Sequestration of Ni(II) onto graphene oxide from synthetic wastewater as affected by coexisting constituents

Abstract

This article examines the sequestration of Ni(II) onto graphene oxide (GO) by an adsorption process using batch technique. The role of contact time, medium pH, and coexisting constituents like humic acid (HA) and/or fulvic acid (FA) in the adsorption of Ni(II) onto GO was studied. The results indicated that the adsorption of Ni(II) onto GO increased from ~20 to ~95% at pH 2.0–9.0, and then maintained the high level with increasing pH. Kinetic data showed that the adsorption obtained equilibrium quickly and was fitted well by the pseudo-second-order equation. The presence of HA/FA imposing a positive role Ni(II) adsorption onto GO was found at pH < 8.0, whereas a negative role in the adsorption of Ni(II) onto GO was observed at pH > 8.0. The thermodynamic analysis from the temperature-dependent adsorption isotherms suggests that the adsorption of Ni(II) onto GO is spontaneous and endothermic. Experimental results provided evidence that the adsorption of Ni(II) onto GO was mainly attributed to surface complexation. These findings indicate that GO is a suitable material in the solidification and immobilization of Ni(II) from aqueous solutions in the wastewater treatment.