Microfiltration of calcium sulfate from phosphoric acid solution with ceramic membrane

In the production of wet phosphoric acid, the flocculating setting method is usually used for the removal of solids, such as calcium sulfate, but the result is less-than-ideal. The ceramic membrane of pore size 500 nm was used to separate calcium sulfate from phosphoric acid solution. The stability of ceramic membrane in phosphoric acid, the operating conditions of ceramic membrane and the effect of backflushing on the recovery of membrane flux were investigated respectively. The results show that the three-point bending strength decreases with the increase of corrosion time, which is still above 45 MPa after 400 d. In the conditions of trans-membrane pressure (TMP) 0.2 MPa, cross-flow velocity(CFV) 3 m/s, temperature 303 K, backflushing pressure 0.5 MPa, the permeate flux of ceramic membrane is greater than 400 L/(m²·h), and the permeate turbidity is less than 0.3 NTU. Backflushing is benefit to the removal of the cake layer of calcium sulfate. This research supplies some supports to the industrial application of ceramic membrane in phosphoric acid.