Research Progress in Removal of Strontium and Cesium From Radioactive Wastewater by Metal Sulfides

Radioactive strontium and cesium, generated by nuclear power plants, present significant threats top human health and ecological safety due to their long half-lives and strong bio-accumulation. Given these risks, finding ways to remove strontium and cesium has become an urgent priority. Among numerous treatment technologies, adsorption stands out as one of the most widely adopted and efficient approaches for water treatment, owing to its high efficiency, safety, selectivity, and ease of operation. In recent years, advancements in nanotechnology have highlighted metal sulfides as a promising class of adsorbents, thanks to their unique layered structures and excellent physical and chemical properties. These are layered composite compounds, formed by combining metal or semi-metal cations with sulfur anions in the form of M_xS_y, can be categorized into binary, ternary and multi-component metal sulfides. Compared with traditional materials, metal sulfide-based materials offer many merits such as versatile preparation methods, large specific surface areas, rapid adsorption kinetics, large adsorption capacities, and excellent thermal and chemical stability. However, to fully leverage the potential of metal sulfides in strontium and cesium removal and promote their practical application, it is necessary to gain a comprehensive and in-depth understanding of their adsorption behavior to elucidate the microscopic mechanisms by which they capture and immobilize target pollutants from the aqueous phase. The adsorption properties are influenced not only by the physical and chemical properties of the adsorbents, but also by external factors such as initial pollutant concentration, pH value, temperature and the presence of competing ions. This paper provides a brief overview of the structure, properties, and synthesis methods of metal sulfide materials. It focuses on reviewing and discussing recent research progress in the adsorption and removal of radioactive strontium and cesium using metal sulfide materials. Through in-depth discussion and analysis of adsorption performance and mechanisms, the prominent challenges, particularly the difficulty in efficiently separating and recovering used adsorbents, as well as challenges in practical water applications, secondary pollution, and other issues are identified. Finally, future development directions for metal sulfides and their composites, with the aim of advancing the practical application of these adsorbents in the remediation of radioactive contamination are explored.