Graphene oxide/Fe3O4/polyaniline nanocomposite as an efficient adsorbent for the extraction and preconcentration of ultra-trace levels of cadmium in rice and tea samples

Abstract

The magnetic graphene oxide–polyaniline (MGOPA) nanocomposite was synthesized through oxidative polymerization of aniline and at the presence of Fe3O4–GO. The composite was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction analysis, and vibrating sample magnetometry. The as-synthesized adsorbent was used for the extraction and preconcentration of the ultra-trace amount of cadmium, followed by electrothermal atomic absorption spectrometry detections. Different parameters, in particular sample pH, adsorbent dose, sample volume, adsorption time, eluent type, and desorption time, were investigated. The optimum conditions were pH 8, a sample volume of 40 mL, 4.0 × 10–3 g of MGOPA, and 2 mL of nitric acid solution (2.0 mol L−1) as eluent. The responses were linear in the range of 1.0 × 10–2–1.5 × 10–1 µg L−1 with a detection limit of 3.6 × 10–3 µg L−1 and a relative standard deviation of 4.2% at 5.0 × 10–2 µg L−1. Also, excellent recoveries (90–95%) were obtained with an enrichment factor of 400. Further studies showed that the adsorption of Cd(II) onto the MGOPA follows the Langmuir isotherm with the maximum adsorption capacity of 1.4 × 102 mg g−1. The proposed method was successfully used for the determination of cadmium in different tea and rice samples.