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التبادل الايوني السائل لاستخلاص بعض العناصر باستعمال مركبات عضوية وتطبيق الطريقة على فصل وقياس العناصر في نماذج بيئية وحياتية == Liquid Ion Exchange to Extract Certain Elements Using Organic Compounds and the Application of the Method on the Separation and Measurement of the Elements in Environmental and Vital Samples
Author name:
صفاء مجيد حميد الحساني
Supervisor name:
رافع قدوري الكبيسي | خليل ابراهيم حسين
General topic:
Chemistry
Specific topic:
Chemistry
Degree:
Doctorate
University:
University of Baghdad
Language:
English
University location:
Baghdad
First pages:
25T1891 - p.pdf
Abstract:
iquid ion exchange method is one of solvent extraction applications used for separation and spectrophotometric determination of Lead (II) and Aluminium (III) as chloroanion complexes (PbCl4=, PbCl3 - , AlCl4 - ) byusing the crown ether 15C5 dissolved in chloroform as organic reagent.Where Pb(II) is extracted from HCl media whilst Al(III) is extracted from neutral NaCl media. The first step determined the maximum absorbance wave length for ion pair association complex extracted to the organic phase the results were λmax=241nm for Pb(II) and λmax=240nm for Al (III) by using crown ether 15C5 dissolved in chloroform as a blank, these wave lengths are used for absorbance measurements which belong to ion pair association complex extracted to organic phase. On the other hand prepared calibrationcurve for each ion according to its spectrophotometric method.Results demonstrated that the optimum concentration of HCl in aqueous phase (2M) was necessary to the formation and stability of Lead chloroanion complex (PbCl4 =, PbCl3 - ) as well as effect to increase stability of liquid ion exchanger [Na15C5]+;Cl - in organic phase by common ion effect. While NaCl optimum concentration for Pb(II) was (0.4M) and for Al(III) (1.2M), NaCl contributed in the formation of Aluminium chloroanion complex AlCl4 - also it contributed in the formation of liquid anion exchanger [Na 15C5]+;Cl - in the organic phase. Liquid ion exchange was based on thermodynamic equilibrium and metal ion concentration in aqueous phase which was one of thermodynamic value which rolled the equilibrium of extraction process where this concentration of metal ion is converted to chloroanion complex and participates in the liquid ion exchange method with Cl - which is found on liquid ion exchanger. The optimum concentration of Pb(II) was (50μg/5mL) and for Al(III) was (100μg/5mL).Solvent extraction was indirect method depended on thermodynamic and kinetic laws so we determined optimum shaking time of the two immiscible phases, the results showed that (10min.) was the optimum shaking time for each ions. Stoichiometry of ion pair association complexes was demonstrated by two methods : slope analysis method and slope ratio method, the results clarified the extracted species for both ions were [1 : 1]+;anion - [metal : 15C5]+; anion - the most probable structure of Pb(II) complexes were [Na15C5]+; PbCl3 - or [Na15C5]+; HPbCl4 - and for Al(III) was [Na15C5]+; AlCl4 - . Other study was effect of the structure and polarity of organic solvents, the results showed that chloroform was the best solvent for both ions and there isn’t any linear relation between dielectric constant for organic solvent used and distribution ratio (D) values and there was an effect of organic solvent structure giving increase in distribution ratio (D) and absorbance values led to rising extraction efficiency by formation of contact ion pair or solvent separated ion pair.Thermodynamic study showed the liquid ion exchange was endothermic reaction and for both ions, from the high values of entropy reflects the reaction was entropic in region. Also study the effect of agreement between crown ether cavity size and alkali, alkaline earth metal cations, the results showed the major effect was for agreement, which gave higher distribution ratio (D) and absorbance values. As well study the interferences effect of some anions, all this anions gave interferences and cause reduces of distribution ratio (D) and absorbance values depending on anion nature and structure. Whilst electrolyte salts gave an increase in distribution ratio (D) and absorbance values where electrolyte salts destroyed the hydration shell of metal ion and enhancement of the chance to form chloroanion complex of metal ions and rising extraction efficiency. Methanol presence in aqueous phase increase distribution ratio (D) and absorbance values for both ions due to methanol decline water polarity and destroyed the hydration shell of metalions.Cryptands C221 and C222 were used as organic reagent to compare extraction efficiency with using of crown ether 15C5 as organic reagent firstly determined the maximum absorbance wave length for ion pair association complex extracted to the organic phase which was for Pb(II) λmax=277nm with C221 and λmax=276nm with C222, for Al(III) λmax=281nm with C221 and λmax=275nm with C222. Optimum concentration of HCl for Pb(II) was (0.8M) with C221 and (1.2M) with C222. And optimum concentration of KCl (0.4M) for Pb(II) with C221 and C222 and for Al(III) (0.8M) with C221 and (0.5M) with C222. While metal ion optimum concentration for Pb(II) was (80μg/5mL) with C221 and (70μg/5mL) with C222 and for Al(III) (50μg/5mL) with C221 and (40μg/5mL) with C222. Optimum shaking time was 15min. for Pb(II) and Al(III) with both cryptands C221 and C222.Stoichiometry by using two spectrophotometric method slope analysis method and slope ratio method showed that extracted species were [1 : 1]+;anion - [metal : Cryp.]+; anion - for Pb(II) and Al(III) with both cryptands C221 and C222. In addition to study the effect of agreement between cryptands cage size and alkali, alkaline earth metal cations, the results showed the major effect was for agreement, which gave higher distribution ratio (D) and absorbance values. The distribution ratio (D) and absorbance values by usingcryptands were higher than those obtained by using crown ether due to cryptate effect.For spectrophotometric determination of elements study in different environmental and vital samples prepared calibration curves for each ions at optimum conditions by using 15C5 at optimum condition for liquid ion exchange method of each metal ion, samples solution prepared according to wet digestion method and spectrophotometric determination were carried out optimum condition for liquid ion exchange method of each metal ion. By return to calibration curves determined Lead and Aluminium amount in these samples.
