Visible light-driven photocatalytic rapid degradation of organic contaminants engaging manganese dioxide-incorporated iron oxide three dimensional nanoflowers

Ultrahigh Dispersion of Fe3O4 NPs on Cellulose Nanofibers: Unlocking Superior Visible-Light Photocatalysis

Constructing cost-effective and efficient photocatalysts is crucial for removing harmful contaminants from water sources, ensuring a greener and healthier environment. In this study, highly dispersed magnetic iron oxide (Fe3O4) nanoparticles (NPs) were successfully decorated on cellulose nanofibers (CNFs) by using a simple interfacial strategy. Four hybrid materials (Fe3O4-CNF1, Fe3O4-CNF2, Fe3O4-CNF3, and Fe3O4-CNF4) were systematically synthesized, with Fe3O4-CNF4 identified as the most efficient photocatalyst. The optimized Fe3O4-CNF4 hybrid exhibited a high surface area (54.12 m2/g), enhanced light utilization, and improved charge separation, leading to superior photocatalytic performance. It achieved a 95% removal rate of Rhodamine B (RhB) in 120 min and 99% removal rate of Methylene Blue (MB) in 150 min when exposed to visible irradiation. Moreover, Fe3O4-CNF4 demonstrated excellent recyclability, maintaining high efficiency over five reuse cycles with only ∼7% activity loss. Stability tests under varying catalyst concentrations and pH conditions further confirmed its robustness. Additionally, the primary active species, potential degradation pathways of MB, and the underlying reaction mechanism were systematically analyzed. These findings highlight Fe3O4-CNF4 as a promising visible-light-responsive and reusable photocatalyst for wastewater treatment.

An environmentally friendly chitosan-loaded BiOCOOH/BiYO3 photocatalyst for efficient photocatalytic degradation of tetracycline

In this work, the photocatalyst BiOCOOH/BiYO3/Chitosan (CS) was prepared by using CS as the carrier and adsorbent. The performance of the material was studied through the photocatalytic degradation of tetracycline (TC) in water. Theoretical calculations and experiments demonstrate that the formation of BiOCOOH/BiYO3 heterojunctions improves the separation of photogenerated carriers and the absorption of visible light by the material. The introduction of CS improves the difficulties in material recovery, demonstrating exceptional degradation ability for TC under the action of adsorption and photocatalysis. Adsorption kinetics studies indicate that the adsorption of TC by BiOCOOH/BiYO3/CS fits the pseudo-second-order model better, while the adsorption at different concentrations of TC is more suitably described by the Freundlich isotherm model. The synthesis of BiOCOOH/BiYO3/CS was confirmed by the analysis of XRD, XPS, and FTIR. UV-vis DRS showed that the synthesis of BiOCOOH/BiYO3/CS broadened the range of light absorbed by the material. The testing results of PL and transient photocurrent density indicate that BiOCOOH/BiYO3 exhibits a higher efficiency in separating photogenerated charge carriers. After 5 cycles of reuse, the degradation efficiency can still reach 90 % of the initial efficiency, indicating that CS-based photocatalytic composite catalysts have practical application potential in the field of water pollution treatment.

In Situ Preparation of MnO2 on the Catechol/Silane-Coated Polypropylene Nonwoven Fabrics for Effective Removal of Cationic Dyes

Previous studies have confirmed that MnOx removes heavy metal ions and organic pollutants from water with dual effects of adsorption and oxidation coupling, significantly improving the ability to remove impurities. Nanometal oxides have a highly reactive surface but tend to agglomerate during preparation and are challenging to recycle after use. A common method is to combine nano-MnO2 with Fe3O4 to prepare magnetic materials for easy recycling. Our previous research has confirmed that catechol (CA) and (3-aminopropyl) triethoxysilane (KH550) can be co-deposited on the surface of polypropylene nonwovens to form a stable CK coating under alkaline conditions. In addition, the coating has many active groups, including hydroxyl groups, amino groups, etc. This study further investigates the secondary reactivity of CK coatings. The coordination of catechol groups and metal ions was used to anchor manganese ions to the coating. Meanwhile, the hydroxyl and amino groups were used to reduce manganese ions to Mn4+ in situ to prepare PP-(CK-MnO2). We found that the sample had an excellent decolorization effect on cationic dyes but was limited to anionic dyes. The decolorization mechanism of cationic dyes was further discussed. The results showed that the decolorization of cationic dyes had a dual effect of adsorption and oxidative degradation. Under acidic conditions, its oxidation properties were enhanced. It can be used as a highly effective decolorizing agent for cationic dyes, and the decolorization behavior is consistent with the first-order kinetics. As the pH increases, its oxidation properties gradually decrease. Although the electrostatic adsorption effect was enhanced, the overall decolorization performance was significantly reduced. Recycling experiments have proved that it can maintain >90% removal rate after five cycles. This study also demonstrated that the CK coating has dopamine-like properties, which can coordinate with metal ions to prepare metal-organic hybrid materials.

Photocatalytic PAN Nanofibrous Membrane through Anchoring a Nanoflower-Branched CoAl-LDH@PANI Heterojunction for Organic Hazards Degradation and Oil-Containing Emulsified Wastewater Separation

The synergistic treatment of oily wastewater containing organic hazards and emulsified oils remains a big challenge for membrane separation technology. Herein, the photocatalytic membrane, which combined the physical barrier and catalytic oxidation-driven degradation functionality, was fabricated via anchoring a nanoflower-branched CoAl-LDH@PANI Z-scheme heterojunction onto a porous polyacrylonitrile mat and using tannic acid as an adhesive. The assembly of such a Z-scheme heterojunction offered the superior photocatalytic degradation performance of soluble dyes and tetracycline (up to 94.3%) to the membrane with the improved photocatalytic activity of 2.33 times compared with the CoAl-LDH@pPAN membrane. Quenching experiments suggested that the •O2- was the most reactive oxygen species in the catalytic reaction system of the composite membrane. The greatly enhanced photocatalytic activity was attributed to the effective inhibition of photogenerated hole-electron combination using PANI as a carrier, with charge transferring from LDH to PANI. The possible photocatalytic degradation mechanism was proposed based on VB-XPS, electron spin resonance spectroscopy, and DRS technologies, which was confirmed by density functional theory calculation. Meanwhile, benefiting from the superhydrophilic/oleophobic feature and low oil adhesion, the membrane exhibited high permeability for isooctane emulsion (3990.39 L·m-2·h-1), high structure stability, and satisfactory cycling performance. This work provided a strategy to develop superwetting and photocatalytic composite membranes for treating complex multicomponent pollutants in the chemical industry.

In situ Mo-doped ZnIn2S4/Ni-Ni Hofmann-type coordination polymer composites for photocatalytic hydrogen evolution reaction

Solar energy-assisted hydrogen production technology is an essential tool for exploring hydrogen energy. To date, semiconductors have been used as the primary photocatalyst to generate hydrogen via photocatalytic water splitting. However, the high photogenerated electron-hole recombination rate of semiconductor photocatalysts results in a low hydrogen production rate. Herein, the synergistic effect of Mo-ion doping and the incorporation of Ni-based Hofmann-type coordination polymer (Ni-Ni HCP) on the photocatalytic performance of ZnIn2S4 (ZIS) is investigated. The hydrogen production rate of the prepared in-situ Mo doped ZnIn2S4 wrapped Ni-Ni HCP (Ni-Ni HCP/Mo-ZIS) sample under visible-light irradiation is 26.7 mmol g-1h-1, which is 10 times that of pure ZIS. Hydrogen production rate test, microscopic characterization, and density functional theory calculation confirm that the proposed dual modulation approach (combined ion doping and heterogeneous structure construction) could effectively increase the photocatalytic efficiency of ZIS. The stability of prepared samples is also examined by four-cycle photocatalytic hydrogen production tests. The proposed integrated method opens a new route for advancing renewable energy technology towards a sustainable future.

Advancing sustainable water treatment strategies: harnessing magnetite-based photocatalysts and techno-economic analysis for enhanced wastewater management in the context of SDGs

Herein, we explore the holistic integration of magnetite-based photocatalysts and techno-economic analysis (TEA) as a sustainable approach in wastewater treatment aligned with the Sustainable Development Goals (SDGs). While considerable attention has been devoted to photocatalytic dye degradation, the nexus between these processes and techno-economic considerations remains relatively unexplored. The review comprehensively examines the fundamental characteristics of magnetite-based photocatalysts, encompassing synthesis methods, composition, and unique properties. It investigates their efficacy in photocatalytic degradation, addressing homogeneous and heterogeneous aspects while discussing strategies to optimize photodegradation efficiency, including curbing electron-hole recombination and mitigating scavenging effects and interference by ions and humic acid. Moreover, the management aspects of magnetite-based photocatalysts are examined, focusing on their reusability and regeneration post-dye removal, along with the potential for reusing treated wastewater in relevant industrial applications. From a techno-economic perspective, the study evaluates the financial feasibility of deploying magnetite-based photocatalysts in wastewater treatment, correlating reduced pollution and the marketing of treated water with social, economic, and environmental objectives. By advocating the integration of magnetite-based photocatalysts and TEA, this paper contributes insights into scalable and profitable sustainable wastewater treatment practices. It underscores the alignment of these practices with SDGs, emphasizing a comprehensive and holistic approach to managing wastewater in ways that meet environmental, economic, and societal objectives.

Fabrication of Ru loaded MgB2 with guar gum hybrid for photocatalytic degradation of crystal violet

Today, dyes/pigment-based materials are confronting a serious issue in harming marine ecology. Annihilate these serious water pollutants using photoactive 2D nanohybrid catalysts showed promising comparativeness over available photocatalysts. In the present work, a facile route to decorate Ruthenium (Ru) on 2D MgB2 flower-like nanostructures was developed via ecofriendly guar gum biopolymer substantial template (MgB2/GG@Ru NFS) and its photocatalytic performance was reported. Synthesis of MgB2@Ru, MgB2/GG@Ru NFS and commercial MgB2, was studied by FTIR, XRD, FE-SEM, EDX, AFM, TEM, UV-vis spectra, and XPS analysis. From the results, the MgB2/GG@Ru NFS exhibited a superior photocatalytic performance (99.7 %) than its precursors MgB2@Ru (79.7 %), and MgB2 (53.7 %), with the degradation efficiency of the crystal violet (CV) within 100 min under visible light irradiation. The proposed photo-catalyst MgB2/GG@Ru NFS showed negligible loss of photocatalytic activity even after five successive cycles, revealing its reusability and enhanced stability due to the network structure. The photocatalytic mechanism for MgB2/GG@Ru NFS was evaluated by trapping experiment of active species, verifying that superoxide (O2-) and electron (e-) contributed significant role in the dye degradation.

New Insights on Designing the Next-Generation Materials for Electrochemical Synthesis of Reactive Oxidative Species Towards Efficient and Scalable Water Treatment: A Review and Perspectives

Electrochemical water remediation technologies offer several advantages and flexibility for water treatment and degradation of contaminants. These technologies generate reactive oxidative species (ROS) that degrade pollutants. For the implementation of these technologies at an industrial scale, efficient, scalable, and cost-effective in-situ ROS synthesis is necessary to degrade complex pollutant mixtures, treat large amount of contaminated water, and clean water in a reasonable amount of time and cost. These targets are directly dependent on the materials used to generate the ROS, such as electrodes and catalysts. Here, we review the key design aspects of electrocatalytic materials for efficient in-situ ROS generation. We present a mechanistic understanding of ROS generation, including their reaction pathways, and integrate this with the key design considerations of the materials and the overall electrochemical reactor/cell. This involves tunning the interfacial interactions between the electrolyte and electrode which can enhance the ROS generation rate up to ~ 40% as discussed in this review. We also summarized the current and emerging materials for water remediation cells and created a structured dataset of about 500 electrodes and 130 catalysts used for ROS generation and water treatment. A perspective on accelerating the discovery and designing of the next generation electrocatalytic materials is discussed through the application of integrated experimental and computational workflows. Overall, this article provides a comprehensive review and perspectives on designing and discovering materials for ROS synthesis, which are critical not only for successful implementation of electrochemical water remediation technologies but also for other electrochemical applications.

A review on degradation of organic dyes by using metal oxide semiconductors

The discharge of organic dye pollutants in natural water bodies has put forward a big challenge of providing clean water to a large part of the population. As the population is increasing with time, only underground water is not sufficient to complete the water requirements of everyone everywhere. Purification of wastewater and its reuse is the only way to fulfill the water needs. Nanotechnology has been used very efficiently for wastewater treatment via photocatalytic degradation of dye molecules. In the past few years, a lot of investigations have been done to enhance the photocatalytic activity of metal oxide semiconductors for water purification. In this review, we have discussed the different methods of synthesis of various metal oxide semiconductor nanoparticles, energy band gap, their role as efficient photocatalysts, radiations used for photocatalytic reactions, and their degradation efficiency to degrade the dye pollutants. We have also discussed the nanocomposites of metal oxide with graphene. These nanocomposites have been utilized as the efficient photocatalyst due to unique characteristics of graphene such as extended range of light absorption, separation of charges, and high capacity of adsorption of the dye pollutants.

Hierarchical 3D Flower-like Metal Oxides Micro/Nanostructures: Fabrication, Surface Modification, Their Crucial Role in Environmental Decontamination, Mechanistic Insights, and Future Perspectives

Hierarchical micro/nanostructures are constructed by micro-scaled objects with nanoarchitectures belonging to an interesting class of crystalline materials that has significant applications in diverse fields. Featured with a large surface-to-volume ratio, facile mass transportation, high stability against aggregation, structurally enhanced adsorption, and catalytical performances, three dimenisional (3D) hierarchical metal oxides have been considered as versatile functional materials for waste-water treatment. Due to the ineffectiveness of traditional water purification protocols for reclamation of water, lately, the use of hierarchical metal oxides has emerged as an appealing platform for the remediation of water pollution owing to their fascinating and tailorable physiochemical properties. The present review highlights various approaches to the tunable synthesis of hierarchical structures along with their surface modification strategies to enhance their efficiencies for the removal of different noxious substances. Besides, their applications for the eradication of organic and inorganic contaminants have been discussed comprehensively with their plausible mechanistic pathways. Finally, overlooked aspects in this field as well as the major roadblocks to the implementation of these metal oxide architectures for large-scale treatment of wastewater are provided here. Moreover, the potential ways to tackle these issues are also presented which may be useful for the transformation of current water treatment technologies.

Mechanochemically interlocked cubane copper complex interface for WOLED

In the rapid development of organic light-emitting diodes (OLEDs), phosphorescent transition metal complexes have played a crucial role as the most promising candidates for next generation display and lighting applications. However, most devices are fabricated using iridium and platinum-based complexes which are expensive and available in very limited quantities, whereas using relatively abundant organometallic complexes for fabrication results mostly in inefficient performance results. To overcome these issues, we have synthesized tetra copper iodide with tetra triphenyl cage like structure (denoted as CIPh) as an emerging class of luminescent material by mechanochemical grinding followed by thermal treatment for application in white OLED. The CIPh complex exhibits considerable quantum yield and a millisecond decay lifetime. Phosphorescent OLEDs were fabricated using CIPh complex as emitter shows a remarkable performance with external quantum efficiency and current efficiency of 5.28 % and 22.76 cd/A, with a high brightness of 4200 cd m^-2, respectively. White OLEDs were also fabricated with a fluorescent blue and phosphorescent red emitted with (CIPh) as green emitter and achieved an impressive CRI of 82 with an EQE of over 3 %. This is the first ever attempt at fabricating WOLEDs using organocopper complex.

Adsorptive removal of some Cl-VOC's as dangerous environmental pollutants using feather-like γ-Al2O3 derived from aluminium waste with life cycle analysis

Herein, we designed a cost-effective preparation method of nanocomposite γ-Al₂O₃ derived from Al-waste. The produced material has a feather-like morphology, and its adsorption of some chlorinated volatile organic compounds (Cl-VOC's) such as benzyl chloride, chloroform and carbon tetrachloride (C₇H₇Cl, CHCl₃ and CCl₄) was investigated due to their potential carcinogenic effect on humans. It showed a characteristic efficiency towards the adsorptive removal of these compounds over a long period, i.e., eight continuous weeks, at ambient temperature and atmospheric pressure. After 8-weeks, the adsorbed amounts of these compounds were determined as: 325.3 mg C₇H₇Cl, 247.6 mg CHCl₃ and 253.3 mg CCl₄ per g of γ-Al₂O_3, respectively. CCl₄ was also found to be dissociatively adsorbed on the surface of γ-Al₂O₃, whereas CHCl₃ and C₇H₇Cl were found to be associatively adsorbed. The prepared γ-Al₂O₃ has a relatively high surface area (i.e., 192.2 m². g^-1) and mesoporosity with different pore diameters in the range of 25-47 Å. Furthermore, environmental impacts of the nanocomposite γ-Al₂O₃ preparation were evaluated using life cycle assessment. For prepartion of adsorbent utilising 1 kg of scrap aluminium wire, it was observed that potential energy demand was 288 MJ, climate change potential was 19 kg CO₂ equivalent, acidification potential was 0.115 kg SO₂ equivalent and eutrophication potential was 0.018 kg PO₄^3- equivalent.

Fabrication of Fe3O4-incorporated MnO2 nanoflowers as electrodes for enhanced asymmetric supercapacitor performance

Manganese dioxide (MnO2) is considered a promising aspirant for energy storage materials on account of its higher theoretical capacitance along with low capital cost.