Patent ID: 7858058

Claim:
A method for at least partially removing a soluble alkali metal or ammonium salt of a divalent anion from an aqueous, alkali metal or ammonium ion and divalent anion-containing brine solution comprising the following steps: a) obtaining an alkali metal or ammonium ion and divalent anion-containing brine solution having a sodium chloride concentration between 150 g/L and saturation, or having a sodium chloride concentration above saturation in the presence of a crystal growth inhibitor for sodium chloride, said brine solution optionally comprising a crystal growth inhibitor for the alkali metal or ammonium salt of said divalent anion; b) adding, if the concentration of the crystal growth inhibitor for the alkali metal or ammonium salt of the divalent anion (the divalent anion comprising salt) in the brine solution is less than 20 mg/L, an amount of said crystal growth inhibitor for the alkali metal or ammonium salt of the divalent anion such that said brine solution comprises at least 20 mg/L of said crystal growth inhibitor; c) subjecting said solution to a membrane filtration step, thereby separating the brine solution into a brine stream being supersaturated for said divalent anion-comprising salt, and a brine stream being undersaturated for said divalent anion-comprising salt; d) adding, if the concentration of the crystal growth inhibitor for the alkali metal or ammonium salt of the divalent anion in the brine stream being supersaturated for said divalent-anion comprising salt is less than 20 mg/L, an amount of said crystal growth inhibitor such that said brine stream comprises at least 20 mg/L of said crystal growth inhibitor; e) subjecting the brine stream being supersaturated for the divalent anion-comprising salt to a crystallization process; and f) removing crystallized alkali metal or ammonium salt of the divalent anion.