Efficiency of SPIONs functionalized with polyethylene glycol bis (amine) for heavy metal removal

Hybrid magnetic nanoparticles based on poly(methylmethacrylate) (PMMA) and super-paramagnetic iron oxide nanopaticles (SPIONs) with selective surface modification has been developed for heavy metal removal by applying external magnetic fields. The nanoparticles were prepared by the emulsion polymerization technique in an aqueous suspension of SPIONs. The hydrolysis of carboxyl functional group was then applied for grafting polyethylene glycol bis(amine)(PEG-bis(amine)) onto the PMMA-coated SPIONs. The morphology, the chemical structure and the magnetic properties of the grafted nano particles were investigated. The efficiency of the hybrid nanoparticles for heavy metal removal were conducted on Pb(II), Hg(II), Cu(II) and Co(II) in aqueous solutions. The metal concentration in the solutions after separation by the hybrid nanoparticles was determined by inductively coupled plasma optical emission spectrometer (ICP-OES). The results show the heavy metal uptake ratios of 0.08, 0.04, 0.03, and 0.01 mM per gramme of the grafted SPIONs for Pb(II), Hg(II), Cu(II), and Cu(II), respectively. A competitive removal of Cu(II), Pb(II), Co(II) and Hg(II) ions in mixed metal salt solutions has also been studied. The heavy metal removal efficiency of the hybrid nanoparitcles was found to depend on the cation radius, in accordance with capture of metal ions by the amine group. (C) 2016 Elsevier B.V. All rights reserved.

Design, Synthesis and Characterization of New Nanoparticle Stabilizers and Their Application in Catalysis

Ilaria Biondi

In recent years, a strong emphasis in research towards creating sustainable and environmental friendly chemical processes has propelled the development of novel types of catalytic systems that combine advantages from homogeneous and heterogeneous processes. In this respect, transition metal based nanoparticles, TM-NPs, are excellent candidates with properties that offer high efficiency, high selectivity and the possibility of recycling. However, due to the particularly small size, within the nanoscale, TM-NPs are generally only kinetically stable and must be supported or stabilized by molecular systems to prevent aggregation into larger, less active materials. The work presented herein concerns the design, synthesis, characterisation and the applications of new TM-NP protecting agents, which are based on polymers functionalized with components that compose ionic liquids, P-ILs. Specifically, these P-ILs feature a hydrophobic poly-norbornene framework prepared using Ring Opening Metathesis Polymerization, ROMP, with pendant imidazolium-based ionic liquid substituents that allow fine tuning of the polymer solubility by anion-exchange. In Chapter 2, an aqueous, soluble P-IL containing the 1,2-dimethylimidazolium methane-sulphonate substituent and its use in the synthesis of aqueous gold NP, GNP, solutions is described. These particular TM-NPs were characterized by UV-VIS spectroscopy and Transmission Electron Microscopy, TEM. Subsequently, the P-IL/GNP solutions were used to catalyse the reduction of p-nitrophenol and the hydrogenation of cinnamaldehyde, both reactions are found to exhibit excellent activity under mild conditions. In Chapter 3, the potential of aqueous P-IL stabilizers to transfer GNPs from water to hydrophobic ILs and organic solvents is demonstrated. Using an anion-exchange process, the phase change does not result in GNP aggregation, as confirmed by UV-VIS spectroscopy and TEM analysis. Moreover, the same P-ILs were used as a protecting agents for the synthesis of aqueous rhodium NPs, RhNPs, which have been applied in the catalytic hydrogenation of natural compounds, including limonene, cinnamaldehyde, citral and α- and β-ionones. Through anion-exchange, the aqueous P-IL stabilized RhNPs are readily transferred into hydrophobic ILs, then used as catalysts in the hydrogenation of styrene and limonene. The stabilized RhNPs exhibited good activity, even after recycling. X-ray Photoelectron Spectroscopy, XPS, analysis demonstrated conclusively that the anion exchange and phase transfer of the Rh/Au-NP-IL system. In Chapter 4, three P-ILs containing poly-oxy linker groups, strategically placed between the poly-norbornene framework and the ionic groups, are described. The linkers provide additional stabilization through steric stabilization and coordination via the ether functional groups. These P-ILs were used to stabilize aqueous GNPs, which were characterized by UV-VIS spectroscopy and TEM. Their application in the reduction of p-nitrophenol reduction was demonstrated. Preliminary studies on the stabilization mode of PILs shown that the polymers, despite the presence of ionic groups, can stabilize electrostatically stabilized aqueous GNPs which otherwise aggregate in presence of water soluble imidazolium-based ILs. Moreover, they display good efficiency in terms of steric stabilization, comparable to systems featuring the poly-vinylpyrrolidone, PVP.

EPFL2011

Design, Synthesis and Characterization of New Nanoparticle Stabilizers and Their Application in Catalysis

Ilaria Biondi

EPFL2011