Heavy Metal Removal from Paint Industries Wastewater Using Wood Ash as an Adsorbent (A Case of Zemilli Paint Factory
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Date
2011-06
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Addis Ababauniversity
Abstract
Wastewater generated from Zemilli Paint Factory creates a wastewater that has a potential
hazard to the environment by introducing various contaminants such as heavy metals into soil
and water resources. The adsorption characteristics of Co2+ and Pb2+ ions found in waste water
onto a wood ash surfaces were investigated with respect to changes in the pH of solution,
adsorbent dose and contact time. The aim of this work was to evaluate the fundamental aspects
of sorption of Pb (II) and Co (II) metal species using wood ash. Batch adsorption experiments
were carried out in order to evaluate the metal uptake and to optimize condition of the
adsorption. The optimized value of pH, adsorbent dosage and contact time were obtained. The
results revealed that removal of 94% for cobalt at a pH of 8, 20gm/l adsorbent dose and 90
minute contact time was obtained; and 97% removal of lead is obtained at a PH of 10, 20 gm/l
adsorbent dose and 90minute contact time. pH of Sample is adjusted to the required level by
using 1M HCl and NaOH solution. Pb uptake increases with an increased with pH and became
maximum at a pH of 10. But, uptake of Co best achieved at pH 8. Adsorbent dose affect uptake
of both metal ions positively; and contact time gets equilibrium at 90 min of contact (shaking)
time. The Langmuir isotherm was demonstrated to provide the best correlation for the adsorption
of lead and cobalt on to wood ash. Based on the result the pseudo second-order kinetic model
provided the best correlation of the experimental data. In the desorption study the cationic forms
of heavy metals were first complexes with a Na2EDTA in order to recover water-soluble
polymers and to obtain a heavy metal complexes with EDTA. This desorption study revealed
that, the higher desorption efficiencies of up to 90% for Co2+ and up to 78% for Pb2+ was
achieved by using the solution of Na2EDTA at Temperature of 30
o
C, 2 hour mixing time, solid
to liquid ratio of 5 and 2M Na2EDTA as Desorption solution. The adsorption column was
designed using different parameters for Zemilli Paint Factory waste water and on the basis of the
results obtained from the experiment, by using such necessary data; also size the dimensions of
the adsorption column. Wood ash is an abundant resource in every part of the country; it is
recommended that, wood ash can effectively be applied as an absorbent for the removal of Co
(II) and Pb (II) ions from paint waste water.
Key words: lead, cobalt, heavy metal, wood ash, atomic adsorption spectrometer, paint, paint
waste water, Adsorption
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Keywords
lead, cobalt, heavy metal, wood ash, atomic adsorption spectrometer, paint, paint waste water, Adsorption