Thermodynamics of sorption of platinum on superparamagnetic nanoparticles functionalized with mercapto groups

The adsorption of Pt(IV) by iron oxide (Fe3O4) superparamagnetic nanoparticles (SPION) functionalized with 3-mercaptopropionic acid (3-MPA) is investigated by means of inductively coupled plasma optical emission spectrometry and isothermal titration calorimetry. Experimental ICP data are better fitted by Langmuir rather than Freundlich isotherms. The whole thermodynamic parameters and maximum loading capacity for the adsorption process of Pt(IV) on the functionalized SPION nanoparticles (SPION@3-MPA) are obtained. The process is enthalpy-driven, while entropy is largely unfavourable suggesting that some other interaction should be present in addition to the electrostatic ones with the coverage surface. When compared to other thiol-functionalized materials, the SPION@3-MPA can be considered an interesting adsorbent for Pt(IV), especially with respect to the short contact time evidenced.