Adsorption of hexavalent chromium ions from aqueous solution by graphene nanosheets: kinetic and thermodynamic studies

Abstract

In the present study, a batch system was used to investigate the adsorption of chromium (VI) ions from an aqueous solution by graphene nanosheets. Graphene is decorated with functional groups containing oxygen such as epoxy and hydroxyl on the basal plane. The large negative charge density available on graphene causes effective adsorption of chromium (VI) ions from aqueous solutions. The adsorption capacity and rate of chromium (VI) ions at different temperatures, adsorbent dosages, initial concentrations, and contact times were evaluated. The kinetic study illustrated that the adsorption of chromium (VI) ions onto graphene obeys the pseudo-second-order model with activation energy of 21.91 kJ mol -1 . The chromium (VI) ions adsorption was well explained using Dubinin-Radushkevich isotherm model. The values of standard enthalpy, entropy, and Gibbs free energy changes at 25°C were calculated as 686.07 kJ mol -1 , 2.38 kJ mol -1 K -1 , and -22.43 kJ mol -1 , respectively. In this work, graphene was prepared via a green method. Transmission electron microscopy, Fourier transform-infrared spectroscopy, energy-dispersive X-ray analysis, powder X-ray diffraction, Boehm's titration, and N 2 adsorption-desorption techniques revealed a high-quality few-layer nanosheets of graphene with surface area and inter-planar spacing of 594.7 m 2 g -1 and 3.6 Å , respectively.

Adsorption of Cr(VI) from aqueous solution on graphene oxide (GO) prepared from graphite: equilibrium, kinetic and thermodynamic studies

“…Therefore, the contact between Cr 2 O 7 2− and active sites of graphene is very weak at low temperature leading to lower removal efficiency. Conversely, at higher temperature, the kinetic energy of the active species Cr 2 O 7 2− overcomes the attraction potential energy between Cr 2 O 7 2− and active sites available on graphene (Goharshadi and Moghaddam 2015).…”

“…This is probably due to quick saturation of limited available adsorbent sites at higher concentration (Dehghani et al 2015). At lower concentration, the removal of Cr(VI) is maximum due to the ratio of the available surface area of adsorbent to the initial number of moles of Cr(VI) ions that is large (Goharshadi and Moghaddam 2015).…”

“…From the figure S5, it is clear that removal efficiency of Cr(VI) ions from aqueous solution increases rapidly up to 40 min. The higher adsorption of initial stages is perhaps due to higher availability of adsorption sites which saturates with progress of adsorption reaction (Goharshadi and Moghaddam 2015).…”

Potential use of algae for heavy metal bioremediation, a critical review

“…However, treating wastewater containing heavy metal ions is a major economic challenge. The main physicochemical approaches to remove heavy metal ions from wastewaters include chemical precipitation [11], ion exchange [12], electrokinetic [13], membrane processing [14], and adsorption [15,16]. The high costs of chemicals at industrial scales, and incomplete removal of the heavy metal ions are among the main limiting factors in the development of physicochemical approaches.…”

Optimización del Proceso de Adsorción de Cr(VI) sobre Carbón Activado de Origen Bituminoso

“…Por otro lado, el Cr(VI) es considerado como un agente carcinogénico y mutagénico, 500 veces más tóxico para animales y seres humanos que el Cr(III). Entre los efectos que el Cr(VI) puede tener sobre la salud humana están las reacciones alérgicas, problemas respiratorios, debilitamiento del sistema inmunológico, daño a los riñones e hígado, cáncer de pulmón e incluso la muerte Goharshadi y Moghaddam, 2015). En respuesta a esta situación, los gobiernos han legislado y definido los límites de concentración de Cr(VI) en aguas residuales.…”