title: Mechanisms controlling adsorption of natural organic matter on surfactant-modified iron oxide-coated sand.
abstract: Mechanisms contributing to the adsorption of natural organic matter (NOM) on surfactant-modified iron oxide-coated sand (IOCS) were explored by microscopic surface characterization techniques and adsorption tests. Electrostatic interactions that were thought to be from the positively charged, surface-coated surfactant, hexadecyltrimethyl ammonium (HDTMA), seemed to be unimportant, likely because the outward-pointing tail groups of the surface-coated HDTMA monolayers hindered the interactions. Improved hydrophobic interactions followed by ligand exchange are believed to be the dominant mechanisms. Atomic force microscopy (AFM) force analysis with chemically modified tips was used to explore the adsorption mechanisms between NOM and IOCS, where an iron oxide-coated mica surface was utilized as a substitute for the IOCS surface. It demonstrates the changes of pull-on forces and the increases in hydrophobic interactions from the modification of IOCS with HDTMA.
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Chunli
authors.initials: C
authors.lastname: Ding
authors.forename: Chii
authors.initials: C
authors.lastname: Shang
mesh_terms: D000327:Adsorption; D003102:Colloids; D005290:Ferric Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008024:Ligands; D008823:Micelles; D009930:Organic Chemicals / Q000302:isolation & purification*; D012822:Silicon Dioxide / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D055672:Static Electricity; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature
chemical_list: D003102:Colloids; D005290:Ferric Compounds; D008024:Ligands; D008823:Micelles; D009930:Organic Chemicals; D013501:Surface-Active Agents; C000499:ferric oxide; D012822:Silicon Dioxide