http://hdl.handle.net/10204/2250 2013-05-24T07:19:56Z http://hdl.handle.net/10204/6735 Title: Chromium(VI) removal from water using fixed bed column of polypyrrole/Fe3O4 nanocomposite Authors: Bhaumik, M; Setshedi, K; Maity, A; Onyango, M.S Abstract: The adsorption of Cr(VI) using polypyrrole/Fe3O4nanocomposite adsorbent was investigated in a continuous flow fixed-bed column. The effects of composition of the nanocomposite, adsorbent mass, influent Cr(VI) concentration and flow rate on the adsorption characteristics of adsorbent was explored at pH 2. Experimental results confirmed that the breakthrough curves were dependent on bed mass, initial Cr(VI) concentration and flow rate. Three kinetic models; Yoon–Nelson, Thomas, Bohart–Adams were applied to the experimental data to predict the breakthrough curves using linear regression and to determine the characteristic parameters of the column that are useful for process design. The Yoon–Nelson and Thomas models were found appropriate for description of the whole breakthrough curves, whereas the Bohart– Adams model could only predict the initial part of the breakthrough curves. Using environmental water, the PPy/Fe3O4nanocomposite demonstrated its effectiveness in Cr(VI) removal below acceptable level by processing 5.04 L water with initial 76.59 mg/L Cr(VI) concentration using only 2 g of adsorbent mass. It can be concluded therefore that PPy/Fe3O4media provides alternative solution to ameliorate water contaminated with Cr(VI). Description: Copyright: 2013 Elsevier. This is a ABSTRACT ONLY. The definitive version is published in Separation and Purification Technology, Vol.110, pp11-19 2013-06-07T00:00:00Z http://hdl.handle.net/10204/6711 Title: Solar absorption and thermal emission properties of multiwall carbon nanotube/nickel oxide nanocomposite thin films synthesized by sol-gel process Authors: Roro, KT; Tile, N; Mwakikunga, B; Yalisi, B; Forbes, A Abstract: Multiwall carbon nanotubes (MWCNTs)/nickel oxide (NiO) nanocomposites were successfully prepared by a sol–gel process and coated on an aluminium substrate. The MWCNTs were chemically functionalized and then added into NiO alcogels, and magnetic stirred for homogeneous dispersion into the NiO matrix solution. The morphology of the resulting nanocomposite thin films showed that the MWCNTs were embedded in the NiO nano-particle matrix, while HRTEM confirmed that the MWCNTs were surrounded by the NiO nano-particles. Raman spectra for functionalized MWCNTs displayed a red shift from the pristine MWCNTs suggesting successful purification/functionalization. The spectrum for the MWCNTs/NiO nanocomposite indicated the presence of both the TO and LO phonons of NiO, and the D and G bands of the MWCNTs. Red and blue shifts of the NiO phonons and the MWCNT phonons suggested that the vibrational properties of both materials were changed to form new nanocomposite vibrational properties. Despite unoptimized layer thickness and composition, the solar absorptance of the functionalized MWCNTs/NiO nanocomposite films was 0.84 (for a single layer). The thermal emittance at 100 °C was approximately 0.2. These results suggest that MWCNTs/NiO nanocomposite materials are suitable for solar thermal applications. Description: Copyright: 2012 Elsevier. This is an ABSTRACT ONLY. The definitive version is published in Materials Science and Engineering: B, vol. 177(8), pp 581–587 2012-05-01T00:00:00Z http://hdl.handle.net/10204/6660 Title: High efficient removal of chromium (VI) using glycine doped polypyrrole adsorbent from aqueous solution Authors: Ballav, N; Maity, A; Mishra, SB Abstract: Glycine doped polypyrrole (PPy-gly) adsorbent was prepared via in situ polymerization of pyrrole (Py) monomer in the presence of glycine (gly) for the removal of Cr(VI). Formation of PPy homopolymer and inclusion of gly in the PPy matrix were confirmed by ATR-FTIR and XRD, respectively. Field emission scanning electron microscopic imaging of PPy-gly revealed the formation of nearly spherical agglomerated particles. The adsorption of Cr(VI) onto the PPy-gly adsorbent was highly pH dependent and removal efficiency by PPy-gly was much higher compared to PPy homopolymer. The kinetic process followed pseudo-second-order rate model with equilibrium reached within 30–150 min. Intra-particle diffusion model was also applied for better understanding of kinetic mechanism. Isotherm data fitted well with the Langmuir isotherm model with maximum adsorption capacity of 217.39–232.55 mg/g at 25–45 °C. Desorption experiment showed PPy-gly can be regenerated and reused for three consecutive cycles without loss of its removal efficiency. The adsorption process for the removal of Cr(VI) was governed by the ionic interaction between protonated amine groups of gly and ions. Description: Copyright: 2012 Elsevier. This is an ABSTRACT ONLY. The definitive version is published in Chemical Engineering Journal, vol. 198-199, pp 536–546 2012-08-01T00:00:00Z http://hdl.handle.net/10204/6635 Title: Hot wire and spark pyrolysis as simple new routes to silicon nanoparticle synthesis Authors: Scriba, MR; Britton, DT; Härting, M Abstract: Monocrystalline silicon nanoparticles with a mean diameter of between 30 and 40 nm have been synthesised by hot wire thermal catalytic and spark pyrolysis at a pressure of 40 and 80 mbar respectively. For the production a mixture of the precursor gases, silane and diborane or silane and phosphine were used. While hot wire pyrolysis always results in multifaceted particles, those produced by spark pyrolysis are spherical. Electrical resistance measurements of compressed powders showed that boron doped silicon powders have a much higher conductivity than those doped with phosphorus. TEM and XPS analysis reveals that the difference in electrical resistivity between boron an phosphorus doped particles can be attributed to phosphorus dopants being located at the surface of the particles where an oxide layer is also observed. In contrast, boron doped particles are far less oxidised and the dopant atoms can be found in the core of the particle. The results demonstrate that hot wire and spark pyrolysis offer a new simple route to the production of monocrystalline doped silicon nanoparticles suitable for printed electrical devices. Description: Nanostructured Materials and Nanotechnology VI: A collection of papers presented at the 36th International Conference on Advanced Ceramics and Composites January 22-27, 2012, Daytona Beach, Florida. Published by Wiley-Blackwell 2012-11-01T00:00:00Z