The Adsorptive Power of Nylon–Gelatin–Hematite Composite: Study on NaCl Solution Adsorption Through Equilibrium, Kinetic, and Thermodynamic Approach

The development of composite adsorbent materials is a promising strategy for saline water treatment. In this study, a nylon–gelatin–hematite composite with a porous structure was investigated for NaCl ion removal. The porous matrix and functional groups on the polymer and hematite surfaces facilitated Na+ and Cl− adsorption through electrostatic interactions and surface adsorption mechanisms. Adsorption performance was evaluated using a batch method with variations in adsorbent dosage, contact time, and temperature. Functional groups were confirmed by Fourier-transform infrared (FTIR) spectroscopy. Adsorption performance was evaluated through measurements of salinity, total dissolved solids, and electrical conductivity. The adsorption behavior was examined through equilibrium, kinetic, and thermodynamic analyses to elucidate the underlying mechanism and efficiency. The FTIR spectra confirmed characteristic vibrations of nylon, gelatin, and hematite, indicating the successful formation of the composite. Equilibrium data fitted well with the Freundlich isotherm models (R2 > 0.99) at dosage variation, suggesting favorable multilayer adsorption on heterogeneous surfaces. The maximum adsorption capacity qmax reached 1.626 mg/g. Kinetic studies revealed that the adsorption process followed a pseudo-first-order model, indicating a dominant physisorption mechanism. Negative Gibbs free energy values (ΔG = -1.905 to -2.139 kJ/mol) confirmed the spontaneous adsorption process.