Abstract
<p>Further to the previous study on the extractive recovery of V(V) from HCl solution by some alkanols, the extraction of V(V) from HCl solutions by 1-pentanol and 3-methyl -1-butanol (isomers) dissolved in n-heptane were investigated in the present study, still propelled by the need to proffering viable alternatives to the scarce and relatively costly organophosphorous extractants, and also compare the extraction efficiency of straight- and branched-chain extractants. At the studied pH range (0.5-4.0) with 1-penttanol as extractant, the percentage V(V) extraction (extraction efficiency, E%) reached optimum E%= 40.0 at pH of 3.0 and for 3-methyl-1-butanol, optimum E% was 36.7 at pH 2.0. Increasing concentration of HCl at the studied range (1.0 – 6.0 mol L<sup>-1</sup>) was found to have an appreciable effect on percentage V(V) extraction. With both extractants, E% peaked at 5.0 and 6.0 mol L<sup>-1</sup>HCl with values 70.0 and 66.7% for 1-pentanol and 3-methyl-1-butanol respectively.</p><p>With increase in the concentration of extractants, both extractants produced a trend of increased/decreased in E% for V(V), suggesting the extraction of two different species. The optimal percentage extraction values were 70.0 and 66.7% observed at log [1-pentanol] = 0.86 mol L<sup>-1</sup> and log[3-methyl-1-butanol]=0.86 mol L<sup>-1 </sup>, in that order. The determined enthalpy change. for 1-pentanol and 3-methyl-1-butanol systems were -80.4/120 kJ mol<sup>-1 </sup>and -203.0/254.7 kJ mol<sup>-1</sup> respectively, indicating exothermic/endothermic extraction processes. The isomer 3- methyl -1-butanol gave a higher extraction efficiency after a three-stage extraction (E% = 92.5) than 1-pentanol (E% = 83.4). Recycling experiment revealed both to be recyclable. From slope analysis, analytical and spectra data, the extracted complexes have been formulated as VO<sub>2</sub>Cl.nROH and (VO<sub>2</sub>Cl)<sub>m</sub>.nROH (where m&gt;&gt; n) at low and high concentrations of extractant, respectively. On the whole, 3-methyl-1-butanol was assessed as fairly better as an extractant for vanadium (V) at lower temperature experimental conditions. The effect of methyl branched-chain played an insignificant role on the extraction.</p>
Highlights
Vanadium applications in various fields of human endeavours modern technology, as well as its extraction in form of cationic vanadium (V) have been reported in recent work (Ojo and Oyegoke, 2013)
Further to the previous study on the extractive recovery of V(V) from HCl solution by some alkanols, the extraction of V(V) from HCl solutions by 1-pentanol and 3-methyl -1-butanol dissolved in n-heptane were investigated in the present study, still propelled by the need to proffering viable alternatives to the scarce and relatively costly organophosphorous extractants, and compare the extraction efficiency of straight- and branched-chain extractants
The chemicals NH4VO3, KCl, Na2WO4.2H2O, HCl, HNO3, H3PO4, and the reagents 1–pentanol, 3-methyl-1-butanol and n – heptane were purchased from the British Drug House Limited (BDH)
Summary
Vanadium applications in various fields of human endeavours modern technology, as well as its extraction in form of cationic vanadium (V) have been reported in recent work (Ojo and Oyegoke, 2013). In the previous work reported by the current authors, vanadium (V) was extracted from HCl solutions by 1–butanol and 1–octanol with remarkable efficiencies, (Ojo & Oyegoke, 2013). It is a common knowledge that several alkanols such as 1–pentanol (Figure 1) and 3-methyl-1-butanol (Figure 2) share similar electronic and solvating properties with those previously investigated, and at least superficially, are expected to have the potentiality for V (V) extraction. The presence of methyl branched–chain is expected to bring a new dimension of disparity in steric hindrance of the extractants, and probably influence the extraction efficiency. It is in the light of this that 1–pentanol (straight–chain) and 3-methyl-1-butanol (branched–chain) were investigated as extractants for V (V) from HCl solutions
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