Enhanced adsorption capacity and selectivity towards salicylic acid in water by a cationic polymer functionalized 3-D ordered macroporous adsorbent

Abstract

3-D ordered macroporous (3DOM) materials have exhibited advantages in the adsorption field. Their monodisperse macropores undergo facile modification, and the interconnected cavities enhance accessibility to the active sites, while the short diffusion path of the thin pore walls accelerates material exchange. A 3DOM material can increase the number of adsorption sites by the grafting of a polymer chain with functional groups from the pore wall of the 3DOM resin. In this study, different amounts of the cationic polymer poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) were grafted from the pore wall of a 3DOM cross-linked polystyrene (3DOM CLPS-g-PDMAEMA) via surface-initiated atom transfer radical polymerization (SI-ATRP) and salicylic acid (SA) was employed as the model adsorbate. PDMAEMA chains can adopt a more extended conformation in water. Therefore, the adsorption capacity increases with the grafted amount due to the increasing number of adsorption sites and the extended chain conformation. The 3DOM CLPS-g-PDMAEMA exhibits a very high adsorption capacity towards SA (390 mg g⁻¹ when the initial concentration of SA is 500 mg L⁻¹) which is even higher than that of activated carbon. Moreover, the 3DOM adsorbent also exhibits a high adsorption selectivity between SA and phenol, and the selectivity coefficient for SA reaches 45.8 in the presence of phenol. The 3DOM adsorbent is also reusable and can be regenerated by sodium hydroxide solution. The results of fifteen adsorption–desorption cycles show that all the adsorption capacities maintain above 85% of the original SA loading capacity. We envision that novel 3DOM polymeric adsorption will play a significant role in developing a new generation adsorbent.