Chemical modification of Amberlite XAD-4 by carbonyl groups for phenol adsorption from wastewater

Two carbonyl groups modified XAD-4 resins (XAD-4-I and XAD-4-II) were synthesized by chemically modifying Amberlite XAD-4 with carbon tetrachloride and benzoyl chloride according to the Friedel-Crafts reaction. After the chemical modification, the Brunauer-Emmet-Teller (BET) surface area and pore volume of the resins increased about 50% while their median pore size remained constant. More importantly, the modified resins adsorbed about 20% more phenol from aqueous solutions than the original XAD-4 at 298, 308 and 318. K, respectively; and the modified resins could be used directly in water without pre-wetting. The Freundlich and Sips models fitted the isotherm data better than the Langmuir model. Analysis of isosteric adsorption enthalpy indicated that XAD-4 has a more heterogeneous surface than the modified resins. Adsorption kinetics data suggested that the three resins could reach equilibrium within 1. h, and the pseudo-first-order and pseudo-second-order rate models could describe the kinetic data effectively. At a phenol feed concentration of 574.0. mg/L, the dynamic adsorption capacities of XAD-4, XAD-4-I and XAD-4-II were measured to be 80.6, 94.8 and 93.6. mg/g, respectively. Desorption experiments showed that the used resins could be regenerated completely by a 50% (v/v) ethanol aqueous solution.