Extraction of HNO3 with solutions of zirconium salt of dibutyl hydrogen phosphate in 30% tributyl phosphate and in xylene

Abstract

Zirconium salt of dibutyl hydrogen phosphate (ZS HDBP) dissolved in xylene or 30% tributyl phosphate (TBP) + xylene mixture extracts noticeable amounts of HNO3 at its low concentrations in the aqueous phase, when extraction of HNO3 with straight HDBP itself is not observed. IR data show that DBP− and NO 3 − ions compete for coordination to Zr, which also adds from 2 to 4 HDBP molecules. With a further increase in the HDBP concentration, the HDBP and HNO3 molecules compete for coordination in the outer coordination sphere of zirconium. Inflections in the S-shaped dependence of the HNO3 concentration in the organic phase on the [Zr]:[HDBP] molar ratio lie within the interval from 1:8 to 1:12, which corresponds to filling of the Zr outer sphere with HDBP molecules. In the presence of TBP, these curves become smooth and have no apparent inflection.