Development of nanosilver-coated geopolymer beads (AgGP) from fly ash and baluko shells for antimicrobial applications

Abstract

Geopolymers are a class of materials formed from treating alumina (Al 2 O 3 ) and silica (SiO 2 ) containing materials with an alkali activator. They are most notable for being environmentally-friendly substitutes to Ordinary Portland Cement; however, recent findings have shown that they may have potential as support matrices for antimicrobial agents such as nanosilver, particularly with the addition of foaming agents and setting time accelerators. In this study, nanosilver-coated geopolymer beads (AgGP) were made from fly ash (FA), calcined Baluko shells or pen shells (BS), and hydrogen peroxide (H). Addition of BS and H reduces the setting time and increases the porosity of the geopolymer beads. The beads were then dipped in AgNO 3 and NaBH 4 respectively to provide the nanosilver coating. When immersed in water, a controlled release of silver ions leaches out from the beads, neutralizing any bacteria in the water. It was found that the AgGP removed as much as 99.96% of the E. coli in a suspension originally at 105 CFU/mL.