Effect of Crosslinker Concentration on Polyacrylic Acid Hydrogel for H2S Adsorption: Molecular Dynamic Simulation Study

The safe and efficient removal of hydrogen sulfide (H2S) from natural gas is essential to prevent environmental hazards and equipment corrosion. This study investigates the influence of crosslinker concentration on the H2S adsorption performance of tetraethylenepentamine (TEPA) impregnated polyacrylic acid (PAA) hydrogels through a combination of experimental analysis and molecular dynamics (MD) simulations. The synthesized hydrogel samples were experimentally characterized using Fourier-Transform Infrared Spectroscopy (FTIR) to identify the functional groups. MD simulations were performed to optimize and equilibrate the molecular structures. Simulated X-ray diffraction (XRD) patterns were generated to analyze the structural characteristics of the models. Grand Canonical Monte Carlo (GCMC) simulations were used to investigate H2S adsorption under different temperatures and pressures. The results reveal that increasing the crosslinker concentration reduces the hydrogel’s H2S adsorption capacity (down to 1.5 mmol/g) by limiting available adsorption sites, restricting swelling, and negatively affecting TEPA distribution. Conversely, lower crosslinker concentrations enhance H2S uptake (up to 3 mmol/g) by promoting polymer chain flexibility and enabling more effective TEPA–H2S interactions. This integrated experimental and simulation study provides insight into the adsorption mechanisms of H2S, offering valuable guidance for the development of high-performance amine-impregnated polymer hydrogels for industrial gas purification applications.