Simultaneous separation and preconcentration of lead and cadmium from water and vegetable samples using a diethylenetriamine-modified magnetic graphene oxide nanocomposite

An efficient adsorbent, diethylenetriamine-functionalized magnetic graphene oxide nanocomposite (GO-Fe3O4-DETA), was synthesized through the formation of amide linkage bonds between the amine groups of diethylenetriamine and the oxygen-containing functional groups (e.g., epoxy and carboxyl groups) of graphene oxide. The prepared adsorbent was characterized by scanning electron microscopy, vibrating sample magnetometry and Fourier transform infrared spectroscopy. The synthesized GO-Fe3O4-DETA was applied as an efficient adsorbent for the simultaneous extraction and preconcentration of trace quantities of lead and cadmium ions from water and vegetable samples. Following extraction, the ions were determined by flame atomic absorption spectrometry. Several important parameters influencing the extraction efficiency, such as pH, amount of adsorbent, extraction time, elution conditions, sample volume, interfering ions and adsorption capacity, were studied and optimized. Under the optimum extraction conditions, the calibration curves were linear in the range of 1.35 to 110 mu g L-1 for Pb(II) and 1.40 to 120 mu g L-1 for Cd(II) in the initial solution. The limits of detection were 0.38 mu g L-1 and 0.40 mg L-1 for lead and cadmium, respectively. Precisions, expressed as relative standard deviations, were 1.86% and 2.38% for Pb(II) and Cd(II), respectively. The preconcentration factors were 167 for lead and 150 for cadmium and the maximum adsorption capacity of the modified adsorbent was found to be 172.41 and 59.88 mg g(-1) for lead and cadmium, respectively. The recoveries in the case of real samples varied within the range of 94.4-103.9% confirming the good performance of the method in various water and vegetable samples.