Home – Home – Jornals – Chemistry for Sustainable Development 2017 number 5

The paper carried out distilling off hydrofluoric acid from model and process acid fluoride-sulphate solutions. Conditions for the most complete distilling off process of hydrofluoric acid from fluoride-sulphate solutions were determined and proposed. Fluorosulphonic acid is formed in large amounts, as demonstrated for model solutions containing hydrofluoric and sulphuric acids. Herewith, with increasing the concentration of acids, their interaction degree rises and fluorosulphonic acid is formed, as demonstrated. An increase in heating temperature of the mixture leads to a substantial increase in acidity due to HSO₃F content decrease. The larger the concentration of acids (especially, sulphuric) is, the higher heating temperatures are required to decompose HSO₃F, as established. The formation of fluorosulphonic acid may have a significant effect on the degree of distilling off hydrofluoric acid, as shown. The energetic and economic costs in processing of 1 m³ of process acid fluoride-sulphate solution are calculated with account of the initial concentration of HF of 78 g/L. Considering sulphuric acid regeneration and having excluded lime content for its neutralization, energy costs for processing of the same solution upon heating to 140 ℃ do not exceed 4500 RUB. The findings explain high solubility of lanthanide fluorides compared to their dissolution in monobasic acids, as noted in a series of papers. Our earlier observations of decreasing the concentration of fluorine determinable by potentiometric titration relatively to initially introduced one at pH correction by using sulphuric acid, unlike that with nitric or hydrochloric ones were also explained.