title: The influence of humic acid and clay content on the transport of polymer-coated iron nanoparticles through sand.
abstract: The introduction of nanoscale zero valent iron (nZVI) into the subsurface has recently received significant attention as a potentially effective method for remediation of source zones of chlorinated solvents present as dense nonaqueous phase liquids (DNAPL). One of the challenges in the deployment of nZVI is to achieve good subsurface nZVI mobility to permit delivery of the nZVI to the target treatment zone. Stabilization of nZVI with various polymers has shown promise for enhancing nZVI subsurface mobility, but the impact of subsurface conditions on nZVI mobility has not been fully explored. In this study, the effect of humic acid and kaolinite on the transport of polymer-stabilized nZVI (carboxylmethyl cellulose-surface modified nZVI, CMC90K-RNIP) in sand was investigated using column experiments. In addition, effects of electrolytes on the stability of CMC90K-RNIP in the presence of humic acid, and the stability of humic acid-coated reactive nanoscale iron particles (HA-RNIP) at various humic acid concentrations were investigated. Humic acid enhanced the mobility of bare RNIP, whereas the transport of CMC90K-RNIP was not significantly affected by humic acid injected as a background solution, except at the highest concentration of 500mg/L. At lower pore water velocity, the effect of humic acid on the transport of CMC90K-RNIP was greater than that at high water velocity. Adding kaolinite up to 2% by weight to the sand column reduced the retention of CMC90K-RNIP, but further increases in kaolinite content (to 5%) did not significantly affect nZVI retention. The impact of kaolinite on nZVI retention was more pronounced at lower pore water velocities.
authors: Chemical Engineering Program, Texas A&M University at Qatar, Education City, PO Box 23874, Doha, Qatar. Electronic address: bahngmi.jung@qatar.tamu.edu.
authors: Bahngmi
authors: B
authors: Jung
authors: Department of Civil and Environmental Engineering, University of Western Ontario, London, ON N6A 5B9, Canada.
authors: Denis
authors: D
authors: O'Carroll
authors: Department of Civil Engineering, University of Toronto, 35 Saint George St., Toronto, ON M5S 1A4, Canada.
authors: Brent
authors: B
authors: Sleep
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D000077215:Clay; D006812:Humic Substances; D007501:Iron / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008956:Models, Chemical; D011108:Polymers / Q000737:chemistry*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D006812:Humic Substances; D011108:Polymers; D014874:Water Pollutants, Chemical; D007501:Iron; D000077215:Clay
keywords: Colloid stability; Humic acid; Kaolinite; Nanoscale zero valent iron; Surface stabilizer