Abstract:
Adsorption is one of the most widely applied techniques for environmental remediation of
Cr (VI). Waste effluent containing Cr (VI) causes a serious environmental problem.
Commercially available activated carbon adsorbents are the one that usually applied for the
removal of Cr (VI). However; these adsorbents are expensive materials and need to be
replaced by cheaper but effective adsorbents. In this study, locally available biomasses
obtained from avocado kernel seeds, juniperus procera sawdust and papaya peels were
investigated as adsorbents for the removal of Cr (VI). The study employed batch method to
investigate the efficiency of the adsorbents. Parameters that influence adsorption such as:
effects of pH, adsorbents dose, initial concentration, contact time, and temperature were
optimized (pH: 1 for all of untreated and activated carbon of juniperus procera sawdust
adsorbents, 2 and 3 for activated carbon of avocado kernel seeds and papaya peels found
optimal respectively, adsorbents dose: 0.5 g, [Cr (VI)]: 5 mg/L, contact time: 160 min and
temperature: 40 oC). To understand the adsorption isotherm, the Langmuir and Freundlich
adsorption isotherm models were investigated and the data was found best fit to Freundlich
isotherm model indicating that the heterogeneity of the adsorbents surface. Kinetic studies
were made and the pseudo-second order kinetic model was found to be more suitable for
describing the experimental data. Thermodynamic parameters (ΔGo
, ΔHo
and ΔSo
) have also
been calculated and found that the adsorption process as feasible, spontaneous and
exothermic in nature. The positive values of the entropy change suggest that the increased
randomness at solid-liquid interfaces during the adsorption. Finally, the efficiencies of the
adsorbents towards the removal of chromium from tannery wastewater were also examined
and it was found as they have capacity to remove chromium from wastewater solution.
Keywords: Adsorption; adsorbents; chromium (VI); isotherms; Adsorption kinetic;
thermodynamic of adsorption.
