pH‐Dependent thermoresponsive poly[2‐(diethylamino)ethyl acrylamide]‐grafted PVDF membranes with switchable wettability for efficient emulsion separation

Efficient and selective capture of various mercury species from water using an exfoliated thiocellulose

The primary challenge in mercury (Hg) adsorbents for large-scale practical applications is to achieve the balance between performance and economy. This work attempts to address this issue by synthesizing an exfoliated thiocellulose (CU-SH) with high thiol density and hierarchical porosity using in-situ ligands grafting combined with chemical stripping. The prepared CU-SH shows remarkable physical stability and chemical resistance, and the micron sized fiber is conducive to separation from water. Hg(II) adsorption tests in water demonstrate that CU-SH has broad working pH range (1-12), fast kinetics (0.64 g/(mg‧min)), high adsorption capacity (652.9 mg/g), outstanding selectivity (Kd = 6.2 × 106 mg/L), and excellent reusability (R > 95 % after 20 cycles). Importantly, CU-SH exhibits good resistance to various coexisting ions and organic matter, and can efficiently remove Hg(II) from different real water. CU-SH can be made into a Point of Use (POU) device for continuous and efficient removal of Hg(II) from drinking water. 0.1 g CU-SH filled device can purify 3.2 L of Hg(II) (0.5 ppm) contaminated tap water before the breakthrough point of 2 ppb. Moreover, CU-SH also reveals good adsorption affinity for Hg-dissolved organic matter complexes (Hg(II)-DOM) in water, chloro(phenyl)mercury (PMC) in organic media and Hg0 vapor in air, suggesting the great practical potential of CU-SH.

Biomimetic materials in oil/water separation: Focusing on switchable wettabilities and applications

Clean water resources are crucial for human society, as the leakage and discharge of oily wastewater not only harm the economy but also disrupt our living environment. Therefore, there is an urgent need for efficient oil-water separation technology. Surfaces with switchable superwetting behavior have garnered significant attention due to their importance in both fundamental research and practical applications. This review introduces the fundamental principles of wettability in the oil-water separation process, the basic theory of switchable wettability, and the mechanisms involved in oil-water separation. Subsequently, the review discusses the research progress, challenges, and issues associated with three conventional types of special wettability materials: superhydrophobic/superoleophilic materials, superhydrophilic/superoleophobic materials, and superhydrophilic/underwater superoleophobic materials. Most importantly, it provides a detailed exploration of recent advancements in switchable wettability smart materials, which combine elements of traditional special wettability materials. These include stimulus-responsive smart materials, pre-wetting-induced materials, and Janus materials. The discussion covers key response factors, detailed examples of representative works, design concepts, and fabrication strategies. Finally, the review offers a comprehensive summary of switchable superwetting smart materials, encompassing their advantages and disadvantages, persistent challenges, and future prospects.

Multiple strategies to control the hydrophilic-hydrophobic balance of P(DMA-co-DMAEMA-co-QDMAEMA) coatings

The regulation of the hydrophilic-hydrophobic balance of polymers has an important influence not only on their aggregation behavior in aqueous solution, but also on their adhesion properties on the surface of substrates and the applications of the modified surfaces. Based on this, a random copolymer poly(dopamine methacrylamide-co-2-(dimethylamino)ethyl methacrylate) (P(DMA-co-DMAEMA)) was synthesized as a starting polymer to generate P(DMA-co-DMAEMA-co-QDMAEMA) (PDDQ) derivatives by a programmable quaternization of the DMAEMA precursor. By adjusting the pH or temperature, both the aggregation behavior in aqueous solutions and the surface adhesive behavior on the substrate surfaces of PDDQ copolymers were regulated due to the hydrophilic-hydrophobic balance. Specifically, the surface adsorption of PDDQ copolymers on surfaces was enhanced by the increased hydrophobicity of PDDQ. Stainless steel meshes (SSM) modified with the PDDQ0 copolymer without quaternization showed a superoleophobicity in acidic aqueous media, which endowed it with improved oil-water separation performance. In addition, the hydrophilic-hydrophobic balance of PDDQs and their coatings could also be tuned by changing the ratio of DMAEMA to QDMAEMA in the copolymer. From PDDQ0 to PDDQ100, by increasing the hydrophilic QDMAEMA component of PDDQ copolymers, anti-protein properties and oil/water separation efficiency of the modified surfaces were also enhanced gradually. The results provided a reference for designing P(DMA-co-DMAEMA-co-QDMAEMA) coatings in different application environments.

Synthesis and Study of Thermoresponsive Amphiphilic Copolymers via RAFT Polymerization

Synthesis and study of well-defined thermoresponsive amphiphilic copolymers with various compositions were reported. Kinetics of the reversible addition-fragmentation chain transfer (RAFT) (co)polymerization of styrene (St) and oligo(ethylene glycol) methyl ether methacrylate (PEO5MEMA) was studied by size exclusion chromatography (SEC) and 1H NMR spectroscopy, which allows calculating not only (co)polymerization parameters but also gives valuable information on RAFT (co)polymerization kinetics, process control, and chain propagation. Molecular weight Mn and dispersity Đ of the copolymers were determined by SEC with triple detection. The detailed investigation of styrene and PEO5MEMA (co)polymerization showed that both monomers prefer cross-polymerization due to their low reactivity ratios (r1 < 1, r2 < 1); therefore, the distribution of monomeric units across the copolymer chain of p(St-co-PEO5MEMA) with various compositions is almost ideally statistical or azeotropic. The thermoresponsive properties of p(St-co-PEO5MEMA) copolymers in aqueous solutions as a function of different hydrophilic/hydrophobic substituent ratios were evaluated by measuring the changes in hydrodynamic parameters under applied temperature using the dynamic light scattering method (DLS).

Research Progress in Gas Separation Using Hollow Fiber Membrane Contactors

In recent years, gas-liquid membrane contactors have attracted increasing attention. A membrane contactor is a device that realizes gas-liquid or liquid-liquid mass transfer without being dispersed in another phase. The membrane gas absorption method combines the advantages of chemical absorption and membrane separation, in addition to exhibiting high selectivity, modularity, and compactness. This paper introduces the operating principle and wetting mechanism of hollow membrane contactors, shows the latest research progress of membrane contactors in gas separation, especially for the removal of carbon dioxide from gas mixtures by membrane contactors, and summarizes the main aspects of membrane materials, absorbents, and membrane contactor structures. Furthermore, recommendations are provided for the existing deficiencies or unsolved problems (such as membrane wetting), and the status and progress of membrane contactors are discussed.

Zwitterionic Polymer Brush Grafted on Polyvinylidene Difluoride Membrane Promoting Enhanced Ultrafiltration Performance with Augmented Antifouling Property

Superhydrophilic zwitterions on the membrane surface have been widely exploited to improve antifouling properties. However, the problematic formation of a <20 nm zwitterionic layer on the hydrophilic surface remains a challenge in wastewater treatment. In this work, we focused on the energy consumption and time control of polymerization and improved the strong hydrophilicity of the modified polyvinylidene difluoride (PVDF) membrane. The sulfobetaine methacrylate (SBMA) monomer was treated with UV-light through polymerization on the PVDF membrane at a variable time interval of 30 to 300 s to grow a poly-SBMA (PSBMA) chain and improve the membrane hydrophilicity. We examined the physiochemical properties of as-prepared PVDF and PVDF-PSBMA_x using numeric analytical tools. Then, the zwitterionic polymer with controlled performance was grafted onto the SBMA through UV-light treatment to improve its antifouling properties. The PVDF-PSBMA_120s modified membrane exhibited a greater flux rate and indicated bovine serum albumin (BSA) rejection performance. PVDF-PSBMA_120s and unmodified PVDF membranes were examined for their antifouling performance using up to three cycles dynamic test using BSA as foulant. The PVDF-modified PSBMA polymer improved the antifouling properties in this experiment. Overall, the resulting membrane demonstrated an enhancement in the hydrophilicity and permeability of the membrane and simultaneously augmented its antifouling properties.