▎ 摘　　要

The green and simple synthesized novel graphene/MnO2-QD (quantum dot) nanocomposites are reported in the present work. The nanocomposite was applied as solid-phase extraction (SPE) adsorbent for removing Ni2+ and Cr6+ heavy metal ions from water and wastewater samples. Graphene (G) and MnO2 as the nanocomposite components were successfully synthesized by totally green methods. Pomegranate juice was applied to prepare graphene nanosheets and wheat extract for MnO2-QDs. The nanocomposite was subsequently characterized by UV-Vis spectroscopy, Fourier transformed infrared spectroscopy, Raman spectrum, high-resolution transmission electron microscope, field-emission scanning electron microscope, and X-ray diffraction techniques. The particle size distribution of MnO2-QDs was in the range of 2-6 nm. Important experimental variables that could affect SPE performance (removal time and temperature, dosage of adsorbent and analyte, pH values) were investigated and optimized. Under optimized conditions, the limits of detection of heavy metal elements ranged from 0.33 to 0.58 mg L-1. Repeatability and reproducibility of the proposed method investigated and varied between 3.9% and 5.82%, and 7.63% and 9.21% (n = 5), respectively. For real sample analysis, river water and a tool of factory wastewater samples were studied. The present approach was successfully applied to removing target heavy metals in real samples.