Selective arsenic removal in complex aquatic environments: Mechanistic insights, sorbent design, and environmental...

Arsenic contamination in aquatic systems poses severe risks to human health and water security, yet its selective removal is complicated by the pervasive presence of competing anions such as phosphate, silicate, sulfate, and fluoride. Conventional non-selective adsorption strategies often fail under these conditions because they cannot effectively distinguish arsenic from coexisting anions, falling short of the dual demands of precision and safety in water remediation. To overcome these challenges, mechanism-oriented approaches that exploit intrinsic differences between arsenic and competing species have emerged as a promising pathway for precise remediation. This review critically examines the physicochemical contrasts-including differences in metal complexation ability, geometric compatibility, acid-base properties, and electrostatic behavior-that underpin selective arsenic uptake. Four key mechanistic pathways are delineated: inner-sphere complexation, geometric complementarity, hydrogen bonding, and electrostatic interactions, each evaluated for its strengths, limitations, and environmental relevance. Building on these insights, we analyze mechanism-guided material design strategies, including metal-based sorbents, molecularly imprinted polymers, and organic-functionalized materials, with emphasis on the dominant factors governing their selective performance. Finally, we assess how environmental drivers such as pH, solute concentration, coexisting cations, natural organic matter, and dynamic conditions interact with mechanistic pathways to regulate arsenic selectivity in realistic water matrices. By linking mechanistic understanding with material innovation and environmental regulation, this review establishes a comprehensive framework for precision remediation of arsenic-contaminated waters, providing strategies to reduce exposure risks, safeguard water quality, and support sustainable water resource management.