لیما طیبی

A novel post-synthetic modification of magnetite@MIL-53(Fe)-NH2 core-shell nanocomposite was performed to extract ultra-trace amounts of Pd(II) ions from the real samples. To explore and optimise the effect of parameters on the preconcentration design of the experiment was employed. The highest removal efficiency in the adsorption step was obtained using the following condition: pH of sample, 6.5; adsorption time, 3.8 min; magnetite@MIL-53(Fe)-NHPITC NPs amount, 20 mg. The highest extraction recovery (%) was achieved using 0.8 mL of 0.85 mol L−1 HCl as the desorbing solution; and by applying an elution time of 3.5 min. Afterwards, to study the equilibrium data, various adsorption isotherm models were explored. The data showed that the Langmuir model describes the adsorption process better than the other models. Eventually, the maximum adsorption capacity and model constant equal to 100 mg g−1 and 0.11 L mg−1, were obtained, respectively. Besides, the kinetic data were well fitted to the pseudo-second-order based on the highest correlation coefficient that was achieved. The limit of detection, the limit of quantification, and the linear range of the proposed method were 0.05 μg L−1, 0.2 μg L−1, and 0.2–100 μg L−1 (r2 = 0.9936), respectively. The precision was explored as relative standard deviation value at three concentration of 0.5, 10, 75 ng mL−1 (n = 3) that was 12.5%, 9.3% and 6.6%, respectively. Ultimately, the new magnetic adsorbent could be employed for extraction/quantification of ultra-trace amounts of Pd(II) ions in real samples and the relative recovery values were obtained in the range of 88–102%.