Pakistan Research Repository

STUDIES ON THE SOURCES OF METALS LIKE CHROMIUM, NICKEL AND LEAD IN THE ENVIRONMENT AND THEIR DETOXICATION

Gulzar, Shahida (2000) STUDIES ON THE SOURCES OF METALS LIKE CHROMIUM, NICKEL AND LEAD IN THE ENVIRONMENT AND THEIR DETOXICATION. PhD thesis, University of Karachi, Karachi.

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Abstract

Using Polyaminocarboxylic acids like CDTA, DTPA & EDTA for detoxification of Pb(II), Za(II) & Cr (III&VI) in presence of essential ions e.g. Fe(III), Za(II)& Ca (II), their complexation of different pH was studied potentiometerically. DTPA was found comparatively stronger acid than CDTA & EDTA as it showed maximum complexation with Fe(III),Zn(II) & Pb (II) at pH below 2, Competiton of selected metals soward PAC acids with respect to concentration ratio at different pH as well as selection of the conditions for the complexation of toxic metals with PAC acids in presence of essential metals were also discussed. PAC complexes of Fe(III) were studied & Fe(III) DTPA was selected as target compound for spectrophotometeric study at max 440mm. Quantitatively determined the percentages of exchange of Fe(II),Za(II) & Ca(II) on addition of Pb(II),Ni(II)& Cr(III&VI), At Ph 4,7 & 9 at 30 C, when Ni (II) was added to iron complex, 63 to above 90% Fe (III) was exchanged wheread Chromium couldnot manage to exchange iron from its complex. During the competition of Fe(III)&Pb(II) at pH 7&9 at 65-90%of iron was exchanged from its DTPA complex, further increase was expected on raising the temperature to 60 C while from its CDTA complex, only 40% iron was removed. On interaction of Zn(H) was replaced with Pb(II) of pH 9 at max 250mm & 95% of Za(II) was replaced with Pb(II),Similarly the displaced amount of Ca(II) from its complex on additions of Pb(II) was 93% under similar experimental conditions. To make Cr(VI)less toxic, an antioxidant like ascorbic acid was used and redox potential of CDTA & DTPA complexes were determined at pH 4 & 7, PAC acids also have been used and compared as autioxidant at pH 2,4 & 7.DTPA might successfully reduce Cr(VI) at lower pH i.e. 0.1M HCI solution. Finally the domestic industrial effluents were analyzed to determine the above mentioned toxic ions by absorption spectrophotometer

Item Type:Thesis (PhD)
Uncontrolled Keywords:chromium, nickel, lead, detoxication, polyaminocarboxylic acids, toxicity, heavy metal, pac acids, cdta, dtpa, edta
Subjects:Physical Sciences (f) > Chemistry(f2)
ID Code:906
Deposited By:Mr. Muhammad Asif
Deposited On:08 Nov 2006
Last Modified:04 Oct 2007 21:03

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