title: Colloidal activated carbon for in-situ groundwater remediation--Transport characteristics and adsorption of organic compounds in water-saturated sediment columns.
abstract: Colloidal activated carbon can be considered as a versatile adsorbent and carrier material for in-situ groundwater remediation. In analogy to other nanoremediation approaches, activated carbon colloids (ACC) can be injected into the subsurface as aqueous suspensions. Deposition of ACC on the sediment creates a sorption barrier against further spreading of hydrophobic pollutants. This study deals with the optimization of ACC and their suspensions with a focus on suspension stability, ACC mobility in saturated porous media and sorption efficiency towards organic contaminants. ACC with an appropriate particle size range (d50=0.8μm) were obtained from a commercial powdered activated carbon product by means of wet-grinding. Among the various methods tested for stabilization of ACC suspensions, addition of humic acid (HA) and carboxymethyl cellulose (CMC) showed the best results. Due to electrosteric stabilization by adsorption of CMC, suspensions remained stable even at high ACC concentrations (11gL(-1)) and conditions typical of very hard water (5mM divalent cations). Furthermore, CMC-stabilized ACC showed high mobility in a water-saturated sandy sediment column (filter coefficient λ=0.2m(-1)). Such mobility is a pre-requisite for in-situ installation of sorption or reaction barriers by simple injection-well or direct-push application of ACC suspensions. Column experiments with organic model compounds proved the efficacy of ACC deposits on sediment for contaminant adsorption and retardation under flow-through conditions.
authors.affiliation: Helmholtz Centre for Environmental Research, UFZ, Department of Environmental Engineering, Permoserstr. 15, D-04318 Leipzig, Germany. Electronic address: anett.georgi@ufz.de.
authors.forename: Anett
authors.initials: A
authors.lastname: Georgi
authors.affiliation: Department of Civil and Environmental Engineering, Texas Tech University, 911 Boston Avenue, Lubbock, TX, 79405, USA.
authors.forename: Ariette
authors.initials: A
authors.lastname: Schierz
authors.affiliation: Helmholtz Centre for Environmental Research, UFZ, Department of Environmental Engineering, Permoserstr. 15, D-04318 Leipzig, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Mackenzie
authors.affiliation: Helmholtz Centre for Environmental Research, UFZ, Department of Environmental Engineering, Permoserstr. 15, D-04318 Leipzig, Germany.
authors.forename: Frank-Dieter
authors.initials: FD
authors.lastname: Kopinke
mesh_terms: D000327:Adsorption; D002266:Carboxymethylcellulose Sodium / Q000737:chemistry; D002606:Charcoal / Q000737:chemistry*; D003102:Colloids / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D019015:Geologic Sediments; D060587:Groundwater / Q000737:chemistry*; D006812:Humic Substances; D062070:Hydrology / Q000379:methods; D009930:Organic Chemicals / Q000032:analysis / Q000737:chemistry; D010316:Particle Size; D016062:Porosity; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D003102:Colloids; D006812:Humic Substances; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D002606:Charcoal; D002266:Carboxymethylcellulose Sodium
keywords: Colloidal activated carbon; Contaminant retardation; Groundwater; Nanoremediation; Particle transport; Plume; Sorption barrier