title: Outside-in trimming of humic substances during ozonation in a membrane contactor.
abstract: This paper addresses the change of molecular size distribution of humic substances (HS) during ozonation in a membrane contactor. It focuses on the characterization and identification of some small ozonation products. The membrane contactor setup allows very precise control of ozone transfer into the solution as well as precise sampling of the products in time. The molecular size distribution was followed by gel permeation chromatography (GPC). Characterization and identification of small ozonation products was performed by membrane nanofiltration and high-performance liquid chromatography (HPLC). Measurements on molecular size distribution indicate that during the ozonation process the size of the HS molecules decreases slowly and only small highly oxidated compounds are being split off the larger molecules. Pyruvic acid, formic acid, methylglyoxal, and acetaldehyde could be identified by substantial peaks. Glyoxilic acid and glyoxal were identified to a lesser extent. This suggests that HS molecules consist of a relatively stable backbone network structure and that the HS molecule degrades according to an outside-in trimming mechanism.
authors.affiliation: Faculty of Science and Technology, Membrane Technology Group, University of Twente, P.O. box 217, 7500AE Enschede, The Netherlands.
authors.forename: R H S
authors.initials: RH
authors.lastname: Jansen
authors.forename: A
authors.initials: A
authors.lastname: Zwijnenburg
authors.forename: W G J
authors.initials: WG
authors.lastname: Van Der Meer
authors.forename: M
authors.initials: M
authors.lastname: Wessling
mesh_terms: D000079:Acetaldehyde / Q000032:analysis; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D005561:Formates / Q000032:analysis; D006812:Humic Substances / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D010126:Ozone / Q000737:chemistry*; D011765:Pyruvaldehyde / Q000032:analysis; D019289:Pyruvic Acid / Q000032:analysis
chemical_list: D005561:Formates; D006812:Humic Substances; C030544:formic acid; D010126:Ozone; D011765:Pyruvaldehyde; D019289:Pyruvic Acid; D000079:Acetaldehyde