Fabrication of a nitrogen-rich GO composite for selective removal of Cu2+ in aqueous solutions

Abstract

Graphene oxide (GO) based composites are renowned for their adsorption properties toward metal ions from mono-/multi-component systems. However, it is difficult for a newly-developed adsorbent to possess high adsorption capacity and good selectivity. By modifying GO with a nitrogen-rich organic molecule, 3,5-diamino-1,2,4-triazole (DAT), through a facile nucleophilic reaction, the developed GO-DAT composite could selectively adsorb Cu²⁺ of low concentrations from aqueous solutions with high efficiency. Several characterization techniques confirmed that DAT was successfully bound to GO through the formation of C=N bonds, which greatly improved its thermal stability. In addition, more active adsorption sites could be also offered to complex with Cu²⁺ to achieve excellent adsorption effects. The adsorption investigation was implemented in-depth by evaluating the conditional parameters (Contact time, initial adsorbate concentration, temperature, and pH effect) on the adsorption process. For the kinetic and isothermal studies, the adsorption data could be better fitted by the linear pseudo-second-order model and linear Langmuir model, respectively, suggesting the chemical adsorption dominated the intermolecular interactions between GO-DAT composite and Cu²⁺, and a higher adsorption capacity of 0.63mmol g⁻¹ at equilibrium could be observed. The proposed GO-DAT composite also exhibited excellent reusability, implying that it is an effective adsorbent for the removal of Cu²⁺ from aqueous solutions.