Three-dimensional magnetic graphitic carbon nitride composites as high-performance adsorbent for removal Pb 2+ from aqueous solution

Abstract Three-Dimensional magnetic nanocomposite (Fe 3 O 4 @g-C 3 N 4 ) was first prepared and used to removal Pb 2+ from aqueous solution by adsorption method. Various of techniques were used to character Fe 3 O 4 @g-C 3 N 4 such as scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and thermo-gravimetric analyzer (TGA). Batch experiments with different pH, initial concentration, contact time and ionic strength were used to evaluate the adsorption performance of Fe 3 O 4 @g-C 3 N 4 . The adsorption kinetics data followed pseudo-second-order model. The isothermal adsorption equilibrium data were best described by Langmuir model and predicated adsorption capacity was 423.73 mg g −1 for Pb 2+ . The result of X-ray photoelectron spectroscopy (XPS) survey spectrum suggested that the main adsorption mechanism of Fe 3 O 4 @g-C 3 N 4 for Pb 2+ is the coordination between conjugated π-electron pairs of heptazine (C 6 N 7 ) units or triazine ring (C 3 N 3 ) units and sp 2 C N with metal ions. By comparing the adsorption capacities of Fe 3 O 4 , g-C 3 N 4 and Fe 3 O 4 @g-C 3 N 4 , it can be found that the adsorption capacity of g-C 3 N 4 would increase by increasing the layer spacing. Fe 3 O 4 @g-C 3 N 4 could be regenerated by HNO 3 and the adsorption capacity of regenerative Fe 3 O 4 @g-C 3 N 4 could maintain 89.3% after five cycles. The adsorption capacity of Fe 3 O 4 @g-C 3 N 4 for Pb 2+ is 121.42 mg g −1 in acid electrolytic zinc residue percolate. Therefore, the Fe 3 O 4 @g-C 3 N 4 is a potential adsorbent for removing Pb 2+ from wastewater.