Nanocomposite substrate-supported nanofiltration membrane for efficient treatment of rare earth wastewater

The incorporation of nanomaterials into the selective layer of nanofiltration membranes can effectively enhance membrane performance. However, the agglomeration of nanoparticles inevitably leads to defects in the membrane PA layer. To address this issue, this paper reports a novel nanocomposite substrate-supported thin-film composite (TFC) nanofiltration membrane with good stability and excellent separation performance. Inorganic two-dimensional O–MoS2 nanosheets were embedded into a polysulfone (PSF) substrate by a non-solvent-induced phase transition method. The PSF/O–MoS2 nanocomposite was used as a support for the interfacial polymerization between piperazine and tricarbonyl chloride. The pore morphology of the nanocomposites changed dramatically as the O–MoS2 content increased. With the optimal content of O–MoS2 in substrates was 0.06 wt%, the pore structure of the substrate changed from a larger irregular bubble pore structure to a finger-like pore structure. The nanocomposite matrix-supported TFC membrane exhibited 1.7 times higher water flux and better salt removal compared to the control membrane. Meanwhile, the obtained nanofiltration membranes showed excellent separation performance in treating simulated rare earth wastewater (P507) containing surfactants with a desalination rate of 97.08%. The desalination rate also reached 95% in a 24- h performance test on real rare earth wastewater (50-fold dilution), demonstrating its great potential for industrial applications. This work also highlights that modification of substrates with functional nanomaterials can provide a versatile approach to enhance the separation performance and stability of TFC membranes.