A pore-size tunable superhydrophobic membrane for high-flux membrane distillation

Polyvinylidene Fluoride-Based Nanowire-Imprinted Membranes with High Flux for Efficient and Selective Separation of Artemisinin/Artemether

A traditional phase transformation method is commonly used to prepare molecular imprinting membranes for selective separation. However, traditional molecularly imprinted polymers are mostly micron-sized particles, and the imprinting sites in their membrane are easily embedded, leading to a reduced adsorption capacity and decreased selectivity. In this study, an ultra-long nanowire with a diameter of about 15 nm was synthesized for the separation of artemisinin (ART), and its adsorption capacity was as high as 198.29 mg g-1 after imprinting polymerization. Molecular imprinting membranes were prepared, using polyvinylidene fluoride (PVDF), polyethersulfone (PES), and polysulfone (PSF) as the membrane matrix, for comparison. The average membrane pore size of PVDF-MIM was about 480 nm, and PVDF-MIM had the highest adsorption capacity (69 mg g-1) for ART. The optimal flow rate for PVDF-MIM's dynamic adsorption of ART was 7 mL min-1. Under this optimal flow rate, selectivity experiments were carried out to obtain the separation factor of PVDF-MIM (α = 8.37), which was much higher than the corresponding values of PES-MIM and PSF-MIM. In addition, the hydrophobicity and low flux of PES-MIM and PSF-MIM lead to higher non-specific adsorption. The hydrophobicity of PVDF-MIM is lower than that of PES-MIM and PSF-MIM, which greatly reduces the non-specific adsorption of the membrane, thus increasing the selectivity of the membranes. Therefore, the effective density of the imprinting sites in the pores and the membrane structure are the main factors determining the efficient separation of molecularly imprinted membranes.

Electrosprayed CNTs on Electrospun PVDF-Co-HFP Membrane for Robust Membrane Distillation

In this investigation, the electrospraying of CNTs on an electrospun PVDF-Co-HFP membrane was carried out to fabricate robust membranes for the membrane distillation (MD) process. A CNT-modified PVDF-Co-HFP membrane was heat pressed and characterized for water contact angle, liquid entry pressure (LEP), pore size distribution, tensile strength, and surface morphology. A higher water contact angle, higher liquid entry pressure (LEP), and higher tensile strength were observed in the electrosprayed CNT-coated PVDF-Co-HFP membrane than in the pristine membrane. The MD process test was conducted at varying feed temperatures using a 3.5 wt. % simulated seawater feed solution. The CNT-modified membrane showed an enhancement in the temperature polarization coefficient (TPC) and water permeation flux up to 16% and 24.6%, respectively. Field-effect scanning electron microscopy (FESEM) images of the PVDF-Co-HFP and CNT-modified membranes were observed before and after the MD process. Energy dispersive spectroscopy (EDS) confirmed the presence of inorganic salt ions deposited on the membrane surface after the DCMD process. Permeate water quality and rejection of inorganic salt ions were quantitatively analyzed using ion chromatography (IC) and inductively coupled plasma-mass spectrometry (ICP-MS). The water permeation flux during the 24-h continuous DCMD operation remained constant with a >99.8% inorganic salt rejection.

Research progress on eco-friendly superhydrophobic materials in environment, energy and biology

In the past few years, bioinspired eco-friendly superhydrophobic materials (EFSMs) have made great breakthroughs, especially in the fields of environment, energy and biology, which have made remarkable contributions to the sustainable development of the natural environment. However, some potential challenges still exist, which urgently need to be systematically summarized to guide the future development of this field. Herein, in this review, initially, we discuss the five typical superhydrophobic models, namely, the Wenzel, Cassie, Wenzel-Cassie, "lotus", and "gecko" models. Then, the existence of superhydrophobic creatures in nature and artificial EFSMs are summarized. Then, we focus on the applications of EFSMs in the fields of environment (self-cleaning, wastewater purification, and membrane distillation), energy (solar evaporation, heat accumulation, and batteries), and biology (biosensors, biomedicine, antibacterial, and food packaging). Finally, the challenges and developments of eco-friendly superhydrophobic materials are highlighted.

Recent Advances in Multifunctional Mechanical-Chemical Superhydrophobic Materials

In recent years, biology-inspired superhydrophobic technology has attracted extensive attention and has been widely used in self-cleaning, anti-icing, oil-water separation, and other fields. However, the poor durability restricts its application in practice; thus, it is urgent to systematically summarize it so that scientists can guide the future development of this field. Here, in this review, we first elucidated five kinds of typical superhydrophobic models, namely, Young's equation, Wenzel, Cassie-Baxter, Wenzel-Cassie, "Lotus," and "Gecko" models. Then, we summarized the improvement in mechanical stability and chemical stability of superhydrophobic surface. Later, the durability test methods such as mechanical test methods and chemical test methods are discussed. Afterwards, we displayed the applications of multifunctional mechanical-chemical superhydrophobic materials, namely, anti-fogging, self-cleaning, oil-water separation, antibacterial, membrane distillation, battery, and anti-icing. Finally, the outlook and challenge of mechanical-chemical superhydrophobic materials are highlighted.