Advancements in oil-water separation: The role of molybdenum and tungsten disulfide as cutting-edge 2D nanomaterials

This article reviews recent strides in synthesizing, functionalizing, and utilizing molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂) nanomaterials owing to their exceptional wetting properties, which facilitate oil-water separation. Among various materials explored, they have also emerged as particularly promising candidates due to their high surface area, tunable surface chemistry, and unique layered structure. The two-dimensional (2D) morphology offers abundant active sites, enhanced interaction with water molecules, and the ability to engineer surface wettability at the nanoscale, all of which are highly advantageous for efficient oil-water separation. Distinct separation mechanisms, performance benchmarks, and potential integration into practical separation setups were meticulously surveyed and analyzed. Furthermore, to elucidate the superiority of MoS₂ and WS₂ 2D nanomaterials over alternative methodologies for oil-water separation, we comprehensively examined other techniques, including membrane processes, electrocoagulation, adsorption with modified materials, and biological methods. For instance, the high membrane, operational, and maintenance costs, scaling, fouling, expensive production steps, high energy consumption, and complex operations are significant limitations of other processes for oil-water separation. On the other hand, the MoS₂ and WS₂ nanomaterials provide sustainable and effective oil-water separation performance compared to other processes owing to their unique properties, such as superior reusability, high separation efficiency, excellent hydrophobicity (water-repelling) and oleophilicity (oil-attracting) features, significant chemical and thermal stability, and enhanced photocatalytic properties. This review showed that the oil-water separation efficiency of the MoS₂ and WS₂-based materials was 70–100 %. The highest oil-water separation efficiency of 100 % is observed using cellulose acetate -MoS₂ fibrous sponge from a toluene-water mixture at a pH of 8. Nevertheless, while MoS₂ and WS₂ nanomaterials promise oil-water separation owing to their unique properties, their limitations, such as cost, scalability, environmental concerns, agglomeration, regeneration challenges, and potential toxicity, must be carefully addressed. Consequently, further research and development are necessary to overcome these hurdles and fully realize their potential in practical applications.