Enhanced bacterial inactivation by activated carbon modified with nano-sized silver oxides: Performance and mechanism

In this study, nano-sized silver oxides were loaded on activated carbon (nAg 2 O/AC) through a facile impregnation-calcination method for enhanced bacterial inactivation from drinking water , in which Escherichia coli ( E. coli ) was used as target bacteria. XRD and SEM characterization confirmed that nano-sized Ag 2 O particles (50–200 nm) were successfully prepared and uniformly distributed on the surfaces and pores of AC. Due to the structural reducing groups of AC, surface-bound Ag(I) was partially converted to Ag in the nAg 2 O matrix and the resulted Ag could sterilize E. coli directly. More importantly, surface-bound Ag could catalyze O 2 and H 2 O to generate reactive oxygen species (ROS) for oxidation sterilization, thus significantly enhanced the inactivation efficiency from 0.8 log 10  CFU/mL (nAg 2 O control) and 0.2 log 10  CFU/mL (AC control) to 6.0 log 10  CFU/mL in the nAg 2 O/AC system. The inactivation process was highly pH-dependent, and neutral pH was favorable for sterilization. A sterilization efficiency of 5.2 log 10  CFU/mL could still be achieved after 5 running cycles, indicating stable sterilization performance of nAg 2 O/AC. In addition, the nAg 2 O/AC also exhibited excellent renewability since a sterilization efficiency of 5.8 log 10  CFU/mL was obtained after nAg 2 O being stripped and reloaded on the AC. These results demonstrated that nAg 2 O-modified AC is an efficient material for sterilization in water treatment .