Abstract: Cobalt ferrite (CoFe2O4) nanoparticles prepared via co-precipitation method were modified with tetraethoxysilane (TEOS) and additional funkcionalized with 3-mercaptopropyl trimethoxysilane (MPTMS) with purpose of cleaning waste water contaminated with heavy metal ions (Pb2+ and Hg2+).
The influence of different experimental parameters (reaction time, reaction temperature and different TEOS:MPTMS ratios) on silica coating of CoFe2O4 nanoparticles and additional on thiol group was systematically studied. Silanes adsorb to the particle surface with alkoxy (Si(OR)4) groups at one end, while functional substituents (-SH) at the opposite end stay extended into surrounding aqueous medium and chemically interact with heavy metal contaminates.
Thiol functionalized CoFe2O4 nanoparticles were characterized using IR spectroscopy, X-ray diffraction (XRD), transmission electron microscopy/high-resolution transmission electron microscopy (TEM/HRTEM), energy-dispersive X-ray spectroscopy (EDXS) and vibrating-sample magnetometer (VSM).
The thiol functionalized CoFe2O4 nanoparticles were used for Pb2+ and Hg2+ions adsorption from aqueous media. Effect of treatment has been demonstrated using atomic absorption spectroscopy (AAS).Keywords: cobalt ferrite, magnetic nanoparticles, tetraethoxysilane, 3-mercaptopropyl trimetoxysilane, thiol group, lead, mercury, adsorptionPublished: 02.12.2014; Views: 1294; Downloads: 82 Full text (5,22 MB)
Abstract: This thesis aims to explain the process of porous bead synthesis. The porous beads were prepared from a multiple emulsion water-in-oil-in-water (W/OW) system. The W/O/W multiple emulsion was made up of a High Internal Phase Emulsion (HIPE (primary emulsion)) and a suspension phase. The HIPE consisted of pentaerythritol tetrakis (3 mercaptopropionate) (TT) in combination with either divinyl adipate (DVA) or trimethylolpropane triacrylate (TMPTA) and an internal phase volume fraction of 80 %. The suspension phase consisted of an aqueous phase with dissolved surfactants which stabilised the secondary emulsion. The surfactants which stabilised the secondary emulsion were polyvinylpyrrolidone K30 (PVP K30) and polyvinylpyrrolidone K90 (PVP K90).
The polymerisation was carried out thermally at first for 24 hours and later under UV light and daylight, as the thermally initiated polymerisation was unsuccessful due to coalesence. The beads that were obtained using the photoinitiated polymerisation were porous with a mostly bicontinuous structure and varying diameters. The viscosity of the primary emulsion (HIPE) had the greatest influence on the stability of the entire W/O/W emulsion. By adding more than 5 wt. % of toluene to the primary emulsion, the emulsion broke down and did not successfully polymerise. Another important factor was the ratio of the functional groups in the case of TT-co-TMPTA, which greatly affected the yield and structure of the obtained beads.
The diameters of the spherical particles were dependent on the viscosity, monomer ratio and surfactant used in the suspension phase. The inner structure of the beads was mostly bicontinuous with occasional pores that resembled a polyHIPE structure.
The obtained beads had a yield of up to 80 % in the case of TT-co-DVA and a yield of up to 90 % in the case of TMPTA-co-DVAKeywords: polyHIPE, thiol-ene, suspension polymerisation, porous beads, HIPEPublished: 17.09.2019; Views: 33; Downloads: 10 Full text (3,56 MB)