Abstract

Sanae Baki Senhaji*, Ahmed Elyahyaoui

DOI : http://dx.doi.org/10.13005/ojc/310339

The extraction of zinc with 3-methyl-2 (1H)-quinoxalinethione LH, is investigated in nitrate solution as a function of pHrange 2-6, and analytical concentrations of  NO^-₃ anions (C_NO3) and extractant (C_LH). The extraction mechanism with LH,is determined on the basis of the variation of the distribution coefficient D with pH,  C_NO3 and C_LH. As a result, the partition equilibrium involves complexing phenomenon, ion-pair formation, and 1H⁺ exchange reaction. The overall extraction constants are logK_01.5 = 5.1, and logK_11.5 = -0.6. The extraction complexes are found to be Zn(LH2)∫(NO3)∫+2 and Zn(L) (LH)∫-1 (NO3) with l = 1 or 2. The hydrolysis reaction of Zn(II) is evaluated and it is found that it results in the formation of Zn(OH)⁺and Zn(OH)_2aq species, at pH >5.6. Zinc shows maximum percent extraction (75%) with the pH 4.7 at low organic ligand concentration (0.01M).

liquid-liquid Extraction; zinc; 3-methyl-quinoxaline-2-thione; nitrate medium; pH range; 2-6

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