Graphene quantum dots coated on quartz sand as efficient and low-cost adsorbent for removal of Hg2+ and Pb2+ from aqueous solutions

Herein, a novel, efficient and inexpensive adsorbent based on graphene quantum dots (GQDs) coated on quartz sand (GQDs|QS) for removal of Hg2+ and Pb2+ from aqueous solutions was reported. The GQDs|QS was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray powder diffraction techniques. To optimize operation parameters and study removal efficiency of the prepared adsorbent, a batch removal system followed by anodic stripping voltammetry technique was used during the experiments. The maximum adsorption capacity of GQDs|QS for Hg2+ and Pb2+ were calculated 24.65 and 24.92 mg g(-1), respectively, which reveal more improved adsorption capacitance of the GQDs|QS in comparison with nontreated QS. According to experimental results, adsorption of Hg2+ and Pb2+ on the developed adsorbent follows pseudo-second order kinetic model. In addition, equilibrium experimental data appropriately fit with the Langmuir isotherm (R-2 > 0.99). It was found that the stability and removal performance of the GQDs|QS strongly depend to the particle size of GQDs. Due to low cost, stability and effectiveness of the GQDs|QS, it could be used as a suitable choice for water treatment in industrial scale. (c) 2018 American Institute of Chemical Engineers Environ Prog, 38: S24-S31, 2019