A method for forming an insoluble adduct using an acidic medium is provided. A chemical process utilizes acidic media to change the solubility behavior of metal solutes. The method can utilize Group 1 soluble alkali metals but can also be extended to any other soluble salts discussed under the solubility rules. The insoluble salts can be Group 2 alkaline earth metals or other insoluble salts. The insoluble adduct can have the designation XYZ where X is a soluble metal from a metal hydroxide or a metal oxide, Y is an insoluble metal from an insoluble metal hydroxide or an insoluble metal oxide, and Z is the acid ion from an aqueous acidic media.

A method for forming an insoluble adduct using an acidic medium is provided. A chemical process utilizes acidic media to change the solubility behavior of metal solutes. The method can utilize Group 1 soluble alkali metals but can also be extended to any other soluble salts discussed under the solubility rules. The insoluble salts can be Group 2 alkaline earth metals or other insoluble salts. The insoluble adduct can have the designation XYZ where X is a soluble metal from a metal hydroxide or a metal oxide, Y is an insoluble metal from an insoluble metal hydroxide or an insoluble metal oxide, and Z is the acid ion from an aqueous acidic media.

A method of producing potassium sulfate by employing sodium sulfate and potassium chloride sources is disclosed. The method includes a crystallization process that yields a mother liquor containing sulfate, sodium and chloride. The mother liquor is directed to an anion segregation unit that produces a reject or retentate rich in sulfate which is recycled and employed in the production of the potassium sulfate. Further, the anion segregation unit produces a permeate that is depleted in sulfate but includes sodium and chloride and is directed to a sodium chloride crystallizer for producing sodium chloride.

A method of producing potassium sulfate by employing sodium sulfate and potassium chloride sources is disclosed. The method includes a crystallization process that yields a mother liquor containing sulfate, sodium and chloride. The mother liquor is directed to an anion segregation unit that produces a reject or retentate rich in sulfate which is recycled and employed in the production of the potassium sulfate. Further, the anion segregation unit produces a permeate that is depleted in sulfate but includes sodium and chloride and is directed to a sodium chloride crystallizer for producing sodium chloride.

A method of producing potassium sulfate by employing sodium sulfate and potassium chloride sources is disclosed. The method includes a crystallization process that yields a mother liquor containing sulfate, sodium and chloride. The mother liquor is directed to an anion segregation unit that produces a reject or retentate rich in sulfate which is recycled and employed in the production of the potassium sulfate. Further, the anion segregation unit produces a permeate that is depleted in sulfate but includes sodium and chloride and is directed to a sodium chloride crystallizer for producing sodium chloride.

A method of producing potassium sulfate by employing sodium sulfate and potassium chloride sources is disclosed. The method includes a crystallization process that yields a mother liquor containing sulfate, sodium and chloride. The mother liquor is directed to an anion segregation unit that produces a reject or retentate rich in sulfate which is recycled and employed in the production of the potassium sulfate. Further, the anion segregation unit produces a permeate that is depleted in sulfate but includes sodium and chloride and is directed to a sodium chloride crystallizer for producing sodium chloride.

The present invention relates to a process for producing sodium sulphate from phosphogypsum, comprising: a step (101) of lixiviation of phosphogypsum by means of a basic solution so as to obtain a sodium sulphate solution (S) containing metal impurities, said basic solution comprising a chelating agent suitable for forming complexes with at least one part of said metal impurities, at least one first step (103, 104) of filtration of the sodium sulphate solution by a nanofiltration membrane (NF1, NF2), so as to form a concentrate (C1, C2) containing said complexes and a permeate (P1, P2), a step (105) of evaporation of the permeate (P1, P2) so as to form anhydrous sodium sulphate.

The present invention relates to a process for producing sodium sulphate from phosphogypsum, comprising: a step (101) of lixiviation of phosphogypsum by means of a basic solution so as to obtain a sodium sulphate solution (S) containing metal impurities, said basic solution comprising a chelating agent suitable for forming complexes with at least one part of said metal impurities, at least one first step (103, 104) of filtration of the sodium sulphate solution by a nanofiltration membrane (NF1, NF2), so as to form a concentrate (C1, C2) containing said complexes and a permeate (P1, P2), a step (105) of evaporation of the permeate (P1, P2) so as to form anhydrous sodium sulphate.

A method of treating fly ash containing sodium sulfate from a recovery boiler of a chemical pulp mill. This method includes at least the following steps: a) ash is dissolved in an aqueous solution and the pH of the solution is adjusted with alkali for precipitating impurities, b) the solution is filtered for removing the impurities containing precipitate, c) sodium sulfate is crystallized from the solution and the crystals are separated from the solution by filtering or by centrifugation, and d) the crystallized sodium sulfate is used as initial material for producing sodium and sulfur containing chemicals or as process chemical.

A method of treating fly ash containing sodium sulfate from a recovery boiler of a chemical pulp mill. This method includes at least the following steps: a) ash is dissolved in an aqueous solution and the pH of the solution is adjusted with alkali for precipitating impurities, b) the solution is filtered for removing the impurities containing precipitate, c) sodium sulfate is crystallized from the solution and the crystals are separated from the solution by filtering or by centrifugation, and d) the crystallized sodium sulfate is used as initial material for producing sodium and sulfur containing chemicals or as process chemical.