Mathematical model of precipitation of barium and strontium nitrates from nitric acid solutions and their mutual effect

A mathematical model describing the solubility of barium, strontium, and lead nitrates in nitric acid solutions containing 0 to 14 M HNO3 in the temperature range from 0 to 90°С with the error no larger than 7% was developed. The model is based on the reactions of metal precipitation in the form of Me(NO3)2 at HNO3 concentrations of up to 7–8 M and Ме(NO3)2·2HNO3 at higher nitric acid concentrations, and also on the assumed formation of soluble metal nitrate complexes MeNO3 +. A sharp increase in the barium solubility at HNO3 concentrations lower than 0.5 M and temperatures of 50 and 90°С was interpreted assuming the possible formation of dimeric oxocations Ba2O2 + or associates Ba2(OH)2 2+. A model describing the solubility of barium nitrate in the presence of strontium nitrate in HNO3 solutions at HNO3 concentrations in the range from 0 to 5 M was also suggested.