Sustainable, highly effective selenate removal using electrochlorination facility–obtained magnesium precipitate: An approach to in situ layered double hydroxide formation

Abstract

We proposed a sustainable selenate (Se(VI)) removal method using in situ layered double hydroxide (LDH) formation and calcined magnesium precipitate (CMP) derived from an electrochlorination facility. During kinetic experiments, the optimal removal conditions were identified by adjusting pH and Al dosage, which enabled a notable Se(VI) removal efficiency (127 mg/g-CMP). The initial release of Mg ions from CMP was confirmed to occur via Al-ion hydrolysis. Subsequently, after the pH adjustment process, Se(VI) could be sequestered via outer-sphere complexation within the interlayer space of the brucite-like sheets in LDH. The reusability of precipitated sludges (LDHS and calcined LDHS (LDOS)), which can be secondary wastes, was also evaluated as Se(VI) adsorbents. The results confirmed the high maximum adsorption capacity of LDOS (42.1 mg/g), demonstrating its performance comparable to that of reported adsorbents. This study highlights the potential of the in situ LDH formation method for Se(VI) removal and the possibility of transforming magnesium precipitate into sustainable resources. © 2025 The Authors