Remediation of lead, cadmium and copper polluted waters by onion skins (Allium Cepa)
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Date
2016
Authors
Waweru, Beatrice W.
Mwangi, Isaac W.
Murungi, Jane
Wanjau, Ruth N.
Msagati, T.A.M.
Manohah, Ram
Journal Title
Journal ISSN
Volume Title
Publisher
International Journal of Agriculture Innovations and Research
Abstract
The chemical structure of water makes it have
special properties due to lopsided electrical charge that
enable water to be a solvent for ionic compounds. That
dissolving power is very important for life and has
contributed to 97 % of the world’s water being salty. As
water interacts with the environmental matrix, it dissolves
ionic material at different concentrations which may render
this vital commodity polluted with dissolved matter of both
organic and inorganic origin. Presence of heavy metals in
water is a worldwide environmental concern due to pollution.
Therefore, there is need to find a sustainable and affordable
method to remove such pollutants from water to render it
safe. This study investigated the sorption efficiency and
mechanism of onionskin in both their raw and modified
forms on the removal of lead, copper and cadmium in
aqueous media. The modification of the study material was
done by anchoring ethylene-1, 2-diamine (EDA) within the
structure of the onionskins. This was anticipated to improve
the quality of the adsorbent material for application on the
removal process. Sorption parameters were optimized and
the respective optimal values applied. Experimental results
confirmed that best sorption pH range for the metals was
ranging between 4.0 -6.0 which is within the physiological pH
of water. It was also realized that the sorbent material could
remove 90 % of the metals within the first 20 minutes of
contact. The experimental data was analysed using
Freundlich and Langmuir adsorption isotherms and found
out that the three metal ions fitted best in Langmuir model.
However, the unmodified onionskin leached soluble organic
substances in the form of colour and smell thus causing a
secondary pollution. This was overcome by modification of
the material. The sorption capacities for lead, cadmium and
copper were found to be 71.85, 68.03 and 79.36 mg g-1 in the
modified sorbent material respectively and 87.49, 96.99 and
90.8 mg g-1 in the same order for the unmodified form.
Despite the sorption capacity not improving, the effect of
secondary pollution was minimized from 15.1 mg L-1 to 7.9
mg L-1 thus improving the quality of the sorbent material.
The resulting material was then applied on environmental
water samples whose concentration was determined and
thereafter spiked with lead, cadmium and copper ions of
varying concentration. The maximum percent recoveries
were determined as 87.8±0.01%, 80.6±0.01% and 77.1±% for
lead, cadmium and copper ions respectively. This indicated
that the material which initially had no useful purpose with
disposal problems has potential application for remediation
of metal laden waters
Description
Research paper
Keywords
Citation
International Journal of Agriculture Innovations and Research Volume 4, Issue 5, ISSN (Online) 2319-1473