Methylene Blue Degradation Efficiency Research Articles

Zirconium and cerium dioxide fabricated activated carbon-based nanocomposites for enhanced adsorption and photocatalytic removal of methylene blue and tetracycline hydrochloride

Activated carbon (AC) is a porous, amorphous form of carbon known for its strong adsorption capacity, making it highly effective for use in wastewater treatment. In this investigation, AC-based nanocomposites (NCs) loaded with zirconium dioxide and cerium dioxide nanoparticles (ZrO2/CeO2 NPs) were successfully synthesized for the effective elimination of methylene blue (MB) and tetracycline hydrochloride (TCH). The AC-ZrO2/CeO2 NCs have a size of 231.83 nm, a zeta potential of −20.07 mV, and a PDI value of 0.160. The adsorption capacities of AC-ZrO2/CeO2 NCs for MB and TCH were proved in agreement with the Langmuir isotherm and pseudo 1st order kinetic model, respectively. The maximum adsorption capacities were determined to be 75.54 mg/g for MB and 26.75 mg/g for TCH. Notably, AC-ZrO2/CeO2 NCs exhibited superior photocatalytic degradation efficiency for MB and TCH under sunlight irradiation with removal efficiencies reaching up to 97.91% and 82.40% within 90 min, respectively. The t1/2 for the photo-degradation process of MB and TCH were 11.55 min and 44.37 min. Analysis of active species trapping confirmed the involvement of hole (h+), superoxide anion (•O2−), and hydroxyl radical (•OH) in the degradation mechanism. Furthermore, the residual solution post-contaminant removal exhibited minimal toxicity towards Artemia salina and NIH3T3 cells. Importantly, the NCs did not exhibit antibacterial activity against tested pathogens post-absorption/degradation of TCH. Thus, AC-ZrO2/CeO2 NCs could be a promising nanomaterial for wastewater treatment applications.

Tailoring the geometry of visible and near-infrared light active CuSe nanostructure for enhanced photocatalytic activity

Semiconductor photocatalysts play a pivotal role in fostering a sustainable environment by harnessing solar energy directly into chemical energy to achieve various photocatalytic processes. Therefore, a visible-infrared active photocatalyst is the next level of demand for solving the alarming environmental issues. In this regard, the present article reports the investigations of crucial mechanisms and conditions leading to pure and defect-free hexagonal 2D CuSe nanosheets (NSs) and the influence of their structural architecture on visible-infrared active photocatalytic performance. Here, it was achieved by the conventional hydrothermal method by varying the pH of the reaction mixture. XRD analysis was used to examine the crystal structure and lattice parameters of CuSe NSs. The presence of H+ ions was suggested to significantly influence the observed anisotropic crystallite growth across different pH conditions. EDS and XPS analysis exhibited the purity and stoichiometry of 2D CuSe NSs, revealing that the obtained stoichiometry was consistent with CuSe composition. The morphological characteristics were investigated using FE-SEM as well as HR-TEM analyses, and the specific surface area was determined using Brunauer-Emmett-Teller analysis in which a significant change occurred in response to the variation in reaction conditions. The optical properties of optimized 2D CuSe NSs show excellent absorption in the visible and near-infrared region utilizing full solar with a notable decrease in emission intensity, suggesting a reduction in recombination rates due to pH-induced changes in the nanoarchitecture. Herein, methylene blue, a well-established model dye, was used as a probe to assess the photocatalytic activity of the synthesized CuSe NSs. Notably, the CuSe NSs synthesized under neutral conditions demonstrate a remarkable methylene blue degradation efficiency, reaching approximately 98 % within approximately 45 minutes, indicating a high degradation rate. Finally, an in-depth exploration into the intricacies of photocatalytic performance, degradation mechanisms, and the recyclability test was conducted, accompanied by a thorough investigation into the feasibility of CuSe NSs for their practical application in photocatalytic wastewater treatment.

Novel green synthesis approach of eco-friendly magnetic/semiconductor nanocomposites as magnetically separable and reusable photocatalyst for organic dye degradation

Eco-friendly and effective separation of photocatalytic nanoparticles from the reaction mixture is crucial to facilitate their repeated use in photocatalysis. The development of magnetic/semiconductor nanocomposites with high catalytic performance and easy separation is an efficient strategy for wastewater treatments. In this study, we explore the potential of combination of magnetic (CoFe2O4) and semiconductor (ZnS) synthesized via a green approach using Moringa oleifera leaf extract as magnetically separable photocatalysts for dye degradation. X-ray diffraction analysis confirmed the presence of the cubic spinel ferrite phase of CoFe2O4 and the cubic zinc blend phase of ZnS within the nanocomposites. The micrographs illustrated nearly spherical nanoparticles with average particle sizes of 12 nm for CoFe2O4 and 26 nm for CoFe2O4/ZnS, respectively. The presence of SO suggested the incorporation of ZnS on the surface of CoFe2O4/ZnS nanocomposites. The UV–visible spectra revealed an increase in the band gap energy from 3.7 to 4.5 eV with increasing ZnS concentrations. Magnetic properties analysis signified that the CoFe2O4/ZnS nanocomposites exhibited ferromagnetic characteristics. The optimal degradation efficiency of photodegradation methylene blue was observed for CoFe2O4/ZnS 50 %, achieving 78.3 % degradation within 80 min with intervals 20 min. The magnetically separable capability allows for the recycling of nanocomposites after three consecutive cycles. Therefore, CoFe2O4/ZnS nanocomposites emerge as promising candidates as separable photocatalysts for the removal of organic pollutants in environments.

Pd octahedra nanocubes mediated photo-fenton catalytic performance for sustainable degradation of methylene blue

This research utilized a typical solvothermal approach, by employing Na2PdCl4 as the synthetic precursor, L-ascorbic acid (AA) as the reductant agent, and polyvinylpyrrolidone (PVP) as the practical surfactant, palladium (Pd) octahedra was finally effectively synthesized by the hydrothermal and solvothermal methods. Subsequently, characterizations of Pd octahedra were conducted by using TEM, XPS, XRD, and other analytical methods. Whereafter, Pd octahedra displayed a consistent shape and size, featuring a distinctive tip-shaped structure, which conferred upon them outstanding optical absorption properties within the near-infrared (NIR) region. Consequently, under NIR laser exposure, Pd octahedra could elevate local reaction temperature via in-situ photothermal conversion, thereby stimulating the formation of active sites of Fenton catalysts. The Photo-Fenton catalytic activity of Pd octahedra was investigated by using methylene blue (MB) as a model pollutant. The degradation efficiency of MB reached 94.8 % within 35 min under 808 nm laser irradiation, and the removal rate of MB by Pd octahedra could still reach more than 90 % after five cycles of use. All the results manifest that Pd octahedra exhibit excellent purification performance for MB dyestuff wastewater.

Synthesis and photocatalytic activity of zinc-doped copper sulfide with porous nanotubes structures

Zinc-doped copper sulfide (Zn-doped CuS) particles were synthesized by a hydrothermal method in EG (EG) solutions of different concentrations. The results showed that the concentration of EG could regulate the structural morphology of Zn-doped CuS, and the Zn-doped CuS formed in pure EG had a porous nanotubular structure, and its photocatalytic degradation efficiency of methylene blue was as high as 96 % under visible light with good stability. SEM and TEM imaging confirmed that the diameter of the Zn-doped CuS with porous nanotubular structure was 100 nm, and the wall thickness was 30 nm. This study presents a strategy to enhance the photocatalytic activity and performance of CuS for environmental applications through EG concentration and zinc doping.

Modeling and experimental verification for photodegradation in a spinning disk reactor

The spinning disk reactor has been regarded as a process intensification device in photochemical processes, which decreases the light path length by the thin film formation created by centrifugal force. A reliable reactor model was indispensable for the practical application of photoreactors. Our previous studies proposed a spinning disk reactor with elliptic-cylindrical and cylindrical spoilers for photochemical process intensification, and then hydrodynamic parameters of liquid film thickness, photon absorption rate, and residence time distribution were obtained. Based on the obtained parameters, herein, a reactor model was further established for the description of photodegradation reaction in the innovative spinning disk reactor. Different non-ideal flow models were employed during the model development, including the tanks-in-series model and axial dispersion model. The apparent reaction rate constant of a spinning disk reactor with spoilers was determined by the photon absorption rate, which was in the range of 0.088–0.268 s−1. The reactor model was verified by the experiments on photodegradation of Methylene Blue under different disk configurations and operating conditions. The degradation efficiency of Methylene Blue could reach up to 89.8 % in 25 min at N = 200 r/min, Q = 60 L/h, and I0 = 8 mW/cm2. The deviation between predicted and experimental Methylene Blue degradation efficiencies was within ± 20 %, confirming the rationality of the reactor model. The developed model lays the foundation for the scaling-up and commercial applications of the novel spinning disk reactors.

Bimetal Cu/Ni-BTC@SiO2 metal-organic framework as high performance photocatalyst for degradation of azo dyes under visible light irradiation

There has been significant attention on the efficient degradation of pollutants in wastewater using metal-organic frameworks (MOFs) photocatalytic methods over the past decade. Herein, we examined the elimination of two different types of water-contaminating dyes, specifically cationic dye methylene blue (MB) and anionic dye methyl orange (MO), through the application of bimetal Cu/Ni-BTC@SiO2 MOF as high performance photocatalyst. The bimetal Cu/Ni-BTC@SiO2 photocatalyst was synthesized and characterized by XRD, FTIR, SEM, TEM, TGA, BET, DRS, and VSM techniques. The examination of the impact of different operational factors on the elimination of pollutants involved a comprehensive analysis of variables including the photocatalyst type, initial pollutant concentration, quantity of photocatalyst, and pH levels. The highest removal efficiency for MO and MB dyes by the photocatalyst was found to be 98 and 71%, respectively, within 60 min. In the fifth reaction stage, degradation efficiency for MO and MB was 76 and 56% respectively. Kinetic investigations demonstrated that, in the context of the uptake of MB and MO dyes, the interparticle diffusion, and pseudo-second-order models emerged as possessing the most robust correlation coefficients with the experimental data, registering values of 0.988 and 0.961, respectively. The examination of isotherms reveals that the isotherm models proposed by BET, and Anderson (V) demonstrate the highest level of conformity with the empirical data for the decomposition of MB and MO dyes, correspondingly. The TOC levels decreased significantly from 51 to 14 and 47 to 3 mg/L for MB and MO dyes, indicating the effective mineralization process using Cu/Ni-BTC@SiO2.

Clam Shell-Derived Hydroxyapatite: A Green Approach for the Photocatalytic Degradation of a Model Pollutant from the Textile Industry.

This work aims to evaluate the potential use of natural wastes (in particular, clam shells) to synthesize one of the most well-known and versatile materials from the phosphate mineral group, hydroxyapatite (HAP). The obtained material was characterized in terms of morphology and composition using several analytical methods (scanning electron microscopy-SEM, X-ray diffraction-XRD, X-ray fluorescence-XRF, Fourier transform infrared spectroscopy-FTIR, thermal analysis-TGA, and evaluation of the porosity and specific surface characteristics by the Brunauer-Emmett-Teller-BET method) in order to confirm the successful synthesis of the material and to evaluate the presence of potential secondary phases. The developed material was further doped with iron oxide (HAP-Fe) using a microwave-assisted method, and both materials were evaluated in terms of photocatalytic activity determined by the photodecomposition of methylene blue (MB) which served as a contaminant model. The best results (approx. 33% MB degradation efficiency, after 120 min. of exposure) were obtained for the hydroxyapatite material, superior to the HAP-Fe composite (approx. 27%). The utilization of hydroxyapatite obtained from clam shells underscores the importance of sustainable and eco-friendly practices in materials syntheses. By repurposing waste materials from the seafood industry, we not only reduce environmental impact, but also create a valuable resource with diverse applications, contributing to advancements in both healthcare and environmental protection.

Synthesis of type-II TiO2 nanoparticle/ZnO nanorods heterostructure for enhanced photocatalytic activity

A type-II TiO2/ZnO heterostructure is fabricated by coating TiO2 nanoparticles (2, 4 and 6 layers) over ZnO nanorods using sol–gel method to obtain the optimized system with enhanced photocatalytic activity. TiO2/ZnO:6 layer exhibited a higher optical absorption and lowest bandgap value among the synthesized samples. A lower photoluminescence (PL) intensity is noticed for TiO2/ZnO:6 layer sample, ensuring efficient reduction of carrier recombination rate. Moreover, TiO2/ZnO:6 layer exhibited maximum methylene blue (MB) and phenolphthalein dyes degradation efficiency of 86.3% and 76.5% respectively under UV light illumination for 180 min. Our study proposes that formation of type-II heterostructure enhances the photocatalytic activity.

Preparation of modified wood-based metal nanoparticles synthesized in situ and efficient removal of organic pollutants from wastewater

Wood has excellent properties such as biodegradability, high reactivity and rich channel skeleton structure. However, the defects such as hole blockage and limited specific surface area limit the application of wood-based materials in wastewater treatment. Therefore, in this research, wood substrates (DTWS) were treated using a deep eutectic solvent method, which was able to remove both lignin and hemicellulose from wood. Wood-based carriers with high specific surface area and high chemical activity were formed. The DTWS-Ag material was formed by growing Ag nanoparticles (NPs) in wood channels by hydrothermal method. The results showed that with the increase of lignin and hemicellulose removal, the degradation performance of DTWS-Ag material showed a volcanic trend due to the interaction between Ag and the inner wall of the pipe. The pore size and the amount of Ag NPs are very important to the degradation rate of dye molecules. DTWS-4-Ag composite material makes wood pore diameter and Ag NPs production reach a high balance, so that it has the highest degree of reduction. DTWS-4-Ag showed high catalytic degradation efficiency and stability for methylene blue degradation, with the degradation efficiency up to 98.3 %. This low-cost, renewable wood-based filter has high dye degradation efficiency and can be widely used in practical wastewater treatment.

Facile construction of Bi2WO6/TiO2 microspheres heterojunction for boosting photocatalytic degradation of organic dyes

Flower-like Bi2WO6 microspheres and TiO2 spherical particles were prepared by a facile hydrothermal method without any surfactant or template. A unique Z-Scheme Bi2WO6/TiO2 heterojunction was successfully synthesized via a simple physical mixing method. The effect of mass ratio on the structure, morphology, optical properties, BET surface area and photocatalytic performance evaluated by degradation of organic dyes including Rhodamine B (RhB), methylene blue (MB) and methyl orange (MO) under solar irradiation was systemically investigated. When the mass ratio of Bi2WO6 to TiO2 was 1:4, the Bi2WO6/TiO2 composites exhibited the highest photocatalytic degradation efficiency, the highest degradation efficiency of RhB and MB reached 95.2 % and 89.3 %, which could be attributed to the construction of heterojunction structure between TiO2 and Bi2WO6. The optical absorption capacity of Bi2WO6/TiO2 composites was stronger than pure TiO2. Furthermore, the radicalquenching experiments proved that ·O2– and h+ played crucial roles in the photocatalytic reaction. The suitable band structure of Bi2WO6 and TiO2 revealed the Z-Scheme pathway and possible photocatalytic mechanism of Bi2WO6/TiO2 composites for organic dyes degradation. Thus, the direct Z-scheme Bi2WO6/TiO2 heterojunction effectively promoted separation of photogenerated electron-hole pairs, resulting in higher photocatalytic activity.

Two-stage hydrothermal process driven visible light sensitive photocatalytic m-ZnWO4/m-WO3 heterojunction composite materials

The current study reports on the facile two-step hydrothermal synthesis of heterojunction m-ZnWO4/m-WO3 composite powders for visible light sensitive photocatalytic applications. The ZnWO4 particles start crystallizing on the surface of the WO3 powder in the second stage of the reaction in a basic medium. The phases of the composite powders were confirmed using x-ray diffraction analysis. The monoclinic cubic shaped WO3 and rod shaped ZnWO4 morphologies were disclosed from the field emission scanning electron microscope images. Strong interfacial adhesion between ZnWO4 and WO3 was unveiled from the high-resolution transmission electron microscopy study. The optimized composite 5ZW exhibits a calculated bandgap of 2.58 eV, positioning it within the visible light wavelength range (λ = 400–700 nm). Furthermore, there is a notable enhancement in the average lifetime of the electron–hole pair recombination rate, which is extended to 30.3 ns. The composite 5ZW demonstrated 96% methylene blue dye degradation efficiency within 420 min under visible light irradiation at pH 12. Due to the optimal phase fraction and strong interfacial adhesion between ZnWO4 and WO3, the heterojunction scheme seemed to be highly efficient in the 5ZW composite. Hence, it is believed that a two-step hydrothermal method can be a proficient route to prepare heterojunction composites m-ZnWO4/m-WO3 in alkali conditions with visible light active photodegradation efficiency.

TiO2-N/Polystyrene photocatalyst-combined Corona Plasma Treatment for Methylene Blue Degradation

<span>This study employed the corona plasma method combined with TiO<sub>2</sub>-N/PS photocatalyst to degrade dye pollutants. The plasma reactor consisted of two needle-shaped stainless steel electrodes connected to a voltage of 8 kV. Methylene blue (MB) solution was used as a model pollutant with varied initial concentrations of 10, 50, and 100 ppm. The degradation efficiency was evaluated based on the absorbance of the degraded MB solution measured using a UV-Vis spectrophotometer. The results exhibited that the longer plasma treatment duration caused the absorbance value of the degraded MB to decrease, and then the MB degradation efficiency increased. MB-10 demonstrated a maximum degradation efficiency of 99.40% after plasma treatment for 30 minutes. Meanwhile, MB-50 and MB-100 reached maximum degradation efficiencies of 95.29 and 86.55% efficiency after plasma treatment for 60 minutes. The greater initial MB concentration caused the longer degradation process. Furthermore, the results revealed no increase in degradation efficiency due to the addition of TiO<sub>2</sub>-N/PS photocatalyst into the plasma treatment. The degradation efficiencies of MB-10, MB-50, and MB-100 under TiO<sub>2</sub>-N/PS-combined plasma treatment for 30 min were 94.48, 81.57, and 5.22%, respectively. This suggests the possibility that the UV light generated during the plasma process cannot activate the TiO<sub>2</sub>-N/PS photocatalyst.</span>

Improving Photocatalytic Performance through Incorporation of Various Cations in A-site of Double Perovskite Material (Cs0.50MA0.50)2SnI6 for Degradation of Methylene Blue Dye Pollutant under Visible Light Irradiation

In this article, undoped double perovskite materials like caesium tin iodide (Cs2SnI6), methyl ammonium tin iodide [MA2SnI6: MA denotes CH3NH3+] and mixed double perovskite material [(Cs0.50MA0.50)2SnI6] were synthesized using a wet chemical methodology. The crystal structure confirmation, optical properties, thermal properties, surface morphology and presence of elemental composition of the prepared samples using XRD, UV, TGA and FESEM-EDAX analyses were thoroughly investigated. The synthesized materials were employed as photocatalysts to degrade methylene blue dye within 120 min under visible light. An increase in the optical properties of the synthesized double perovskite materials was confirmed by ultraviolet (UV) analysis, which showed that the introduction of various cations into the perovskite material at the A-site shifted the photoluminescence (PL) emission peak to the red. TGA results demonstrated that (Cs0.50MA0.50)2SnI6 has greater thermal stability, which was confirmed by the presence of 43% of sample despite the temperature reaching almost 870 ºC. Doped double perovskite material (Cs0.50MA0.50)2SnI6 exhibited increased photocatalytic activity, with methylene blue dye degradation efficiency attaining 89% after 120 min of visible light irradiation, which is greater than pure double perovskite materials. The photocatalytic degradation of methylene blue dye is mostly facilitated by hydroxyl radicals and holes, according to a radical trapping experiment that we conducted by employing different scavengers. The results of the current work showed that doped double perovskite materials [(Cs0.50MA0.50)2SnI6] exhibit high thermal stability as well as higher photocatalytic activity than pure double perovskite materials. A possible photocatalytic reaction process is also diagrammatically using the band positions of double perovskite materials found using Mott-Schottky plots , which confirms that the synthesized double perovskite material has an N-type semiconductor nature.

Growth of CuS nanowire on copper mesh for efficient solar-driven water evaporation and wastewater purification

This study proposed a multifunctional material, CuS nanowire, grown on a copper mesh (CM), for application in wastewater purification. CuS/CM could rapidly evaporate and collect water under solar irradiation. CuS nanowires were successfully synthesized on CM through a liquid–solid reaction at room temperature, followed by sulfidation. Water evaporation experiments conducted using meshes suspended in water to determine the most efficient configuration revealed that CuS/CM was the most efficient material. Owing to the localized surface plasmon resonance induced by oxygen vacancies, CuS/CM exhibited a high water evaporation rate (4.0523 kg·m-2h−1 @ 3 sun) and energy conversion efficiency (96.1 %) in Structure A with a vertical length of 4 cm under 3 sun irradiation. To evaluate its effectiveness in wastewater treatment, CuS/CM was used to evaporate and collect methylene blue (MB)-contaminated water at rates of 1.5747 and 0.8624 kg·m-2h−1. Furthermore, CuS/CM demonstrated photocatalytic activity during MB degradation. Under xenon lamp illumination for 6 h, CuS/CM exhibited a 73 % degradation efficiency for MB, indicating its photocatalytic properties. CuS/CM effectively purify dyeing wastewater due to their fast water evaporation rate and the photocatalytic capability of CuS, making them promising for wastewater treatment and desalination applications.

Carbon based cobalt titanate perovskite nanocomposite: Synthesis, characterization, and excellent visible light driven photocatalytic performance

Titanium-based perovskite oxides are the promising photocatalysts for an efficient degradation of organic pollutants. However, charge carriers recombination and wide band gap energy are still the main challenges in their visible-light-driven photocatalytic applications of Titanate perovskites, ATiO3. The immobilization of Titanium-based perovskites on a carbonaceous substrate such as nitrogen-rich carbon nitride, can be considered as an excellent option for enhancing photocatalytic performance. Here, the CoTiO3/C3N5 nanocomposite was synthesized by simple reflux method and used for photocatalytic degradation of three organic pollutants including methylene blue (MB), tetracycline hydrochloride (TC), and bisphenol A (BPA). The results indicated that the photocatalytic activity of the CoTiO3 perovskite was considerably improved by introducing C3N5 nanosheets and fabricating CoTP/C3N5 nanocomposite. The crystalline structure of CoTiO3/C3N5 (CoTP/C3N5) nanocomposites was confirmed successfully by XRD analysis. The specific surface area of the synthesized CoTP/C3N5 nanocomposite was 8.15 m2/g calculated by N2 adsorption–desorption technology. In the 60th minute of the photocatalytic process, the degradation efficiency of MB, TC, and BPA by CoTP/C3N5 were obtained as 98.70, 60.33, and 92.90 %, respectively, which were higher than pristine CoTiO3 nanorods and C3N5 nanosheets. Electrochemical impedance analysis shows that the CoTP/C3N5 nanocomposite has good electrochemical performance. The improvement photocatalytic activity CoTP/C3N5 can be attributed to the suppressing the recombination of photogenerated electrons and holes and good electrochemical performance with high electron transfer capability. The results achieved from UV–Visible Diffused Reflectance Spectroscopy (DRS), mott-schottky measurements and the photocatalytic degradation experiments in the presence of scavengers confirmed the significantly accelerating the Z-scheme charge transfer mechanism where photoexcited carriers can migrate between CoTiO3 perovskite and C3N5 nanosheets.

Effective degradation of synthetic micropollutants and real textile wastewater via a visible light-activated persulfate system using novel spinach leaf-derived biochar

A novel biochar (BC), derived from spinach leaves, was utilized as an activator for persulfate (PS) in the degradation of methylene blue (MB) dye under visible light conditions. Thorough analyses were conducted to characterize the physical and chemical properties of the biochar. The (BC + light)/PS system exhibited superior MB degradation efficiency at 83.36%, surpassing the performance of (BC + light)/hydrogen peroxide and (BC + light)/peroxymonosulfate systems. The optimal conditions were ascertained through the implementation of response surface methodology. Moreover, the (BC + light)/PS system demonstrated notable degradation ratios of 90.82%, 81.88%, and 84.82% for bromothymol blue dye, paracetamol, and chlorpyrifos, respectively, under optimal conditions. The predominant reactive species responsible for MB degradation were identified as sulfate radicals. Notably, the proposed system consistently achieved high removal efficiencies of 99.02%, 96.97%, 94.94%, 92%, and 90.35% for MB in five consecutive runs. The applicability of the suggested system was further validated through its effectiveness in treating real textile wastewater, exhibiting a substantial MB removal efficiency of 98.31% and dissolved organic carbon mineralization of 87.49%.

In-situ one-pot synthesis, characterization of magnetic hydrochar and its application as Fenton-like catalyst for the degradation of methylene blue dye

The widespread use of dyes in various industries has led to alarming levels of water pollution, posing significant environmental and health risks. This study presents biochar being a carbon-rich source, produced from Acacia koa pod covers has been used as a sustainable source to prepare Ak/BC-Fe3O4 magnetic nanocomposite, subsequently employed for Fenton-like degradation of methylene blue (MB) dye. FESEM-EDS revealed that the synthesized nanocomposite has a morphology of spherical magnetic nanoparticles being embedded on the biochar base and EDS further confirmed the synthesis of magnetic biochar by detecting only C, O, and Fe. The nanocomposite is mesoporous with a pore volume of 0.03204 cm3/g and a surface area of 7.11 m2/g as shown by the BET results. XRD substantiated the presence of an amorphous structure of biochar and the presence of ultra-small crystallites of Fe3O4 nanoparticles. FTIR signified the presence of specific functional groups for Fe–O and biochar whereas, XPS showed the peaks at 712.39 and 725.78 eV indicated the coexistence of Fe2+ and Fe3+. The nanocomposite is superparamagnetic with a saturation magnetization of 8.64 emu/g having remarkable magnetic separation capacity. Fenton-like degradation of MB dye in the presence of H2O2 revealed a first-order reaction with removal efficiency ranging between 82 and 96% in 120 min with convenient recycling ability for 7 cycles. Hence, this study underscores the outstanding characteristics and MB degradation efficiency of Ak/BC–Fe3O4, emphasizing its synthesis from sustainable plant biomass as a promising solution to address water pollution challenges associated with dye contamination.

Facile one-step preparation of Co2CrO4 spinel from heterometallic compounds – Structural, magnetic, electrical and photocatalytic studies

Two isostructural heterometallic complex salts with mononuclear units, [NH(CH3)2(C2H5)][Cr(terpy)2][CoCl4]2 (1) and [NH(CH3)(C2H5)2][Cr(terpy)2][CoCl4]2 (2), were synthesized using a building block approach and characterized by single-crystal and powder X-ray diffraction (XRD), impedance spectroscopy and magnetization measurements. They exhibit particular humidity-sensing properties and very high proton conductivity at room temperature. The magnetization of complexes shows the high spin state of 3/2 for tetrahedrally coordinated CoII ions, which on cooling remain in the paramagnetic state within the CrIII network, which is antiferromagnetically correlated. The prepared compounds were thoroughly explored as single-source precursors for the formation of the spinel oxide Co2CrO4 by their thermal decomposition. By optimizing the annealing temperature, heating/cooling rates and holding times, the phase composition of thermal processing of 1 or 2 was evaluated: phase pure spinel Co2CrO4 was obtained by thermal treatment already at 450 °C. The structure, morphology, and optical properties of spinel oxides prepared at different temperatures were characterized using powder XRD, field emission scanning electron microscopy (SEM) and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), while electrical and magnetic by impedance spectroscopy and magnetization measurements. The determined band gap energy and nanosized crystallites prompted us to investigate the photocatalytic activity of spinel oxide produced at 450 °C in the degradation of dyes Rhodamine B (RhB) and Methylene blue (MB) under Vis irradiation without and with assistance of hydrogen peroxide (H2O2). The results show that the Co2CrO4/H2O2 system exhibits a significantly higher photoactivity response; the degradation efficiency of MB and RhB was found to be 86.1% and 80.3%, respectively. The electrical conductivity spectra and the activation energy for the DC conductivity demonstrate the electronically semiconducting behaviour of the Co2CrO4 oxide. The Co2CrO4 spinel has a ferrimagnetic ground state, with mixed CoII and CoIII ions on the tetrahedral and octahedral sites: CoII having a high spin state on both sites and CoIII having a high spin state on the tetrahedral site and a low spin state on the octahedral site. Different thermal treatments affect the magnetization according to the different sizes of the obtained crystallites.

Carbide lime as substrates to boost energy recuperation and dyestuff removal in constructed wetland-microbial fuel cell integrated with copper oxide/carbon cloth cathode.

Methylene blue (MB) was regarded as a highly toxic and hazardous substance owing to its irreparable hazard and deplorable damage on the ecosystem and the human body. The treatment of this colorant wastewater appeared to be one of the towering challenges in wastewater treatment. In this study, a microbial fuel cell coupled with constructed wetland (CW-MFC) with effective MB elimination and its energy recuperation concurrently based on the incorporation of carbide lime as a substrate in a new copper oxide-loaded on carbon cloth (CuO/CC) cathode system was studied. The crucial influencing parameters were also delved, and the MB degradation and chemical oxygen demand (COD) removal efficiencies were correspondingly incremented by 97.3% and 89.1% with maximum power output up to 74.1 mW m-2 at optimal conditions (0.2 g L-1 carbide lime loading and 500 Ω external resistance). The carbide lime with high calcium ion content was greatly conducive for the enrichment of critical microorganism and metabolic activities. The relative abundances of functional bacteria including Proteobacteria and Actinobacteriota were vividly increased. Moreover, the impressive results obtained in printed ink wastewater treatment with a COD removal efficiency of 81.3% and a maximum power density of 58.2 mW m-2, which showcased the potential application of CW-MFC.