Adsorption of catechol on a weak-base anion exchanger prepared by a novel template-induced method: Batch tests

In this work, a weak-base anion exchanger (TIR) was synthesized through a novel simplified strategy based on the principle of surface imprinting polymer (SIP) to selectively remove the catechol from aqueous solution. The chloromethylated polystyrene beads (CMPS), diethylamine and catechol were employed as the carrier, amination reagent and template respectively in the study. The N2 adsorption-desorption isotherms and Fourier-transform infrared spectroscopy (FT-IR) indicated that the functional group had been successfully grafted onto the CMPS, which directly constructed template-induced adsorption sites in the pore structure. When the solution was neutral, both TIR and CR could reach the maximum adsorption capacity of catechol. Fitting results of adsorption isotherms suggested that catechol adsorption on the TIR surface might occur in a monolayer manner and was endothermic. The maximum adsorption capacity of TIR (1.60 mmol/g) fitted by Langmuir model was almost twice than that of conventional resin (CR), while the kinetic properties of TIR did not decrease significantly. In the salt (NaCl or Na2SO4) concentration range of 20 to 80 g/L, the adsorption capacity of TIR was about 10% to 50% higher than that of CR. For resorcinol and quinol, as two competitors in binary system, the selectivity coefficients (α) of TIR to catechol were 1.49 and 5.83, respectively, which were significantly higher than those of CR (0.72 and 1.58, respectively). Adsorption behaviors in different solvents and FT-IR spectra after adsorption verify that the main interactions between TIR and catechol were electrostatic attraction, hydrogen bonding, hydrophobic interaction and π-π interaction. The regeneration experiment and FT-IR spectrum after desorption showed that the structure of TIR was stable before and after desorption, and the desorption rate could reach more than 90%. This study showed TIR had a superior selective adsorption capacity for catechol and provided a facile strategy to prepare selective adsorbent for the target phenolic pollutant.