Removal of phenols from aqueous solution by XAD-4 resin

The experiments on the adsorption of phenols from aqueous solution by Amber lite XAD-4, a polystyrene-divinylbenzene resin without functional group, we re carried out under different conditions. The phenols studied in this rese arch include 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2-n itrophenol, 2,4-dinitrophenol, 2-methylphenol, and 2,4-dimethylphenol. The experimental observations indicate that adsorption behavior of various phen ols by XAD-4 resin could be described by either Langmuir or Freundlich mode ls. The removals of phenols by XAD-4 resin for solutions of different pH va ried significantly and can be explained by the species distribution of phen ols in aqueous solutions. Phenols were effectively removed by XAD-4 resin a t acidic conditions where the presence of molecular phenol species dominate s. The removal decreased sharply for alkaline solutions where the negativel y-charged ionic species is the dominant phenol species. The proposed adsorp tion equilibrium model adequately describes the sorption behavior of phenol s by XAD-4 resin. The presence of functional groups on the benzene ring of various phenols plays an important role on the extent of adsorption. The re movals of phenols by adsorption were found to correlate with the octanol/wa ter partition coefficients of various phenol compounds. (C) 2000 Elsevier S cience B.V. All rights reserved.