Removal of the Alizarin Red S Anionic Dye Using Graphene Nanocomposites: A study on Kinetics under Dynamic Conditions

The present paper reports kinetic studies of the adsorption of molecules of the Alizarin Red C (ARS) anionic dye on two types of graphene nanomaterials, mesoporous carbon (MPC) and polyquinone/graphene (PQ/G) nanocomposite. It was established that the MPC has a very high specific surface area (2,850 m(2) g(-1)), and the specific pore volume is 2.13 cm(3) g(-1). As for the PQ/G, its specific surface area was found to be 44 m(2) g(-1), with the specific pore volume being equal to 0.11 cm(3) g(-1); however, it can be assumed that during the synthesis, the PQ/G surface has been modified by phenolic groups having the ability to form chemical bonds between the adsorbent and the dye molecules. The adsorption capacity of the materials was determined spectrophotometrically at the wavelength of 660 nm. The results of a kinetic study under dynamic conditions (continuous feeding of the solution through the adsorbent bed) showed: for the MPC - the adsorption capacity of 2,923 mg g(-1) within the equilibrium contact time of 80 min, and for the PQ/G nanocomposite - 3,290 mg g(-1) within about 120 min. To reveal the mechanisms of the ARS adsorption on the graphene-based adsorbents under study, the experimental kinetic data were processed by implementing the diffusion (intraparticle diffusion and Boyd) and chemical reaction (pseudo-first-order, pseudo-second-order, and Elovich) models. (c) 2019 Elsevier Ltd. All rights reserved.