Assessment of solar photocatalytic wastewater disinfection and microcontaminants removal by modified-allophane nanoclays based on TiO2, Fe and ZnO at laboratory and pilot scale

Allophane (ALPH) nanoparticles have been traditionally employed for in-situ decontamination of soil and sediments, water and industrial effluents as well as medical therapies. In contrast, their development for water purification has not been well investigated. This study assessed for the first time the capability of several modified ALPH nanoclays as potential photocatalysts for water disinfection and decontamination. Concentrations ranged from 0 to 200 mg L-1 of pristine ALPH, Fe-ALPH, TiO2-ALPH, Fe-TiO2-ALPH, Fe-ZnO-ALPH and ZnO-ALPH were evaluated at laboratory (200 mL) and pilot plant scale (10L-Compound Parabolic Collector, CPC), in demineralized water (DW) and actual urban secondary wastewater effluents (SW) under solar radiation. The photocatalytic efficiency was evaluated through the simultaneous monitoring of the inactivation of Escherichia coli and the removal of imidacloprid and sulfamethoxazole (Contaminants of Emerging Concern, CECs). The best simultaneous disinfection and decontamination performance (80 % & sum;CECs and > 5 Log Reduction Value (LRV) E. coli) was obtained for TiO2-ALPH both in DW and SW at 200 mg/L; while the higher disinfection capability (> 5 LRV in 30 min or 2.5 kJ/L of Q(UV)) was obtained with ZnO-ALPH. Both catalysts were then assessed in 10L-CPCs demonstrating the potential up-scaling of these friendly-photocatalytic materials for wastewater reclamation.