High-Entropy Oxide of (BiZrMoWCeLa)O2 as a Novel Catalyst for Vanadium Redox Flow Batteries.

In this study, new fluorite high-entropy oxide (HEO), (BiZrMoWCeLa)O2, nanoparticles were produced using a surfactant-assisted hydrothermal technique followed by calcination and were used as novel catalytic materials for vanadium redox flow batteries (VRFBs). The HEO calcined at 750 °C (HEO-750) demonstrates superior electrocatalytic activity toward V3+/V2+ and VO2+/VO2+ redox couples compared to those of cells assembled with other samples. The charge-discharge tests further confirm that VRFBs using the HEO-750 catalyst demonstrate excellent Coulombic efficiency, voltage efficiency, and energy efficiency of 97.22, 87.47, and 85.04% at a current density of 80 mA cm-2 and 98.10, 74.76, and 73.34% at a higher current density of 160 mA cm-2, respectively. Moreover, with 500 charge-discharge cycles, there is no discernible degradation. These results are attributed to the calcination heat treatment, which induces the formation of a new single-phase fluorite structure, which facilitates the redox reactions of the vanadium redox couples. Furthermore, a high surface area, wettability, and plenty of oxygen vacancies can give more surface electroactive sites, improving the electrochemical performance, the charge transfer of the redox processes, and the stability of the VRFBs' electrode. This is the first report on the development of fluorite structure HEO nanoparticles in VRFBs, and it opens the door to further research into other HEOs.

Hagenia abyssinica-Biomediated Synthesis of a Magnetic Fe3O4/NiO Nanoadsorbent for Adsorption of Lead from Wastewater.

Magnetic nanocomposite adsorbents are cost-effective, environmentally friendly, easy to use, and highly efficient at removing metals from large volumes of wastewater in a short time by using an external magnetic field. In this study, an Fe3O4/NiO composite nanoadsorbent was prepared by varying the mass percent ratios of NiO (50, 40, 30, 20%), which are denoted Fe3O4/50%NiO, Fe3O4/40%NiO, Fe3O4/30%NiO, and Fe3O4/20%NiO, respectively, using Hagenia abyssinica plant extract as the template/capping agent and a simple mechanical grinding technique. The nanocomposites were characterized using an X-ray diffractometer (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, nitrogen adsorption, and ζ-potential measurements. The adsorption performance of the nanoadsorbent was assessed for the removal of lead (Pb2+) ions from aqueous solutions. Among the composite adsorbents, Fe3O4/50%NiO demonstrated the best Pb(II) removal efficiency (96.65%) from aqueous solutions within 80 min at pH 8, at a 100 mg/L lead concentration and 0.09 g of adsorbent dose. However, with the same parameter, only 62.8% of Pb(II) was removed using Fe3O4 nanoparticles (NPs). The adsorptive performance indicated that the optimum amount of porous material (NiO) in the preparation of the Fe3O4/NiO composite nanoadsorbent, with the aid of H. abyssinica plant extract, enhances the removal of toxic heavy metals from aqueous solutions. Multiple isotherm and kinetic models were used to analyze the equilibrium data. Adsorption isotherm and kinetic studies were found to follow the Freundlich isotherm and pseudo-second-order kinetics, respectively.

Surface Electroactive Sites of Tungstated Zirconia Catalysts for Vanadium Redox Flow Batteries.

Surface electroactive sites for tungstate zirconia (WZ) were created by utilizing tungstate-immobilized UiO-66 as precursors via a double-solvent impregnation method under a mild calcination temperature. The WZ-22-650 catalyst, containing a moderate W content (22%), demonstrated a high density of surface electroactive sites. Proper heat treatment facilitated the binding of oligomeric tungsten clusters to stabilized tetragonal ZrO2, resulting in improved catalytic performance toward the VO2+/VO2+ redox couples compared to other tested samples. The substantial surface area, mesoporous structure, and establishment of new W-O-Zr bonds affirm the firm anchoring of WOx to ZrO2. This robust attachment enhances surface electroactive sites, elevating the electrochemical performance of vanadium redox flow batteries (VRFBs). Charge-discharge tests further demonstrate that the superior voltage efficiency (VE) and energy efficiency (EE) for VRFBs using the WZ-22-650 catalyst are 87.76 and 83.94% at 80 mA cm-2, which are 13.42% VE and 10.88% EE better than heat-treated graphite felt, respectively. Even at a higher current density of 160 mA cm-2, VRFBs utilizing the WZ-22-650 catalyst maintained considerable efficiency, recording VE and EE values of 76.76 and 74.86%, respectively. This facile synthesis method resulted in WZ catalysts displaying superior catalytic activity and excellent cyclability, offering a promising avenue for the development of metal-oxide-based catalysts.

Dodonaea angustifolia Extract-Assisted Green Synthesis of the Cu2O/Al2O3 Nanocomposite for Adsorption of Cd(II) from Water.

The enhanced worldwide concern for the protection and safety of the environment has made the scientific community focus their devotion on novel and highly effective approaches to heavy metals such as cadmium (Cd) pollutant removal. In this research, Dodonaea angustifolia plant extract-mediated Al2O3 and Cu2O nanoparticle (NP) syntheses were accomplished using the coprecipitation method, and the Cu2O/Al2O3 nanocomposite was prepared by simple mixing of Cu2O and Al2O3 NPs for the removal of Cd(II) ions from aqueous solution. Therefore, an efficient green, economical, facile, and eco-friendly synthesis method was employed, which improved the aggregation of individual metal oxide NPs. The chemical and physical properties of the nanocomposite were examined by different characterization techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) surface area analysis. Furthermore, the performances of the nanoadsorbents for the adsorptive eradication of Cd2+ ions from water were investigated. The influence of pH, contact time, initial Cd quantity, and nanocomposite amount on adsorption effectiveness was carefully studied. The adsorption rates of the Cu2O/Al2O3 nanocomposite were rapid, and adsorption equilibrium was attained within 60 min for 97.36% removal of Cd(II) from water. The adsorption isotherm data were best fitted by the pseudo-second-order kinetic and Langmuir isotherm models with the highest adsorption ability of 4.48 mg/g. Therefore, the synthesized Cu2O/Al2O3 nanocomposite could be a potential candidate for a highly efficient adsorbent for heavy metal ion removal from aqueous solutions.

Visible light-driven photocatalytic activity of Cu2O/ZnO/Kaolinite-based composite catalyst for the degradation of organic pollutant.

Herein, we design to synthesize a novel Cu2O/ZnO/kaolinite composite catalyst by co-precipitation method. The synthesized composite catalysts were labeled as 5CZK, 10CZK, 15CZK, and 20CZK which represent 5, 10, 15, and 20% of Cu2O, respectively, on ZnO/kaolinite. The photocatalyst samples were characterized with different instruments. Moreover, the methylene blue (MB) dye was used as a target organic pollutant and the degradation was evaluated under visible light irradiation. The highest performance for the degradation of MB was achieved by 10CZK catalyst and degrades 93% within 105 min. However, ZnO (Z), Cu2O/ZnO (CZ), 5CZK, 15CZK, and 20CZK composite catalysts, degrades 28, 66, 76, 71, and 68% of MB dye, respectively. The enhanced degradation efficiency of 10CZK composites catalyst could be due to the higher adsorption properties from metakaolinite and the light-responsive properties of the Cu2O/ZnO samples under visible light. Hence, the resulting composite catalyst could be applicable for environmental remediation.

Waste tire carbon in synergetic interaction with spent gamma radioactive source for efficient radiocatalytic degradation of organic dye.

Enhanced degradation of organic dye was achieved using two different kinds of waste materials: waste tire granules and spent sealed radioactive sources. Waste tire granules were used as raw material for the production of waste tire char (WTC), which was further utilized as an adsorbent matrix for synergetic adsorption/irradiation degradation of organic dye. The spent radioactive sources were radiographic sealed sources that originate from the industry which generate the high energy radiation. Methylene Blue (MB) was used as an organic model compound. Synthesized WTC has turbostratic structure, irregular shaped particles and developed mesoporous surface. Complete degradation of 0.02 dm3 of 100 mg dm-3 MB solution, having WTC dose of 1.25 g dm-3, was achieved with delivered doze of only 60 Gy. The applied doses were 100 times smaller than those presented in the literature. Degradation pathway was determined: OH radicals that originate from radiolysis of water and from the surface of WTC played the crucial role in the radiocatalytic degradation of MB. Breakage of the aromatic ring of MB appeared by the scission of the double C‒S+Ë­C bond as a result of the attack of OH species on adsorbed and electronically reorganized MB molecule.

Application of graphene-based materials for removal of tetracyclines using adsorption and photocatalytic-degradation: A review.

Tetracyclines are extensively used to treat human and animal infectious diseases due to its effective antimicrobial activities. About 70-90% of its parent materials are released into the environment through urine and feces, implying they are the most frequently detected antibiotics in the environment with high ecological risks. Adsorption and photocatalysis have been promising techniques for the removal of tetracyclines due to effectiveness and efficiency. Graphene-based materials provide promising platforms for adsorptive and photocatalytic removal of tetracyclines from aqueous environment owning to distinctive remarkable physicochemical, optical, and electrical characteristics. Herein, we intensively reviewed the available literatures in order to provide comprehensive insight about the applications and mechanisms of graphene-based materials for removal of tetracyclines via adsorption and phototocatalysis. The synthesis methods of graphene-based materials, the tetracycline adsorption and photocatalytic-degradation conditions, and removal mechanisms have been extensively discussed. Finally concluding remarks and future perspectives have been deduced and recommended to stimulate further researches in the subject. The review study can be used as theoretical guideline for further researchers to improve the current approaches of material synthesis and application towards tetracyclines removal.

Hierarchically porous metal-organic frameworks: synthesis strategies, structure(s), and emerging applications in decontamination.

Metal-organic frameworks (MOFs) with high porosity have received much attention as promising materials for many applications owing to their unique properties. However, to date, most of the reported MOFs have microporous structures, which slow down diffusion/mass transfer and limit the accessibility of bulky molecules to its internal surface. Thus, it is crucial to develop an efficient way to create larger pores (mesoporous and/or macroporous) into microporous MOFs to form hierarchical porous metal-organic frameworks (HP-MOFs), which facilitate the diffusion and mass transfer of guest molecules. HP-MOFs are excellent and promising candidates for environmental applications under the background of environmental contaminations. In this review paper, we are primarily focusing on the latest progress in the preparation of HP-MOFs by employing template-assisted and template-free synthetic approaches for environmental cleaning applications. Particularly, the adsorptive purification of the most common toxic substances, including gases, dyes, heavy metal ions, and antibiotics from the environment using HP-MOFs as adsorbents is briefly discussed. The overall results clearly showed that the superiority of HP-MOFs compared with conventional microporous MOFs. Finally, we summarize the remaining challenges and provide personal perspectives on possible future development of HP-MOFs.

The effect of adding Bi3+ on the performance of a newly developed iron-copper redox flow battery.

In this paper, we propose a new, abundant, cost-effective, non-toxic, and environmentally benign iron-copper redox flow battery (Fe/Cu RFB), which employs Fe2+/Fe3+ and Cu+/Cu0 as the positive and negative electrolytes, respectively. The effect of graphite felt (GF) electrode modification and addition of Bi3+ into the electrolytes on the performance of the Fe/Cu RFB were investigated. It was found that the cell containing Bi3+ in the electrolytes revealed higher coulombic efficiency (89.18%) and energy efficiency (35.24%) than the cell without Bi3+ (CE = 84.10% and EE = 34.43%) at 20 mA cm-2. This is because after adding Bi3+, Cu metal precipitation was not observed on the electrode surface, which indicates that the deposition process was potentially reversible on the electrode material, thus leading to enhanced performance of the battery. Furthermore, the efficiencies of the battery are stable over 10 cycles, which demonstrates that Fe/Cu RFB exhibits good stability on the microwave heat treated GF plus one layer microwave heat treated carbon paper (HT-GF + HT-CP) electrode after adding Bi3+ into the electrolytes.