Water microbial disinfection via supported nAg/Kaolin in a fixed-bed reactor configuration

In this paper we have investigated and demonstrated the antimicrobial capabilities of nano-silver-4 wt%-kaolin (nAg-4-Kn) composite supported on borosilicate glass beads (BGB). Tests have been conducted in a fixed bed reactor on effluent from the secondary clarifier of a conventional wastewater treatment plant (WWTP) in Abu Dhabi, United Arab Emirates (UAE). The prepared BGB with immobilized nAg-4-Kn (nAg-4-Kn/BGB) were characterized using the RAMAN spectroscopy, TEM equipped with EDX and Focus Ion Beam Scanning Electron Microscope (FIB-SEM) techniques. The rate of disinfection was assessed through Luria-Bertani (LB)-agar plate cell counting technique. The results showed complete disinfection after few hours, which was preserved even after several days in repeated runs. The nAg-4-Kn/BGB was reused, demonstrating that the immobilization of nAg-4-Kn was stably achieved, and the activity and integrity of the composites on the BGB were preserved. First order disinfection kinetic constants were estimated to be 2.76 cm h⁻¹ and 2.56 cm h⁻¹ in two consecutive runs. Analyses of the beads after the experiments showed minor losses of nAg from the kaolin matrix thereby corroborating reusability of these materials.