REMOVAL OF SOME HEAVY METALS FROM CONTAMINATED SOILS USING TWO COMPLEXING AGENTS
REMOVAL OF SOME HEAVY METALS FROM CONTAMINATED SOILS USING TWO COMPLEXING AGENTS
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Date
2016-11
Authors
SANI, YAKUBU
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Abstract
A study on the removal of heavy metals from polluted site where metal-works activities are carried out was studied. The soil samples were treated separately with aqueous solution of two complexing agents – namely, tiron and glutamic acid to determine the removal efficiency of heavy metals. Before treatment with the complexing agents, the soils showed remarkably high levels of heavy metals above background concentrations. The distribution pattern were in the following order: Pb> Zn> Cr> Cd> Ni. Across all the sampling locations, Pb showed the highest (199.97 mg Kg-1) mean concentration and Cd (1.35 mg Kg-1) the least mean concentration respectively. Key factors that determine the absorption of heavy metal by complexing agents such as pH, concentration, amount of soil, and contact time were considered and the process optimized by the application of 24 factorial design of experiment. Results indicated optimum removal of Cr 98.81%, Ni 86.00%, Pb 76.18%, Zn 62.63% and Cd 83.95% using tiron while the optimum absorption for glutamic acid was 37.68% Cd, 56.41% Cr, 37.68% Ni, 1.81% Pb, and 63.23% Zn respectively. Optimum removal Cr 98.81% was obtained at pH 3, 25 mg dm-3, 10g amount of soil and 60 minutes contact time. The optimum removal of Ni 86.00% obtained at pH 5, 25 mg dm-3, 10g amount of soil and 60 minutes contact time. Optimum removal of Pb 76.16% was obtained at pH 5, 10 mg dm-3, 5 g amount of soil and 60 minutes contact time. Zn 62.63% was obtained at pH 3, 5g amount of soil and 60 minutes contact time. Cd 83.95% was obtained at pH 5, 25 mg dm-3, 10 g amount of soil and 30 minutes contact time using tiron. This indicates a good yield when compared to other used chelating agents like EDTA, EDDS, and NTA. Optimum removal of glutamic acid was Cr 99.98%, Ni 53.26%, Pb 99.99%, Zn 99.98% and Cd 99.98%.Cd 99.98% obtained at pH 5, concentration of 10 mg dm-3, 10g amount of soil, and 60
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minutes contact time. Cr 99.98% obtained at pH 5, concentration of 25 mg dm-3, 5 g amount of soil, and 60 minutes contact time. Ni 53.26% obtained at 25 mg dm-3 concentration, 10 g of soil, at pH 3, and 60 minutes contact time. The optimum removal of Pb was 99.99% at pH 3, 10 mg dm-3, 10 g amount of soil, and 60 minutes contact time. Optimum removal of Zn was 99.98% achieved at 25 mg dm-3 concentration of glutamic acid, 10 g of soil, 30 minutes contact time, and pH 5. The results of cube plots to show the interaction of the absorption process by factorial design of experiment indicate 83.22% Cr, 9.16% Cd, 61.03% Ni, 69.86% Pb and 59.32% Zn removal by tiron. In conclusion, the results from this study suggested that tiron and glutamic acid have high removal efficiency. However, glutamic acid is more promising extracting agent than tiron.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF MASTER’S DEGREE IN ANALYTICAL CHEMISTRY DEPARTMENT OF CHEMISTRY, FACULTY OF SCIENCE AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA
Keywords
REMOVAL,, HEAVY METALS,, CONTAMINATED SOILS,, TWO COMPLEXING AGENTS,