Extração dos íons Cu(II), Cd(II), Fe(III) e Zn(II) utilizando um sistema aquoso bifásico constituído pelo copolímero L35 e o sal Li2SO4 / Extraction of the ions Cu(II), Cd(II), Fe(III) and Zn(II) using aqueous biphasic system constituted by the copolymer L35 and the salt Li2SO4
AUTOR(ES)
Rafael Baioco Ruy
DATA DE PUBLICAÇÃO
2007
RESUMO
In this work, the extraction behavior of the metal ions Cd (II), Cu(II), Fe(III) and Zn(II) has been separately investigated in aqueous biphasic systems (ABS) formed by the triblock copolymer (Pluronic L35, = 1900.g.mol-1) and the salt Li2SO4, in the presence of extractant agents either soluble or insoluble in water. The extractant thiocyanate (SCN-), iodide (I-), 1-nitroso-2-naphthol (1N2N) and 1-(2-pyridylazo)-2-naphthol (PAN) were used separately. A constant concentration of metal ions (0.50 mmol kg-1), with different extractants concentration of the extractants SCN-, I- and 1N2N were used in ABS. In the absence of the extractant agent, all metal ions showed insignificant partitioning to the top phase. However, the addition of low amounts of the extractant promoted the transfer of the metal ions to the phase enriched in copolymer. The use of SCN- promoted the extraction of metal ions in the order Zn(II) >Fe(III) >Cd(II). This order was observed at ratio [SCN-]/[Mn+]<600, and above this ratio the extraction was quantitative. The substitution of the SCN- by the I- produced different results. The metal ions Cd(II) were quantitatively extracted to the copolymer enriched phase, while the other ions remained in the other phase and this behavior was observed with the ratio [I-]/ [Mn+]>75. The 1N2N was used in different concentration at pH = 6,0 and de ion Cd(II) and Fe(III) had extraction rates as high as 25 %, at ratio [1NN2]/[Mn+ ]= 5. The effect of pH on the extraction was analyzed in the range 1-13. The concentration of metal ions was 0.50 mmol kg-1 and the 1N2N and PAN were 2.5 and 1.5 mmol kg-1, respectively. In general, the efficiency of the extraction increased with the pH increase, except for the pH value equal to 13, due to the formation of metalhydroxyl complexes. The pH = 11 was the most appropriate in the extraction of all of the metal ions. The ions Cd(II), Cu(II), Fe(III) and Zn(II) were extracted by 1N2N (pH = 11) and the extraction values for this ions were 71, 34, 100 and 100 %, respectively. The use of PAN to extract Cd(II) yielded 81 % extraction (pH = 11). The efficiency of the extraction was influenced by variables as: chemical nature of the electrolyte and the extractant agent, stability constant of metal-sulfate, metal-complexant and metal-hydroxyl, amount of extractant agent added to ABS, pH and complex/copolymer interactions.
ASSUNTO(S)
aqueous biphasic system metal ions extraction quimica analitica sistemas aquosos bifásicos extração de íons metálicos química verde green chemistry
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