Para‐substituted 1‐Phenyl‐3‐methyl‐4‐aroyl‐5‐pyrazolones as Selective Extractants for Vanadium(V) from Acidic Chloride Solutions

Abstract

Para‐substituted 4‐aroyl derivatives of 1‐phenyl‐3‐methyl‐5‐pyrazolones (HX), namely, 1‐phenyl‐3‐methyl‐4‐(4‐fluorobenzoyl)‐5‐pyrazolone (HPMFBP) and 1‐phenyl‐3‐methyl‐4‐(4‐toluoyl)‐5‐pyrazolone (HPMTP) were synthesized and examined with regard to the extraction behavior of multivalent metal ions such as magnesium(II), aluminum(III), titanium(IV), vanadium(V), chromium(III), manganese(II), iron(II), and iron(III) that are present in titania waste chloride liquors. For comparison, studies have also been carried out with 1‐phenyl‐3‐methyl‐4‐benzoyl‐5‐pyrazolone (HPMBP). The results demonstrate that vanadium(V) and iron(III) are extracted into chloroform with 4‐aroyl‐5‐pyrazolones as VO2X · HX and FeX3, respectively. On the other hand, magnesium(II), aluminum(III), titanium(IV), chromium(III), manganese(II), and iron(II) were not found to be extracted into the organic phase. The equilibrium constants of vanadium(V) and iron(III) with various 4‐aroyl‐5‐pyrazolones follow the order HPMFBP>HPMBP>HPMTP, which is in accordance with their pKa values. The selectivity between vanadium(V) and iron(III) increases with increasing hydrochloric acid concentration. Further, it is clear from the results that iron(III) is not getting extracted above 1.0 mol dm−3 hydrochloric acid solution. The electronic and IR spectra of the extracted complexes of vanadium(V) and iron(III) were used to further clarify the nature of the extracted complexes. The potential of these reagents for the selective extraction and separation of vanadium(V) from titania waste chloride liquors has also been discussed.