Fractionation of Dye/NaCl Mixtures Using Loose Nanofiltration Membranes Based on the Incorporation of WS2 in Self-Assembled Layer-by-Layer Polymeric Electrolytes

Salt accumulation often occurs in conventional processes for textile wastewater treatment, which affects the dye removal efficiency and water recovery rate. Nanofiltration is a feasible way to fractionate dye/NaCl mixtures. In this study, to enhance the dye/salt separation efficacy, two-dimensional (2D) WS2 nanosheets were incorporated and coordinately bonded to polyelectrolytes for fabricating layer-by-layer hybrid nanofiltration membranes. The incorporation of WS2 enhanced the hydrophilicity and surface negativity of the membrane. Further, the stacking of WS2 nanosheets and their frictionless surface promoted water transportation in polyelectrolyte multilayers. WS2-incorporated membrane (2 wt %) exhibited the highest pure water flux and achieved separation factors of 7238 and 9036 during filtration of Conge red/NaCl and reactive black 5/NaCl binary solutions, respectively. Moreover, the instability of the multilayered polyelectrolyte membrane in high ionic strength solutions was overcome by the incorporation of WS2, and the WS2-incorporated membrane showed better antifouling performance toward model organic foulants.