Amphiphilic hyper-crosslinked porous cyclodextrin polymer with high specific surface area for rapid removal of organic micropollutants

Amphiphilic hyper-crosslinked porous cyclodextrin polymer (PBCD-B-D) with a surface area of 1445 m(2) g(-1) was synthesized for rapid removal of organic micropollutants. Partially benzylated cyclodextrin was crosslinked with 4,4'-bis(chloromethyl)-1,1'-biphenyl and alpha,alpha'-dichloro-p-xylene by the Friedel-Crafts alkylation reaction. The hydrophilicity of the PBCD-B-D surface is modulated by controlling the number of hydroxyl groups on cyclodextrin. Benzylation reaction is more likely to occur at the C-2 and C-6 positions of cyclodextrin hydroxyl groups according to Gaussian computation. Four different water-soluble pollutants (3-phenylphenol, 2-naphthol, p-nitrophenol, and 4-chlorophenol) were selected for adsorption study. The adsorption rate of PBCD-B-D is extremely high, and the removal efficiency reaches above 95% in 1 min. For the adsorption of 3-phenylphenol and 2-naphthol, the rate constants of PBCD-B-D are 827-1187 and 396-413 times larger than those of granular activated carbon (GAC) and beta-cyclodextrin polymer crosslinked with epichlorohydrin (EPI-CDP), respectively. The adsorption capacity of PBCD-B-D is 2 and 4 times higher than that of GAC and EPI-CDP, respectively. The combination of cyclodextrin inclusion mechanism, hydrophobic attraction, and hydrogen bonding allows PBCD-B-D to adsorb both hydrophobic and hydrophilic pollutants. PBCD-B-D can be easily regenerated at room temperature using methanol as eluent. In addition, PBCD-B-D showed excellent adsorption performance towards mixed pollutants at environmentally relevant concentrations. According to the thermodynamic study, the adsorption of organic compounds onto PBCD-B-D belongs to physical adsorption and is spontaneous. PBCD-B-D is a potential novel adsorbent for water treatment owing to its excellent adsorption performance, low cost, and good regenerability.