Tailoring the Structure of Chitosan-Based Porous Carbon Nanofiber Architectures toward Efficient Capacitive Charge Storage and Capacitive Deionization

Nanoconfinement-Driven Energy-Efficient CO2 Capture and Release at High Pressures on a Unique Large-Pore Mesoporous Carbon

Although microporous carbons can perform well for CO2 separations under high pressure conditions, their energy-demanding regeneration may render them a less attractive material option. Here, we developed a large-pore mesoporous carbon with pore sizes centered around 20-30 nm using a templated technical lignin. During the soft-templating process, unique cylindrical supramolecular assemblies form from the copolymer template. This peculiar nanostructuring takes place due to the presence of polyethylene glycol (PEG) segments on both the Pluronic® template and the PEG-grafted lignin derivative (glycol lignin). A large increase in CO2 uptake occurs on the resulting large-pore mesoporous carbon at 270 K close to the saturation pressure (3.2 MPa), owing to capillary condensation. This phenomenon enables a CO2/CH4 selectivity (SCO2/CH4, mol/mol) of 3.7 at 270 K and 3.1 MPa absolute pressure, and a swift pressure swing regeneration process with desorbed CO2 per unit pressure far outperforming a benchmark activated carbon (i.e., notably rapid decrease in the amount of adsorbed CO2 with decreasing pressure). We propose large-pore mesoporous carbons as a novel family of CO2 capture adsorbents, based on the phase-transition behavior shift of CO2 in the nanoconfined environment. This novel material concept may open new horizons for physisorptive CO2 separations with energy-efficient regeneration options.

Interface gypsum deposition in flow-electrode CDI treating brackish water: Impacts and mechanisms

Flow-electrode capacitive deionization (FCDI) is a promising electrically driven technology for brackish water desalination, but it suffers from scaling issues in the concentrate chamber when treating brackish water with high levels of SO42- and Ca2+. In addition, how the key components (e.g., flow electrodes, spacer and ion exchange membranes) induce scaling in the concentrate chamber remains poorly understood. Therefore, this study systematically investigated the roles of the FCDI's components playing in the scaling process. Results showed substantial pressure loss in the concentrate chamber, which increased by 108% due to the scaling. The characterization results revealed that the scale attached to the surface of the spacer and membranes was gypsum. Gypsum crystallization experiments highlighted the crucial role of the cation exchange membrane and spacer in the heterogeneous nucleation process, which significantly shortened the induction time compared to the homogeneous nucleation process. The surface properties, such as the surface energy and surface charge, were found closely related to gypsum nucleation. In summary, the results of this work pave the way for understanding the gypsum nucleation process in FCDI continuously desalinating brackish hard water, potentially aiding in scaling removal and system optimization for broader environmental applications.

A low-cost biocompatible and biodegradable multipurpose resistive ink for monitoring biological systems

Flexible and biocompatible strain sensors are becoming increasingly important in fields such as health monitoring, wearable electronics, and environmental sensing because they offer significant advantages over conventional rigid systems. However, they lack the versatility and ecological and physiological biocompatibility necessary for broader integration within biological systems. Here, we describe the development of an inexpensive water-based plasticized chitosan-carbon black composite ink that can be used to produce conductive and biocompatible strain sensors. The ink can be applied to various surfaces, including skin, internal organs, and other biological tissues, using numerous methods, such as painting, dipping, and stamping. Furthermore, this unprecedented ability to attach and conform to biological surfaces allows the exploration of secondary sensing innovations, such as exploiting skin wrinkles to improve sensitivity. This study demonstrates that the ink exhibits a reliable change in electrical resistance in response to a wide range of motions, from subtle vibrations during speech and heartbeats to extensive articulations, like finger and elbow movements. This exceptional sensitivity range, biocompatibility, and the ink's low cost, biodegradability, and ease of removal enhance its applicability in sustainable, temporary, and customizable sensing solutions, highlighting its potential for versatile applications in human health monitoring, motion detection, and environmental sensing.

The multi-functional system of electrochemical desalination, RhB degradation and Cr (VI) removal

SYNOPSIS

: The single function of salt removal limits the further development of the CDI system. A multi-function CDI device is proposed to achieve electrochemical desalination, organics degradation and dichromate ion removal.

Integrated hierarchical porous lignin-based carbon electrode for boosting membrane-free capacitive deionization areal adsorption capacity

The development of high value-added lignin-based functional porous carbon electrodes with excellent properties from sustainable industry lignin powder remains a challenge. This work aims to create robust, binder-free, conductive additives-free, and current collector-free monolithic porous carbon electrodes using industrial lignin powder for membrane-free capacitive deionization (CDI). The material exhibits high mechanical strength, hierarchical porosity structure, large uniform size, and thickness of just a few millimetres (<2.6 mm). In a three-electrode supercapacitor system, the areal specific capacitance of CLCA300-3-1.0 reaches 5.03-1.02 F cm-2 when the scan rate between 1 and 20 mV s-1 in 1 M NaCl solution. As CDI electrodes, the charge efficiency of CLCA300-3-1.0 at different voltages of 1.2 V, 1.4 V and 1.6 V is 0.53, 0.72 and 0.71, respectively. The energy consumption of CLCA280-3-1.0, CLCA300-3-1.0 and CLCA320-3-1.0 tested at 1.2 V are 3.27, 3.40 and 3.25 Wh m-3, respectively. In addition, with thickness increasing to 1.5 mm, the developed CLCA300-3-1.5 electrode exhibits an areal adsorption capacity of 0.46 mg cm-2, and relative highly capacity retention of 84.78 % after 70 cycles. The impressive desalination performance is attributed to the well-designed hierarchical porosity, superhydrophilicity and robust monolithic structure.

Solubilization of chitosan in biologically relevant solvents by a low-temperature solvent-exchange method for developing biocompatible chitosan materials

Chitosan has great potential for biomedical applications. However, the intractable solubility of chitosan is a major bottleneck hampering its utilization. In this work, we report a low-temperature solvent-exchange method to solubilize chitosan in biologically relevant solvents (bio-solvents) including water, salines, and cell culture media. Chitosan was firstly dissolved in ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate (EMIM Ac). The chitosan/IL solution was then dialyzed against bio-solvents at 4 °C, during which a solvent exchange process took place. At the end of 24 h dialysis, aqueous chitosan pseudosolutions formed. Low temperature is found to be crucial for efficient solubilization of chitosan during the solvent exchange process. Increasing temperature to 50 °C leads to the formation of solid chitosan hydrogel. Chitosan in the water-based pseudosolution presents as positively charged particles. The pseudosolution shows a high positive zeta potential of about +52.6 mV and good colloidal stability. The water-based pseudosolutions with different amounts of chitosan contents exhibit the rheological features of weak liquid gels. By using these pseudosolutions, the fabrication of various chitosan materials is realized readily. Both chitosan pseudosolution and its downstream products are highly biocompatible. In this strategy, using IL as a solvent-medium and processing a low-temperature solvent exchange are the two key parameters to solubilize chitosan.

Biobased chitosan-derived self-nitrogen-doped porous carbon nanofibers containing nitrogen-doped zeolites for efficient removal of uremic toxins during hemodialysis

Highly efficient adsorbents are needed to remove uremic toxins and reduce the economic and societal burden of the current dialysis treatments in resource-limited environments. In this study, nanostructured porous carbon nanofibers with nitrogen-doped zeolites (NZ-PCNF) were prepared, by electrospinning zeolites with chitosan-poly(ethylene oxide) blends, followed by a one-step carbonization process, without further activation steps or aggressive chemical additives for N-doping. The results showed that N-zeolites were successfully integrated into an ultrafine carbon nanofiber network, with a uniform nanofiber diameter of approximately 25 nm, hierarchical porous structure (micro- and mesopores), and high specific surface area (639.29 m2/g), facilitating uremic toxin diffusion and adsorption. The self-N-doped structure in the NZ-PCNF removed more creatinine (∼1.8 times) than the porous carbon nanofibers when using the same weight of precursor materials. Cytotoxicity and hemolysis tests were performed to verify the safety of NZ-PCNF. This study provides a novel strategy for transforming chitosan-based materials into state-of-the-art porous carbon nanofiber/zeolite self-N-doped composites, affording an efficient bioderived adsorbent for the removal of uremic toxins in patients with chronic kidney disease.

A mini review on metal-organic framework-based electrode materials for capacitive deionization

Capacitive deionization (CDI) is an electrochemical method of extracting ions from solution at potentials below electrolysis. It has various applications ranging from water remediation and desalination to heavy metal removal and selective resource recovery. A CDI device applies an electrical charge across two porous electrodes to attract and remove ions without producing waste products. It is generally considered environmentally friendly and promising for sustainability, yet ion removal efficiency still falls short of more established filtration methods. Commercially available activated carbon is typically used for CDI, and its ion adsorption capacity is low at approximately 20-30 mg g-1. Recently, much interest has been in the highly porous and well-structured family of materials known as metal-organic frameworks (MOFs). Most MOFs are poor conductors of electricity and cannot be directly used to make electrodes. A common workaround is to pyrolyze the MOF to convert its organic components to carbon while maintaining its underlying microstructure. However, most MOF-derived materials only retain partial microstructure after pyrolysis and cannot inherit the robust porosity of the parent MOFs. This review provides a systematic breakdown of structure-performance relationships between a MOF-derived material and its CDI performance based on recent works. This review also serves as a starting point for researchers interested in developing MOF-derived materials for CDI applications.

Unraveling the Ion Uptake Capacitive Deionization of Sea- and Highly Saline-Water by Sulfur and Nitrogen Co-Doped Porous Carbon Modified with Molybdenum Sulfide

In parallel to the depletion of potable water reservoirs, novel technologies have been developed for seawater softening, as it is the most abundant source for generating deionized water. Although salt removal at subosmotic pressures and ambient temperatures by applying low-operating potentials with high energy efficiency made capacitive deionization (CDI) an advantageous water-softening process, its practical application is limited by insufficient ion removal capacity and low concentration influent. The performance of a CDI system is in progress with engineering the electrode active materials, also facilitating the advance design in highly saline- and seawater study. Herein, an innovative strategy was developed to provide high-performance CDI systems based on efficient and electrochemical ion-uptake active materials with a simple initial preparation. Nitrogen-doped porous carbons (N-pCs) received benefits from a high specific surface area and good surface wettability. The N-pCs were modified with molybdenum oxide/sulfide intercalative array and developed as CDI electrode active materials for desalination of both low/medium saline- and seawater. The MoS2/S,N-pC electrode materials exhibited perfect optimized salt adsorption capacity (SACs) of 47.9 mg g-1 when compared to N-pC (37.9 mg g-1) and MoO3/N-pC (39.6 mg g-1) counterparts at 1.4 V in a 750 ppm NaCl solution. In addition, the assembled CDI cells exhibited reasonable cycle stability and retained 96.7% of their initial SAC in continuous CDI cycles for 128,000 s. The fabricated CDI cell rendered an excellent salt removal efficiency (SRE, %) of 13.34% from the real seawater sample at 1.2 V. In detail, the SRE % of the NaCl, KCl, MgCl2, and CaCl2 soluble salts with respect to seawater sample exhibited a remarkable SRE % of 30.8%, 36%, 32.6%, and 19.3%, respectively. These SRE % values (>13.34%) provide convincing evidence on the reasonable ion uptake capability of the fabricated CDI cells for removing Na+, K+, Mg2+, and Ca2+ ions compared to other soluble component. The advanced cell design parallel to the promising outcomes provided herein makes these CDI systems immensely propitious for efficient water softening.

Promising hepatoprotective agents from the natural sources: a study of scientific evidence

Background

Natural bioactive components derived from plant secondary metabolites have been pronounced as valuable alternatives for anticipating and subsiding hepatotoxic effects and its chronic complications based on experimental verification. The focus of this review is to elucidate the commonly used modern medicine for the treatment of liver disease and how major phytoconstituents have been tested for hepatoprotective activity, mechanism of action of some promising agents from natural sources, and clinical trial data for treating in patients with different liver diseases by the aid of natural phytoconstituents.

Main text

The review shows fifteen major isolated phytoconstituents, their biological sources, chemical structures, utilized plant parts, type of extracts used, hepatoprotective assay method, and their possible mechanism of action on the hepatoprotection. Nine promising hepatoprotective leads from natural sources with their chemistry and hepatoprotective mechanism are mentioned briefly. The review further includes the recent clinical trial studies of some hepatoprotective leads and their clinical outcome with different liver disease patients. Scientific studies revealed that antioxidant properties are the central mechanism for the phytoconstituents to subside different disease pathways by upsurging antioxidant defense system of cells, scavenging free radicals, down surging lipid peroxidation, improving anti-inflammatory potential, and further protecting the hepatic cell injury. In this review, we summarize recent development of natural product-based hepatoprotective leads and their curative potential for various sort of liver diseases. Furthermore, the usefulness of hit and lead molecules from natural sources for significant clinical benefit to discover new drug molecule and downsizing the problems of medication and chemical-induced hepatotoxic effects is extrapolated.

Conclusion

Further research are encouraged to elucidate the pharmacological principle of these natural-based chemical agents which will stimulate future pharmaceutical development of therapeutically beneficial hepatoprotective regimens.

Construction of self-supporting ultra-micropores lignin-based carbon nanofibers with high areal desalination capacity

Lignin is a renewable biomacromolecule that can be used as precursors for carbon materials. In this work, highly flexible lignin-based carbon nanofibers with abundant ultra-micropores are constructed via electrospinning, oxidative stabilization and carbonization. The results indicate that replacing PAN with 80 % lignin is feasible in regulating ultra-micropores. The synthesized L4P1-CNFs possess many attractive properties (e.g., pore size distribution, electrochemical and deionization property) compared with that produced from other non-renewable precursors or more-complexed processes. It shows excellent electrochemical double-layer capacitance in 6 M KOH (233 to 162 F g^-1 at 0.5 to 5 A g^-1) and 1 M NaCl (158 to 82 F g^-1 at 0.5 to 5 A g^-1) electrolytes. Upon assembling into CDI cells, the average salt adsorption rate could reach 1.79 mg g^-1 min^-1 at 1.2 V and 3.32 mg g^-1 min^-1 at 2 V in 500 mg L^-1. Benefiting from the excellent flexibility, we innovatively stack four layers of L4P1-CNFs to improve the areal electrosorption capacity to 0.0817 mg cm^-2 at 500 mg L^-1, significantly higher than that of traditional carbon-based electrodes. The good desalination property makes lignin-based carbon nanofibers ideal for practical, low-cost capacitive deionization applications.