Controllable synthesis of zeolitic imidazolate frameworks and the peanut shell carbon composite for sensitive and selective detection of Pb2+ and Cd2+ ions

Zeolitic imidazolate frameworks (ZIF) and the peanut shell carbon (PSC) composite (ZIF-8 @PSC) nanocomposite is successfully fabricated and exhibits superior current response for simultaneously detecting Pb2+ and Cd2+. The obtained composite has been characterized via SEM, TEM, XRD, FTIR, N2 adsorption-desorption methods. The suitable pore structure of ZIF-8 @PSC with the highest mesoporous ratio (ca. 11%) is conducive to mass transportation and charge transfer. The available specific surface area (236.6 m2 g−1), the lowest internal resistance (81.8 Ohm) as well as the synergistic effect between ZIF and PSC in ZIF-8 @PSC(4−1) electrode contribute to the enhanced current signals for the detection of Pb2+ and Cd2+ in aqueous solution. Additionally, the cyclic voltammetry investigation reveals that the kinetic process of the target heavy metal ions on the surface of the ZIF-8 @PSC(4−1) electrode is controlled by diffusion, which is verified by the Warburg impedance in low frequency region. Under the optimum conditions, the peak currents are linearly related with the concentration of Pb2+ and Cd2+ in the range of 0.1–8 µM (Pb2+) and 0.06–9 µM (Cd2+), and the corresponding limit of detection is 8.25 nM (S/N = 3) and 16 nM (S/N = 3), respectively, which are superior to other reported results. Based on the outstanding selectivity, stability, repeatability, and reproducibility, the analytical performance for the detection of the metal ions is assessed individually and simultaneously. It is found that the obtained method exhibits simultaneous sensing ability toward Cd(II) and Pb(II). During the multi-component sample, the detection and quantification of Pb(II) is more sensitive. Finally, the proposed method is applied to detect Pb2+ and Cd2+ in domestic sewage and satisfactory results have been achieved.