Elimination of Escherichia coli in a Packed Column Containing Jujube Seed Kernel Granular Activated Carbon Coated With Silver Nanoparticles (Ag-NPs/GAC)

Abstract

This study aims to develop a filter material capable of inhibiting bacterial growth and eliminating microorganisms from filtered water. Granular activated carbon (GAC) was prepared from jujube seed kernels by a chemical activation method whereby the kernels were heated at 650°C for 3 h in the presence of varied concentrations of phosphoric acid (H3PO4) (1, 2 and 3 M). Silver nanoparticles (Ag-NPs) were prepared using the polysaccharide reduction method with AgNO3 at two concentrations (2 and 4 mmol). The Ag-NPs obtained were characterised by a UV–visible spectrophotometer, optical microscope and microorganism inhibition test. GAC was coated with Ag-NPs by impregnating it with a fixed concentration of Ag-NPs in a supersaturated solution. The resulting GAC and Ag-NPs/GAC were characterised using several methods (pH, point zero charge and FTIR). The leakage of Ag fixed on GAC was evaluated. The antimicrobial properties of the synthesised Ag-NPs/GAC were investigated using inhibition zone, impregnation and column techniques against E. coli. The best nanoparticle shape with a large reactive surface was obtained after treatment with 2 mmol of AgNO3. There was no leaching of Ag ions in the treated water after passage through the bed. Except for the GAC not impregnated with Ag-NPs, no E. coli CFU/mL was found in the filtered water obtained from Ag-NPs/GAC beds at all tested pHs after 2–3 days of operation.