Decolorization of Synthetic Melanoidin using Activated Carbon from Sweet Sorghum (Sorghum bicolor (L.) Moench) Bagasse

Author : Nisola, Vic Jayson Magdaong
Major Adviser : Valencia, Jeanne Michelle T.
Committee Members : Capunitan, Jewel A.; Migo, Veronica P.
Year : 2017
Month : July
Type : Thesis
Degree: BS
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Activated carbon produced from sweet sorghum bagasse (SSB) was used to decolorize synthetic melanoidin solutions. Based on the proximate analysis conducted on SSB, the fixed carbon content (5.69%) of SSB falls below the average fixed carbon content for lignocellulosic materials. After the synthesis of activated carbon from SSB, it was characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray fluorescence spectroscopy (XRF). SEM analysis showed that porous surface structures were developed on the SSB AC after activation. Furthermore, FTIR analysis confirmed the presence of hydroxyl and carbonyl surface functional groups that may aid in the adsorption process. Moreover, heavy metals were found on the surface of SSB AC, as confirmed by XRF analysis, which are not likely to leach out of the surface when the carbon is used as an adsorbent. A two-level 2³ factorial experiment was conducted to determine the factors that significantly affect the adsorption of melanoidin on the synthesized SSB activated carbon. It was found that the major factors that contribute to % decolorization were the initial pH and the adsorbent loading. Results showed that at lower pH, % decolorization is greater. It was attributed to the charge interactions between the adsorbent and the adsorbate. Furthermore, it was also observed that a greater amount of adsorbent loading would result in higher decolorization values due to greater amounts of porous sites that the melanoidin could adhere to. The highest observed values for the % decolorization is 30. 63% occurring at pH 4, 12 g/L adsorbent loading, and (-) 120 mesh particle size. A comparative study between the performance of commercial activated carbon and SSB activated carbon was conducted using batch adsorption experiments. It was found that the commercial activated carbon follows a Freundlich isotherm model (K? value of 1.093, n value of 0.9056 and R² of 0.9351) in its adsorption mechanism suggesting a non-ideal, reversible adsorption on flat heterogeneous surface while SSB activated carbon follows the Langmuir isotherm (qₘₐₓ value of 588 .23 ppm PtCo/g, Kₗ value of 2.60 x 10⁻⁴, and R² of 0.9389) wherein its probable adsorption mechanism is monolayer adsorption on homogeneous flat surfaces.

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