Browsing by Author "Gervas, Charles"

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    Functionalized Mesoporous Organo-Silica Nanosorbents for Removal of Chromium (III) Ions from Tanneries Wastewater
    (Springer Link, 2016) Gervas, Charles; Mubofu, Egid B.; Mdoe, James; Revaprasadu, Neerish
    Organo-silica mesoporous materials with cyano functional groups were prepared by a one pot co-condensation of 2-cyanoethyltriethoxysilane (CETS) and tetraethoxysilane (TEOS) at ratios of 1:4 and 1:9 using either sunflower oil or n-dodecylamine as templating agents. The tethered cyano groups were used as adsorption sites or hydrolysed to carboxylic surface functional groups. The prepared materials were characterized by diffuse reflectance infrared Fourier transform spectroscopy, atomic force microscopy (AFM), Brunauer, Emmettt and Teller, thermogravimetric analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Results indicated that materials with cyano and carboxylic surface groups were successfully prepared. AFM results indicated that primary particles with irregular shapes and grain size ranging from 0.28 ± 0.03 to 0.46 ± 0.08 µm were obtained depending on the CETS to TEOS ratio used and the structure directing template. SEM and TEM micrographs depict spherical like morphology of the same size as portrayed by AFM results. Sunflower cyano functionalized micelle template silica (MTS-S-CN) at a ratio of 1:9 had surface area of 760.5 m2/g and average pore diameters of 3.5 nm while MTS-S-CN at a ratio 1:4 had pore diameter of 10.1 nm with surface area of 734.1 m2/g. On the other hand, the MTS-S-COOH (1:9) had surface area of 975.9 m2/g with pore diameter of 4.6 nm whereas MTS-S-COOH (1:4) had surface area of 740.1 m2/g with pore diameter of 6.3 nm. The materials were used in adsorption studies of Cr(III) ions from tannery wastewater. Cr(III) ions removal ranged from 48 to 83 % depending on the adsorbent functional group and the organosilyl groups to silica ratio. This study has indicated that materials prepared were good adsorbents with an adsorption maximum of 19.7 mg Cr(III) ions per g of adsorbent.
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    Lead(II) halide cinnamaldehyde thiosemicarbazone complexes as single source precursors for oleylamine-capped lead sulfide nanoparticles
    (Journal of Materials Science: Materials in Electronics, 2018) Masikane, Siphamandla C; Mlowe, Sixberth; Gervas, Charles; Revaprasadu, Neerish; Pawar, Amol S; Garje, Shivram S
    Different PbX2 (X = AcO, Cl, Br, I) metal salts were complexed to cinnamaldehyde thiosemicarbazone ligand. The resulting complexes were characterised using Fourier Transform Infrared spectroscopy, 1H and 13C {1H} Nuclear Magnetic Resonance spectroscopy, elemental analysis and thermogravimetric analysis techniques. They were then used as single source precursors for the preparation of lead sulfide (PbS) nanoparticles using the colloidal thermolysis route where oleylamine is used as the passivating agent. Each SSP is thermolysed at reaction temperatures of 190, 230 and 270 °C. Predominantly cubic-shaped PbS nanoparticles were obtained, with an exception of the truncated nanocubes obtained from thermolysis of the SSP prepared from lead bromide. Varying particle sizes are obtained when the halogen is varied, ranging from ca. 50 to 400 nm. The optical absorbance of the PbS nanoparticles in the UV-Vis- NIR range was found to be blue-shifted when compared to bulk PbS.
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    Phase pure Ni3S2 and NiS from bis(N′-ethyl-N-piperazinylcarbodithioato-S,S′)–nickel(II) via solvent thermolysis and aerosol assisted chemical vapour deposition.
    (New Journal of Chemistry, 2018) Gervas, Charles; Mlowe, Sixberth; Akerman, Matthew P; Revaprasadu, Neerish
    A bis(N′-ethyl-N-piperazinylcarbodithioato-S,S′)–nickel(II) complex was prepared and characterized using infrared spectroscopy, thermogravimetric and elemental analyses. The crystal X-ray structure for bis(N′-ethyl-N-piperazinylcarbodithioato-S,S′)–nickel(II) was determined. The complex was subsequently used as a single source precursor (SSP) for the synthesis of phase pure Ni3S2 and NiS nanoparticles and thin films via hot injection thermolysis and aerosol assisted chemical vapour deposition (AACVD) routes, respectively. For the hot injection thermolysis route, hexadecylamine (HDA) and oleylamine (OLA) were used as capping groups at varying temperatures. Chloroform was used as the solvent in the AACVD experiments. Powder X-ray revealed that the capping group does not change the phase of nanoparticles formed whereas the AACVD technique produced different phases. Variation of temperature did not affect the phase purity of the nanomaterials formed. The morphology of the thin films obtained via AACVD depended largely on the deposition temperature, whereas for the nanoparticles, temperature and the capping group had a significant impact.