Interpenetrating Polymer Network Gels of SA-Al/PVA@ME for Selective Removal of Heat-Stable Salts from Monoethanolamine Solutions

The precise removal of heat-stable salts (HSS) from an amine solution remains a challenge where the current separation process can cause ineligible amine loss and decrease the CO2 capture efficiency. This work proposed an interpenetrating polymer network gel (SA-Al/PVA@ME) constructed with sodium alginate (SA), aluminum ions, and poly(vinyl alcohol) (PVA), followed by melamine encapsulation. The formulation of the adsorbent was optimized by orthogonal experiments, leading to an HSS adsorption capacity of 128.28 mg·g–1 in monoethanolamine solution. The encapsulation of melamine (ME) promoted its adsorption affinity for HSS with a slight decrease of capacity. The kinetics and isotherms studies verify the adsorption behavior, and the mechanism was revealed through Fourier transform infrared, Brunauer–Emmett–Teller, scanning electron microscopy–energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy analysis, suggesting the comprehensive effect of synergistic electrostatic interaction, ion exchange, coordination bonding, hydrogen bonding, and steric hindrance. The results suggest a new strategy to formulate adsorbents with high HSS removal efficiency and good selectivity over amine.