Sorption of pentachlorophenol to organo-clay complexes prepared by polycondensation reactions of humic precursors

Abstract

The surfactant-modified bentonite has been focused on the adsorption of hydrophobic organic contaminants in aqueous solutions, because the surfactant (e.g. quaternary alkylammonium salt) intercalation leads to the formation of highly hydrophobic domains. Humic substances (HSs) can serve as naturally occurring surfactants of higher affinity to hydrophobic organic contaminants, such as pentachlorophenol (PCP). However, HSs cannot be loaded into interlayer of montmorillonite in bentonite (Bent) because of their larger size. In the present study, the humin-like substance (HuLS) was loaded to the montmorillonite interlayer via polycondensation reactions of glycine and catechol as humic precursors. The montmorillonite basal spacing was expanded by forming the HuLS-bentonite complex (HuLS-Bent), showing the intercalation. The Freundlich adsorption coefficients of PCP for HuLS-Bent and Bent (K f) were evaluated at pH 4.0, 5.5 and 6.5. While K f values decreased with an increase in pH, K f values for the HuLS-Bent (83-1,220) were larger than the reported values for other organically modified clays (19-100 at pH 3-6). These results suggest that the prepared HuLS-Bent is effective in the removal of PCP from water.