Extraction Mechanism of Bismuth(III) with Trioctylmethylammonium Nitrate

The mechanism for extracting bismuth(III) from an HNO3 aqueous solution into a trioctylmethylammonium nitrate (TOMA•NO3) xylene solution was studied at 25°C. The distribution ratio of bismuth(III) was measured as functions of the bismuth(III) concentration and the HNO3 concentration in aqueous solution, and the TOMA•NO3 concentration in xylene. By taking into consideration the dimerization of TOMA•NO3 in xylene, the extraction equilibrium of bismuth(III) from nitric acid was determined to be Bi3+aq+3NO-3, aq+1.5(TOMA•NO3)2, org•(TOMA+)3•Bi(NO3)3-6, org. The conditional extraction constant from 1M H2SO4 was obtained as log Kex=4.2.