Application of MoS42−intercalated magnetic layered double hydroxide for preconcentration of cadmium and lead from water samples

Abstract

A MoS₄²⁻-intercalated magnetic FeMgAl layered double hydroxide (Fe₃O₄@MoS₄²⁻-FeMgAl LDH) nanocomposite was synthesised via hydrothermal assisted exfoliation. The material was applied as the adsorbent for extraction, preconcentration and removal of cadmium ions (Cd²⁺) and lead ions Pb²⁺ from wastewater and river water. The structural properties and morphologies of the adsorbent were determined by transmission electron microscopy (TEM), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS), Fourier transform infrared spectroscopy (FTIR), zeta potential and X-ray diffraction (XRD). The parameters influencing preconcentration and the adsorptive removal process were optimised using the central composite design (CCD) method. The concentration of Cd²⁺ and Pb²⁺ in the samples was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The preconcentration method developed in the study was ultrasound-assisted magnetic solid phase extraction (UA-MSPE). Under optimum conditions, linearity was 0.1-800 µg/L with a correlation of determination (R²) of 0.9987. The uncertainty of the slope and the uncertainty of the intercept were both lower than the uncertainty of the calibration indicating good precision, selection of standards closest to a blank and wide range. Precision expressed as %RSD for both intra-day (n = 27) and inter-day (n = 9) were found to be 3.3 % and 7.0 % respectively. The limit of detection (n = 10) and limit of quantification (n = 10) of the UA-MSPE/ICP-OES were 0.03 µg/L and 0.10 µg/L. The developed method was applied for real sample analysis. Herein, influent wastewater was reported as 1.77 ± 0.14 and 6.53 ± 0.33 ug/L for Cd²⁺ and Pb²⁺, respectively while the effluent was reported at 0.96 ± 0.07 and 2.57 ± 0.13 ug/L, respectively. River water samples were found to be 0.45 ± 0.01 and 1.23 ± 0.04 ug/L, respectively proving that the adsorbent is capable of preconcentrating the target analytes.