Berhanu, Assefa (PhD)Berihu, Gebrecherkos2019-10-212023-11-102019-10-212023-11-102019-07http://etd.aau.edu.et/handle/12345678/19530Discharge of untreated chromium containing tannery wastewater into the environment poses a serious environmental and health problem. Finding an environmentally safe and cost effective method which is efficient enough to meet the regulatory standards of industrial wastewater discharge presents unique challenges. There is need for environmentally friendly and cost effective methods for their removal. The present study investigated the adsorptive removal of chromium ions from Ethiopian tannery share company site using thermally modified chicken eggshells because it is high removal capacity, low cost and easy accessibility. Characterization of the adsorbent such as proximate analysis, surface charge, Fourier transform infrared radiation spectroscopy, surface area and X- ray diffraction was done prior to bio sorption process. Thermally modified eggshell was assessed in batch mode adsorption experiment for percentage chromium removal and milligrams per gram chromium uptake as a function of contact time, pH, and dose of the adsorbent and initial concentration. The effect of factors such as one factor effect and interaction effects were investigated by central composite design (CCD). The maximum percent removal was obtained 99.505 % at optimum pH =7, adsorbent dose=1g/100ml, contact time 120min and 80mg/L of initial chromium ion concentration. Sorption kinetics of chromium adsorption by Thermally modified eggshell was predicted reliably using a pseudo-first order, pseudo-second order and intra particle diffusion model. The kinetic adsorption data well fitted to pseudo-second order. Equilibrium uptakes were evaluated using Langmuir, Freundlich and Temkin adsorption isotherm models. The equilibrium data well fitted into Langmuir isotherm. The study demonstrated the efficacy of Thermally modified chicken eggshells and presents it as a viable low-cost adsorbent for bioremediation.en-USChromiumCalcinated eggshellAdsorption isothermAdsorption kineticsThesis