MECHANISM(S) CONTROLLING SORPTION OF NEUTRAL ORGANIC CONTAMINANTS BY SURFACTANT-DERIVED AND NATURAL ORGANIC-MATTER

Layer silicate clays modified with cationic surfactants (organoclays) such as hexadecyltrimethylammonium (HDTMA) are effective sorbents for neutral organic contaminants (NOCs) and may be useful for in-situ and ex-situ remediation of contaminated soils and waters. In this study, t he sorptive characteristics of organoclays were compared in terms of m agnitude and mechanism to those of natural soil organic matter. The da ta presented here support multiple mechanisms controlling the sorption of aqueous-phase NOCs on organoclays including solvation of the catio nic ammonium centers, the alkyl chains of HDTMA, and the mineral surfa ces and solute partitioning. In contrast, solute partitioning appears to be the singular mechanism for the sorption of aqueous-phase NOCs by natural soil organic matter. Organic contaminant sorption by the surf actant-derived organic matter of organoclays is substantially higher t han by natural soil organic matter due to the existence of multiple so rptive mechanisms for organoclays and the greater solvency of their or ganic phases.