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

Abstract

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)₂²⁺. 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.