Nanodiamonds in Filtration and Adsorption Systems: Structure-Property Relationships, Immobilization Strategies, and...

Nanodiamonds (NDs) combine the exceptional hardness, chemical durability, and thermal stability of bulk diamond with a high surface-to-volume ratio and widely tunable surface chemistry. These properties enable broad control over surface charge, polarity, hydration, and interfacial interactions, making NDs attractive for adsorption and water-treatment applications. Nevertheless, their practical potential in these fields remains substantially underdeveloped relative to the depth of accumulated physicochemical knowledge. This review critically examines known and filtration-relevant interactions between ND surfaces and dissolved species, and evaluates how these interactions could be exploited in adsorption and filtration technologies. We compare the two technologically relevant ND classes-detonation nanodiamonds (DNDs) and high-pressure high-temperature (HPHT) NDs-and analyze the consequences of surface termination, defect structure, nitrogen content, and colloidal state for zeta potential, hydration, and interfacial reactivity in aqueous environments. A particular focus is placed on hydrogenated NDs, which exhibit an unusual combination of strongly positive electrokinetic response, pronounced interfacial water structuring, and surface electronic effects associated with charge transfer and particle structure that distinguish them from oxidized NDs and other carbon nanomaterials. We systematically review documented interactions between ND surfaces and relevant pollutant classes: multivalent metal ions, charged organic molecules, PFAS, and biomolecules, drawing on literature from water treatment, biomedicine, and chromatography to establish the breadth of ND interfacial chemistry. A central argument of this review is that the functional unit in ND-based filtration is the accessible ND surface: immobilization strategies that preserve surface exposure-electrostatic deposition, covalent grafting, and thermally assisted stabilization on inorganic supports-are critically distinguished from embedded composite approaches where ND surfaces are mostly buried and rendered passive. We identify the translation of these immobilization strategies to polymer membrane supports as the principal unresolved engineering challenge, and outline the role of ND structural heterogeneity, long-term surface stability, and scalable deaggregation as key scientific priorities for realizing the full potential of NDs in next-generation filtration systems.