“Small amount for multiple times” of H2O2 feeding way in MoS2-Fex heterogeneous fenton for enhancing sulfadiazine degradation

Size-Dependent Catalysis in Fenton-like Chemistry: From Nanoparticles to Single Atoms

State-of-the-art Fenton-like reactions are crucial in advanced oxidation processes (AOPs) for water purification. This review explores the latest advancements in heterogeneous metal-based catalysts within AOPs, covering nanoparticles (NPs), single-atom catalysts (SACs), and ultra-small atom clusters. A distinct connection between the physical properties of these catalysts, such as size, degree of unsaturation, electronic structure, and oxidation state, and their impacts on catalytic behavior and efficacy in Fenton-like reactions. In-depth comparative analysis of metal NPs and SACs is conducted focusing on how particle size variations and metal-support interactions affect oxidation species and pathways. The review highlights the cutting-edge characterization techniques and theoretical calculations, indispensable for deciphering the complex electronic and structural characteristics of active sites in downsized metal particles. Additionally, the review underscores innovative strategies for immobilizing these catalysts onto membrane surfaces, offering a solution to the inherent challenges of powdered catalysts. Recent advances in pilot-scale or engineering applications of Fenton-like-based devices are also summarized for the first time. The paper concludes by charting new research directions, emphasizing advanced catalyst design, precise identification of reactive oxygen species, and in-depth mechanistic studies. These efforts aim to enhance the application potential of nanotechnology-based AOPs in real-world wastewater treatment.

MoS2-based nanocomposites and aerogels for antibiotic pollutants removal from wastewater by photocatalytic degradation process: A review

Photocatalytic technologies based on molybdenum disulfide (MoS2) catalysts are effective, eco-friendly, and promising for antibiotic pollutants treatment. The technologies used by MoS2-based nanocomposites and aerogels for efficient degradation of antibiotics are reviewed in detail for the first time in this paper. The fundamental aspects of MoS2 were comprehensively scrutinized, encompassing crystal structure, optical properties, and photocatalytic principle. Then, the main synthesized methods and advantages/disadvantages for the preparation of MoS2-based nanocomposites and aerogels were systematically presented. Besides, a comprehensive overview of diverse MoS2-based nanocomposites and aerogels photo-degradation systems that enhanced the degradation of antibiotic pollutants were revealed. Meanwhile, the photo-degradation mechanism concentrated on the photoelectron transfer pathways and reactive oxygen species (ROS) were systematically evaluated. Finally, the challenges and perspectives for deeply development of MoS2-based nanocomposites and aerogels were discussed. This review may help researchers to deeply understand the research status of MoS2-based nanocomposites and aerogels for antibiotics removal, and makes clear the photo-degradation mechanism from photoelectron transfer pathways and ROS aspects of MoS2-based nanocomposites and aerogels.

Metal-Organic Frameworks Marry Sponge: New Opportunities for Advanced Water Treatment

Metal-organic frameworks (MOFs) have garnered attention across various fields due to their noteworthy features like high specific surface area, substantial porosity, and adjustable performance. In the realm of water treatment, MOFs exhibit great potential for eliminating pollutants such as organics, heavy metals, and oils. Nonetheless, the inherent powder characteristics of MOFs pose challenges in terms of recycling, pipeline blockage, and even secondary pollution in practical applications. Addressing these issues, the incorporation of MOFs into sponges proves to be an effective solution. Strategies like one-pot synthesis, in situ growth, and impregnation are commonly employed for loading MOFs onto sponges. This review comprehensively explores the synthesis strategies of MOFs and sponges, along with their applications in water treatment, aiming to contribute to the ongoing advancement of MOF materials.

Surface anchoring of nickel sulfide clusters as active sites and cocatalysts for photocatalytic antibiotic degradation and bacterial inactivation

Achieving photocatalytic antibiotic degradation and bacterial inactivation with high efficiency remains a challenging mission to originate a clean environment. In this work, ultra-small NiS clusters were in-situ grew on photoactive ZnIn₂S₄ nanoflower supports to form a NiS/ZnIn₂S₄ heterojunction, in which a strong and surface-limited binding was formed between the NiS clusters and ZnIn₂S₄ supports. The in-situ formed NiS clusters not only appeased interfacial charge transfer resistance of the heterojunction but also eventuated a strong built-in electric field, resulting a fast electron migration from ZnIn₂S₄ to NiS clusters functioned as cocatalyst and active sites to boost the separation efficiency of photogenerated carriers. As a result, the optimal 2NiS/ZnIn₂S₄ heterojunction expressed a higher photocatalytic Escherichia inactivation activity (99.23 % for 3 h) and a raised antibiotic degradation performance, including tetracycline (60 % for 20 min), ofloxacin (62 % for 20 min), oxytetracycline (63 % for 20 min) compared to that of pure ZnIn₂S₄ (39.14 % for Escherichia inactivation and 44 % for tetracycline degradation). This work furnishes a great promise to develop inorganic clusters coupled photocatalysts for light-driven environmental application.

FeMo@porous carbon derived from MIL-53(Fe)@MoO3 as excellent heterogeneous electro-Fenton catalyst: Co-catalysis of Mo

An ultra-efficient electro-Fenton catalyst with porous carbon coated Fe-Mo metal (FeMo@PC), was prepared by calcining MIL-53(Fe)@MoO₃. This FeMo@PC-2 exhibited impressive catalytic performance for sulfamethazine (SMT) degradation with a high turnover frequency value (7.89 L/(g·min)), much better than most of reported catalysts. The mineralization current efficiency and electric energy consumption were 83.2% and 0.03 kWh/g_TOC, respectively, at low current (5 mA) and small dosage of catalyst (25.0 mg/L). The removal rate of heterogeneous electro-Fenton (Hetero-EF) process catalyzed by FeMo@PC-2 was 4.58 times that of Fe@PC/Hetero-EF process. Because the internal-micro-electrolysis occurred between PC and Fe⁰, while the co-catalysis of Mo accelerated the rate-limiting step of the Fe³⁺/Fe²⁺ cycle and greatly improved the H₂O₂ utilization efficiency. The results of radical scavenger experiments and electron paramagnetic resonance confirmed the main role of surface-bound hydroxyl radical oxidation. This process was feasible to remove diverse organic contaminants such as phenol, 2,4-dichlorophenoxyacetic acid, carbamazepine and SMT. This paper enlightened the importance of the doped Mo, which could greatly improve the activity of the iron-carbon heterogeneous catalyst derived from metal-organic frameworks in EF process for efficient removal of organic contaminants.

Switching of radical and nonradical pathways through the surface defects of Fe3O4/MoOxSy in a Fenton-like reaction

Coexistence of radical and nonradical reaction pathways during advanced oxidation processes (AOPs) makes it challenging to obtain flexible regulation of high efficiency and selectivity for the requirement of diverse degradation. Herein, a series of Fe₃O₄/MoO_xS_y samples coupling peroxymonosulfate (PMS) systems enabled the switching of radical and nonradical pathways through the inclusion of defects and adjustment of Mo⁴⁺/Mo⁶⁺ ratios. The silicon cladding operation introduced defects by disrupting the original lattice of Fe₃O₄ and MoO_xS. Meanwhile, the abundance of defective electrons increased the amount of Mo⁴⁺ on the catalyst surface, promoting PMS decomposition with a maximum k value up to 1.530 min^-1 and a maximum free radical contribution of 81.33%. The Mo⁴⁺/Mo⁶⁺ ratio in the catalyst was similarly altered by different Fe contents, and Mo⁶⁺ contributed to the production of ¹O₂, allowing the whole system to attain a nonradical species-dominated (68.26%) pathway. The radical species-dominated system has a high chemical oxygen demand (COD) removal rate for actual wastewater treatment. Conversely, the nonradical species-dominated system can considerably improve the biodegradability of wastewater (biochemical oxygen demand (BOD)/COD = 0.997). The tunable hybrid reaction pathways will expand the targeted applications of AOPs.

Recent Progress of Metal Sulfide Photocatalysts for Solar Energy Conversion

Artificial photosynthetic solar-to-chemical cycles enable an entire environment to operate in a more complex, yet effective, way to perform natural photosynthesis. However, such artificial systems suffer from a lack of well-established photocatalysts with the ability to harvest the solar spectrum and rich catalytic active-site density. Benefiting from extensive experimental and theoretical investigations, this bottleneck may be overcome by devising a photocatalytic platform based on metal sulfides with predominant electronic, physical, and chemical properties. These tunable properties can endow them with abundant active sites, favorable light utilization, and expedited charge transportation for solar-to-chemical conversion. Here, it is described how some vital lessons extracted from previous investigations are employed to promote the further development of metal sulfides for artificial photosynthesis, including water splitting, CO₂ reduction, N₂ reduction, and pollutant removal. Their functions, properties, synthetic strategies, emerging issues, design principles, and intrinsic functional mechanisms for photocatalytic redox reactions are discussed in detail. Finally, the associated challenges and prospects for the utilization of metal sulfides are highlighted and future development trends in photocatalysis are envisioned.

High-efficient peroxymonosulfate activation for rapid atrazine degradation by FeSx@MoS2 derived from MIL-88A(Fe)

FeS_x@MoS₂-x (FM-x, x implied real Mo/Fe content ratios) in which FeS_x derived from MIL-88A deposited on the surface of MoS₂ with a tight heterogeneous interface were synthesized for peroxymonosulfate (PMS) activation to degrade atrazine (ATZ). The catalytic performance of FM-0.96 was greatly improved due to the rapid regeneration of Fe²⁺ resulting from the interfacial interaction. FM-0.96 could completely degrade 10.0 mg/L ATZ within 1.0 min, and the toxicities for most of its intermediates were greatly reduced. The k value of FM-0.96 was 320 and 40 times higher than that of the MoS₂ and FeS_x, respectively. The SO₄·^-, ·OH and ¹O₂ were mainly responsible for ATZ degradation in FM-0.96/PMS system, and the conversion pathway of ¹O₂ was analyzed. Furthermore, the long-term continuous operation for ATZ degradation was achieved using a fixed membrane reactor. This work provides deep insights into metal sulfide composites derived from metal-organic frameworks for removing pollutants by activating PMS.

Efficient removal of neonicotinoid by singlet oxygen dominated MoSx/ceramic membrane-integrated Fenton-like process

Removal of neonicotinoids (NEOs) from contaminated water is of great importance for both ecological environment and human health. However, conventional Fenton process might be insufficient for NEOs removal due to short lifetime for generated HO^• and limited Fe³⁺/Fe²⁺ redox cycle. Advancing Fenton process to produce singlet oxygen can be an effective route to improve its efficacy for NEOs removal. Herein, we developed a molybdenum sulfide modified ceramic membrane-integrated Fenton-like system to achieve efficient catalytic removal of NEOs. The reduced Mo⁰ and Mo⁴⁺ could promote the reduction process of Fe³⁺ to Fe²⁺, improving the activation efficiency of hydrogen peroxide (H₂O₂) and the generation of superoxide radical (O₂^•-). Consequently, the coexisting Mo⁶⁺ reacted with O₂^•- to generate ¹O₂. The membrane enabled the pollutants to adequately contact oxidants due to the enhanced convective mass transfer. The functionalized membrane exhibited stable catalytic performance for clothianidin (CLO, a kind of NEOs, 10 mg/L) removal (degradation efficiency > 85%). The presence of ¹O₂ enabled the dechlorination and hydroxylation of CLO and thus reduced the toxicity of wastewater. Our work sheds light on the use of functionalized ceramic membrane integrated catalytic Fenton system for effective environmental remediation.