Comparative study on antibacterial activities and removal of iron ions from water using novel modified sand with silver through the hydrothermal technique

The hydrothermal-calcination technique was used to modify raw sand with silver (Ag) at different weight percentages: 2%, 5%, and 10% using silver nitrate. The raw and sand-coated Ag nanoparticle samples were analyzed using various techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analysis. The antibacterial properties of the raw and modified sand samples were evaluated using the zone of inhibition test and the minimum inhibitory concentration (MIC) method. This study aims to determine the efficiency of sand-coated Ag nanoparticles in removing iron ions and bacteria, specifically Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), compared to raw sand. The results showed that the Ag content in the modified sand increased proportionally with the silver nitrate concentration. The modification of raw sand with 2% Ag nanoparticles resulted in a significant increase in surface area (85.78%), adsorption pore diameter (138%), and micropore volume (65.65%). The sand modified with 2% Ag exhibited a 31.29% higher removal efficiency and 14.6 mg/g greater adsorption capacity for iron ions than raw sand. A feed pH level between 4 and 10 was found to be optimal for iron removal efficiency (99.95%) using a 1.5 g/L sand-coated with 2% Ag. The maximum adsorption capacity of iron ions obtained in this study was 64 mg/g using sand-coated 2%Ag (dose = 0.2 g/L) at 24 °C in 4 h. Studies utilizing zone of inhibition and MIC methods revealed that the modified sand exhibits strong antibacterial properties against both Gram-positive and Gram-negative strains. In contrast, the raw sand shows no antibacterial activity. All sand-coated Ag nanoparticle samples achieved 100% growth inhibition at 72 µg/mL.