Jabasingh, Anuradha(Perofessor)Teshome, Awugchew2018-07-272023-11-102018-07-272023-11-102015-07http://etd.aau.edu.et/handle/12345678/10194This research proposed coffee husk as a low-cost material for production of activated carbon and investigated its application for adsorption of Cr(VI) from aqueous solution. The initial work involved, the optimization of process parameters involved in preparation of activated carbon by chemical activation using H3PO4. Four parameters such as concentration of H3PO4, impregnation ratio, carbonization temperature and holding time were optimized by Response Surface Method (RSM) using Box-Behnken design technique and the produced activated carbon applied for Cr(VI) adsorption. RSM revealed that the effect of on operational parameters on Iodine number and yield of coffee husk activated carbon was best described by quadratic polynomial model. Analysis of variance (ANOVA) revealed a good agreement between experimental and predicted value. The characterization result showed that the coffee husk activated carbon has good properties and compared favourably with other reference activated carbons. FTIR test and point of zero charge pH, showed the presence of acidic functional groups on surface. Cr(VI) adsorption shows that the system was pH dependent. The linear regression analysis of kinetic data confirmed that pseudo-second order rate expression best fitted for all temperature. Langmuir equation was found to fit the equilibrium data for Cr(VI) adsorption with monolayer capacity of 78.74, 84.03 and 92.59 mg/g at 25, 35 and 45oC respectively. Thermodynamic analysis asserted endothermic and spontaneous nature of the system with involvement of chemical adsorption process. Key word; Activated carbon, Coffee husk, process optimization, Cr(VI) adsorptionenActivated carbonCoffee huskProcess optimizationCr(VI) adsorptionThesis