Browsing by Author "Foya, Huruma"

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    Adsorption of maleic and oxalic acids on activated carbon prepared from tamarind seeds and cassava peels
    (University of Dar es Salaam, 2013) Foya, Huruma
    This study reports an investigation on the adsorption of maleic and oxalic acids onto activated carbons prepared from tamarind seeds and cassava peels by chemical and physical activation methods. This is because the adsorptive properties of activated carbon as reported in the literature depend on activation conditions, the nature of precursor and adsorbate. The activated carbons were characterized by iodine number, Attenuated Total Internal Reflectance Infrared (ATR-FTIR) and pH. Equilibrium studies of maleic and oxalic acids were conducted (room temperature, adsorbent dosage = 0.1 g and natural pH of solution) by batch adsorption method. The chemically activated carbons prepared at 400 to 800 oC had iodine number (445.5 to 1117.6 mg/g) while activated carbons prepared by physical activation method at 700 to 900 oC had iodine number (202.0 to 632.0 mg/g). The ATR-FTIR analysis of the prepared activated carbons mostly showed peaks for lactone (1739 cm-1), aromatic ring vibrations (1568 – 1504 cm-1) and pyrones structures (1433 – 1366 cm-1). The maximum adsorption efficiencies were 86.5 and 94.3 % at room temperature (26 ± 2 oC) for maleic and oxalic acids, respectively. The adsorption processes of maleic and oxalic acids could be well described by pseudo-second order kinetic model with correlation coefficient greater than 0.975 indicating chemisorption processes. The adsorption of maleic and oxalic acids on tamarind seeds and cassava peels activated carbons were best described by Langmuir and Freundlich isotherms, respectively. The maximum monolayer adsorption capacities of oxalic acid were 91.77 and 420.12 mg/g for cassava peels and decorticated tamarind seeds activated carbons, respectively. The maximum monolayer adsorption capacities of maleic acid were 305.60, 613.13 and 723.38 mg/g for tamarind seed testa, cassava peels and decorticated tamarind seeds activated carbons, respectively. The highest value of maximum monolayer adsorption capacity (723.38 mg/g) was higher than that reported in the literature (522.32 to 615.17 mg/g). This could be linked to the high basicity (pH = 9.55) and high adsorption potential in fine pores for a highly microporous activated carbon (iodine number = 632.0 mg/g). The adsorption process was favourable for all tested activated carbons as the Freundlich parameter (1/n) values were less than unity.