Seawater desalination effectively produces fresh water, yet brine byproducts raise significant environmental concerns. Strontium, a valuable resource in brine, is increasingly sought after due to diminishing terrestrial mineral sources. However, its recovery is challenging because strontium ion (Sr 2+ ) and calcium ion (Ca 2+ ) exhibit similar physicochemical behaviors in the aqueous phase, necessitating advanced recovery technologies. This study proposes an integrated recovery process for seawater reverse osmosis (SWRO) brine combining oxalate-based precipitation and ion exchange. In the pretreatment stage, NaOH and oxalate were employed to sequentially remove magnesium and calcium interferences. Specifically, oxalate addition at a 1.6 molar ratio relative to Ca 2+ preferentially precipitated calcium, drastically increasing the Sr 2+ /Ca 2+ ratio from 0.016 to 2.5, indicating a notable enhancement in Sr 2+ relative to Ca 2+ . For the enrichment of Sr 2+ from the pretreated solution, an ion-exchange column was employed. Two consecutive concentration cycles yielded a Sr-enriched solution exceeding 4 g/L. A post-IEX Ca 2+ removal step further reduced residual calcium, achieving a maximum Sr 2+ /Ca 2+ ratio of 28.6, with a Sr 2+ concentration of approximately 2 g/L. These results demonstrate that an integrated process using sequential oxalate-based precipitation and ion exchange achieves high efficiency in Ca 2+ removal, enhancing the overall feasibility of the Sr 2+ recovery process.
Moon et al. (2026) studied this question.