Purification of phosphoric acid by minimizing iron, copper, cadmium and fluoride

Commercial phosphoric acid manufactured using wet process has been purified by minimizing the iron, cadmium, copper and fluoride content. Bentonite clay is found suitable for removal of humic acids and suspended materials from crude phosphoric acid. An attempt to minimize the iron content by the addition of potassium sulfate, calcium sulfate, sodium sulfate, individually; silicon dioxide + sodium carbonate + potassium sulfate, in combination, and potassium amyl xanthate is the main goal of this work. The efficiency of potassium amyl xanthate in minimizing iron content was found 79.19% with a small decrease of P2O5. Temperature, stirring time and the amount of additives were studied. Minimizing of fluoride from phosphoric acid is carried out using silicon dioxide followed by the addition of sodium carbonate. Adjusting the stoichiometric amounts, additives and heating temperature, the efficiency of minimizing of fluoride is 93.89%. Copper and cadmium were also removed.