Preparation of modified silica gel supported silver nanoparticles and its evaluation using zone of inhibition for water disinfection

In this work, preparation of modified silica gel supported silver nanoparticles and its evaluation using zone of inhibition for water disinfection were investigated. The silica contents of the teff straw [TS] and teff straw ash [TSA] are 5.92 and 92.21 %, respectively. The calcinated TS ash at 700 °C was mixed with NaOH solution. The solution is then neutralized with HCl solution and then gel formation using the sol gel method. The silica gel yield was recorded and characterized. The SG with major silica functional group, amorphous structure, high porosity from the morphology, high surface area of 807.163 m²/g, pore volume of 0.34 cm³/g, pore diameter of 1.70 nm and silica gel purity of 99.39 % were achieved at a calcination temperature of 700 °C. It is then; further modified using trimethylchlorosilane (TMCS)/ethanol/hexane at different volumetric ratio and the resulting product is modified silica gel (MSG). MSG has excellent hydrophobic properties that have been required during water treatment. In this method, MSG with a major silica functional group, well ordered structure due to the TMCS modifier, maximum surface area of 510.40 m²/g was achieved at volumetric ratio of 0.25:0.25:1 of TMCS/ethanol/hexane, respectively. Then, MSG supported AgNPs (MSG-AgNPs) was prepared by mixing different concentrations of AgNPs-MSG and characterized. The MSG-AgNPs have shown AgNPs on the surface of MSG from the EDX result, different absorbance, pore from the morphology, with a maximum surface area of 475.0 m²/g was obtained at 1.5 mM of AgNPs concentrations. The performance of MSG-AgNPs was evaluated using zone of inhibition measurement and batch disinfection studies against E. coli and S. aureus. At 1.5 x 10⁸ CFU/mL initial bacterial concentrations, the maximum inhibition zone diameter was 12.80 and 14.30 mm for E. coli and S. aureus, respectively.