High-efficiency struvite synthesis utilizing magnesium-rich brine from hydrate-based desalination

Concentrated brine generated during desalination and enriched with dissolved ions is an environmental concern and a valuable resource for recovery. In this study, an integrated strategy combining hydrate-based desalination (HBD) with ion recovery and subsequent struvite synthesis was developed using mineral-rich brine derived from representative saline matrices, including seawater and saline water collected from the Mekong Delta. HBD achieved a brine recovery of ∼30%, with enrichment factors ranging from 1.2 to 1.4 for major ions, this indicated effective ion concentration and significant potential of this process for resource valorization, particularly magnesium (Mg). The Mg2+-rich saline stream was further purified to remove coexisting impurities, particularly Ca2+, via ethanol-assisted solvent crystallization. The recovered Mg was subsequently used for struvite (MgNH4PO4·6H2O) synthesis via chemical precipitation method. Under optimized conditions (pH ∼ 8 and reaction time of 60 min), struvite was obtained with a recovery efficiency exceeding 90%. Comprehensive physicochemical characterization confirmed the formation of struvite with the desired stoichiometric composition and high purity (>85%). These findings demonstrate the feasibility of transforming hydrate desalination brine from a waste by-product into a value-added agricultural resource, contributing to sustainable desalination and circular resource management in saline-affected regions.