A resource-efficient and portable nanotechnology-enabled disinfection system: Performance studies and a novel strategy to recycle spent material

Abstract

The paper describes developing a point-of-use disinfection system consisting of a film-forming nanocomposite packed in a nylon sachet. The composite film consists of silver nanoparticles embedded in a matrix containing chitosan, reduced graphene oxide, and tannic acid. The long-term ability of the portable sachet bag to release silver ions and disinfect surface and groundwater is demonstrated. The sachet bag's disinfection potential is demonstrated by taking Escherichia coli MTCC 443 as the model microorganism. The system produced a complete and consistent 3 log10 reduction of E. coli over multiple cycles of use. The paper also describes a green recycling approach to utilise spent composite film and prevent AgNPs from entering the waste stream. The spent nanocomposite film is transformed into a concrete micro-crack sealant through a soft chemical route. The sealant's ability to plug micro-cracks in concrete is demonstrated, and the mechanism of sealant interaction with concrete is proposed. The sealant can fill cracks and solidify in an alkaline environment. The concrete cube specimens repaired with sealant showed enhanced compressive strength compared to the residual concrete cube specimens. The possible leaching of residual silver from the sealant in concrete is investigated via toxicity characteristic leaching procedure analysis. The study demonstrates that silver leaching is negligible (< 0.05 mg/L) and well below the permissible limit of 5 mg/L.