CoFe2O4 modified bentonite-based mixed matrix loose nanofiltration membranes for effective wastewater treatment

Mixed-matrix membranes (MMMs) with an ideal polymer/hydrophilic flux enhancer interface considerably recuperates the separation and purification performance of membrane. In this direction, a novel CoFe2O4 functionalized natural clay-bentonite (CoFe2O4@BT) material as a compatible flux enhancer was synthesized for preparation of mixed matrix based in polyethersulfone (PES) matrix. Here, the influences of CoFe2O4@BT on the morphology and performance of the MMMs membranes were systematically investigated using various analytical techniques. Meanwhile, the water flux and sepration eficiency of the CoFe2O4@BT-PES membranes significantly enhanced due to the incorporation of CoFe2O4@BT that altered hydrophilicity, pore and surface characteristic features. The water flux as well as separation efficiency range up to 95%, 94.69%, 94.16% of Congo red (CR), Crystal violet (CV), and humic acid (HA) respectively. Meanwhile, the fouling parameters demonstrated that the CoFe2O4@BT-PES membranes exhibited better antifouling property in the long term experiment comparing with commercial polyamide membrane. CoFe2O4@BT material incorporated membranes showed less decline ratio and a better recovery ratio. The high rejection of dyes with a high permeation flux of the newly designed membranes indicated an amazing possibility for dye purification. In this study, a potential dye mechanism for composite membranes impacted by synthetic CoFe2O4@BT was also put forth. Within the context of application considerations for environmental protection, new materials stock in membranes show good potential for the separation of different organic contaminants.

Suitability of Adenosine Derivatives in Improving the Activity and Stability of Cytochrome c under Stress: Insights into the Effect of Phosphate Groups

It is well known that adenosine and its phosphate derivatives play a crucial role in biological phenomena such as apoptosis and cell signaling and act as the energy currency of the cell. Although their interactions with various proteins and enzymes have been described, the focus of this work is to demonstrate the effect of the phosphate group on the activity and stability of the native heme metalloprotein cytochrome c (Cyt c), which is important from both biological and industrial aspects. In situ and in silico characterizations are used to correlate the relationship between the binding affinity of adenosine and its phosphate groups with unfolding behavior, corresponding peroxidase activities, and stability factors. Interaction of adenosine (ADN), adenosine monophosphate (AMP), adenosine 5'-diphosphate (ADP), and adenosine 5'-triphosphate (ATP) with Cyt c increases peroxidase-like activity by up to 1.8-6.5-fold compared to native Cyt c. This activity is significantly maintained even after multiple stress conditions such as oxidative stress and the presence of a chaotropic agent such as guanidine hydrochloride (GuHCl). With binding affinities on the order of ADN < AMP < ADP < ATP, adenosine derivatives were found to stabilize Cyt c by varying the secondary structural features of the protein. Thus, in addition to being a fundamental study, the current work also proposes a way of stabilizing protein systems to be used for real-time biocatalytic applications.

Aging-Responsive Phase Transition of VOOH to V10O24·nH2O vs Zn2+ Storage Performance as a Rechargeable Aqueous Zn-Ion Battery Cathode

Vanadium oxyhydroxide has been recently investigated as a starting material to synthesize different phases of vanadium oxides by electrochemical or thermal conversion and has been used as an aqueous zinc-ion battery (AZIB) cathode. However, the low-valent vanadium oxides have poor phase stability under ambient conditions. So far, there is no study on understanding the phase evolution of such low-valent vanadium oxides and their effect on the electrochemical performance toward hosting the Zn²⁺ ions. The primary goal of the work is to develop a high-performance AZIB cathode, and the highlight of the current work is the insight into the auto-oxidation-induced phase transition of VOOH to V₁₀O₂₄·nH₂O under ambient conditions and Zn²⁺ intercalation behavior thereon as an aqueous zinc-ion battery cathode. Herein, we demonstrate that hydrothermally synthesized VOOH undergoes a phase transition to V₁₀O₂₄·nH₂O during both the electrochemical cycling and aerial aging over 38-45 days. However, continued aging till 150 days at room temperature in an open atmosphere exhibited an increased interlayer water content in the V₁₀O₂₄·nH₂O, which was associated with a morphological change with different surface area/porosity characteristics and notably reduced charge transfer/diffusion resistance as an aqueous zinc-ion battery cathode. Although the fresh VOOH cathode had impressive specific capacity at rate performance, (326 mAh/g capacity at 0.1 A/g current and 104 mAh/g capacity at 4 A/g current) the cathode suffered from a continuous capacity decay. Interestingly, the aged VOOH electrodes showed gradually decreasing specific capacity with aging at low current and however followed the reverse order at high current. At a comparable specific power of ∼64-66 W/kg, the fresh VOOH and aged VOOH after 60, 120, and 150 days of aging showed the respective energy densities of 208.3, 281.2, 269.2, and 240.6 Wh/kg. Among all the VOOH materials, the 150 day-aged VOOH cathode exhibited the highest energy density at a power density beyond 1000 W/kg. Thanks to the improved kinetics, the 150 day-aged VOOH cathode delivered a considerable energy density of 39.7 Wh/kg with a high specific power of 4466 W/kg. Also, it showed excellent cycling performance with only 0.002% capacity loss per cycle over 20 300 cycles at 10 A/g.

Developing High-Performance In-Plane Flexible Aqueous Zinc-Ion Batteries with Laser-Scribed Carbon-Supported All Electrodeposited Electrodes

Developing high-performance, safer, and affordable flexible batteries is of urgent need to power the fast-growing flexible electronics market. In this respect, zinc-ion chemistry employing aqueous-based electrolytes represents a promising combination considering the safety, cost efficiency, and both high energy and high-power output. Herein, we represent a high-performance flexible in-plane aqueous zinc-ion miniaturized battery constructed with all electrodeposited electrodes, i.e., MnO₂ cathode and zinc anode with polyimide-derived interdigital patterned laser-scribed carbon (LSC) as the current collector as well as the template for electrodeposition. The LSC possesses a cross-linked network of graphitic carbon sheet, which offers large surface area over low footprint and ensures active materials loading with a robust conductive network. The LSC with high zincophilic characteristic also offers dendrite-free zinc deposition with very low Zn²⁺ plating stripping overpotential. Benefitting from the Zn//MnO₂-rich redox chemistry, the ability of the 3D LSC network to uniformly distribute reaction sites, and the architectural merits of in-plane interdigitated electrode configuration, we report very high capacity values of ∼549 mAh/g (or ∼523 μAh/cm²) and 148 mAh/g (or 140 μAh/cm²) at 0.1 A/g (0.095 mA/cm²) and 2 A/g (1.9 mA/cm²) currents, respectively. The device was also able to maintain a high capacity of 196 mAh/g (areal capacity of 76.19 μAh/cm²) at 1 A/g (0.95 mA/cm²) current after 1350 cycles. The flexibility of the device was demonstrated in polyacryl amide (PAM) gel polymer soaked with a 2 M ZnSO₄ and 0.2 M MnSO₄ electrolyte, which exhibited a comparable specific capacity of ∼102-110 mAh/g in flat condition and different bending (100° or 160° bending) conditions. The device does not use any conventional current collector, separator, and conductive or polymer additives. The overall process is highly scalable and can be completed in less than a couple of hours.

Presenting B-DNA as macromolecular crowding agent to improve efficacy of cytochrome c under various stresses

Existence of numerous biomolecules results in biological fluids to be extremely crowded. Thus, Macromolecular crowding is an essential phenomenon to sustain active conformation of proteins in biological systems. Herein, double helical deoxyribonucleic acid (B-DNA) is presented for the first time as a biomacromolecular crowding system for sustainable packaging of cytochrome c (Cyt C). The peroxidase activity of Cyt C was investigated in the presence of various concentrations of B-DNA (from salmon milt). At an optimized concentration of 0.125 mg/mL B-DNA, an 11-fold higher catalytic activity was found than in native Cyt C with improved stability. Molecular docking and spectroscopic analyses revealed that electrostatic and H-bonding are the main interactions between DNA and Cyt C that affect the structural stability and activity of the protein. Moreover, the catalytic activity and stability of the protein were further investigated in the presence of severe process conditions by UV-visible, circular dichroism, and Fourier-transform infrared spectroscopies. Molecularly crowded Cyt C showed significantly higher activity and stability under severe environments such as high temperature (110 °C), oxidative stress, high pH (pH 10) and biological (trypsin) and chemical denaturants (urea) compared to bare Cyt C. The observed results support the suitability of DNA-based macromolecular crowding media as a viable and effective stabilizer of proteins against multiple stresses.

Bioinspired engineering protein nanofibrils-based multilayered self-cleaning membranes for universal water purification

Proteinaceous materials are promising for membranes due to greater mechanical strength, in-built functionalities, amphiphilicity and high molecular loading capacity. Herein, a novel strategy of functionalization of silk nanofibrils with metal oxyhydroxide and fabrication of ultrafast permeable multi-layered and self-cleaning membrane was demonstrated. Typically, 1.9 µm thick multilayered membrane efficiently purifies macromolecules, dyes, pharmaceutical, surfactants and oil-water emulsion contaminated wastewater with rejection rate > 89% with the flux rate > 883 Lm²h^-1. Further, the potential of the multilayered membrane was tested for series of different feed concentrations of fluoride and As (V) to validate the commercial applicability of the multilayered membranes for industry wastewater. Notably, even at higher concentration of 10-30 mgL^-1, >96% for fluoride and >87% for As (V) rejection was obtained. Furthermore, the functionalized multilayered membrane exhibited outstanding performance for fluoride removal in real water streams, where, it purifies approximately 4710 L.m^-2 in two consecutive cycles, before the quality of the effluents no longer meets WHO criteria. However, the remarkable separation efficiency principally attributed to adsorption sites on the surface of the membrane. Thus, various regeneration strategies were established based on the nature of pollutants. More importantly, photocatalytic Fenton-like reaction assisted self-cleaning property of the multilayered membrane is demonstrated for regeneration of organic fouled membrane. Overall, the present multilayered membrane exhibits superior performance in purifying organic, inorganic contaminated water and oil-water emulsion with excellent recyclability; hence, envisaged its application for Universal water purification.

Restructuring thin film composite membrane interfaces using biopolymer as a sustainable alternative to prevent organic fouling

Replacing polyamide (PA) layer in commercially successful thin film composite (TFC) membranes prepared via interfacial polymerization has been challenging task. Lately, PA is under scrutiny due to its increasing fouling propensity for highly contaminated waters. To mitigate the bio and organic fouling on PA layer in nanofiltration (NF) membranes in a long run, present study attempts to create a new interfacial thin film asymmetric structure using biopolymer chitosan as sustainable alternative. Herein, the effect of chitosan-silver on porous support structure and filtration performance were systematically investigated. Further, the membranes were characterized for their functionality and surface characteristics using ATR-IR, FESEM, AFM, UV-vis spectroscopy and contact angle measurements, respectively. New asymmetric membrane performances in cross flow process were evaluated in terms of pure water flux, NaCl (∼40 %), red brown/organic dye (>98 %) and tannery wastewater flux and rejection (>98 %). With a higher pure water flux (>100 L m^-2 h^-1) compared to control (40 L m^-2 h^-1) at 4 bar, membrane showed exceptional antifouling behaviors in comparison to commercial PA membrane. Further, surface characteristics of the membranes before and after rigorous testing were evaluated using AFM micrographs and SEM imaging.

Fe-Al based nanocomposite reinforced hydrothermal carbon: Efficient and robust absorbent for anionic dyes

Nanocomposites with ultrahigh adsorption capabilities are highly desired for efficient wastewater remediation. Unfortunately, most of the nanomaterial based adsorbents showing inevitable limitation such as leaching and agglomeration led to the emerging field of carbonaceous hybrid materials with nanocomposites. Herein, we demonstrated a simple and low-temperature hydrothermal assisted preparation of Fe-Al based nanocomposites immobilized using carbon spheres. Towards this, we have approached two different routes one is hybridizing with nanocomposite and another is doping on the surface of the carbon spheres. Iron doping played a dual-faceted role of active site for robust adsorption as well as induce magnetic property to the composites. The micro-cleaners have been extensively characterized for their physicochemical properties and adsorption capacities using FTIR, Raman, XRD, BET isotherms and XPS techniques. Remarkably, microcleaners shows robust adsorption where >99% removal was obtained within 10 min for 50 mg L^-1 concentrated Eriochrome Black T (EBT) dye using 0.01 g of materials. Further, adsorption data followed the pseudo second order kinetics while the equilibrium data fitted perfectly into the Langmuir adsorption equation. As synthesized user friendly microcleaner (HTC-2) exhibits maximum adsorption capacity (q_max) of 564.97 mg g^-1 for EBT dye at pH 4. Hence, the preliminary results highlight the potential of the composites to be used in pretreatment steps of industry effluents.

Engineering a Biopolymer-Based Ultrafast Permeable Aerogel Membrane Decorated with Task-Specific Fe-Al Nanocomposites for Robust Water Purification

The present work demonstrates an innovative strategy for robust water purification using an engineered aerogel membrane fabricated from biopolymers and task-specific Fe-Al-based nanocomposites. The as-prepared ethylenediaminetetraacetate dianhydride cross-linked chitosan- and agarose (7:3 weight ratio)-based aerogel membrane decorated with α-FeOOH- and γ-AlOOH-based nanocomposites was characterized using various analytical tools, which suggested formation of a highly stable network interconnected through covalent and electrostatic interactions. The optimized bionanocomposite-based aerogel (BNC-AG-0.1) membrane showed macroporous and partial unidirectional short-range channels with an ultralow density of 0.021 g·m^-2, a high swelling ratio of 1974%, and a remarkable pure water flux of 19,228 L·m^-2·h^-1 (>6-fold higher flux compared to the reported aerogel membranes). The aerogel membranes were successfully utilized for purification of diverse pollutants such as dyes, emerging pollutants (EPs), arsenate, and fluoride in a continuous flow method under gravitational force. The BNC-AG-0.1 membrane exhibits high rejection (95-98.6%) for both cationic and anionic dyes with a flux rate of 1150-1375 L·m^-2·h^-1 and a rejection of 89-92% for EPs with a flux rate of 1098-1165 L·m^-2·h^-1. Moreover, the BNC-AG-0.1 membrane showed a q_max of 102.45 mg·g^-1 (at pH 6.5) for As(V) with >93% rejection at a flow rate of 1000 L·m^-2·h^-1. Furthermore, the aerogel membrane showed an excellent removal efficiency (92%) of arsenic up to the 10th cycle and hence demonstrated as a potential adsorption-based membrane for arsenic-free potable water. On the other hand, the BNC-AG-0.1 membrane showed a q_max of 81.56 mg·g^-1 (at pH 6.5) for F^- removal with >99% rejection at a flow rate of 250 L·m^-2·h^-1. When applied for real-water purification, approximately 4734 L of safe drinking water (the F^- concentration is less than the WHO permissible limit) per square meter of the aerogel membrane can be obtained with a flux rate of 250 L·m^-2·h^-1. Overall, the prepared aerogel membrane showed robust removal of a variety of contaminants with ultrafast water permeation and established excellent recyclability.