Thermal transformation of seawater electrolysis-derived brucite into MgO: An approach for arsenic immobilization in aqueous system

This study investigates the applicability of seawater electrolysis-derived brucite precipitate (MP) as a low-cost precursor for preparing MgO adsorbents that effectively immobilize arsenic in water. The brucite was thermally transformed at various calcination temperatures (400–800 °C) to optimize the physicochemical properties of the resulting MgO-based adsorbents, and the adsorption performance for both arsenite (As(Ⅲ)) and arsenate (As(Ⅴ)) was systematically evaluated. The calcined product at 400°C (CMP-400) exhibited rapid kinetics, high adsorption capacities (up to 523 mg/g for As(Ⅲ), 335 mg/g for As(Ⅴ) calculated by the Sips adsorption model), and stable removal efficiencies across a wide pH range (3–10) likely due to the hydration of MgO surface. Batch experiments under varying pH conditions, ionic strength, and coexisting ions suggested that inner-sphere surface complexation was the dominant adsorption pathway for both arsenic species. Adsorption tests using synthetic groundwater containing As(Ⅲ) and As(Ⅴ) confirmed the practical applicability of CMP, with total arsenic concentrations below the US EPA guideline (10 μg/L). These findings demonstrate the potential of repurposing industrial brucite waste into high-performance, sustainable adsorbents for arsenic remediation. • Industrial brucite precipitate from seawater electrolysis was thermally converted to MgO for arsenic adsorption. • Calcination at 400 °C yielded MgO (CMP-400) with high surface area and superior adsorption performance. • CMP-400 effectively removed both As(III) and As(V) across a wide pH range. • The practical applicability of CMP-400 was validated in synthetic groundwater, meeting the 10 μg/L guideline.