6AUTHOR EMAIL: mason42@llnl.gov 7
RECEIVED DATE 8 TITLE RUNNING HEAD: NMR spectroscopic investigation of divalent metal sorption 9 ABSTRACT 10Environmental and geochemical systems containing paramagnetic species could benefit 11 by using nuclear magnetic resonance (NMR) spectroscopy due to the sensitivity of the spectral 12 response to small amounts paramagnetic interactions. In this study, we apply commonly used 13 solid-state NMR spectroscopic methods combined with chemometrics analysis to probe sorption 14 behavior of the paramagnetic cations Cu 2+ and Ni 2+ at the amorphous silica surface. We exploit 15 the unique properties of paramagnets to derive meaningful structural information in these 16 systems at low, environmentally relevant cation surface loadings by comparing the NMR 17 response of sorption samples to paramagnetic free samples. These data suggest that simple 18 sorption models where the cation sorbs as inner sphere complexes at negatively charged, 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 deprotonated silanol sites is appropriate. These results help constrain sorption models that are 20 used to describe metal fate and transport. 21