Using of g-C3N4 nanosheets for the highly efficient scavenging of heavy metals at environmental relevant concentrations

Graphitic-C3N4 (g-C3N4) nanosheets were prepared by a simple thermal and ultrasonic method. The crystal structure, surface functional groups and morphology of g-C3N4 were characterized by XRD, FITR, SEM, TEM and XPS. The scavenging of heavy metals on g-C3N4 was investigated at environmental relevant concentrations by using batch experiments. The results indicated that g-C3N4 showed high adsorption capacities of 137.4 mg/g for Co(II), 136.9 mg/g for Ni(II), 134.1 mg/g for Cu(II), and 138.0 mg/g for Zn(II), respectively. The Temkin, Freundlich and Langmuir models were used to simulate the adsorption isotherms of heavy metals, demonstrating that the adsorption fitted well with Langmuir model. The ionic strength exhibited little effect on the adsorption of heavy metals on g-C3N4, indicating that the adsorption mechanism of Co(II), Ni(II), Cu(II), Zn(II) on g-C3N4 was mainly dominated by inner-sphere complexation. The thermodynamic data calculated from adsorption isotherms suggested that the adsorption of heavy metals on g-C3N4 was an endothermic and spontaneous process. These results demonstrated that the g-C3N4 was a potential material for the scavenging of heavy metals in water. (C) 2018 Elsevier B.V. All rights reserved.