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CR(VI) ADSORPTION ON ENGINEERED IRON OXIDE NANOPARTICLES: EXPLORING COMPLEXATION PROCESSES AND WATER CHEMISTRY
Pan, Z., X. Zhu, A. Satpathy, W. Li, J.D. Fortner, and D.E. Giammar.
Environmental Science & Technology 53(20):11913-11921

Cr(VI) adsorption affinity to 8 nm surface-functionalized superparamagnetic magnetite nanoparticles was measured for surface coatings with trimethyloctadecylammonium bromide (CTAB) and stearic acid (SA) functional groups. Cr(VI) adsorbed more strongly to the CTAB coating than to SA-coated materials due to electrostatic interactions between positively charged CTAB and anionic Cr(VI) species. Cr(VI) adsorption by CTAB- and SA-coated materials increased with decreasing pH (4.5-10), which could be simulated by a surface complexation model. Cr(VI) removal performance by the nanocomposite was evaluated for two realistic drinking water compositions. The co-occurrence of divalent cations (Ca2+ and Mg2+) and Cr(VI) resulted in decreased Cr(VI) adsorption as particles were destabilized. This led to aggregation and lower effective surface area, confirming the importance of the overall water composition on the performance of novel engineered nanomaterials for water treatment applications.



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