Advances in Green Nanotechnology for Water Treatment: A Systematic Review of Uranium and Thorium Removal from Water.

This systematic review evaluates the application of green-synthesized nanoparticles for the removal of uranium (U) and thorium (Th) from contaminated water sources. The study focuses on the synthesis methods, adsorption performance, operational parameters, and environmental implications associated with these nanomaterials. Following PRISMA guidelines, studies published between 2015 and 2025 were identified through searches conducted in the Scopus and Web of Science databases. The review highlights the predominance of iron-based nanoparticles, biochar-derived materials, and biopolymer-based composites, many of which demonstrated removal efficiencies exceeding 90% and high adsorption capacities for U (VI) and Th (IV). Key factors influencing performance include solution pH, adsorbent dosage, contaminant concentration, and contact time. The review also examines adsorption mechanisms, regeneration potential, scalability challenges, and concerns related to environmental safety and nanoparticle recovery. Although the reported results demonstrate significant potential for radionuclide remediation, most studies remain limited to laboratory-scale experiments using synthetic water. This review synthesizes current knowledge, identifies existing research gaps, and discusses future directions required to support the practical implementation of green nanotechnologies for sustainable water treatment.