Elucidating the impacts of cobalt (II) ions on extracellular electron transfer and pollutant degradation by anodic biofilms in bioelectrochemical systems during industrial wastewater treatment

Electrogenic biofilms in bioelectrochemical systems (BES) are critical in wastewater treatment. Industrial effluents often contain cobalt (Co2+); however, its impact on biofilms is unknown. This study investigated how increasing Co2+ concentrations (0-30 mg/L) affect BES biofilm community dynamics, extracellular polymeric substances, microbial metabolism, electron transfer gene expression, and electrochemical performance. The research revealed that as Co2+ concentrations increased, power generation progressively declined, from 345.43 ± 4.07 mW/m2 at 0 mg/L to 160.51 ± 0.86 mW/m2 at 30 mg/L Co2+. However, 5 mg/L Co2+ had less effect. The Co2+ removal efficiency in the reactors fed with 5 and 10 mg/L concentrations exceeded 99% and 94%, respectively. However, at 20 and 30 mg/L, the removal efficiency decreased substantially, likely because of reduced biofilm viability. FTIR indicated the participation of biofilm functional groups in Co2+ uptake. XPS revealed Co2+ presence in biofilms as CoO and Co(OH)2, indicating precipitation also aided removal. Cyclic voltammetry and electrochemical impedance spectroscopy tests revealed that 5 mg/L Co2+ had little impact on the electrocatalytic activity, while higher concentrations impaired it. Furthermore, at a concentration of 5 mg/L Co2+, there was an increase in the proportion of the genus Anaeromusa-Anaeroarcus, while the genus Geobacter declined at all tested Co2+ concentrations. Additionally, higher concentrations of Co2+ suppressed the expression of extracellular electron transfer genes but increased the expression of Co2+-resistance genes. Overall, this study establishes how Co2+ impacts electrogenic biofilm composition, function, and treatment efficacy, laying the groundwork for the optimized application of BES in remediating Co2+-contaminated wastewater.

Dense, Three-Dimensional, Highly Absorbent, Graphene Oxide Aerogel Coating on ZnCo2O4/ZnO Particles Exerts a Synergistic Catalytic Effect for Ammonium Perchlorate Thermal Decomposition

As a new type of carbon material, graphene oxide aerogel (GA) is widely used in catalysis due to its porous structure, high-efficiency adsorption, and superb conductivity. In this study, GA was prepared into a dense coating layer surrounding ZnCo₂O₄/ZnO particles to form a composite GA-ZnCo₂O₄/ZnO by means of a hydrothermal, blast drying, and vacuum-freeze-drying approach applied to catalyze the thermal decomposition of ammonium perchlorate (AP). The physicochemical properties of the obtained GA-ZnCo₂O₄/ZnO were characterized by different analytical methods. Scanning electron microscopy (SEM) analysis exhibited that GA is coated on the surface of ZnCo₂O₄/ZnO, forming a dense layer. Brunner Emmet Teller (BET) measurement results show that GA-ZnCo₂O₄/ZnO has a smooth macropore distribution curve and a larger specific surface area. Moreover, The catalytic effect investigation on AP with GA-ZnCo₂O₄/ZnO: the high temperature decomposition (HTD) peak temperature of AP in the presence of 5 wt % GA-ZnCo₂O₄/ZnO was reduced from 441 to 294 °C, and the exotherm of AP was expanded from 205 to 1275 J/g at a heating rate of 15 °C/min. Through the calculation, GA-ZnCo₂O₄/ZnO makes the activation energy and Gibbs free energy of the AP pyrolysis lower so that the reaction is easier to occur. Thermogravimetric-mass (TG-MS) spectrometry revealed that during thermal decomposition of AP, GA-ZnCo₂O₄/ZnO leveraged the synergistic catalysis of ZnCo₂O₄/ZnO and GA that boosted the flow of electrons from ClO₄^- to O₂ and increased the absorption of the gas product to accelerate the AP pyrolysis. These results provided a facile strategy to prepare GA-based composite catalysts with extraordinary application prospects in the domain of solid propellants.

Glycerol-controlled synthesis of a series of cobalt acid composites and their catalytic decomposition toward several energetic materials

One of the challenges in solid propellant formulation is the ability to extend the combustion performance by efficiently catalyzing the decomposition of energetic additives.

Cobalt oxide nanoparticle-decorated reduced graphene oxide (Co3O4–rGO): active and sustainable nanoelectrodes for water oxidation reaction

Herein, cobalt oxide (Co₃O₄)-decorated reduced graphene oxide (rGO)-based nanoelectrodes were fabricated by the chemical reduction method for electrocatalytic water oxidation reactions.

Freestanding CuS nanowalls: ionic liquid-assisted synthesis and prominent catalytic performance for the decomposition of ammonium perchlorate

Freestanding CuS nanowalls, with excellent catalytic activity for AP thermal decomposition, were grown and assembled at the [C₁₀mim]Br-modulated liquid–liquid interface.

A facile one-pot solvothermal synthesis of CoFe2O4/RGO and its excellent catalytic activity on thermal decomposition of ammonium perchlorate

A novel catalyst CoFe₂O₄/RGO has been synthesized and shows enhanced catalytic activity on thermal decomposition of ammonium perchlorate.