Abstract:
The effect of heavy metals on the environment, public health and aquatic life is a matter of
serious concern globally. The removal and recovery of these toxic heavy metal ions from
wastewaters is of great importance from an environmental point of view. Among the various
techniques used for heavy metals removal, adsorption has been proved to be an excellent,
effective and superior process of waste water treatment. In this study, the adsorption potential of
an orange peel towards metal ions such as Pb(II), Cu(II), Cr(VI) and Cd(II) was investigated.
Batch adsorption experiments were performed and experimental parameters including pH,
contact time, metal ion concentration and adsorbent dose were optimized for both MOP and
UMOP. The residual metal ion concentrations and surface functional groups were determined
using flame Atomic Absorption Spectrophotometer (FAAS) and Fourier Transform Infrared
(FTIR), respectively. The experimental results indicated that the optimum conditions for Pb(II),
Cu(II), Cr(VI) and Cd(II) ions adsorption were achieved. The adsorption efficiencies were found
to be mainly pH dependent and tend to increase with increase in pH of the solution up to 6
except for chromium. Both Freundlich and Langmuir isotherm models were applied to the
experimental data but Langmuir isotherm model fitted with the equilibrium data well. Kinetic
parameters of adsorption such as pseudo-first order and second-order models were tested and
the experimental data fitted with the pseudo-first order kinetic model. A desorption study for the
solid support regeneration was also conducted and the desorption efficiency of the adsorbent
decreased as number of cycles increased. The present study revealed that modified orange peel
could be used as an efficient sorbent for the removal of heavy metal ions from waste water and
that chemical modification of the orange peel using sodium hydroxide enhanced adsorption
capacity.
