title: Effects of Rhamnolipid and Carboxymethylcellulose Coatings on Reactivity of Palladium-Doped Nanoscale Zerovalent Iron Particles.
abstract: Nanoscale zerovalent iron (NZVI) particles are often coated with polymeric surface modifiers for improved colloidal stability and transport during remediation of contaminated aquifers. Doping the NZVI surface with palladium (Pd-NZVI) increases its reactivity to pollutants such as trichloroethylene (TCE). In this study, we investigate the effects of coating Pd-NZVI with two surface modifiers of very different molecular size: rhamnolipid (RL, anionic biosurfactant, M.W. 600 g mol(-1)) and carboxymethylcellulose (CMC, anionic polyelectrolyte, M.W. 700 000 g mol(-1)) on TCE degradation. RL loadings of 13-133 mg TOC/g NZVI inhibited deposition of Pd in a concentration-dependent manner, thus limiting the number of available Pd sites and decreasing the TCE degradation reaction rate constant from 0.191 h(-1) to 0.027 h(-1). Furthermore, the presence of RL in solution had an additional inhibitory effect on the reactivity of Pd-NZVI by interacting with the exposed Pd deposits after they were formed. In contrast, CMC had no effect on reactivity at loadings up to 167 mg TOC/g NZVI. There was a lack of correlation between Pd-NZVI aggregate sizes and TCE reaction rates, and is explained by cryo-transmission electron microscopy images that show open, porous aggregate structures where TCE would be able to easily access Pd sites.
authors.affiliation: Department of Civil Engineering, McGill University , Montreal, Quebec H3A 0C3, Canada.
authors.forename: Sourjya
authors.initials: S
authors.lastname: Bhattacharjee
authors.affiliation: Department of Chemical Engineering, McGill University , Montreal, Quebec H3A 0C5, Canada.
authors.forename: Mohan
authors.initials: M
authors.lastname: Basnet
authors.affiliation: Department of Chemical Engineering, McGill University , Montreal, Quebec H3A 0C5, Canada.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Tufenkji
authors.affiliation: Department of Civil Engineering, McGill University , Montreal, Quebec H3A 0C3, Canada.
authors.forename: Subhasis
authors.initials: S
authors.lastname: Ghoshal
mesh_terms: D002266:Carboxymethylcellulose Sodium / Q000737:chemistry*; D004573:Electrolytes / Q000737:chemistry*; D006017:Glycolipids / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*; D014241:Trichloroethylene / Q000737:chemistry*; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D004573:Electrolytes; D006017:Glycolipids; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; C418382:rhamnolipid; D014241:Trichloroethylene; D010165:Palladium; D007501:Iron; D002266:Carboxymethylcellulose Sodium