Chromium Removal from Tannery Wastewater using Calcinated Eggshells as an Adsorbent: A Case study of Ethiopian Tannery Share Company, Ethiopia.
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Date
2019-07
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Addis Ababa University
Abstract
Discharge 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.
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Keywords
Chromium, Calcinated eggshell, Adsorption isotherm, Adsorption kinetics