Removal of Trace Toxic Oxyanions from Hypersaline Brines Using Temperature Swing Solvent Extraction

Hypersaline brines are problematic to remediate since existing desalination methods are unsuitable for high salinities. Furthermore, the ubiquitous presence of micropollutants in brines can complicate desalination and treatment efforts. Here, we demonstrate temperature swing solvent extraction, TSSE, for the desalination of high-salinity brines containing trace concentrations of toxic oxyanions selenate and arsenate and environmentally relevant anions phosphate and sulfate. TSSE showed excellent rejection toward all four trace anions, with as little as 0.20% of the oxyanions ending up in the product water. Through regression analysis of the partitioning behavior of a series of anions (chloride, nitrate, acetate, sulfate, carbonate, and phosphate) in biphasic diisopropylamine-water-salt systems against 16 ion-specific parameters, the solubility limit of the salt in pure water was identified as a principal factor governing the fate and transport of the salt.