Effect of polymethylene chain length of 4-acylbis(1-phenyl-3-methyl-5-pyrazolones) on the extraction of vanadium(V): Synergistic effect with neutral organophosphorus extractants

Abstract

Various 4-acylbis(1-phenyl-3-methyl-5-pyrazolones), namely, 4-adipoylbis(1-phenyl-3-methyl-5-pyrazolone) (H(2)AdBP), 4-sebacoylbis(1-phenyl-3-methyl-5-pyrazolone) (H2SbBP) and 4-dodecandioylbis(1-phenyl-3-methyl-5-pyrazolone) (H(2)DdBP) were synthesized and examined with regard to the solvent extraction behavior of vanadium(V) and other multivalent metal ions that are present in the waste chloride liquors of titanium mineral-processing industry. The results demonstrate that vanadium(V) is selectively extracted into chloroform with 4-acylbis(1-phenyl-3-methyl-5-pyrazolones) as VO2(HX), where H2X refers to the 4-acylbis(1-phenyl-3-methyl-5-pyrazolone) and K,,v(v) denotes the equilibrium constant. On the other hand, magnesium(II), aluminum(III), titanium(IV), chromium(III), manganese(II), iron(II), and iron(III), were not found to be extracted into the organic phase. The K-ex,K-V(V) values of various 4-acylbispyrazolone derivatives follow the order H2SbBP > H(2)DdBP > H(2)AdBP. Solid complexes of vanadium(V) with various 4-acylbis(1-phenyl-3-methyl-5-pyrazolones) have been isolated and characterized by elemental analyses and IR spectral data to further clarify the nature of the extracted complexes. The synergistic effect on the addition of various neutral organophosphorus extractants to the metal-chelate system has been investigated, revealing significant enhancement in the extraction efficiency of vanadium(V). The equilibrium constants of the synergistically extracted complexes have been correlated with the donor ability of the phosphoryl oxygen of the neutral organophosphorus extractants in terms of their P-31 NMR chemical shifts and their basicity values (K-H = nitric acid uptake constant). The potential of these reagents as extractants for the separation and recovery of vanadium(V) from the waste chloride liquors of the titanium mineral processing industry has also been assessed.