Comparative Evaluation of Industrial Phosphoric Acids Desulfation Capabilities of Limes and Barium Carbonate

Industrial phosphoric acid is an omnipresent product in the food industry and in the production of fertilisers and detergents. The presence of impurities in the raw material results in a relatively charged acid with various chemical species at the expense of its quality and use. These impurities include sulfate ions that precipitate into phosphoric acid during its manufacture. A desulfation is thus necessary. This study focuses on the reduction of free sulfates in phosphoric acid as impurities. This resulted in the use of three different adjuvants: lime, limestone, and barium carbonate. Three initial sulfate levels mainly contained in phosphoric acid were investigated: 2%, 4% and 6%. After experimentation, the comparison between the resulting yields allows considering barium carbonate as the most effective adjuvant. The desulfation efficiency was 95% in a very short stirring time of 15 min, independently of the initial sulphate content of phosphoric acid. The tests carried out with lime and limestone also lead to very interesting desulfation rates for phosphoric acid with an initial sulfate content of 2 or 4%.