Molecular dynamics study of the interactions between phenolic compounds and alginate/alginic acid chains

Abstract

The potential use of alginates and algae-based materials for removal of phenols from aqueous solutions is an area of growing interest. However, no theoretical studies have been made so far explaining the mechanism of phenols binding to alginates. The molecular dynamics simulations were performed to elucidate the nature of interactions between alginates/alginate acid and three different phenolic compounds (phenol, o-chlorophenol and p-chlorophenol). Both the composition of alginate chains and the effect of pH (expressed in terms of ionization of the alginate carboxyl groups) were studied. The results indicate that alginates interact with phenols mainly through the formation of hydrogen bonds involving the hydroxyl groups of phenols and both hydroxyl and carboxyl groups of alginates. The influence of hydrophobic interactions is more significant in the case of alginic acid. Roughly estimated sorption capacities are in agreement with the experimental data. Further, the ‘mixed’ mechanism of sorption in which both hydrogen bonding and hydrophobic interactions play a role is the most probable for algae-based sorbents.