Development of Cellulose Filter Papers Modified with ZnO-Based Nanoparticles to Instantly Disinfect Water with No Need for Energy

Filters with large pore sizes, such as microfiltration (MF), have gained attraction for the development of gravity-driven point-of-use (POU) technologies to supply safe water to people, suffering from a lack of access to safe drinking water. In this study, cost-effective commercial cellulose filter papers were coated with cationic polymers polydopamine (PDA), polyethyleneimine (PEI) for entrapping bacteria, and different antibacterial ZnO-based nanoparticles, including ZnO, ZnO/MPA and ZnO/CS/Ag2O. The antibacterial activities of the nanoparticles were evaluated to show synergistic effects (4 times stronger than ZnO nanoparticles). The effects of the surface modification and the number of sheets of paper on the flow rate and the bacterial removal efficiency were studied. The results showed that although the modified papers have a lower flow rate (from 25 to 35%) than the pristine papers, the modified papers can filter ~ 91% to 99.92% of E. coli, which can meet the WHO standards. Furthermore, the released Zn and Ag in the filtrate were below the WHO’s limits. Therefore, the modified filters can be recommended for gravity-driven POU technology for water disinfection, which is in demand in low- and middle-income countries.