Intensifying heterogeneous TiO 2 photocatalysis for bromate reduction using the NETmix photoreactor.

This work focuses on the intensification of BrO3 - (200 μg L-1 ) reduction by TiO2 -assisted heterogeneous photocatalysis, using the NETmix mili-photoreactor illuminated by UVA light-emitting diodes (UVA-LEDs). The mili-photoreactor was assembled in two configurations: i) catalyst deposition on the channels and chambers of a back stainless steel slab (SSS) and ii) catalyst deposition on the front borosilicate glass slab (BGS), allowing the study of front-side (FSI) and back-side (BSI) illumination mechanisms, respectively. The BrO3 - reduction rate in aqueous solution was assessed as a function of: i) pH; ii) dissolved oxygen (DO); iii) addition of formic acid (CH2 O2 ) as a sacrificial agent (SA); iv) photocatalyst film thickness; v) illumination mechanism; vi) irradiation intensity; vii) temperature; and viii) water matrix. Higher BrO3 - reduction rates were observed using the FSI mechanism and lower pH values. Nitrogen injection (to eliminate DO) did not significantly improve the reaction rate and the addition of CH2 O2 had a negative effect at pH 6.5. Neither temperature nor irradiance increase showed a considerable improvement on the reduction rate. Moreover, TiO2 film remains stable for at least 13 consecutive reactions without significant catalyst leaching. The chemically pre-treated fresh water (FW) matrix negatively affected the reaction rate when compared with the synthetic water (SW), under the best operational conditions (SSS: pH = 5.5, 287 mg of TiO2 , 25 °C, SA absence, [DO] = 232-263 μM). This was associated with the presence of both inorganic and organic matter at much higher concentrations than BrO3 - . Notwithstanding, heterogeneous TiO2 photocatalysis, using the NETmix mili-photoreactor, was successfully applied to fresh water, achieving [BrO3 - ] < 10 μg L-1 (guideline value) after 2-hour reaction.