Browsing by Author "Makene, Joseph"

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    Preparation of cashew nut shell liquid templated thiol-silica composites and their application in heavy metal adsorption front aqueous solutions.
    (University of Dar es Salaam, 2011) Makene, Joseph
    A range of thick-silica composites (TSC) were successfully prepared using cashew nut shell liquid (CNSL) or one of its phenolic constituents, the cardanol, "templates. The procedure involved formation of a CNSL/ cardanol emulsion in a water-ethanol system into which thiol containing alkoxysilane and a silica precursor, viz., tetraethoxysilane (TAOS), were simultaneously added at various ratios. Aging of the reaction mixture at room temperature for 18 hours gave a pasty material which afforded finely powdered particles upon template extraction and drying. The resulting materials were characterized by Diffuse Reflectance Fourier Transform Infrared and acid titration. The results showed that indeed the thiol group was attached onto the silica surface framework with loadings ranging from 1.7 to 2.5 mmol/ g. Efficiency of the resulting Thiol Silica Composite (TSC) in removing heavy metal ions from aqueous solution was studied using Pb2 ion solutions. Results were obtained from batch experiments, by monitoring the Pb2+ ion depletion in suspensions containing I'SC particles. They were then discussed in relation to loading and template type. As a general trend, the metal ion removal efficiency was found to increase with thiol group loading and use of low cost surfactant (cardanol or CNSL) as template. The experimental data were found to correlate well with the Langmuir model than the Freundlich model indicating a monolayer adsorption process. The maximum PbZ* ion adsorption on the material was found to be 64.5 mg/ g.