Loading of Silver (I) Ion in L-Cysteine-Functionalized Silica Gel Material for Aquatic Purification

The L-cysteine-functionalized silica (SG-Cys^-Na⁺) matrix was effectively loaded with silver (I) ions using the batch sorption technique. Optimal Ag(I) loading into SG-Cys^-Na⁺ reached 98% at pH_i = 6, 80 rpm, 1 mg L^-1, and a temperature of 55 °C. The Langmuir isotherm was found to be suitable for Ag(I) binding onto SG-Cys^-Na⁺ active sites, forming a homogeneous monolayer (R² = 0.999), as confirmed by FTIR spectroscopy. XRD analysis indicated matrix stability and the absence of Ag₂O and Ag(0) phases, observed from diffraction peaks. The pseudo-second-order model (R² > 0.999) suggested chemisorption-controlled adsorption, involving chemical bonding between silver ions and SG-Cys^-Na⁺ surface. Thermodynamic parameters were calculated, indicating higher initial concentrations leading to increased equilibrium constants, negative ΔG values, positive ΔS values, and negative ΔH. This study aimed to explore silver ion saturation on silica surfaces and the underlying association mechanisms. The capability to capture and load silver (I) ions onto functionalized silica gel materials holds promise for environmental and water purification applications.