Composite on the basis of hydrated zirconium dioxide and graphene oxide for removal of organic and inorganic components from water

The aim of the investigation is to develop multifunctional adsorbent, which is able to remove both inorganic ions and molecular organic substances from aqueous solutions. Oxidized graphene has been obtained by Hammer’s method. The composite, which includes hydrated zirconium dioxide and graphene oxide (» 2 mass. %), has been synthesized by deposition from sol containing dispersed particles of the carbon material. The adsorbent as well as its constituents were investigated with methods of XRD analysis, FTIR spectroscopy, TEM and standard contact porosimetry involving octane (ideally wetting liquids) and water as working liquids. Strong hydration of graphene oxide in water has been found: the volume of micro- and mesopores in water medium is higher than that in octane. It means that the oxidized graphene behaves similarly to ion exchange polymers. This is evidently due to its hydrophilic functional groups (hydroxyle carboxyl and epoxy groups). High specific surface area of graphene oxide reaches 1200 (in the organic solvent) or 2250 m 2 g –1 (in aqueous medium). It has been shown that graphene covers the particles of the inorganic matrix loosening its structure within the wide interval of pore size (from 10 nm to 1.5 µm). As found, adsorption isotherms of Pb(II) and HCrO 4 - ions obeys with Langmuir model. The filler improves adsorption of Pb(II) 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. Other reason can be electrostatic repulsion of anions due to the shift of the point of zero charge of the composite to acidic field. By reason of the carbon filler, the oxide material acquires the capability to adsorb both slightly dissociated (phenol) and molecular (lactose) organic substances. When the initial content of phenol is 5 mg dm –3 , it is possible to reduce its content in water down to maximal permeable concentration. After adsorption, the content of lactose is much lower than this parameter. It means, that the composite provides practically complete removal of organics from water.