Hybrid adsorptive tailored 2D nanomaterials for enhanced Cr/As removal from groundwater: A critical review

Chromium (Cr) and arsenic (As) contamination in groundwater remains a global threat due to their valence-dependent toxicity, complex speciation, and high mobility in subsurface environments. Two-dimensional (2D) nanomaterials have emerged as selective adsorbents for remediating these toxic oxyanions through atomically thin structures, high surface energy, and tunable surface chemistry. However, structure–activity relationships for Cr/As removal by 2D materials remain unclear, leading to irrational modifications and ambiguous synergistic mechanisms, hindering environmental applicability. This review provides a novel and comprehensive analysis of tailored 2D nanomaterials for enhanced Cr/As removal, establishing a multi-mechanism framework in which adsorption, AOTs, ion exchange, and precipitation are critically analyzed. On this basis, responsive smart adsorbents—materials whose adsorption or regeneration properties can be regulated by pH, temperature, and light stimuli (e.g., thermoresponsive MOFs)—and microbial fuel cells (MFCs) are proposed. Representative material families—such as the first-discovered graphene, transition metal compounds, highly conductive MXenes and MBenes, ion-exchange-rich cationic inorganic frameworks, porous MOFs and COFs, bandgap-tunable g-C 3 N 4 , inherently inert h-BN, and emerging 2D materials—are comparatively evaluated in terms of removal performance and applicability. Modification strategies are systematically analyzed to activate surface sites and facilitate charge carrier migration. Finally, a future roadmap for atomic-level stabilization, including single-atom/diatomic catalysts, nanoconfinement, nanozymes, and self-powered systems, is discussed to connect laboratory studies with prospects and challenges, such as device architecture, field-scale validation, and 2D material stability. Overall, tailored 2D materials—surpassing inefficient, high-cost traditional materials and single technology—achieve cleaner Cr/As removal with higher adsorption capacity and excellent cycling stability.