Abstract
Research and development of two-dimensional transition metal dichalcogenides (TMDC) (e.g., molybdenum disulfide [MoS(2)]) in electronic, optical, and catalytic applications has been growing rapidly. However, there is little known regarding the behavior of these particles once released into aquatic environments. Therefore, an in-depth study regarding the fate and transport of two popular types of MoS(2) nanomaterials, lithiated (MoS(2)-Li) and Pluronic PF-87 dispersed (MoS(2)-PL), was conducted in saturated porous media (quartz sand) to identify which form would be least mobile in aquatic environments. The electrokinetic properties and hydrodynamic diameters of MoS(2) as a function of ionic strength and pH were determined using a zeta potential analyzer and dynamic light scattering techniques. Results suggest that the stability is significantly decreased beginning at 10 and 31.6 mM KCl, for MoS(2)-PL and MoS(2)-Li, respectively. Transport study results from breakthrough curves, column dissections, and release experiments suggest that MoS(2)-PL exhibits a greater affinity to be irreversibly bound to quartz surfaces as compared with the MoS(2)-Li at a similar ionic strength. Derjaguin-Landau-Verwey-Overbeek theory was used to help explain the unique interactions between the MoS(2)-PL and MoS(2)-Li surfaces between particles and with the quartz collectors. Overall, the results suggest that the fate and transport of MoS(2) is dependent on the type of MoS(2) that enters the environment, where MoS(2)-PL will be least mobile and more likely be deposited in porous media from pluronic-quartz interactions, whereas MoS(2)-Li will travel greater distances and have a greater tendency to be remobilized in sand columns.