Preparation of PVDF-g-PAA-PAMAM membrane for efficient removal of copper ions

Selective and Controlled Grafting from PVDF-Based Materials by Oxygen-Tolerant Green-Light-Mediated ATRP

Poly(vinylidene fluoride) (PVDF) shows excellent chemical and thermal resistance and displays high dielectric strength and unique piezoelectricity, which are enabling for applications in membranes, electric insulators, sensors, or power generators. However, its low polarity and lack of functional groups limit wider applications. While inert, PVDF has been modified by grafting polymer chains by atom transfer radical polymerization (ATRP), albeit via an unclear mechanism, given the strong C-F bonds. Herein, we applied eosin Y and green-light-mediated ATRP to modify PVDF-based materials. The method gave nearly quantitative (meth)acrylate monomer conversions within 2 h without deoxygenation and without the formation of unattached homopolymers, as confirmed by control experiments and DOSY NMR measurements. The gamma distribution model that accounts for broadly dispersed polymers in DOSY experiments was essential and serves as a powerful tool for the analysis of PVDF. The NMR analysis of poly(methyl acrylate) graft chain-ends on PVDF-CTFE (statistical copolymer with chlorotrifluoroethylene) was carried out successfully for the first time and showed up to 23 grafts per PVDF-CTFE chain. The grafting density was tunable depending on the solvent composition and light intensity during the grafting. The initiation proceeded either from the C-Cl sites of PVDF-CTFE or via unsaturations in the PVDF backbones. The dehydrofluorinated PVDF was 20 times more active than saturated PVDF during the grafting. The method was successfully applied to modify PVDF, PVDF-HFP, and Viton A401C. The obtained PVDF-CTFE-g-PnBMA materials were investigated in more detail. They featured slightly lower crystallinity than PVDF-CTFE (12-18 vs 24.3%) and had greatly improved mechanical performance: Young's moduli of up to 488 MPa, ductility of 316%, and toughness of 46 × 106 J/m3.

Radiation‐Induced Admicellar Graft Polymerization of 2‐Hydroxyethyl Methacrylate onto Polyvinylidene Fluoride Membranes Using an Electron Beam Accelerator

The efficiency of admicellar graft polymerization in functionalizing polyvinylidene fluoride (PVDF) membranes was explored. The effect of 2‐hydroxyethyl methacrylate (HEMA) concentration and the absorbed dose was investigated using a simultaneous method of radiation‐induced graft polymerization. The degree of grafting increased with raising the absorbed dose and HEMA concentration. The Fourier transform infrared (FTIR) peak for C–O stretch and the asymmetric and symmetric stretching of the C–O–C bridge, respectively, proved the presence of poly(2‐hydroxyethyl methacrylate) (PHEMA) on the modified PVDF. As the grafting yield increased, rougher surfaces were observed. According to contact angle analysis, the grafted membrane with a higher grafting yield outperformed the low grafting yield membrane in terms of water flux and hydrophilicity.

The Adsorption of Heavy Metal Ions by Poly (Amidoamine) Dendrimer-Functionalized Nanomaterials: A Review

Rapid industrialization has resulted in serious heavy metal pollution. The removal of heavy metal ions from solutions is very important for environmental safety and human health. Poly (amidoamine) (PAMAM) dendrimers are artificial macromolecular materials with unique physical and chemical properties. Abundant amide bonds and amino functional groups provide them with a high affinity for heavy metal ions. Herein, PAMAM-functionalized adsorbents are reviewed in terms of different nanomaterial substrates. Approaches in which PAMAM is grafted onto the surfaces of substrates are described in detail. The adsorption isotherms and kinetics of these adsorbents are also discussed. The effects of PAMAM generation, pH, adsorbent dosage, adsorption time, thermodynamics, and ionic strength on adsorption performance are summarized. Adsorption mechanisms and the further functionalization of PAMAM-grafted adsorbents are reviewed. In addition to the positive results, existing problems are also put forward in order to provide a reference for the optimization of PAMAM-grafted adsorbents of heavy metal ions.

A recognition strategy combining effective boron affinity technology and surface imprinting to prepare highly selective and easily recyclable polymer membrane for separation of drug molecule

Cellulose acetate membrane (CAM) has become one of the most widely used membrane materials by virtue of stability and hydrophilicity. In this work, to achieve the aim of selective recognition and separation of drug molecule shikimic acid (SA), an effective recognition tactics was proposed by combining boron affinity technology with surface imprinting strategy based on cellulose acetate membrane with low price and biocompatibility. The supporting CAM material was prepared through the phase inversion technique by continuous adjustment of different factors including solvent type and kinds of pore-forming agents, and the optimal CAM with multistage structure and highly porosity was applied for the imprinting of SA. Then the imprinted polymer membrane (MIPs-CAM) was developed via boron affinity surface imprinting polymerization. Various methods (FT-IR, UV-vis, SEM, XPS, AFM and TGA) were used to characterize the structure, morphology, elemental composition, surface roughness and thermal property of the obtained membrane. The as-prepared MIPs-CAM showed homogeneous and abundant imprinted layer, good thermal stability. The batch adsorption results showed that the MIPs-CAM had fast adsorption kinetics, specific recognition ability, and the adsorption capacity could obtain 63.598 mg g^-1, which was two times higher than that of non-imprinted membrane (NIPs-CAM). The adsorption isotherms conformed to the Langmuir isotherm and the adsorption processes were spontaneous and endothermic. Additionally, the adsorption capacity of MIPs-CAM still reached 85% of the initial result after five cycles. The experimental results revealed that the molecularly imprinted membrane possessed the advantages of high selectivity and easy recovery compared with the traditional molecular imprinted polymers for SA separation. These results indicate that boron affinity MIPs-CAM with high performance will provide a promising platform for the separation and purification of other cis-diol drug molecules from environmental resources.

PVDF/SiO2-g-CDs blended membrane for fluorescence detection and adsorption of metal ions

The preparation method of PVDF/SiO₂-g-CDs blended membrane was that the silanized modified carbon dots (CDs) were grafted onto the PVDF/SiO₂ blended membrane surface. The surface composition, morphology, hydrophilicity, fluorescence performance and metal ions adsorption performance of PVDF/SiO₂-g-CDs blended membrane were studied. The fluorescence quenching effect of the membrane with Hg²⁺ and Fe³⁺ was obvious. The quenching mechanism was the complexation of metal ions with the functional groups of CDs including -NH₂, -OH and -COOH. The optical detection limits of PVDF/SiO₂-g-CDs blended membrane for Hg²⁺ was 1.6 nM in the linear range of 0.0025-20 μM, and the optical detection limits for Fe³⁺ was 2.1 μM in the linear range of 0.5-5000 μM. The maximum adsorption capacity of PVDF/SiO₂-g-CDs blended membrane for Fe³⁺ was 47.04 mg·g^-1. The adsorption of the membrane conformed to the pseudo-second-order kinetics and Langumir model, and belonged to monolayer chemical adsorption on the membrane surface. Through adsorption thermodynamic analysis, adsorption was a spontaneous endothermic process. The recovery rate of fluorescence and adsorption capacity could still be maintained above 82% after five cycles. The PVDF/SiO₂-g-CDs blended membrane had the ability to regenerate. In summary, the PVDF/SiO₂-g-CDs blended membrane had the dual functions of detecting and adsorbing metal ions, and had broad application prospects in sewage treatment.

A Review: Adsorption and Removal of Heavy Metals Based on Polyamide-amines Composites

In recent years, the problem of heavy metal pollution has become increasingly prominent, so it is urgent to develop new heavy metal adsorption materials. Compared with many adsorbents, the polyamide-amine dendrimers (PAMAMs) have attracted extensive attention of researchers due to its advantages of macro-molecular cavity, abundant surface functional groups, non-toxicity, high efficiency and easy modification. But in fact, it is not very suitable as an adsorbent because of its solubility and difficulty in separation, which also limits its application in environmental remediation. Therefore, in order to make up for the shortcomings of this material to a certain extent, the synthesis and development of polymer composite materials based on PAMAMs are increasingly prominent in the direction of solving heavy metal pollution. In this paper, the application of composites based on PAMAMs and inorganic or organic components in the adsorption of heavy metal ions is reviewed. Finally, the prospects and challenges of PAMAMs composites for removal of heavy metal ions in water environment are discussed.

Poly (Amidehydrazide) Hydrogel Particles for Removal of Cu2+ and Cd2+ Ions from Water

Poly(amidoamine)s (PAMAM) are very effective in the removal of heavy metal ions from water due to their abundant amine and amide functional groups, which have a high binding ability to heavy metal ions. We synthesized a new class of hyperbranched poly(amidehydrazide) (PAMH) hydrogel particles from dihydrazides and N,N'-methylenebisacrylamide (MBA) monomer by using the A2 + B4 polycondensation reaction in an inverse suspension polymerization process. In Cd2+ and Cu2+ ion sorption tests, the synthesized dihydrazide-based PAMH hydrogel particles exhibited sorption capacities of 85 mg/g for copper and 47 mg/g for cadmium. Interestingly, the PAMH showed only a 10% decrease in sorption ability in an acidic condition (pH = 4) compared to the diamine-based hyperbranched PAMAM, which showed a ~90% decrease in sorption ability at pH of 4. In addition, PAMH hydrogel particles remove trace amounts of copper (0.67 ppm) and cadmium (0.5 ppm) in water, below the detection limit.

GO/Bi2S3 Doped PVDF/TPU Nanofiber Membrane with Enhanced Photothermal Performance

Photothermal conversion materials have attracted wide attention due to their efficient utilization of light energy. In this study, a (GO)/Bi2S3-PVDF/TPU composite nanofiber membrane was systematically developed, comprising GO/Bi2S3 nanoparticles (NPs) as a photothermal conversion component and PVDF/TPU composite nanofibers as the substrate. The GO/Bi2S3 NPs were synthesized in a one-step way and the PVDF/TPU nanofibers were obtained from a uniformly mixed co-solution by electrospinning. GO nanoparticles with excellent solar harvesting endow the GO/Bi2S3-PVDF/TPU membrane with favorable photothermal conversion. In addition, the introduction of Bi2S3 NPs further enhances the broadband absorption and photothermal conversion properties of the GO/Bi2S3-PVDF/TPU composite membrane due to its perfect broadband absorption performance and coordination with GO. Finally, the results show that the GO/Bi2S3-PVDF/TPU composite membrane has the highest light absorption rate (about 95%) in the wavelength range of 400-2500 nm. In the 300 s irradiation process, the temperature changes in the GO/Bi2S3-PVDF/TPU composite membrane were the most significant and rapid, and the equilibrium temperature of the same irradiation time was 81 °C. Due to the presence of TPU, the mechanical strength of the composite film was enhanced, which is beneficial for its operational performance. Besides this, the morphology, composition, and thermal property of the membranes were evaluated by corresponding test methods.

The Recent Progress in Modification of Polymeric Membranes Using Organic Macromolecules for Water Treatment

For decades, the water deficit has been a severe global issue. A reliable supply of water is needed to ensure sustainable economic development in population growth, industrialization and urbanization. To solve this major challenge, membrane-based water treatment technology has attracted a great deal of attention to produce clean drinking water from groundwater, seawater and brackish water. The emergence of nanotechnology in membrane science has opened new frontiers in the development of advanced polymeric membranes to enhance filtration performance. Nevertheless, some obstacles such as fouling and trade-off of membrane selectivity and permeability of water have hindered the development of traditional polymeric membranes for real applications. To overcome these issues, the modification of membranes has been pursued. The use of macromolecules for membrane modification has attracted wide interests in recent years owing to their interesting chemical and structural properties. Membranes modified with macromolecules have exhibited improved anti-fouling properties due to the alteration of their physiochemical properties in terms of the membrane morphology, porosity, surface charge, wettability, and durability. This review provides a comprehensive review of the progress made in the development of macromolecule modified polymeric membranes. The role of macromolecules in polymeric membranes and the advancement of these membrane materials for water solution are presented. The challenges and future directions for this subject are highlighted.