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Cocoa shells for heavy metal removal from acidic solutions.
N Meunier1, J Laroulandie, J F Blais
1Institut National de la Recherche Scientifique (INRS-ETE), Université du Québec, 2800 rue Einstein, bureau 105, C.P. 7500, QC, G1V 4C7, Sainte-Foy, Canada. blaisjf@inrs.uquebec.ca
Bioresource Technology
|October 25, 2003
Summary
Cocoa shells effectively remove heavy metals from acidic industrial wastewater. These natural adsorbents show high efficiency for lead removal, even in complex multi-metal solutions.
Area of Science:
- Environmental Science
- Materials Science
- Chemical Engineering
Background:
- Industrial processes generate acidic effluents containing toxic heavy metals, necessitating cost-effective removal solutions.
- Developing sustainable and efficient adsorbents is crucial for environmental remediation and decontamination technologies.
Purpose of the Study:
- To evaluate the heavy metal removal efficiency of cocoa shells from acidic solutions.
- To investigate the influence of solution composition on heavy metal adsorption by cocoa shells.
Main Methods:
- Adsorption experiments using cocoa shells at varying concentrations (5-40 g/l).
- Testing with single-metal solutions (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) and a multi-metal solution.
- Analysis of adsorption in a real industrial effluent from metal-contaminated soil leaching.
Main Results:
- Cocoa shells demonstrated a specific heavy metal fixation order: Pb>Cr>Cd=Cu=Fe>Zn=Co>Mn=Ni=Al.
- High lead removal efficiency was observed in very acidic solutions (q(max)=6.2 mg Pb/g at pH 2).
- Lead adsorption was unaffected by the presence of other metals; maximum uptake occurred within 2 hours.
Conclusions:
- Cocoa shells are a promising, efficient biosorbent for removing heavy metals, particularly lead, from acidic industrial effluents.
- The adsorption process involves a pH increase and the release of alkali and alkaline earth metals from the cocoa shells.