Low cost fertilizer industry waste material called carbon slurry, produced in generators
of fuel oil-based industrial generators, was converted into an effective and efficient
adsorbent for the removal of hexavalent chromium(VI) from aqueous solutions. The waste
was chemically treated, activated, characterized, and used for the adsorption of chromium.
The work involves batch experiments to investigate the effect of contact time, pH,
temperature, concentration, and adsorbent dose on the extent of adsorption by carbon
slurry. The maximum adsorption was found at 70min, 2.0 pH, 4.0g/L dose, and 303K temperature.
Maximum adsorption capacity (15.24mg/g) of Cr(VI) on carbon slurry was observed at
100mg/L initial Cr(VI) concentration. Langmuir and Freundlich adsorption isotherm
models were applied to analyze adsorption data, and both were found to be applicable
to this adsorption system, in terms of relatively high regression values. Thermodynamic
parameters showed that the adsorption of Cr(VI) onto carbon slurry was feasible, spontaneous,
and exothermic under the studied conditions. Kinetics of adsorption was found to follow
the pseudo-second-order rate equation. Column studies have been carried out to compare
these with the batch capacities. The recovery of Cr(VI) and chemical regeneration
of the spent column have also been tried. In all, the results indicated that the adsorbent
used in this work proved to be effective material for the treatment of chromium-bearing
aqueous solutions.
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