Adsorption of naphthalene onto macroporous and hypercrosslinked polymeric adsorbent: Effect of pore structure of adsorbents on thermodynamic and kinetic properties

Polymeric adsorbents have been widely studied for the removal of organic pollutants from waste streams. In this research, a hypercrosslinked polymeric adsorbent (NDA-150) and a macroporous polymeric adsorbent (XAD-4), which have the same matrix of poly(styrene-divinylbenzene) and similar surface area, were chose as model adsorbents to investigate their adsorption characteristics. The adsorption isotherms and kinetics of naphthalene onto two adsorbents from aqueous solutions were investigated. The equilibrium data were correlated with Polanyi–Manes–Dubinin equation, and the adsorption enthalpy changes (ΔHmeas) were determined. The good fits of Polanyi–Manes–Dubinin equation and high-exothermic adsorption enthalpies indicated that micropore filling was involved during the adsorption of naphthalene onto two adsorbents. The superior adsorption capacity of hypercrosslinked adsorbent compared to macroporous adsorbent was mainly due to its larger micropore volume. The adsorption of naphthalene onto two polymeric adsorbents was a pseudo-second-order process, controlled by intra-particle diffusion. The kinetic data also demonstrated that the adsorption rate of macroporous adsorbent (XAD-4) was faster than that of hypercrosslinked adsorbent (NDA-150) because it has more suitable porous structure for transporting the adsorbate into the adsorption sites.