Impact of key geochemical parameters on the highly efficient sequestration of Pb(II) and Cd(II) in water using g-C3N4 nanosheets

Graphitic-C3N4 (g-C3N4) nanosheets were synthesized successfully and characterized by SEM, TEM, FI-TR, XRD, BET and XPS. A series of experimental results for the removal of Pb(II) and Cd(II) from wastewater were investigated. The g-C3N4 nanosheets exhibited high adsorption capacity towards Pb(II) and Cd(II), which can reach 395.54 mg/g and 206.40 mg/g at T = 333 K, pH = 6.3, CNaNO3 = 0.01 mol/L. The adsorption kinetics of Pb(II) and Cd(II) complied with the pseudo-second-order model. The Freundlich and Langmuir models were used to simulate the adsorption isotherms of Pb(II) and Cd(II), and the results revealed that the adsorption of Pb(II) on g-C3N4 nanosheets coincided with monolayer adsorption, while the Cd(II) on g-C3N4 nanosheets coincided with multilayer adsorption. The thermodynamic parameters (ΔG0 < 0, ΔH0 > 0) revealed that the adsorption process was a spontaneous endothermic process. The experimental results revealed that the as-prepared g-C3N4 nanosheets can be utilized as a friendly, efficient and economical adsorbent for the purification of wastewater.