Adsorption of arsenic in groundwater in Cambodia using magnesium oxide

Abstract

This study investigates the potential use of brucite precipitate (MP), produced by seawater electrolysis, as an inexpensive precursor for creating MgO adsorbents capable of efficiently immobilize arsenic in water. To optimize the physicochemical properties of the resulting MgO-based adsorbents, the brucite was thermally transformed at different calcination temperatures (400–800 °C, CMP-400, CMP-500, CMP-600, and CMP-800). The adsorption performance for both arsenite (As(III)) and arsenate (As(V)) was systematically evaluated. The 400°C calcined product (CMP-400) demonstrated excellent adsorption capacities (up to 523 mg/g for As(III) and 335 mg/g for As(V) determined using the Sips adsorption model), rapid kinetics, and steady removal efficiencies throughout a broad pH range (3–10), most likely as a result of the hydration of the 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. The practical application of CMP was proven by adsorption studies utilizing synthetic groundwater containing As(III) and As(V), with total arsenic concentrations below the US EPA standard (10 μg/L). These results demonstrate the possibility of repurposing industrial brucite waste into sustainable, high-performing adsorbents for arsenic remediation.