Abstract
Extractive recovery of vanadium (V) from hydrochloric acid solutions using alkanols (1-butanol and 1-octanol) dissolved in n-heptane has been investigated by liquid-liquid extraction, propelled by the need to proffering alternatives to the scarce and relatively costly organophosphorous extractants. At the studied pH range (1.0-4.0), with 1- butanol as extractant, the percentage V(V) extraction (extraction efficiency, E%) reached optimum (E% = 63.3) at pH of 0.5, and for 1-octanol, optimum E% was 73.3 at pH 1.0.Increasing concentration of HCl at the studied range (1.0–6.0 mol L-1) was found to have an appreciable effect on percentage V(V) extraction. With both extractants, E% peaked at 6.0 mol L-1 HCl with values 86.7 and 70.0% for 1-butanol and 1-octanol, respectively. With increase in the concentration of extractants, both extractants produced a trend of increase/decrease in E% for V(V), suggesting the extraction of two different species. The optimal percentage extraction values were 76.7 and 96.7% observed at log[1-butanol] = 0.81 mol L-1 and log[1-octanol] = 0.49 mol L-1, in that order. The determined enthalpy change, ?H, for 1-butanol and 1-octanol systems were -19.9kJ mol-1 and -37.1 kJ mol-1, respectively, indicating exothermic extraction processes. On the number of required extraction stages, 1-octanol gave a higher extraction efficiency after three consecutive extractions (E% = 99.3) than 1-butanol (E% = 88.6). Recycling experiment showed 1-octanol as more recyclable than 1-butanol (Recycling coefficient R.C. = 1.0 for 1-octanol while R.C. > n) at low and high concentrations of extractant, respectively. On the whole, 1-octanol could be adjudged a better extractant for vanadium (V) under the prevailing experimental conditions.
Highlights
With the applications of vanadium in various areas of human endeavours such as heat and corrosion-resistant super-alloys, aerospace materials, catalysts e.t.c. the trials of varied extractants for the solvent extraction of vanadium from its depleted primary sources will continually witness an upsurge
Extractive recovery of vanadium (V) from hydrochloric acid solutions using alkanols (1-butanol and 1-octanol) dissolved in n-heptane has been investigated by liquid-liquid extraction, propelled by the need to proffering alternatives to the scarce and relatively costly organophosphorous extractants
The optimal percentage extraction values were 76.7 and 96.7% observed at log[1-butanol] = 0.81 mol L-1 and log[1-octanol] = 0.49 mol L-1, in that order
Summary
With the applications of vanadium in various areas of human endeavours such as heat and corrosion-resistant super-alloys, aerospace materials, catalysts e.t.c. the trials of varied extractants for the solvent extraction of vanadium from its depleted primary sources will continually witness an upsurge. V(V) has been extracted and separated from associated metal ions from 5.0 mol L-1HCl solution with tri-n-butyl phosphate (TBP) dissolved in kerosene (Thomas et al 2003). Related, was the optimal and appreciable extraction of V(V) as VO2Cl from 6.0 mol L-1 HCl by TBP dissolved in n-hexane reported by the current author (Ojo, Ipinmoroti, & Adeeyinwo, 2007). In contrast were the observations made on V(V) extraction from diluted and concentrated HNO3 solutions where the extraction efficiencies were very low (Ojo, 2010). As a follow up to the V(V)/HCl/TBP/n-hexane extraction study, the author separated V(V) and Mo(VI) from concentrated HCl solutions by co-extracting them using TBP, followed by selective stripping with a remarkable success (Ojo, 2013). The demerit of the TBP/HCl system remains the observed high degradation of TBP at high concentration of HCl, rendering recycling prospects diminutive, and besides TBP is relatively costly
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