Simultaneous and efficient removal of inorganic As(III) and As(V) using a novel YMn binary oxide adsorbent: Performance evaluation and mechanism analysis

Inorganic arsenite (As(III)) and arsenate (As(V)) in water pose significant toxic and carcinogenic risks, making the development of effective strategies to eliminate inorganic arsenic from drinking water a critical priority for ensuring safe water supplies in many regions worldwide. Adsorption is a representative cost-efficient and practical approach for arsenic removal. The study proposed a novel Y-Mn binary oxide to address the limitations of existing single-component adsorbents that cannot effectively target As(III) and As(V) simultaneously. The adsorbent is an amorphous material composed of aggregated nanoscale particles, exhibiting a high specific surface area of 187.27 m²/g. According to batch experiment results, the maximum sorption capacities were 114.8 mg/g (pH = 7.0 ± 0.1) and 137.8 mg/g (pH = 7.0 ± 0.1), respectively, for As(III) and As(V). These sorption reactions proceeded fast and reached a balance within 24 h, adhering to a pseudo-second-order kinetic model. The material exhibited nearly complete independence from competitive ions and variations in ionic strength. The As(V) removal mechanism involved inner-sphere surface complexes being formed by replacing the surface hydroxyl groups/carbonate. Comparatively, the As(III) removal mechanism relied on a coupled oxidation and sorption process, wherein MnO₂ primarily oxidized As(III) to As(V), which was subsequently adsorbed onto the Y-Mn binary oxide surface. Additionally, the adsorbent demonstrated remarkable regeneration capabilities, rendering it a highly promising candidate for repeated utilization in treating drinking water and benefiting environmental modification.