Process for the recovery of sodium sulfate

A process for the recovery of Na2SO4 from a water stream, said process comprising the steps of:

• providing heat to a water stream W0 in a heat-exchanger, wherein water stream W0 comprises Na2SO4, by means of the flow of hot gas, said hot gas discharged from a drying apparatus, to obtain water stream Wi at a temperature Ti;
• feeding the water stream Wi comprising Na2SO4 at a concentration Ci into a membrane distillation unit comprising at least one membrane creating a feed side and a permeate side, wherein the water stream is fed into the feed side of the membrane distillation unit at a temperature Ti greater than the temperature Tp at the permeate side of the membrane distillation unit to obtain a water stream Wf containing Na2SO4 at a concentration Cf>Ci;
• and
• optionally separating solid Na2SO4 from water stream Wf.