• Gondikas, Andreas
• Hofmann, Thilo
• Batka, Vesna Micic
• Velimirovic, Milica
• Kammer, Frank Von Der
• Schmid, Doris

Abstract

The affinity between nanoparticles used in groundwater remediation and aquifer mineral surfaces affect the transport of nanoparticles and therefore the formation of a reactive zone and the effectiveness of the remediation approach as a whole. The surface of nanoscale zero-valent iron (nZVI) particles used in remediation is often modified with a polymeric coating that stabilizes the particles via electrosteric repulsion and hinders homoaggregation. This coating does not necessarily hinder the attachment of nZVI to the physicochemically heterogeneous mineral surfaces of aquifers.<br/><br/>In this study, we investigated the possibility of increasing nZVI mobility in heterogeneous sediments by pre-coating the sediments with sodium humate. The effect of sodium humate on the deposition of polyacrilic acid coated nZVI (PAA-nZVI) was studied in flow-through columns packed with (i) uncoated/coated pure silica sand with varying surface roughness (ii) uncoated/coated glass beads with different ferrihydrite content and (iii) uncoated/coated heterogeneous aquifer material from the contaminated field sites.<br/><br/>When sodium humate was pre-adsorbed onto the collector surfaces, the deposition of PAA-nZVI was significantly reduced in the pure silica collector with rough surfaces and high permeability, but not in the less permeable natural porous media from the contaminated sites. The results further showed that the roughness of the mineral grains enhances the adsorption of sodium humate onto the silica surface, which was not observed with the smooth surfaces of glass beads. For field materials, we only saw a positive effect of the sodium humate pre-coating for carbonate rich sand. The possibility of hindering the PAA-nZVI deposition in porous media by aquifer pre-treatment remains therefore limited to porous media with distinct mineralogy.<br/><br/>This research receives funding from the European Union’s Seventh Framework Programme FP7/2007-2013 under grant agreement n°309517.<br/>

Topics

• nanoparticle
• Deposition
• porous
• impedance spectroscopy
• mineral
• surface
• grain
• mobility
• glass
• reactive
• glass
• laser emission spectroscopy
• Sodium
• permeability
• iron