Herein, hydrophilic ZnO nanoparticles@calcium alginate composite has been prepared by embedding hydrophilic ZnO nanoparticles (NPs) into calcium alginate. The hydrophilic ZnO NPs within the composites can act as a killer of bacteria, while calcium alginate can remove the organic impurities due to its adsorption capacity, thus realizing the purification of water via sterilization and removal of organics. A water purifier based on the composite has been demonstrated, the aerobic bacterial counts of the contaminated water can be decreased from 2240 to 9 cfu mL-1, and the turbidity of the water is decreased to 0.51 NTU, which is below the maximum permissible of Guidelines for Drinking-water Quality designed by the World Health Organization. Sterilization mechanism studies show that the ZnO NPs can cause excessive oxidative stress in cells, inducing bacteria to produce large amounts of intracellular reactive oxygen species (ROS), which leads to the apoptosis of the bacteria.
Keywords: ZnO nanoparticles; calcium alginate; excessive oxidative stress; reactive oxygen species; sterilization; water purification.