Robust antifouling anion exchange membranes modified by graphene oxide (GO)-enhanced Co-deposition of tannic acid and polyethyleneimine

Seeking the adsorption of tetracycline in water by Fe-modified sludge biochar at different pyrolysis temperatures

The composite material SBC-Fe-x with sludge and Fe3+ was developed by different calcination temperatures (600, 700, and 800 °C) for the removal of tetracycline (TC). The adsorption rates of SBC-Fe-600, SBC-Fe-700, and SBC-Fe-800 were 77.5%, 89%, and 91%, respectively. Furthermore, the Langmuir model indicated that the maximum adsorption capacity of SBC-Fe-700 (157.93 mg/g) was three times greater than that of SBC-Fe-600. The conclusions were confirmed by a series of characterizations that SBC-Fe-700 showed a larger specific surface area, well-developed pore structure, rich oxygen-containing functional groups and a high degree of graphitization. The results of pH experiments indicated the broad applicability of SBC-Fe-700 for TC adsorption. In addition, SBC-Fe-700 suggested outstanding performance in different water environments. This work produced a feasible adsorbent for the removal of TC, and a new direction for sludge resource utilization was proposed.

Green Synthesis of Cation Exchange Membranes: A Review

Cation exchange membranes (CEMs) play a significant role in the transition to a more sustainable/green society. They are important components for applications such as water electrolysis, artificial photosynthesis, electrodialysis and fuel cells. Their synthesis, however, is far from being sustainable, affecting safety, health and the environment. This review discusses and evaluates the possibilities of synthesizing CEMs that are more sustainable and green. First, the concepts of green and sustainable chemistry are discussed. Subsequently, this review discusses the fabrication of conventional perfluorinated CEMs and how they violate the green/sustainability principles, eventually leading to environmental and health incidents. Furthermore, the synthesis of green CEMs is presented by dividing the synthesis into three parts: sulfonation, material selection and solvent selection. Innovations in using gaseous SO3 or gas-liquid interfacial plasma technology can make the sulfonation process more sustainable. Regarding the selection of polymers, chitosan, cellulose, polylactic acid, alginate, carrageenan and cellulose are promising alternatives to fossil fuel-based polymers. Finally, water is the most sustainable solvent and many biopolymers are soluble in it. For other polymers, there are a limited number of studies using green solvents. Promising solvents are found back in other membrane, such as dimethyl sulfoxide, Cyrene™, Rhodiasolv® PolarClean, TamiSolve NxG and γ-valerolactone.

Plant Polyphenol Pyrogallol and Polyamine-Based Co-Deposition for High-Efficiency Nanofiltration Membrane Preparation towards Inorganic Salt Removal

The co-deposition between polyphenols and amines has been demonstrated in order to prepare positively charged nanofiltration (NF) membranes for multivalent cation rejection in recent years; however, the low reactivities of the involved polyphenols usually cause a long co-deposition time and unsatisfactory rejection. Herein, a novel plant polyphenol (PG) was co-deposited with tetraethylenepentamine (TEPA) in a much shorter time period to prepare positively charged NF with high multivalent cation rejection membranes. The performance of the co-deposition membranes can be easily controlled by adjusting the mass ratio of PG and TEPA, reaction time, and pH value of the buffer solution. The optimal membrane, prepared under a polyphenol and polyamine mass ratio of 1:1, coating time of 2 h, and pH value of 8.0, shows a decent pure water permeability of 8.43 L m^-2 h^-1 bar^-1 while maintaining a superior 96.24% MgCl₂ rejection. More importantly, the universality of this method was corroborated by employing other amines with different molecular weights in the co-deposition. This work provides new insights for the preparation of high-performance positively charged NF membranes.

Bioactive Edible Sodium Alginate Films Incorporated with Tannic Acid as Antimicrobial and Antioxidative Food Packaging

Currently, biodegradable and functional food packaging materials have attracted more and more attention due to their potential advantages. Biopolymers are one of the promising materials used to produce biodegradable food packaging films, and sodium alginate (SA) is one of the most used polysaccharides. In this work, we explored a novel edible sodium alginate (SA)/tannic acid (TA) film as biodegradable active food packaging material. The impact of TA concentration on the UV light blocking ability, transparency, water vapor barrier ability, mechanical strength, antioxidant, and antimicrobial activity of the SA-TA films was comprehensively investigated. Fourier transform infrared spectroscopy results revealed that strong hydrogen bonding was the main intermolecular interaction between SA and TA. As TA concentration in the films increased, the water vapor permeability (WVP) decreased from 1.24 × 10^-6 to 0.54 × 10^-6 g/m/h/Pa, the DPPH radical scavenging activity increased from 0.008% to 89.02%. Moreover, the incorporation of TA effectively blocked UV light and elevated antimicrobial activity against Escherichia coli. Overall, the SA films with TA exhibited better water vapor barrier ability, remarkable UV-light barrier ability and antioxidant activity while showing a slight decrease in light transmittance. These results indicated the potential application of TA as a functional additive agent for developing multifunctional food packaging materials.

Mussel-inspired tannic acid/polyethyleneimine assembling positively-charged membranes with excellent cation permselectivity

The extraction of valuable target ions through monovalent cation exchange membranes (MCEMs) has been increasingly attracting in modern energy and environmental fields. However, the separation performance of MCEMs in terms of the permselectivity and cation fluxes, is typically restricted by membrane architecture and applied materials. Recently, mussel-inspired surface modification methods have been deployed in new membrane fabrications with special surface characteristics and functions. Herein, a facile layer-by-layer assembly method was designed to construct a series of de novo positively-charged tannic acid/polyethyleneimine (TA/PEI) membranes containing a negatively-charged support membrane and a TA/PEI selective layer. Notably, the peculiar support membrane with a much dense structure and abundant cation exchange groups can enable our TA/PEI membranes to possess high total cation fluxes. The selective layer with vast positive charges ensures mussel-inspired TA/PEI assembled positively-charged membranes to have a high permselectivity. Most importantly, compared with the separation performance of the state-of-the-art MCEMs, the superior separation performance of our developed new MCEMs at 5 mA·cm^-2 and 10 mA·cm^-2 is beyond the current "Upper Bound" plot between Na⁺ flux and the permselectivity (Na⁺/Mg²⁺), which opens new avenues for the construction of MCEMs. Furthermore, high purity of Li⁺ (95.37%) can be obtained through deploying mussel-inspired TA/PEI assembled positively-charged membranes with high permselectivity of Li⁺/Mg²⁺ (13.72), proving its great potentials in the field of resource recovery towards sustainability.

A comprehensive review on the synthesis and applications of ion exchange membranes

Ion exchange membranes (IEMs) are undergoing prosperous development in recent years. More than 30,000 papers which are indexed by Science Citation Index Expanded (SCIE) have been published on IEMs during the past twenty years (2001-2020). Especially, more than 3000 papers are published in the year of 2020, revealing researchers' great interest in this area. This paper firstly reviews the different types (e.g., cation exchange membrane, anion exchange membrane, proton exchange membrane, bipolar membrane) and electrochemical properties (e.g., permselectivity, electrical resistance/ionic conductivity) of IEMs and the corresponding working principles, followed by membrane synthesis methods, including the common solution casting method. Especially, as a promising future direction, green synthesis is critically discussed. IEMs are extensively applied in various applications, which can be generalized into two big categories, where the water-based category mainly includes electrodialysis, diffusion dialysis and membrane capacitive deionization, while the energy-based category mainly includes reverse electrodialysis, fuel cells, redox flow battery and electrolysis for hydrogen production. These applications are comprehensively discussed in this paper. This review may open new possibilities for the future development of IEMs.

Bioinspired adhesive coatings from polyethylenimine and tannic acid complexes exhibiting antifogging, self-cleaning, and antibacterial capabilities

In this work, we develop a simple yet robust method to fabricate a bioinspired adhesive coating based on polyethyleneimine (PEI) and tannic acid (TA) complexes, exhibiting excellent antifogging, self-cleaning, and antibacterial properties. The polyethyleneimine-tannic acid (PEI-TA) complexes coating combined with the bioinspired adhesive property from TA can be effectively and stably coated onto various substrates through a one-step deposition process, and the hydrophilicity of the coated substrates can be significantly enhanced with their water contact angle less than 10°. The bioinspired adhesive coating endows the coated substrates with outstanding antifogging and self-cleaning performance. Moreover, it is found that the PEI-TA coated safety goggles display excellent durability and antifogging capability compared to the commercial antifogging safety goggles and commercial antifogging agents coated safety goggles under 65 ℃ vapor condition for 2 h. Furthermore, the PEI-TA coatings show superior antibacterial activities for Gram-negative Escherichiak coli and Gram-positive Staphylococcus aureus. The antifogging, self-cleaning, and antibacterial coating provides widely potential application prospects in optical and medical devices.

A nanofiltration membrane fabricated on a surfactant activated substrate with improved separation performance and acid resistance

Uniformly dispersed and enhanced amounts of PEI molecules attract drag by SDS exhibit a high crosslinking degree and smooth surface morphology.