Synergetic action of bicarbonate ions on chitosan-silver nanocomposite leading to enhanced water disinfection

Abstract

In the present study, we first report the synergy between bicarbonate ions and silver ions released from a nanocomposite comprising silver nanoparticles, humic acid, and chitosan. The study reveals that bicarbonates, a common anion in water, can significantly enhance silver ions' disinfection ability. The synergy between bicarbonate and silver ions helps improve the disinfection kinetics and reduce the critical concentrations of silver ions required to produce satisfactory biocidal action. A detailed investigation of the disinfection mechanism reveals that the bicarbonates disturb the transmembrane potential gradient (DpH), weaken the proton motive force of microbes (E. coli), and enable an increased penetration of Ag+ into the cell, resulting in enhanced production of reactive oxygen species and cell damage. This synergetic effect could help reduce the costs and the concentration of Ag+ required for disinfection and their associated risks. In addition, cytotoxic studies were performed to understand the influence of residual silver ions and bicarbonate interaction on human health. The study against human cell lines (HaCaT) confirms that AgNC-treated water is safe for consumption. However, a slight reduction in viability is observed at higher concentrations of bicarbonates in combination with silver ions. Based on the study, we believe that a disinfection system that allows the controlled release of silver ions and bicarbonate would be more efficient and sustainable than a conventional supported silver nanoparticle-based disinfection system.