Studies on liquid-liquid extraction of tetravalent hafnium from weakly hydrochloric acid solutions by LIX 84-IC

The extraction of hafnium(IV) from hydrochloric acid solutions by 2-hydroxy-5-nonylacetophenoneoxime (LIX 84-IC) in kerosene has been investigated under different conditions. The extraction of hafnium(IV) at low aqueous acidity is governed by a cation exchange mechanism: MO(aq)2++2HA(org)⇌MOA2+2H+, where M = Hf(IV) and HA = LIX 84-IC. The plot of log D versus log [HCl] gave a straight line with a negative slope of two indicating the exchange of two moles of hydrogen ions for every mole of Hf(IV). Extraction of Hf(IV) increases with increase of extractant concentration. The plot of log D versus log [HA] is linear with slope two indicating the association of 2 mol of extractant with the extracted metal species. Variation of initial metal concentration in the aqueous phase on the extraction of hafnium gave constant the distribution coefficient values, which indicates that the extracted species is mononuclear. Based on the results, the species extracted into the organic phase was postulated to be HfOA2. Addition of sodium salts enhanced the percentage extraction of metal and follows the order NaSCN > NaNO3 > NaCl > Na2SO4. Influence of diluents, temperature, loading capacity of LIX 84-IC, stripping of metal from loaded organic, synergism and extraction behavior of associated elements such as Zr(IV), Ti(IV), Al(III) and Fe(III) was studied.