Adsorption of phenol, bisphenol A and nonylphenol ethoxylates onto hypercrosslinked and aminated adsorbents

The presence of phenolic compounds in aquatic environments poses potential human health and ecological risks. In this study, we evaluated porous resins as adsorbents for removal of three compounds, phenol, bisphenol A and nonylphenol ethoxylates from aqueous solutions. The adsorption isotherms were well fitted by the Langmuir equation, and the strength of the adsorption was affected by the properties of polymeric adsorbent (surface area, pore size, functional group and matrix) and phenolics (distribution coefficient K-OW, adsorption coefficient K-d, water solubility S-w and dissociation constant pK(a)). Four possible interactions, i.e., hydrophobic effect, pi-pi bonds, hydrogen bonding and electrostatic interaction, were discussed to explore the underlying mechanism in the adsorption affinity of phenol and BPA. Hydroxyl on the aromatic rings strengthened the interactions between phenol and aminated polymeric adsorbent and thus the adsorption affinity. Adsorption of NPEO10 to polymeric adsorbents was dominated by pore size and molecular morphology, even on the aminated polymeric adsorbents (MN-100, MN-150). The results from thermodynamic analysis show that the adsorption of BPA and NPEO10 by polymeric adsorbents was thermodynamically favorable and generally endothermic whereas the adsorption process of phenol was exothermic. These results help us better understand the adsorption behavior and mechanism of phenolic compound onto carbon-based adsorbent. (C) 2011 Elsevier Ltd. All rights reserved.