Optimizing separation performance and interfacial adhesion of PDMS/PVDF composite membranes for butanol recovery from aqueous solution

Design of PDMS/PAN composite membranes with ultra-interfacial stability via layer integration

The interfacial interaction between the selective layer and porous substrate directly determines the separation performance and service lifetime of functional composite membranes. Till now, almost all reported polymeric selective layers are physically in contact with the substrate, which is unsatisfactory for long-term operation. Herein, we introduced a functional composite membrane with ultra-interfacial stability via layer integration between the polydimethylsiloxane selective layer and polyacrylonitrile substrate, where a facile light-triggered copolymerization achieved their covalent bonding. The critical load for the failure of the selective layer is 45.73 mN when testing the interfacial adhesion, i.e., 5.8 times higher than that before modification and significantly higher than previous reports. It also achieves superior pervaporation performance with a separation factor of 9.54 and membrane flux of 1245.6 g m-2 h-1 feeding a 1000 ppm phenol/water solution at 60 °C that is significantly higher than the same type of polymeric ones. Not limited to pervaporation, such a strategy sheds light on the design of highly stable composite membranes with different purposes, while the facile photo-trigged technique shows enormous scalability.

PDMS/PVDF Electrospinning Membranes for Water-in-Oil Emulsion Separation and UV Protection

With industry development, the separation of oily wastewater is becoming more critical. Inspired by organisms such as lotus leaves, biomimetic superhydrophobic surfaces with micro-nano structures have shown great potential in this regard. In this work, PDMS/PVDF oil-water separation membranes with designed microstructures were prepared by electrospinning technology. The membrane-forming effect of electrospinning with different ratios of PDMS and PVDF was studied. The study found that membranes with high PDMS content were more likely to form microspheres, and PDMS tended to concentrate on the microspheres. The results also showed that the microspheres would bring better hydrophobicity to the membrane. When the ratio of PDMS to PVDF is 1:2, the membrane has a water contact angle of up to 150° and an oil contact angle of 0°. At this ratio, the separation efficiency of the membrane for the water-in-oil emulsion is 98.7%, and it can still maintain more than 98% after ten separation cycles, which is a good candidate for oil-water separation. Furthermore, microspheres enable the membrane to achieve macroscopic uniformity and microscopic phase separation so that the membranes have both good elongation and fracture strength. In addition, the PDMS/PVDF membranes also exhibit excellent UV resistance, and their UV protection factor is greater than 185, making them a potential UV protective material.

NiSe and CoSe Topological Nodal-Line Semimetals: A Sustainable Platform for Efficient Thermoplasmonics and Solar-Driven Photothermal Membrane Distillation

The control of heat at the nanoscale via the excitation of localized surface plasmons in nanoparticles (NPs) irradiated with light holds great potential in several fields (cancer therapy, catalysis, desalination). To date, most thermoplasmonic applications are based on Ag and Au NPs, whose cost of raw materials inevitably limits the scalability for industrial applications requiring large amounts of photothermal NPs, as in the case of desalination plants. On the other hand, alternative nanomaterials proposed so far exhibit severe restrictions associated with the insufficient photothermal efficacy in the visible, the poor chemical stability, and the challenging scalability. Here, it is demonstrated the outstanding potential of NiSe and CoSe topological nodal-line semimetals for thermoplasmonics. The anisotropic dielectric properties of NiSe and CoSe activate additional plasmonic resonances. Specifically, NiSe and CoSe NPs support multiple localized surface plasmons in the optical range, resulting in a broadband matching with sunlight radiation spectrum. Finally, it is validated the proposed NiSe and CoSe-based thermoplasmonic platform by implementing solar-driven membrane distillation by adopting NiSe and CoSe nanofillers embedded in a polymeric membrane for seawater desalination. Remarkably, replacing Ag with NiSe and CoSe for solar membrane distillation increases the transmembrane flux by 330% and 690%, respectively. Correspondingly, costs of raw materials are also reduced by 24 and 11 times, respectively. The results pave the way for the advent of NiSe and CoSe for efficient and sustainable thermoplasmonics and related applications exploiting sunlight within the paradigm of the circular blue economy.

Bio-inspired fabrication of Ester-functionalized imprinted composite membrane for rapid and high-efficient recovery of lithium ion from seawater

Lithium ion (Li⁺) is one of the important sustainable resource and it's urgently demanded to develop high-selectivity and high-efficient method to extract of Li⁺ from seawater. Hence, we propose the ester-functionalized ion-imprinted membrane (IIMs) with high selectivity and stability for the rebinding and separation of Li⁺ in aqueous medium via ion imprinted technology and membrane separation technology. In this work, the hydrophilic polydimethylsiloxane membranes (PDMS) are synthesized by self-polymerization of dopamine (DA) in aqueous solution, resulting in the fabrication of dense poly-dopamine (PDA) layer on the surface of PDMS (PDMS-PDA). In view of weak bonding forces (such as hydrogen bond, ionic bond and Van der Waals' force) between traditional imprinted polymer and ligand, the ester groups are formed between modified PDMS-PDA and ligand by surface grafting. The obtained Li⁺ imprinted membranes (Li-IIMs) have a suitable cavity and high adsorption capacity toward Li⁺ which reveal a high rebinding capacity (50.872 mg g^-1) toward Li⁺ based on ample rebinding sites and strong affinity force. The superior relative selectivity coefficients (α_Na/Li, α_K/Li and α_Rb/Li are 1.71, 4.56 and 3.80, respectively) can be also achieved. The selectivity factors of Li-IIMs for Na⁺, K⁺ and Rb⁺ are estimated to be 2.52, 2.8 and 3.03 times larger than Li⁺ non-imprinted membranes (Li-NIMs), which imply the superior selectivity of Li-IIMs toward Li⁺. The regeneration ability of Li-IIMs is observed by systematic batch experiments. In summary, it can be concluded that the rebinding capacities of Li-IIMs is slightly decrease after eluting process, owing to the Li-IIMs with outstanding stability performance. Presentation of the method pave a fine prospect for coming true the long-term use of imprinted membrane.

Ultrathin Membranes with a Polymer/Nanofiber Interpenetrated Structure for High-Efficiency Liquid Separations

Ultrathin-film composite membranes comprising an ultrathin polymeric active layer have been extensively explored in gas separation applications benefiting from their extraordinary permeation flux for high-throughput separation. However, the practical realization of an ultrathin active layer in liquid separations is still impeded by the trade-off effect between the membrane thickness (permeation flux) and structural stability (separation factor). Herein, we report a general multiple and alternate spin-coating strategy, collaborating with the interface-decoration layer of copper hydroxide nanofibers (CHNs), to obtain ultrathin and robust polymer-based membranes for high-performance liquid separations. The structural stability arises from the poly(dimethylsiloxane) (PDMS)/CHN interpenetrated structure, which confers the synergistic effect between PDMS and CHNs to concurrently resist PDMS swelling and avoid CHNs from collapsing, while the ultrathin thickness is enabled by the sub-10 nm pore size of the CHN layer, the rapid cross-linking reaction during spin-coating, and the small thickness of the CHN layer. As a result, the as-prepared membrane possesses an exceptional butanol/water separation performance with a flux of 6.18 kg/(m² h) and a separation factor of 31, far exceeding the state-of-the-art polymer membranes. The strategy delineated in this work provides a straightforward method for the design of ultrathin and structurally stable polymer membranes, holding great potential for the practical application of high-efficiency separations.