Capacitive deionization (CDI) technology has gained wide attention for producing clean and portable water to relieve the pressure on water resource shortages. Faradaic materials are considered to be a promising alternative to traditional carbon materials storing charges in the electrical double layers (EDL) that have limitations due to co-ion repulsion. Herein, we have synthesized High-entropy Prussian blue analogues (HEPBA) with the chelation of citrate using a simple one-step hydrothermal method to control their size, crystallinity and composition. The optimized HEPBA-based electrodes used in half-cells show a high specific capacity of similar to 283 F g(-1) at 1 mV s(-1). A high salt adsorption capacity of 36.8 mg g(-1) stable for the 50 cycles tested here was reached in the membrane-free desalination cell based on HEPBA and Ag@C electrodes. This architecture overcomes the typical limitations of low adsorption capacity and co-ion repulsion, enabling efficient operation without the need for an ion-exchange membrane. The improved salt-adsorption capacity is due to the high optimized crystallinity of the HEPBA material and maintenance of the configurational entropy. A series of ex-situ experiments revealed that the desalination and regeneration processes were governed by the redox of the Fe3+/Fe2+ couple, Mn3+/Mn2+ couple, Co3+/Co2+ couple and Cu2+/Cu+ couple while the Ni3+/Ni2+ couple was electrochemically inactive for the HEPBA. Electrodes fabricated using this simple one-step process provide a possibility to obtain optimized HEPBAs for real-life applications.

Microplastic pollution is a global concern infiltrating every aspect of our environment and food chain. Conventional wastewater treatment plants (WWTPs) are ineffective at removing microplastics (MPs), necessitating advanced degradation approaches. Among various techniques, Fenton and photo-Fenton processes emerge as promising solutions. Here, photo-Fenton-like degradation was studied using nitrogen-doped titania (N-TiO2) nanorods decorated with cobalt Prussian blue analogue (N-TiO2/CoPBA) as a visible-light-active photocatalyst. The N-TiO2 nanorods were hydrothermally grown on glass fiber, followed by CoPBA deposition through co-precipitation. The glass fiber serves the dual function of trapping plastic particles and supporting the photocatalyst. FTIR was used to monitor the carbonyl index, indicating progressive oxidation. The observed changes are consistent with oxidative degradation and polymer-chain scission; however, the formation of soluble degradation intermediates and the extent of mineralization were not evaluated in the present study. Under visible-light irradiation in a flow-through reactor, photocatalytic and photo-Fenton-like degradation of polypropylene (PP) MPS were compared, with photo-Fenton-like reactions showing substantial particle volume reduction. Optimizing H2O2 concentration (15 mM, dosing every 24 h) led to a ~90% volume reduction within 48 h while it took several days when H2O2 was not controlled. Post-experiment analysis of the catalyst confirmed its stability, highlighting its potential for long-term application in microplastic removal from water streams.

Marine corrosion is a longstanding issue for underwater materials and structures, where the interlinked challenges of corrosion and biofouling require new approaches to source increasing needs of the marine resources. Herein we introduce environment-friendly chitosan coatings immobilized with corrosion inhibitor of 2-mercaptobenzothiazole (MBT) for active corrosion protection with antifouling properties against marine organisms. The molecular interaction between chitosan and MBT on corrosion resistance and antifouling performance was studied with the coatings where MBT was entrapped, physically associated, or chemically linked to chitosan. The physical association is achieved by the non-covalent π-π stacking between MBT and chitosan-benzophenone-3 (CS-BP-3) copolymer, which improved loading efficiency of MBT and formed a smoother coating. For the first time, MBT was chemically linked to chitosan confirmed by infrared spectroscopy. Electrochemical measurements revealed that both physical association and chemical linkage strategies can enhance the corrosion inhibition dramatically, where the chemical linked coating has a significantly higher corrosion resistance. The corrosion current of the physically associated coatings is a magnitude lower than that of MBT-entrapped coatings, while the coatings formed by chemical linking is even better, about one fifth compared to physically associated coatings. Antifouling activity of these coatings were evaluated against marine mussels (Mytilus coruscus), where chemically linked CS-MBT coating exhibits 10 % settlement after 48 h, compared to 20 % settlement on coatings prepared by physical association. The findings in this work provide a new route to construct coatings that are effective in corrosion inhibition and have long-term antifouling properties.

Surface roughness is known to influence biofouling in marine environments. Different from the conventional antifouling coatings based on hydrophobic polymeric materials such as epoxy and polydimethylsiloxane (PDMS), in this study, naturally occurring compound benzophenone-3 (BP-3) modified chitosan (CS) biopolymer coatings with varied surface roughness were prepared and studied for their antifouling effect for the first time. By regulating the competitive reactions between the reactants, different condensation products can be obtained which result in varied root mean square (RMS) roughness of CS-BP-3 coatings from 7.6 nm to 270.0 nm. It is found that the reaction time influences more than the reaction temperature while defining the surface roughness of CS-BP-3 coatings. Specifically, the coatings of CS-BP-3 prepared from a 2-h reaction led to RMS roughness between 7.6 and 55.18 nm, whereas after 12-h reaction roughness between 82.6 and 270.0 nm were measured. Subsequent antifouling experiments indicate that rougher coatings have a more pronounced effect of preventing the settlement of plantigrade mollusk mimicking the lotus effect. This work demonstrates that bio-inspired materials can be designed to achieve desired functions for practical applications.

Domestic, industrial and agricultural activities require large amounts of water. This necessitates the need for an effective solution to meet the increasing water demand worldwide. A Huge amount of wastewater is generated daily and when this is left untreated, the contaminants present in these effluents may be harmful to the environment. There are various treatment techniques for the abatement of the contaminants present in these wastewaters. Conventional approaches often employed are the biological, physical and chemical methods. Zerovalent metals (ZVMs) such as zero-valent iron, zero-valent zinc, zero-valent aluminium to mention a few have emerged as promising candidates for wastewater treatment applications due to their unique reactivity and ability to facilitate the removal of various contaminants. In this report, a comprehensive review of the mechanisms, efficiency, and emerging technologies associated with ZVM-based water treatment is provided. The underlying objectives for which the review aimed to address include (i) providing an understanding of the ZVMs used in water treatment applications and their properties, (ii) reviewing the mechanisms employed by ZVMs to sequestrate contaminants, (iii) evaluating the efficiency of ZVMs in the removal of contaminants and (iv) exploring the various emerging technologies used in ZVM-based water treatment and to provide some recommendations for future research. It was concluded from the work that ZVMs abate contaminants found in wastewater through an interplay and synergy of physical, chemical and catalytic mechanisms. ZVMs, when used with other treatment techniques, provide better benefits in the treatment of diverse contaminants. To help achieve the full scale utilization of ZVMs potential, sustained research efforts combined with innovative approaches are needed for sustainable and efficient water treatment solutions. The review offers insights into technologies needed to eliminate diverse contaminants from wastewater, addressing important considerations regarding sustainability and future directions of ZVM-based water treatment technologies.

Salt removal from seawater and brackish water by Capacitive deionization (CDI) is an emerging technology that has a potential to contribute to solving global shortages of freshwater. Upon the application of an external voltage to a pair of nanostructured carbon electrodes, ions are removed by electrosorption in the electrical double layer (EDL) of the capacitor. The physical limitation due to repulsion of co-ions can be reduced using intercalation materials that are less sensitive to ion concentration variations. Herein, we report a hollow-concave high-entropy Prussian blue analogue (HEPBA) enhanced electrodes for superior electrochemical and capacitor performances. The half-cell of hollow-concave HEPBA has a high cycling stability of 1000 cycles at a current density of 1 A g−1. Lower energy consumption for desalination estimated over 90 cycles is due to an enhancement of salt adsorption capacity of HEPBA (∼ 26.2 mg g−1). The observed improvement in the electrochemical property is due to synergistic effects from multi-elemental composition that lead to the high entropy and specific surface area. Hollow-concave HEPBA are structurally stable with negligible changes in the lattice parameters during extensive charging and discharging cycles. This simple method offers an opportunity to modify the structure and morphology of PBAs for real-life applications.

Although much progress has been made in recycling components of end-of-life wind turbines, the recycling and reuse of the blades still present significant challenges. A two-stage pyrolysis process was applied in this work to recycle high quality glass fibers from waste wind turbine blades, which were then reused as support to grow heterogeneous photo-Fenton catalyst, zinc oxide nanorods coated by amorphous tin oxide and decorated with nano-zero valent iron (ZnO-SnOx-nZVI) to treat melanoidins, the major pollutant in effluents from distillery and bakery industries with dark brown color and high chemical oxygen demand (COD). Factors influencing the degradation process including pH (3 and 6), the amount of catalyst, and H2O2 dosage, were investigated. More than 97 % decolorization of melanoidin wastewater with 7000 mg/L COD was achieved with only 1/6th of theoretical amount of H2O2 required for Fenton reactions at pH 6. Kinetic studies were conducted to elucidate the correlation between generations of free radicals, unreacted H2O2 at different pH, and the effects on melanoidin degradation, revealing the significant role of pH in both the adsorption of melanoidin and the oxidation potential of radicals. The catalyst was reused three times maintaining 90 % decolorization, thus exhibiting good recyclability. The findings of this work have significant implications in treatment of non-biodegradable organic pollutants, owing to the advantages in avoiding low pH treatment condition, reducing the cost of H2O2, and enhanced chemical stability of photo-Fenton catalyst.

PEGylation is regarded as a common antifouling strategy and the effect is normally linked with surface hydrophilicity of the coatings. Herein, the biopolymer chitosan (CS) was grafted by polyethylene glycol (PEG) of different chain lengths (molecular weight 200, 4 k and 100 k Da) to verify if the hydrophilicity of CS-PEG coatings is crucial in determining antifouling activities and if PEG chain length influences biofouling in marine environment. Properties of copolymers such as melting points and crystallinity are affected by grafting PEG. The water contact angle (WCA) of CS-PEG coatings increases with the chain length of grafted PEG, from 27° to 58°. Photocatalyst of zinc oxide-silver (ZnO/Ag) was also studied and its embedment (2 % to CS-PEG) renders the surface of CS-PEG coatings more hydrophobic with WCA increased from 52° to 86°. Antibacterial, anti-diatom, and anti-biofilm activities of the coatings were evaluated in natural sea water. The bacterial density on CS-PEG coatings was dramatically reduced to 4 × 104 compared to the control of 7 × 104 ind/mm2, and further to 2 × 104 for CS-PEG-ZnO/Ag coatings. CS-PEG coatings also strongly inhibit diatoms (120–200 ind/mm2), but the inclusion of ZnO/Ag did not obviously enhance such effect (50–150 ind/mm2). The findings provide useful insights for designing polymer-based antifouling coatings.

Chitosan (CS), an edible and non-toxic natural biopolymer, has been widely used in food preservation attributed to its intrinsic antimicrobial, biodegradable, and excellent film-forming properties. In this work, we report photocatalyst-loaded chitosan coating on commercial polyethylene (PE) film with enhanced antimicrobial properties for food packaging application. To improve the chemical stability of zinc oxide (ZnO) photocatalyst in acidic chitosan matrix, a thin layer (1–5 nm) of amorphous tin oxide (SnOx) was coated on ZnO nanoparticles. Consequently, the charge transfer efficiency of ZnO is improved and most of the surface defects are retained according to the studies of UV–Vis and fluorescence spectroscopy. The thin SnOx coating on ZnO was observed by high-resolution transmission electron microscopy (HRTEM) and its effects on crystallinity and particle size of ZnO were examined using X-ray diffraction (XRD) and particle sizer, respectively. The addition of ZnO@SnOx particles in chitosan coating increases water contact angle (WCA) and enhances thermal stability of chitosan coating. The antimicrobial activity of chitosan, ZnO-SnOx nanoparticles, and CS-ZnO@SnOx coated PE films were examined against both Gram-negative (E. coli, A. faecalis) and Gram-positive (S. aureus, B. subtilis) bacteria. Compared to the limited antimicrobial effects of chitosan, ZnO-SnOx demonstrates an improved inhibition effect on bacterial growth over 48 h period under light. For the CS-ZnO@SnOx nanocomposite coated PE films, no inhibition zone was observed due to the limitation of disc diffusion method. Meanwhile, there were no bacterial colonies found to develop on the film, rendering this CS nanocomposite coating a good candidate for food packaging applications.

Green hydrogen production from water is one attractive route to non-fossil fuel and a potential source of clean energy. Hydrogen is not only a zero-carbon energy source but can also be utilized as an efficient storage of electrical energy generated through various other sources, such as wind and solar. Cost-effective and environmentally benign direct hydrogen production through neutral water (similar to pH 7) reduction is particularly challenging due to the low concentration of protons. There is currently a major need for easy-to-prepare, robust, as well as active electrode materials. Herein we report three new molecular electrodes that were prepared by anchoring commercially available, and environmentally benign cobalt-containing electrocatalysts with three different ligand frameworks (porphyrin, phthalocyanine, and corrin) on a structurally modified graphite foil surface. Under the studied reaction conditions (over 7 h at 22 degrees C), the electrode with Co-porphyrin is the most efficient for the water reduction with starting similar to 740 mV onset potential (OP) (vs. RHE, current density 2.5 mA/cm(2)) and a Tafel slope (TS) of 103 mV/dec. It is followed by the molecular electrodes having Co-phthalocyanine [825 mV (OP), 138 mV/dec (TS)] and Vitamin-B-12 (Co-corrin moiety) [830 mV (OP), 194 mv/dec (TS)]. A clear time-dependent improvement (>200 mV over 3 h) in the H-2 production overpotential with the Co-porphyrin-containing cathode was observed. This is attributed to the activation due to water coordination to the Co-center. A long-term chronopotentiometric stability test shows a steady production of hydrogen from all three cathode surfaces throughout seven hours, confirmed using an H(2 )needle sensor. At a current density of 10 mA/cm(2), the Co-porphyrin-containing electrode showed a TOF value of 0.45 s(-1) at 870 mV vs. RHE, whereas the Co-phthalocyanine and Vitamin-B-12-containing electrodes showed 0.37 and 0.4 s(-1) at 1.22 V and 1.15 V (vs. RHE), respectively.