Cyclodextrin in Water Treatment and Wastewater Management: Recent Advances, Environmental Applications and Future Perspectives

Water pollution from industrial effluents, agricultural runoff, pharmaceutical residues, heavy metals, and synthetic dyes has emerged as one of the most pressing environmental challenges of the twenty-first century. Conventional treatment technologies often fail to achieve satisfactory removal of emerging and persistent contaminants at trace concentrations. Cyclodextrins (CDs) — cyclic oligosaccharides derived from the enzymatic conversion of starch — have attracted considerable scientific interest as versatile functional materials for water treatment owing to their distinctive truncated-cone architecture, which presents a hydrophilic exterior and a hydrophobic interior cavity capable of encapsulating a broad spectrum of organic and inorganic guest molecules through host–guest inclusion complexation. This narrative review provides a comprehensive and critical synthesis of the recent advances in CD-based materials for water and wastewater treatment, encompassing their structural and physicochemical foundations, cross-linked polymer systems, hybrid nanocomposites incorporating graphene oxide and magnetic nanoparticles, membrane technologies, and catalytic applications. A narrative approach was deliberately adopted because the breadth of the topic — spanning synthetic chemistry, environmental engineering, ecotoxicology, and process scale-up — does not lend itself to the homogeneous study populations, standardised outcome measures, and meta-analytic synthesis that characterise systematic reviews. Specific attention is devoted to the removal of heavy metals, organic micropollutants, pharmaceutical and personal care products, textile dyes, and persistent organic pollutants. Pilot-scale demonstrations, regeneration behaviour, economic considerations, environmental fate, and ecotoxicological implications of CD-based adsorbents are critically examined. Future research directions, including the integration of artificial intelligence for process optimisation, the development of bio-inspired and green-synthesised CD materials, and the scale-up challenges for full-scale implementation, are discussed. The review demonstrates that CD-based materials represent a highly promising platform for next-generation water remediation strategies, whilst also identifying key knowledge gaps that must be addressed to realise their full potential.