Investigation of layered double hydroxide/carbon dot nanocomposite on removal efficiency of Pb2+ from aqueous solution

Abstract

In this study, double layered hydroxide (LDH)/carbon dot (C-dot) nanocomposite was synthesized using coprecipitation and hydrothermal methods, respectively, and used to remove Pb2+ ions from water. The chemical composition and morphology of the Mg-Al LDH/C-dot nanocomposite structure were investigated by Fourier transform infrared spectroscopy (FT-IR), x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and fluorescence spectroscopy (FS). Batch adsorption was accomplished to evaluate the process of Pb2+ adsorption by Mg-Al LDH/C-dot nanocomposite. For this purpose, parameters were optimized such as pH, C-dot to Mg-Al LDH ratio, adsorbent dosage, and contact time. The value obtained are 7, 0.25, 16 mg and 40 min, respectively. The results showed that the adsorption of Pb2+ on the Mg-Al LDH/C-dot nanocomposite has a maximum adsorption capacity of 41.32 (mg.g−1), which can be attributed to the available presence of functional groups. The adsorbent performance was investigated by the Langmuir, Freundlich and Dubinin-Radushkevich isotherms and the pseudo-first-order and pseudo-second-order kinetic models, respectively. Adsorption isotherm followed the Langmuir equation, that demonstrate monolayer adsorption and the pseudo-second-order kinetic model shows that a chemical adsorption controls the reaction rate. According to the results, the Mg-Al LDH/C-dot nanocomposite can be considered as an efficient adsorbent for the adsorption of Pb2+ ion from aqueous solution.