filter for photocatalytic degradation of pharmaceutical compounds.

A photocatalytically active stainless steel filter (P-SSF) was prepared by integrating electrospun TiO2 nanofibers on SSF surface through a hot-press process where a poly(vinylidene fluoride) (PVDF) nanofibers interlayer acted as a binder. By quantifying the photocatalytic oxidation of cimetidine under ultraviolet radiation and assessing the stability of TiO2 nanofibers integrated on the P-SSF against sonication, the optimum thickness of the TiO2 and PVDF layer was found to be 29 and 42 µm, respectively. At 10L/m(2)h flux, 40-90% of cimetidine was oxidized when the thickness of TiO2 layer increased from 10 to 29 µm; however, no further increase of cimetidine oxidation was observed as its thickness increased to 84 µm, maybe due to limited light penetration. At flux conditions of 10, 20, and 50 L/m(2) h, the oxidation efficiencies for cimetidine were found to be 89, 64, and 47%, respectively. This was attributed to reduced contact time of cimetidine within the TiO2 layer. Further, the degradation efficacy of cimetidine was stably maintained for 72 h at a flux of 10 L/m(2) h and a trans-filter pressure of 0.1-0.2 kPa. Overall, our results showed that it can potentially be employed in the treatment of effluents containing organic micropollutants.

Phototransformation of wastewater-derived trace organic contaminants in open-water unit process treatment wetlands.

Open-water cells in unit process treatment wetlands can be used to exploit sunlight photolysis to remove trace organic contaminants from municipal wastewater effluent. To assess the performance of these novel systems, a photochemical model was calibrated using measured photolysis rates for atenolol, carbamazepine, propranolol, and sulfamethoxazole in wetland water under representative conditions. Contaminant transformation by hydroxyl radical ((•)OH) and carbonate radical ((•)CO3(-)) were predicted from steady-state radical concentrations measured at pH values between 8 and 10. Direct photolysis rates and the effects of light screening by dissolved organic matter on photolysis rates were estimated using solar irradiance data, contaminant quantum yields, and light screening factors. The model was applied to predict the land area required for 90% removal of a suite of wastewater-derived organic contaminants by sunlight-induced reactions under a variety of conditions. Results suggest that during summer, open-water cells that receive a million gallons of water per day (i.e., about 4.4 × 10(-2) m(3) s(-1)) of nitrified wastewater effluent can achieve 90% removal of most compounds in an area of about 15 ha. Transformation rates were strongly affected by pH, with some compounds exhibiting faster transformation rates under the high pH conditions associated with photosynthetic algae at the sediment-water interface and other contaminants exhibiting faster transformation rates at the circumneutral pH values characteristic of algae-free cells. Lower dissolved organic carbon concentrations typically resulted in increased transformation rates.