This investigation studies the adsorption of Pt2+ and Au3+ ions from nitrate solutions using nanoparticles of magnetite (Fe3O4) synthesized in this work. The study is carried out by the analysis of the adsorption of Pt2+ and Au3+ ions on the surface of the nanoparticles by modifying several variables: contact time, solution pH, and initial Pt2+ and Au3+ ion concentration. The highly crystalline nature of the magnetite structure with a diameter of around 10 nm was characterized with transmission

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... electron microscopy (TEM) and X-ray diffractometry (XRD). The surface area was determined to be 117.5 m2.g-1. The surface functional groups were investigated with Fourier transform-infrared spectroscopy (FTIR) as well. Batch experiments were carried out to determine the adsorption kinetics and mechanism of Pt2+ and Au3+ by these magnetite nanoparticles. The adsorption process was found to be pH dependent. The adsorption process better followed the pseudo-second-order equation and Freundlich isotherm. It has been found that the equilibrium can be attained in less than 5 min. Immersion microcalorimetry was explored as a new tool to establish the adsorption capacity of the ions under study with promising results.