Nanocomposites and nanomaterials

Graphene oxide and its composites: adsorption properties 
Dzyazko Yu.S.,  Ogenko V.M., Chaban M.O.
 V.I. Vernadskii Institute of General and Inorganic Chemistry of the NAS of Ukraine, 32/34 Palladin ave., 03142 Kyiv, Ukraine
E-mail: dzyazko@gmail.com

Graphene oxide (GO) is a layered material consisting of nanosheets, a thickness of which is one atom (0.54 nm) [1, 2]. As opposed to reduced graphene, vibration spectra for GO indicate carbon-oxygen bonds: COH (attributed both to hydroxyl and carboxyl groups), C=O (related to carboxyl groups) and COC (epoxy groups). Carboxyl groups are mainly placed along the perimeter of GO scales, hydroxyl and epoxide groups are located on their basal plane. GO was obtained by means of chemical exfoliation of exfoliated graphite obtained with electrochemical method. A number of nsnocomposites based on hydrated zirconium dioxide and graphene oxide (GO) were obtained. It was shown that GO nanoparticles (5-6 nm) covers the particles of the inorganic matrix loosening its structure. Agglomerates of GO nanosheets were also included to the nanocomposites. Adsorption of Pb2+ and HCrO4- ions was investigated. As found, adsorption isotherms of Pb2+ and HCrO4- ions obeys with Langmuir model. The filler improves adsorption of Pb2+ ions increasing the capacity in 1.7 times due to its expressed cation exchange properties. Contrary, anion exchange function of the composite is depressed, since the sheets of graphene oxide screen adsorption centers of the inorganic matrix. By reason of the carbon filler, the oxide material acquires the ability to adsorb both slightly dissociated (phenol) and molecular (lactose) organic substances. Despite depressed anion exchange properties, the composite adsorbs phenol that is a weak acid. When the initial concentration of this component is 5 mg dm-3, the nanocomposites remove it down to maximal allowable concentration for tap water (1 µg dm-3). Adsorption is due to hydrophobic regions of GO sheets. 

1.	Chabot V., Higgins D., Yu A., Xiao X., Chen Z., Zhang J. A review of graphene and graphene oxide sponge: material synthesis and applications to energy and the environment // Energy Environ. Sci. 2014. V. 7.1564- 1596. 
2.	Dzyazko Yu.S., Ogenko V.M., Volfkovich Yu.M., Sosenkin V.E., Maltseva T.V., Yatsenko T.V., Kudelko K.O. Composite consisting of hydrated zirconium dioxide and grapheme oxide for removal of organic and inorganic components from water // Chemistry, Physics and Technology of Surface. – 2018. − V. 9, N 4. P. 417-431.