Derived N-doped carbon through core-shell structured metal-organic frameworks as a novel sorbent for dispersive solid phase extraction of Cr(III) and Pb(II) from water samples followed by quantitation through flame atomic absorption spectrometry

Abstract

Highly porous carbon material is one of the most widely used sorbents in removing Cr and Pb from polluted water. Moreover, heavy metal ions of Pb(II) and Cr(III) have become the global health and environmental concerns. A novel nanoporous Zn/Co/C derived from ZIF-8/ZIF-67 core-shell was reported in the present study. The prepared sorbent was used for dispersive solid phase extraction of Cr(III) and Pb(II) ions. The extracted ions were then eluted by the aid of the acidic solution (HNO3) and analyzed via flame atomic absorption spectroscopy (FAAS). The prepared carbon materials were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), N2adsorption-desorption and Fourier transform infrared spectroscopy (FT-IR). The characterization results indicated that the prepared porous carbon surface had functional groups such as -COOH, -OH, CeOeC, etc. which can act as active sites during the adsorption process. The capacity of the sorbent ranged from 520 to 375 mg g −1 . Under the optimum condition, the cal-culated limits of detections were 0.21 and 0.40 μg L −1 for Cr(III) and Pb(II) ions, respectively. The relative standard deviations (RSDs) were lower than 5.0%. The surface area and pore volume of the prepared sorbent were 128 m 2 g −1 and 0.25 cm 3 , respectively. In addition, the effects of foreign ions on the extraction capability of the sorbent were also investigated. The results indicated that the vast majority of transition, alkaline, and earth alkaline metals do not interfere with environmentally relevant concentrations. The presented method was validated through analyzing standard reference material. Different types of real samples were analyzed in order to investigate the capability of the method for facile preconcentration of Cr and Pb ions.