RESUMO
This work highlights the performance of an ultrafiltration ceramic membrane as photocatalyst support and oxidant-catalyst/water contactor to promote sulfate radical advanced oxidation processes (SR-AOPs). Peroxydisulfate (PDS) activation mechanisms include photolysis (UVC irradiation) and chemical electron transfer (TiO2-P25 photocatalysis). The photoreactor is composed of an outer quartz tube (the "window"-radiation entrance to the reactor) and an inner tubular ceramic ultrafiltration membrane, where the catalyst particles (TiO2-P25) are immobilized on the membrane shell-side. PDS stock solution is fed by the lumen side of the membrane, delivering the oxidant to the catalyst particles and to the annular reaction zone (ARZ), being the catalyst and PDS activated by UV light. The design facilitates controlled radial slip of PDS into the catalyst surface and to concurrent water to be treated, flowing with a helix trajectory in the ARZ. Under continuous mode operation, with an UV fluence of 45 mJ cm-2 (residence time of 4.6 s), the UVC/PDS/TiO2 system showed the best removal efficiency for two specific endocrine disrupting chemicals, 17ß-estradiol (E2) and 17α-ethinylestradiol (EE2), spiked (100 µg L-1 each) in demineralized water and urban wastewater after secondary treatment.
Assuntos
Poluentes Químicos da Água , Purificação da Água , Cerâmica , Estradiol/análise , Etinilestradiol/análise , Oxidantes , Oxirredução , Sulfatos , Ultrafiltração , Raios Ultravioleta , Água , Poluentes Químicos da Água/análiseRESUMO
This work aims to integrate several hydrogen peroxide (H2O2) activation mechanisms, photolysis (UVC irradiation), chemical electron transfer (TiO2-P25 photocatalysis), and reaction with TiO2-P25 in dark conditions, for reactive oxygen species (ROS) generation towards the removal of contaminants of emerging concern (CECs), in a single unit operated in continuous-flow mode. An H2O2 stock solution is fed by the lumen side of a tubular ceramic membrane, delivering the oxidant to the (i) catalyst immobilized in the membrane shell-side and (ii) annular reaction zone (ARZ, space between membrane shell-side and outer quartz tube) where CECs contaminated water flows with a helix trajectory, being activated by UV light provided by four lamps placed symmetrically around the reactor. First, the effect of several parameters in the removal of a CEC target molecule, amoxicillin (AMX), was evaluated using a synthetic solution ([AMX]inlet = 2.0 mg L-1): (i) light source (UVA or UVC radiation), (ii) H2O2 dose, (iii) H2O2 injection method (radial permeation vs. upstream injection), and (iv) number of TiO2-P25 layers deposited on the membrane. The UVC/H2O2/TiO2 system with radial addition of H2O2 (20 mg L-1) and 9-TiO2-P25 layers provided the highest AMX removal efficiency (72.2 ± 0.5%) with a UV fluence of 45 mJ cm-2 (residence time of 4.6 s), due to the synergic effect of four mechanisms: (i) AMX photolysis, (ii) H2O2 photocleavage, (iii) TiO2-P25 photoactivation, and (iv) chemical reactions between H2O2 and TiO2-P25. The urban wastewater matrix showed a negative effect on AMX removal (~44%) due to the presence of ROS scavengers and light-filtering species.