Removal of Methylene Blue from Water by BiFeO3/Carbon Fibre Nanocomposite and Its Photocatalytic Regeneration

In Situ Synthesis of Bi2S3/BiFeO3 Nanoflower Hybrid Photocatalyst for Enhanced Photocatalytic Degradation of Organic Pollutants

Photocatalytic degradation of Malachite Green oxalate (MG) in a water body is of significant importance to our health protection, as it could cause various serious diseases. However the photocatalytic activity of most catalysts is still unsatisfactory, due to the poor reactive oxygen species production as a result of sluggish charge separation. Here, innovative nanoflower-shaped Bi2S3/BiFeO3 heterojunctions are prepared via a facile sol-gel method, exhibiting an enhanced reactive oxygen species generation, which leads to the excellent photocatalytic performance toward MG degradation. We verify that interfacing BiFeO3 with Bi2S3 could form a fine junction and offers a built-in field to speed up charge separation at the junction area; as a result, this shows much higher charge separation efficiency. By virtue of the aforementioned advantages, the as-prepared Bi2S3/BiFeO3 heterojunctions exhibit excellent photocatalytic performance toward MG degradation, where more than 99% of MG is removed within 2 h of photocatalysis. The innovative design of nanoflower-like Bi2S3/BiFeO3 heterojunctions may offer new viewpoints in designing highly efficient photocatalysts for environmentally related applications.

Remediation of environmental toxicants using carbonaceous materials: opportunity and challenges

Adsorption and photocatalytic properties of carbonaceous materials, viz., carbon nanotubes (CNTs), fullerene, graphene, graphene oxide, carbon nanofiber nanospheres, and activated carbon, are the legitimate weapons for the remediation of emerging and persistent inorganic/organic contaminants, heavy metals, and radionucleotides from the environment. High surface area, low or non-toxic nature, ease of synthesis, regeneration, and chemical modification of carbonaceous material make them ideal for the removal of toxicants. The research techniques investigated during the last decade for the elimination of environmental toxicants using carbonaceous materials are reviewed to offer comprehensive insight into the mechanism, efficiency, applications, advantages, and shortcomings. Opportunities and challenges associated with carbon materials have been discussed to suggest future perspectives in the remediation of environmental toxicants.

Electrocatalytic performance of Sb-modified Bi25FeO40 for nitrogen fixation

The Haber-Bosch N₂ fixation method suffers from the power-consuming and harsh conditions. In contrast, the electrochemical conversion of N₂ (NRR) at room temperature and atmospheric pressure is considered a promising alternative route. In this study, we synthesized Sb-modified with Bi₂₅FeO₄₀ (BFSO/BFO) by using one-step hydrothermal treatment. The BFSO/BFO catalyst has higher selectivity to NRR than Bi₂₅FeO₄₀ (BFO) under the same applied voltage. Such large interfacial interaction area plays a critical role in transfer electron and enhances the density of current. The resulting BFSO/BFO heterojunction showed significant electrocatalytic activity under controllable voltage, which exhibited favorable average ammonia (NH₃) yield as high as 2.62 μg·h^-1·cm^-2 at -0.2 V versus RHE. Moreover, the stability of the BFSO/BFO composite was evaluated for six cycles and the results were desirable. This study provides a new insight into the design of composite catalysts using BFO, which has high activity and selectivity toward NRR.

Thermal Profiles of Carbon Fiber Based Anisotropic Thin-Films: An Emerging Heat Management Solution for High-Current Flow Electrocatalysis and Electrochemical Applications

Carbon fiber has been extensively used in the photocatalysis, electrocatalysis and energy storage fields as supporting platform and conductive media. However, less attention has been paid with regards to its function in phonon transport and thermal management. We have investigated the effect of current flow direction on the heat management performance of carbon fiber based thin film heaters (CFTFHs) with anisotropic percolation network of carbon fibers (CFs). The anisotropic percolation network of carbon fibers (CFs) formed by roll-to-roll spray coating leads to the anisotropic electrical properties of CFs. As a result, CFs based thin films (CFTFs) have lower sheet resistance when measured parallel to the CFs alignment, compared to when they are aligned perpendicular. Because connectivity and current flow in CFs are critically dependent on the direction alignment of CFs, the saturation temperature (106.4 °C) of CFTFH with parallel aligned carbon fiber is higher than that (117.3 °C) of CFTFH with perpendicular alignment. Therefore, current flow in the same direction as the alignment of CFs is very important to achieve high-performance. Moreover, our study on thermal profile of anisotropic CFTFs under high current flows illustrates that carbon fiber thin films have great potential in thermal management solution for electrocatalytic and electrochemical energy storage applications.

Uptake of Methylene Blue from Aqueous Solution by Naturally Grown Daedalea africana and Phellinus adamantinus Fungi

Herein, Daedalea africana and Phellinus adamantinus were evaluated for the uptake of the methylene blue (MB) dye. Various factors such as pH range, time of exposure, dye concentration, adsorbed quantity, etc. have been studied for the uptake. Adsorption isotherms investigated in this study include the Langmuir and Freundlich isotherms. The Langmuir isotherm has been long known to be the best fit in the process of adsorption. The maximum monolayer adsorption capacity for D. africana was reported to be 0.5210 mol/kg, and it is 1.8387 mol/kg for P. adamantinus at 298 K. The n values 0.8748 and 0.9524 obtained indicate that the dye is favorably adsorbed on both adsorbents. Kinetics data analysis has shown that methylene blue adsorbed on the fungus showed pseudo-second-order chemisorption and film as well as intra particle diffusion. These results reveal that the abovementioned fungi can be used as good sources for the uptake of the MB dye.

Nitrogen Self-Doped Activated Carbons Derived from Bamboo Shoots as Adsorbent for Methylene Blue Adsorption

Bamboo shoots, a promising renewable biomass, mainly consist of carbohydrates and other nitrogen-related compounds, such as proteins, amino acids and nucleotides. In this work, nitrogen self-doped activated carbons derived from bamboo shoots were prepared via a simultaneous carbonization and activation process. The adsorption properties of the prepared samples were evaluated by removing methylene blue from waste water. The factors that affect the adsorption process were examined, including initial concentration, contact time and pH of methylene blue solution. The resulting that BSNC-800-4 performed better in methylene blue removal from waste water, due to its high specific surface area (2270.9 m2 g-1), proper pore size (2.19 nm) and relatively high nitrogen content (1.06%). Its equilibrium data were well fitted to Langmuir isotherm model with a maximum monolayer adsorption capacity of 458 mg g-1 and a removal efficiency of 91.7% at methylene blue concentration of 500 mg L-1. The pseudo-second-order kinetic model could be used to accurately estimate the carbon material's (BSNC-800-4) adsorption process. The adsorption mechanism between methylene blue solution and BSNC-800-4 was controlled by film diffusion. This study provides an alternative way to develop nitrogen self-doped activated carbons to better meet the needs of the adsorption applications.