Nanostructured surfaces

Theoretical prediction of adsorption characteristics of Cr(VI) molecular anions on the surface of carbon nanostructures
V. Borysiuk1, S. Nedilko1, Yu. Hizhnyi1, A. Shyichuk2

1 Taras Shevchenko National University of Kyiv, Volodymyrska Street 64/13, 01601, Kyiv, Ukraine
E-mail: borysyukviktor@gmail.com
2 Adam Mickiewicz University, Department of Rare Earth, Faculty of Chemistry, Umultowska 89b, 61-614 Poznań, Poland

Removing of toxic compounds containing in particular Cr(VI) from industrial wastewater is an urgent technological need. Oxoanions of hexavalent Cr are very harmful to living organisms [1]. One of the most promising methods of removal and storage are grounded on adsorption of oxyanions on artificial adsorbents. Carbon nano-structured materials are just intensively studied as adsorbents for efficient removal and storage of various toxic pollutants. Theoretical modeling of molecular oxyanions adsorption on the CNTs surfaces is a powerful tool that allows prediction of some important properties of materials perspective for removal and storage of oxyanions. 
In this work we presented the results of the electronic structure calculations and related analysis for adsorption of CrO42- oxyanions on several types of CNT surfaces (undoped, B- and N-doped CNT(3,3), CNT(5,5) and grapheme sheets). Graphene sheets were considered as a model approximation for high-diameter CNTs. Geometry-optimized calculations of the electronic structures were carried out at the Density Function Theory (DFT) level within molecular cluster approach using software package Gaussian 09 [2]. Relaxed geometries, binding energies between the adsorbates and the nanotubes, charge states of the adsorbates were calculated and analyzed. 
The results of the calculations were discussed in view of potential application of the CNT-based materials as efficient adsorbents of CrO42- molecular anions. 

1.	Ghashghaee, M., Farzaneh, V. Removal of Cr (VI) Species from Aqueous Solution by Different Nanoporous Materials // Iranian Journal of Toxicology.-2016.- 10(6) .-P. 15-21. 
2.	Frisch M.J., Trucks G.W., Schlegel H.B., et al. // Gaussian 09 (Gaussian, Inc., Wallingford, CT, 2009).