Phenol adsorption on α,α'-dichloro-p-xylene (DCX) and 4,4'-bis(chloromethyl)-1,1'-biphenyl (BCMBP) modified XAD-4 resins from aqueous solutions

The commercial Amberlite XAD-4 resin was post-crosslinked by two crosslinking reagents, α,α'-dichloro-p-xylene (DCX) and 4,4'-bis(chloromethyl)-1,1'-biphenyl (BCMBP) through the Friedel-Crafts reaction and two post-crosslinked resins named DCX and BCMBP modified resins were prepared in this study. Characterization of the two modified resins indicated that DCX and BCMBP were connected on the surface of XAD-4 successfully and the pore diameter distribution of the modified resins was transferred from 2 to 14. nm (XAD-4) to a narrower micro/mesopore region (1-9. nm) and a large amounts of micropores were emerged for the two modified resins. Phenol adsorption experiments showed that the equilibrium adsorption capacity on the two modified resins was greatly enhanced due to emergence of the large number of micropores and the equilibrium adsorption isotherms could be well fitted by the Freundlich equation. The surface energy heterogeneity of the resins could be described as a function of the isosteric adsorption enthalpy and the tested three resins exhibited different surface energetic heterogeneity patterns. Both of the pseudo-first-order and pseudo-second-order rate equations could characterize the kinetic data of phenol adsorption on XAD-4 while only the pseudo-second-order rate equation was appropriate for the modified resins and the micropore diffusion models could describe the kinetic data on the modified resins rather than XAD-4. The dynamic adsorption capacity of phenol on XAD-4, DCX and BCMBP modified XAD-4 resins were predicted to be 80.6, 97.5 and 127.0. mg/g dry resin, respectively, which were very close to the equilibrium adsorption capacity in the batch experiments and the resin column could be completely recovered by less than 7 BV of 75% of ethanol aqueous solution (w/v).