Influence of high intensity ultrasound on wet process phosphoric acid

Abstract

High intensity ultrasound (800 kHz and 80 Wcm -2) is passed through phosphoric acid of different origins and concentrations. Its influence on fluorine content, viscosity, density, colour and tendency to form sludge on ageing is observed. The quantity of fluorine in all samples of acid goes on decreasing with the time of exposure to ultrasound. Due to removal of fluorine by the ultrasound, the tendency of the acids to form sludge also decreases. The evolution of fluorine from the wet process phosphoric acid may be due to the decomposition of H 2SiF 6 present in the acid to HF and SiF 4 by the enormous amount of energy released due to cavitation. The exposed acid thus becomes purer, and can be concentrated and transported easily without sludge formation.