Acrylate-functionalized hyper-cross-linked polymers: Effect of the porogens in the polymerization on their porosity and adsorption from aqueous solution

Abstract

The porogens are the key components in the polymerization process, they do not participate in the polymerization reaction, but play a very important role in the pore structure of the synthetic polymers. Herein, o-xylene and paraffin were applied as the porogens and three acrylate-functionalized hyper-cross-linked polymers were fabricated according to the suspension polymerization and Friedel-Crafts reaction. The Brunauer-Emmett-Teller (BET) surface area (SBET) and pore volume (Vtotal) of the initial copolymers were nearly zero, while the Friedel-Crafts reaction resulted in a steep increase of the SBET and Vtotal. In particular, the resultant polymer, namely, HCP-PDVE-(Xy), using o-xylene as the porogen had the greatest SBET and Vtotal (1126 m2/g and 0.958 cm3/g, respectively), while the SBET and Vtotal of HCP-PDVE-(Lp) using paraffin as the porogen were the lowest (487 m2/g and 0.299 cm3/g, respectively). Meanwhile, HCP-PDVE-(Xy + Lp) using 50 % of o-xylene and 50 % of paraffin as the mixed porogens possessed the intermediate data. More importantly, HCP-PDVE-(Xy) had the hierarchical micro- and meso-porous distribution, while predominant micro-pores were distributed for HCP-PDVE-(Lp) and HCP-PDVE-(Xy + Lp). The equilibrium adsorption indicated that HCP-PDVE-(Xy + Lp) exhibited the largest equilibrium capacity (qe) to phenol while HCP-PDVE-(Xy) owned the largest qe to Rhodamine B. The phenol adsorption was subjected to the micro-pore filling mechanism while the high SBET, Vtotal and the hierarchical micro-/meso-pores were favorable for the adsorption of Rhodamine B. The kinetic adsorption revealed that HCP-PDVE-(Lp) and HCP-PDVE-(Xy + Lp) (20 min) required much less time than HCP-PDVE-(Xy) (50 min) to reach the equilibrium for the phenol adsorption, and the micro-pore diffusion model characterized the kinetic data very well. The dynamic adsorption indicated that the dynamic capacity of phenol adsorbed on HCP-PDVE-(Xy + Lp) was 160.2 mg/g, very close to the qe (163.6 mg/g) in the equilibrium adsorption.