Effects of Mineral Surfaces on Pyrene Partitioning to Well-Characterized Humic Substances
- Jin Hurab and
- Mark A. Schlautman *ab
Mineral surfaces can alter the ability of humic substances (HS) to bind hydrophobic organic contaminants. In this study, complete adsorption (i.e., to avoid HS adsorptive fractionation effects) of a small subset of well-characterized terrestrial and aquatic HS on kaolinite and hematite significantly changed their subsequent organic carbon–normalized partition coefficients K ads oc for pyrene relative to their original respective dissolved organic carbon–normalized partition coefficients K dis oc Parallel experiments with ultrafiltration (UF) fractions obtained from purified Aldrich humic acid (PAHA) (Aldrich Chemical, Milwaukee, WI) gave similar results. The heterogeneity among the PAHA UF fractions was examined via their mineral surface adsorption characteristics and their subsequent ability to bind pyrene. As expected, variations in maximum adsorption densities (q max), Langmuir adsorption constants (Kq ), and pyrene K ads oc values were observed among the PAHA UF fractions. However, general trends of q max, Kq , and pyrene log K ads oc values for the PAHA UF fractions versus the logarithm of their weight-average molecular weights (MWw) did not typically match the corresponding trends obtained with the four aquatic and terrestrial HS. In general, an ideal mixture competitive adsorption model gave reasonable predictions for PAHA sorption to kaolinite and hematite based on their corresponding UF isotherm parameters. Ideal mixture predictions of pyrene partitioning to adsorbed PAHA from the corresponding UF fraction results were better for kaolinite versus hematite, indicating that the underlying mineral surface can alter the effects of HS heterogeneity on hydrophobic organic contaminant sorption.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2004.