Augustus Newton Ebelegi, Jackson Godwin, Nimibofa Ayawei* and Donbebe Wankasi
An amine terminated G 5.0 Polyamidoamine dendrimer was functionalized with Succinic anhydride and immobilized on chromatography grade silica gel to produce a functionalized dendrimer-silica composite (G-5- PAMAM-SGA). The composite was characterized using Fourier Transform-Infra Red spectroscopy, Brunauer Emmett and Teller surface area analysis, Thermogravimetric Analysis, Zeta Potential, and Scanning Electron Microscopy. Adsorption properties of the synthesized composite were studied by batch adsorption method using Cd (II) as adsorbate. The sorption process was analyzed using 6 different isotherm models (Langmuir, Freundlich, Harkins-Jura, Sips, Jossens and Baudu).
The experimental data were best fitted into Jossens isotherm model (R2=0.981) the order of fitting for the models is Jossens>Baudu>Harkins-Jura>Sips>Freundlich>Langmuir. The maximum adsorption capacity of G-5- PAMAM-SGA for Cd (II) was 123.4 mg g-1 and the system was influenced by temperature, initial concentration and pH. Analysis of sorption kinetics reveals that the data fitted better to the pseudo-second-order model than any other kinetic model, signifying that the sorption process involved is chemisorption. Sticking probability (S*=0.9999), suggesting a mixture of chemisorption and physisorption (coordination adsorption). Gibbs free energy of adsorption at 293,303 and 313 K were all negative thus sorption was spontaneous and favorable.
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