M. Tomaszewska, CONCENTRATION OF THE EXTRACTION FLUID FROM SULFURIC-ACID TREATMENT OFPHOSPHOGYPSUM BY MEMBRANE DISTILLATION, Journal of membrane science, 78(3), 1993, pp. 277-282
An attempt was made to apply membrane distillation for the concentrati
on of the sulfuric acid solution obtained after extraction of apatite
phosphogypsum, in order to recover lanthane compounds. The process was
carried out step-wise, till the acid concentration of the solution re
ached 40%. Under such conditions the lantane compounds precipitate aft
er cooling of the solution. The temperature of the feed and the cold s
olution was kept at 333 K and 293 K respectively. The distillation flu
x decreased from 215 dm3/m2-d to 80 dm3/M2-d with the increase of acid
concentration in the feed from 16% to 44%. The acid rejection coeffic
ient was close to 100%, in all experiments performed. The most effecti
ve process was that performed in a flow apparatus, where the membrane
sides were reversed and the distillate condensation was carried direct
ly into a stream of cooling water. The content of lantane compounds in
the precipitate obtained from the concentrated solution amounted to 2
5%. The experiments were performed with sulfuric acid solutions and a
model solution consisting of 12% sulfuric acid saturated with CaSO4.