Journal of Hazardous Materials 166 (2009) 1339–1343 Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Entrapment of iron nanoparticles in calcium alginate beads for groundwater remediation applications Achintya N. Bezbaruah a,∗ , Sita Krajangpan a , Bret J. Chisholm b , Eakalak Khan a , Juan J. Elorza Bermudez a,c a Civil Engineering Department, North Dakota State University, Dept 2470, P.O. Box 6050, Fargo, ND 58108, USA b Center for Nanoscale Science and Engineering, North Dakota State University, Fargo, ND 58102, USA c Department of Civil Engineering, North Dakota State University from University of Burgos, Burgos 09001, Spain article info Article history: Received 29 October 2008 Received in revised form 9 December 2008 Accepted 10 December 2008 Available online 14 December 2008 Keywords: Iron nanoparticle Alginate beads Entrapment Nitrate Groundwater remediation abstract Zero-valent iron nanoparticles (nZVI) have been successfully entrapped in biopolymer, calcium (Ca)- alginate beads. The study has demonstrated the potential use of this technique in environmental remediation using nitrate as a model contaminant. Ca-alginate beads show promise as an entrapment medium for nZVI for possible use in groundwater remediation. Based on scanning electron microscopy images it can be inferred that the alginate gel cluster acts as a bridge that binds the nZVI parti- cles together. Kinetic experiments with 100, 60, and 20mg NO 3 - -N L -1 indicate that 50–73% nitrate-N removal was achieved with entrapped nZVI as compared to 55–73% with bare nZVI over a 2-h period. The controls ran simultaneously show little NO 3 - -N removal. Statistical analysis indicates that there was no significant difference between the reaction rates of bare and entrapped nZVI. The authors have shown for the first time that nZVI can be effectively entrapped in Ca-alginate beads and no significant decrease in the reactivity of nZVI toward the model contaminant (nitrate here) was observed after the entrapment. Published by Elsevier B.V. 1. Introduction In recent years, zero-valent iron (Fe o ) nanoparticles (nZVI) have been used for the removal of various groundwater contam- inants including chlorinated compounds [1,2], pesticides [3–5], heavy metals [6,7], and explosives [8,9] in water. Advantages of nZVI over other zero-valent iron (ZVI) such as microparti- cles (mZVI) and iron filings include higher reactive surface area (25–54 m 2 g -1 for nZVI [5,10,11] and 1 m 2 g -1 for mZVI [5]), faster and more complete reactions, and injectability into the aquifer [12–14]. Because of smaller particle size and relatively higher dispersibil- ity (as compared to other ZVI materials), nZVI becomes mobile in the aquifer [12,13,15]. Further, if present in higher concen- tration, nZVI tend to agglomerate due to magnetic and van der Waals forces and form larger particles that settle into aquifer media pores. Agglomerated particles have decreased specific sur- face and hence lose the very advantage individual nZVI has. The higher mobility, agglomeration, and oxidation by non-target com- pounds in groundwater remain as major challenges for nZVI use for ∗ Corresponding author. Tel.: +1 701 231 7461; fax: +1 701 231 6185. E-mail address: a.bezbaruah@ndsu.edu (A.N. Bezbaruah). groundwater remediation [16]. To overcome these problems, this paper presents work done to entrap nZVI in a porous polymeric hydrogel. Entrapment within calcium (Ca)-alginate beads is one of the most common methods for immobilizing living cells in food and beverage industries [17,18]. Ca-alginate hydrogels and microbeads are also used for drug delivery [19]. In addition, Ca-alginate entrapped bacterial and fungal cells have been used to remediation heavy metals [20–22] and nitrogen [23,24]. Alginate entrapped sur- factants [25], activated carbon [26], and metal hydroxides (Fe 3+ and Ni 2+ ) [27] have been used to recover/treat aqueous copper, organ- ics, and arsenic, respectively. Immobilization of cells in Ca-alginate is a simple and cost effective technique [23]. Porosity in Ca-alginate allows solutes to diffuse into the beads and come in contact with the entrapped cells [28]. Moreover, alginate is nontoxic, biodegrad- able, and nonimmunogenic, and produces thermally irreversible and water insoluble gels [29,30]. The objective of this paper is to demonstrate that iron nanoparticles can be effectively entrapped in a biopolymer matrix (alginate) without significant reduction in their reactivity. nZVI have been entrapped within alginate beads to reduce their mobil- ity/sedimentation in the aquifer. Effectiveness of the entrapped nanoparticles in contaminant remediation was examined with nitrate as the test contaminant. 0304-3894/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.jhazmat.2008.12.054