ABSTRACT This study investigates the arsenic adsorption performance of commercial adsorbents modified with various lanthanum (La) precursors under different pH conditions. Both powder‐type and filter‐type adsorbents were fabricated, and the La(OH) 3 ‐modified adsorbents exhibited superior arsenic removal efficiency in both forms, with more than 98% arsenic removal even under alkaline conditions (pH 8.5). BET analysis confirmed that lanthanum incorporation increased surface area by over 1.5 times compared to the pristine adsorbent. Additionally, FTIR and NH 3 ‐TPD analyses revealed that the presence of acid sites partially contributed to enhanced adsorption performance. Notably, strong acid site signals were observed above 300°C in the La(OH) 3 added samples, suggesting that the improvement in arsenic adsorption efficiency was partly due to the presence of lanthanum. The filter‐type adsorbents, developed by combining La‐modified powders with activated carbon and a binder, retained high adsorption efficiency in flow‐through tests, demonstrating their applicability in practical water treatment systems. These results highlight that the choice of lanthanum precursor and optimization of acid sites are critical factors for designing cost‐effective, scalable, and high‐performance adsorbents for arsenic removal under alkaline conditions.
Byun et al. (2026) studied this question.