6. Wet process of phosphoric acid production: reaction between phosphate rock
and sulphuric acid is enhanced by adding recirculated weak phosphoric acid to allow almost-
complete precipitating calcium sulphate with sulphuric acid (CaSO 4 ? 2H 3 PO 4 ). Then a
dihydrate filter separates the phosphoric acid (26–32% P 2 O 5 ) from the calcium sulphate
dihydrate (CaSO 4 Á2H 2 O)
7. The advanced membrane filtration, replace the traditional solvent extraction, greatly
reducing the waste discharge, which can make all kinds of industrial grade phosphoric
acid.