Ultrathin nanofiltration membrane assembled by polyethyleneimine-grafted graphene quantum dots

Enhancing the water permeability of composite NF membranes through the incorporation of organic ions in the aqueous phase

Composite nanofiltration (NF) membranes prepared using interfacial polymerization (IP) have gained significant attention in the field of wastewater treatment. In this study, sodium camphor sulfonate (CSA-Na) and tetraethylammonium chloride (TEAC) were employed as aqueous phase additives to regulate the diffusion of piperazine (PIP) molecules through electrostatic interactions. The dissociated CSA-Na and TEAC in the aqueous solution formed an organic structure at a certain concentration, restricting the interfacial transport behavior of PIP monomers. The results show that when the content of CSA-Na is 2% w/v, TEAC is 3.9% w/v, that is, the material dosage ratio is 1 : 3, and the NF membrane shows the best performance, with a water flux of 55.61 L m-2 h-1 (test pressure is 0.5 MPa), and MgSO4 rejection rate of more than 98%.

Antifouling graphene oxide membranes for oil-water separation via hydrophobic chain engineering

Engineering surface chemistry to precisely control interfacial interactions is crucial for fabricating superior antifouling coatings and separation membranes. Here, we present a hydrophobic chain engineering strategy to regulate membrane surface at a molecular scale. Hydrophilic phytic acid and hydrophobic perfluorocarboxylic acids are sequentially assembled on a graphene oxide membrane to form an amphiphilic surface. The surface energy is reduced by the introduction of the perfluoroalkyl chains while the surface hydration can be tuned by changing the hydrophobic chain length, thus synergistically optimizing both fouling-resistance and fouling-release properties. It is found that the surface hydration capacity changes nonlinearly as the perfluoroalkyl chain length increases from C₄ to C₁₀, reaching the highest at C₆ as a result of the more uniform water orientation as demonstrated by molecular dynamics simulations. The as-prepared membrane exhibits superior antifouling efficacy (flux decline ratio <10%, flux recovery ratio ~100%) even at high permeance (~620 L m^-2 h^-1 bar^-1) for oil-water separation.

Ultrathin Membranes for Separations: A New Era Driven by Advanced Nanotechnology

Ultrathin membranes are at the forefront of membrane research, offering great opportunities in revolutionizing separations with ultrafast transport. Driven by advanced nanomaterials and manufacturing technology, tremendous progresses are made over the last 15 years in the fabrications and applications of sub-50 nm membranes. Here, an overview of state-of-the-art ultrathin membranes is first introduced, followed by a summary of the fabrication techniques with an emphasis on how to realize such extremely low thickness. Then, different types of ultrathin membranes, categorized based on their structures, that is, network, laminar, or framework structures, are discussed with a focus on the interplays among structure, fabrication methods, and separation performances. Recent research and development trends are highlighted. Meanwhile, the performances and applications of current ultrathin membranes for representative separations (gas separation and liquid separation) are thoroughly analyzed and compared. Last, the challenges in material design, structure construction, and coordination are given, in order to fully realize the potential of ultrathin membranes and facilitate the translation from scientific achievements to industrial productions.