Insight into acidity driven third phase formation of TBP in organic solutions by MD simulation

Nitric acid extraction by tri-n-butyl phosphate (TBP) in dodecane is investigated by molecular dynamics (MD) simulation, for different concentrations of TBP in the range 0.1 M to 2 M with aqueous phase HNO3concentration of 1 M, 2 M and 3 M. The MD studies are carried out considering dissociated as well as molecular forms of HNO3. The simulations showed formation of a third phase consisting of TBP, HNO3 and water which is in agreement with reported experimental results. HNO3, in dissociated form, shows formation of NO3− and H3O+ pockets in the third phase while HNO3 in molecular form remains dispersed in the third phase without such specific formations. The impact of concentrations of the acid and TBP on the third phase formation, reverse micelles of TBP in dodecane and NO3− and H3O+ pockets in the third phase, have been demonstrated. The estimated diffusion coefficient values of TBP and dodecane match well with the reported literature values.