Adsorption from aqueous solution based on the synergism between hydrogen bonding and hydrophobic interactions

The adsorption of aniline, N-methyl aniline, and N,N-dimethyl aniline on carboxyl resin(D152) in different media, water, ethanol, and hexane have been studied. In water the adsorption affinity of three sorbates on D152 increased with an increasing number of methyl groups on N atoms, which indicated that the adsorption of the three sorbates on D152 was driven by a hydrophobic interaction. But the adsorption enthalpy of the three sorbates exceeded the van der Waals force and was in the range of hydrogen bonding interactions, which indicated that the hydrogen bonding also played an important role. In hexane the adsorption affinity decreased with the increasing number of methyl groups on the N atom, presenting the reverse order to that in water. This fact revealed that the hydrogen bonding played a predominant role for the adsorption in hexane. In ethanol, there was no adsorption of three sorbates on D152 resin, because both the van der Waals force and the hydrogen bonding interaction between the resin and sorbate were depressed. The hydrogen bonding between resin and sorbates in water was also depressed, but the hydrogen bonding adsorption remained. This result suggested that there might be a synergetic effect between the van der Waals and hydrogen bonding interactions in the adsorption of sorbate on D152 resin in water. The synergetic effect was explained thermodynamically. (c) 2005 Wiley Periodicals, Inc.