Bismuth phosphinato incorporated antibacterial filter paper for drinking water disinfection

Abstract Lack of safe drinking water is a major concern, mainly in developing countries. Consequently, there is a significant need for affordable technologies to provide clean drinking water. In this paper, two approaches for drinking water disinfection using nanocellulose and the antimicrobial compound phenyl bis-diphenylphosphinato bismuth (III) complex are studied. The first approach investigates the deactivation of bacteria when contaminated water percolates through a filter paper with a microfibrillated cellulose (MFC) coating containing Bi-complex. Antibacterial activity was studied by filtering bacterial broth with a Gram-positive pathogen Staphylococcus aureus as a test strain and measuring live bacteria in the filtrate. The filter composites did not show any sign of instantaneous killing of bacteria, irrespective of the Bi-complex loading or base paper substrate. However, the effluent demonstrated drastic reduction in bacterial population after resting at 37 °C. Bacteria were completely eradicated 24 h after passing through 5 wt% and 10 wt% Bi-coated filters. If also active against locally important drinking water contaminants, this approach could be used for purification of storage water. The second approach uses a Bi-complex loaded nanofibrillated cellulose (NFC) membrane. Herein, complete and immediate exclusion of bacteria was achieved in the NFC membrane when bacterial broth was passed through it at 1 bar. The 2.5 wt% Bi-loaded membrane could significantly minimise the risk of biofilm formation, even after 4 days of contact with bacterial broth. The Bi-complex concentration in the filtrate (130.6 ± 1.9 ppb) from the 2.5 wt% Bi-loaded microfilter was shown to be non-toxic to murine fibroblast cells. This study outlines the proof of concept of two sustainable prototypes for stored or immediate drinking water purification, but the approach would need to be extended to a broader range of relevant contaminating pathogens of drinking water to fully understand its utility.