Abstract
High amount of heavy metal ions like Cr in the environment has been harmful for animal and human health. Bioadsorption of Cr from tannery wastes would be an alternative method to the chemical treatment in tannery industries. Hence, in this study the efficiency of Moringa stenopetala seed extract to adsorption Cr from tannery waste water was investigated. The influence of solution pH, adsorbent concentration, initial concentration of Cr, contact time and temperature on the efficiency of Moringa stenopetala seed extract for the adsorption of Cr from tannery effluent was studied. Results obtained revealed that in strongly acidic condition Moringa stenopetala seed extract was less efficient to remove Cr. However, the result of the present study showed that Moringa stenopetala seed extract at a concentration of 1g/100 ml and pH of 9.5 decreased the concentration of Cr in tannery waste by 99.86%. In addition, the adsorption data was correlated using the Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm models. Among models studied Dubinin-Radushkevich isotherm was the best fit with correlation coefficient of 0.958. Moreover, thermodynamics parameters, such as Gibbs free energy (ÄGo), enthalpy (ÄHo), and entropy (ÄSo) were calculated. Results indicated that the bioadsorption of Cr by Moringa stenopetala seed extract was spontaneous, feasible and endothermic. The results of this study proved that Moringa stenopetala seed extract can be used to remove Cr from tannery effluent.KEYWORDS: Moringa stenopetala, Cr, tannery, pH, temperature, concentration
Highlights
Heavy metal ions are great concern among chemist and among the general population, who are affected with some of the disadvantages associated with them
Several reports have shown that the values for Cr in tannery effluent are considerably higher than the safe limits prescribed by international standards (Shanker et al, 2005)
Defatted cakes were prepared by cold solvent extraction of the powdered seed with hexane fraction and dried in a vacuum oven at 40 0C for 24h (Ibrahim, 2008).Tannery effluent samples were collected from ELICO-Awash Tannery, Addis Ababa, Ethiopia Liquid waste samples were collected from three different sites using plastic sample bottles
Summary
Heavy metal ions are great concern among chemist and among the general population, who are affected with some of the disadvantages associated with them. Some heavy metal ions play important roles in living systems, they are very toxic and capable of causing serious environmental health problems. Chromium (Cr) is a heavy metal used in various industrial processes like in chromplating, wood preserving, textile dyeing, pigmenting, chromium chemical production, pulp and paper industrial and tanning. Tanning process with chromium compounds is one of the most common methods for processing of hides. In the tanning process about 60%70% of chromium reacts with the hides the remaining about 30%-40% of the chromium amount remains in the solid and liquid wastes (especially spent tanning solutions) (Abdulla et al, 2010). The concentration of chromium ion in the tanning waste water varies from 1300 to 2500 ppm (Abdulla et al, 2010)
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