RESEARCH PAPER Transport of poly(acrylic acid) coated 2-line ferrihydrite nanoparticles in saturated aquifer sediments for environmental remediation Aishuang Xiang • Sheng Zhou • Bruce E. Koel • Peter R. Jaffe ´ Received: 2 October 2013 / Accepted: 20 January 2014 / Published online: 13 March 2014 Ó Springer Science+Business Media Dordrecht 2014 Abstract Groundwater remediation using iron oxide and zero-valent iron nanoparticles (NPs) can be effective, but is limited in many applications due to the NP strong retention in groundwater-saturated porous media after injection, the passivation of the porous surface, and the high cost of nanomaterials versus macro scale iron. In this study, we investigated transport of bare and polymer-coated 2-line ferrihydrite NPs (30–300 nm) in saturated aquifer sediments. The influence of poly(acrylic acid) (PAA) polymer coatings was studied on the colloidal stability and transport in sediments packed column tests simulating groundwater flow in saturated sediments. In addition, the influence of calcium cations was investigated by transport measurements using sedi- ments with calcium concentrations in the aqueous phase ranging from 0.5 (typical for most sediments) to 2 mM. Measurements were also made of zeta potential, hydrodynamic diameter, polymer adsorp- tion and desorption properties, and bio-availability of PAA-coated NPs. We found that NP transport through the saturated aquifer sediments was improved by PAA coating and that the transport properties could be tuned by adjusting the polymer concentration. We further discovered that PAA coatings enhanced NP transport, compared to bare NPs, in all calcium-containing experiments tested, however, the presence of calcium always exhibited a negative effect on NP transport. In tests of bioavailability, the iron reduction rate of the coated and bare NPs by Geobacter sulfurreducens was the same, which shows that the PAA coating does not significantly reduce NP Fe(III) bioavailability. Our results demonstrate that much improved transport of iron oxide NP can be achieved in saturated aquifer sediments by introducing negatively charged poly- electrolytes and optimizing polymer concentrations, and furthermore, these coated NPs retain their bio- availability that is needed for applications in bio- environmental remediation. Electronic supplementary material The online version of this article (doi:10.1007/s11051-014-2294-5) contains supple- mentary material, which is available to authorized users. A. Xiang (&) Á B. E. Koel Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA e-mail: aishuang@princeton.edu; xaishuang@gmail.com URL: http://www.linkedin.com/pub/aishuang-xiang-ph-d/ 12/187/716/ B. E. Koel e-mail: bkoel@princeton.edu URL: http://www.princeton.edu/cbe/people/faculty/koel/ S. Zhou Department of Chemistry, Princeton University, Princeton, NJ 08544, USA P. R. Jaffe ´ Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544, USA e-mail: jaffe@princeton.edu URL: https://www.princeton.edu/*jaffe/ 123 J Nanopart Res (2014) 16:2294 DOI 10.1007/s11051-014-2294-5