TY - JOUR
T1 - An X-ray absorption fine structure spectroscopy study of metal sorption to graphene oxide
AU - Showalter, Allison R.
AU - Duster, Thomas A.
AU - Szymanowski, Jennifer E.S.
AU - Na, Chongzheng
AU - Fein, Jeremy B.
AU - Bunker, Bruce A.
N1 - Funding Information:
MRCAT is funded by the U.S. Department of Energy and by its member institutions. Use of the APS was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. A.R.S. wishes to thank the staff at MRCAT, B. Mishra and K. Werellapatha for beamline support and useful conversations. The ICP-OES analyses were conducted at the Center for Environmental Science and Technology (CEST) at the University of Notre Dame. This research was supported, in part, by a fellowship to T.A.D. from the Arthur J. Schmitt Foundation. We thank the two anonymous journal reviewers whose comments and suggestions significantly improved the presentation of this work.
Publisher Copyright:
© 2017 Elsevier Inc.
PY - 2017/12/15
Y1 - 2017/12/15
N2 - Remediation and prevention of environmental contamination by toxic metals is an ongoing issue. Additionally, improving water filtration systems is necessary to prevent toxic metals from circulating through the water supply. Graphene oxide (GO) is a highly sorptive material for a variety of heavy metals under different ionic strength conditions over a wide pH range, making it a promising candidate for use in metal adsorption from contaminated sites or in filtration systems. We present X-ray absorption fine structure (XAFS) spectroscopy results investigating the binding environment of Cd (II), U(VI) and Pb(II) ions onto multi-layered graphene oxide (MLGO). This study shows that the binding environment of each metal onto the MLGO is unique, with different behaviors governing the sorption as a function of pH. For Cd sorption to MLGO, the same mechanism of electrostatic attraction between the MLGO and the Cd+2 ions surrounded by water molecules prevails over the entire pH range studied. The U(VI), present in solution as the uranyl ion, shows only subtle changes as a function of pH, likely due to the varied speciation of uranium in solution. The adsorption of the U to the MLGO is through a covalent, inner-sphere bond. The only metal from this study where the dominant adsorption mechanism to the MLGO changes with pH is Pb. In this case, under lower pH conditions, Pb is bound onto the MLGO through dominantly outer-sphere, electrostatic adsorption, while under higher pH conditions, the bonding changes to be dominated by inner-sphere, covalent adsorption. Since each of the metals in this study show unique binding properties, it is possible that MLGO could be engineered to effectively adsorb specific metal ions from solution and optimize environmental remediation or filtration for each metal.
AB - Remediation and prevention of environmental contamination by toxic metals is an ongoing issue. Additionally, improving water filtration systems is necessary to prevent toxic metals from circulating through the water supply. Graphene oxide (GO) is a highly sorptive material for a variety of heavy metals under different ionic strength conditions over a wide pH range, making it a promising candidate for use in metal adsorption from contaminated sites or in filtration systems. We present X-ray absorption fine structure (XAFS) spectroscopy results investigating the binding environment of Cd (II), U(VI) and Pb(II) ions onto multi-layered graphene oxide (MLGO). This study shows that the binding environment of each metal onto the MLGO is unique, with different behaviors governing the sorption as a function of pH. For Cd sorption to MLGO, the same mechanism of electrostatic attraction between the MLGO and the Cd+2 ions surrounded by water molecules prevails over the entire pH range studied. The U(VI), present in solution as the uranyl ion, shows only subtle changes as a function of pH, likely due to the varied speciation of uranium in solution. The adsorption of the U to the MLGO is through a covalent, inner-sphere bond. The only metal from this study where the dominant adsorption mechanism to the MLGO changes with pH is Pb. In this case, under lower pH conditions, Pb is bound onto the MLGO through dominantly outer-sphere, electrostatic adsorption, while under higher pH conditions, the bonding changes to be dominated by inner-sphere, covalent adsorption. Since each of the metals in this study show unique binding properties, it is possible that MLGO could be engineered to effectively adsorb specific metal ions from solution and optimize environmental remediation or filtration for each metal.
KW - Adsorption
KW - Graphene oxide (GO)
KW - Surface complexation modeling
KW - X-ray absorption fine structure spectroscopy (XAFS)
UR - http://www.scopus.com/inward/record.url?scp=85027518121&partnerID=8YFLogxK
U2 - 10.1016/j.jcis.2017.08.040
DO - 10.1016/j.jcis.2017.08.040
M3 - Article
C2 - 28822863
AN - SCOPUS:85027518121
VL - 508
SP - 75
EP - 86
JO - Journal of Colloid and Interface Science
JF - Journal of Colloid and Interface Science
SN - 0021-9797
ER -