Effective removal of mercury from aqueous solution using thiol-functionalized magnetic nanoparticles

- Thiol-functionalized magnetic nanoparticles were successfully prepared as adsorbents.
- Adsorption capacity of the adsorbent towards Hg(II) was studied.
- Pseudo-second-order and both the Langmuir and Freundlich could describe the data.
- The maximum adsorption capacity of the adsorbent for Hg(II) reaches 344.82 mg/g, by means of thiol groups.
- The exhausted TF-MNPs were a reusable adsorbent with a negligible capacity loss.

The present investigation demonstrates the effective removal of Hg(II) ions from aqueous solution by means of thiol-functionalized magnetic nanoparticles (TF-MNPs). After preparation, TF-MNPs have been characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform-infrared spectroscopy (FT-IR), Thermogravimetric (TG) and vibrating sample magnetometer (VSM). The XRD and FESEM analyses revealed the presence of magnetic nanoparticles with an average particle size of 15-30 nm. The result of FT-IR analysis confirmed that the magnetite nanoparticles have been successfully functionalized by thiol groups. The particles illustrated enough response to a magnetic field, hence they could be easily separated from the aqueous solutions. The amount of the grafted functional groups on the surface was assessed using the TG analysis and was observed to be 34.15%. The adsorption capacity was also investigated as a function of both pH in a range of 2-9 and initial concentration. Pseudo-second-order equation as well as both the Langmuir and Freundlich isotherm models could describe the kinetic data and adsorption equilibrium, respectively. The maximum adsorption capacity of the TF-MNPs was found to be 344.82 mg g−1, which is relatively high. The Hg(II) ions were removed effectively from the surface of TF-MNPs utilizing thiourea in HCl solution. The results also indicated that TF-MNPs could provide improved adsorption capacities for removal of Hg(II) from contaminated water, by means of magnetic separation.

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