Extraction equilibria of lead(II) from nitrate solutions with acidic organophosphorus compounds

The distribution data were numerically analyzed for the extraction of trace lead(II) from 1·0 mol dm⁻³ (Li,H)NO₃ media with toluene solutions of acidic organophosphorus compounds (HR), including di(2‐ethylhexyl)phosphoric acid (D2EHPA) and 2‐ethylhexylphosphonic acid mono‐2‐ethylhexyl ester (HEHEHP). The complex formulations were determined to be \documentclass{article}\pagestyle{empty}$ \overline {{\rm PbR}_2 {\rm (HR)}},{\rm }\overline {{\rm PbR}_2 {\rm (HR)}_4 },{\rm and }\overline {{\rm Pb(NO}_3 {\rm )R}} $ for the D2EHPA system and to be \documentclass{article}\pagestyle{empty}$ \overline {{\rm PbR}_2 {\rm (HR)}_{\rm 3} },{\rm }\overline {{\rm PbR}_2 {\rm (HR)}_4 },{\rm and }\overline {{\rm Pb(NO}_3 {\rm )R(HR)}} $ for the HEHEHP system. In this work, the equilibrium constants for the formation of these complexes were also given at 298 K.