A new dendrimer-functionalized magnetic nanosorbent for the efficient adsorption and subsequent trace measurement of Hg (II) ions in wastewater samples

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A new dendrimer-functionalized magnetic nanosorbent for the efficient adsorption and subsequent trace measurement of Hg (II) ions in wastewater samples was successfully synthesized. The synthesis is accomplished via the Michael addition reaction of the amino groups of the silica-coated magnetic nanoparticles (APTES-modified Fe3O4@SiO2) with the double bond of methyl acrylate followed by the amidation of the resulting methyl ester with ethylene diamine. Following that, some donor functional groups were attached to the dendrimer via a specific chemical reaction to offer a further selectivity to the dendrimer-based nanosorbent. Once the synthesis is accomplished, the as-prepared nanosorbent was characterized by several analytical techniques such as FT-IR, SEM, VSM, TGA and EDX. Following that, Hg (II) ions were adsorbed onto the active sites of the sorbent through the complexation with the dentates (-N, -S) of the dispersed sorbent, which seems to be the cornerstone of the adsorption process. In the next step, the ions were desorbed off the sorbent and measured by a cold vapor atomic absorption spectrometer (CV-AAS). The impact of a number of influential variables such as pH, sorbent dosage, adsorption time, elution features were assessed and subsequently optimized. Under the optimal conditions, a relatively wide linearity was obtained for the analyte of interest in the range of 0.08–6.0 μg/L with the correlation coefficients (R2) of 0.9922 and the method detection limit (MDL) was determined to be 0.03 μg/L. Satisfactory relative recoveries of the analyte varied within 90.0–106.7% with the relative standard deviations (RSD%) of 2.1–5.3%. In addition, a number of experiments with regard to the equilibrium adsorption isotherms of the target ion was performed which well fitted to the Langmuir isotherm model. Finally, the results indicated that the whole method was sensitive, effective and practical for the adsorption and trace measurement of Hg (II) in wastewater samples.