Selective Separation Catalysis Membrane for Highly Efficient Water and Soil Decontamination via a Persulfate-Based Advanced Oxidation Process

Self-Cleaning Antifouling Membrane Engineered by Oxygen-Activated MOF-Derived Catalysts for Efficient Organic Wastewater Treatment

Utilizing membrane separation technology has displayed promising application potential for removing synthetic dyes; however, membrane performance tends to decline over time due to fouling caused by feed solution contaminants, leading to decreased separation efficiency and shortened membrane lifespan. Therefore, improving the antifouling properties of membranes is critical to ensure the long-term efficiency of water treatment systems. In this work, a high-performance catalyst, CuZn@ZC, with remarkable oxygen activation activity, was successfully prepared and subsequently integrated onto the membrane surface via simple pumping filtration, resulting in self-cleaning membranes with superior antifouling capabilities. The results indicated that zero-valence copper containing CuZn@ZC can rapidly and efficiently remove a wide range of dyes under mild natural conditions, accompanied by strong 1O2 and •O2- signals detected in electron paramagnetic resonance spectra. When applied to membrane surfaces, the modified membrane exhibited excellent antifouling and filtration properties, which showed high flux recovery ratios and a superior rejection rate for cationic dyes, attributed to the participation of ROS generated by the activation of natural dissolved oxygen. Moreover, the membrane still retained its structural stability and environmental compatibility during prolonged operation, which is beneficial for advancing the development of sustainable membrane filtration technologies.

Z-scheme heterojunction BiOBr/MIL-100(Fe) visible photocatalytic-permonosulfate degradation of AO7

Metal-organic frameworks (MOFs) have garnered significant interest in the field of photocatalysis. In this study, Z-scheme heterojunction BM-x composites consisting of bismuth bromide oxide (BiOBr) and iron-based metal-organic backbone (MIL-100(Fe)) were successfully synthesized using ethylene glycol as a solvent. The composites were characterized using various techniques. BM-x exhibit abundant functional groups, large specific surface areas, and narrow band gap energy, thus provide numerous active sites for catalytic reactions and respond well to visible light. Notably, BM-7 displays remarkable catalytic activity in a visible light-activated permonosulfate (PMS) system and achieves a degradation rate of 99.02% over 100 mg/L gold orange II (AO7) within 60 min. The effects of BM-7 and PMS addition, initial AO7 concentration, initial pH, inorganic anions, and humic acid on the degradation system were investigated. The proposed mechanism of the Z-scheme heterojunction in the BM-7 photocatalyst demonstrates effective photoelectron transfer from the BiOBr conduction band to the MIL-100(Fe) valence band, resulting in excellent catalytic activity. Radical burst experiments identified 1O2, h+, and ·O2- as the main active substances. BM-7 has high stability and reusability, with a degradation rate reduction of only 14.48% after three recycles. These findings provide valuable insights into using persulfate combined with visible light.

Probe into a novel surfactant-free microemulsion system of ethylene glycol monobutyl ether + water + diesel for crude oil removal and recovery from oily sludge

A novel surfactant-free microemulsion (SFME) system was proposed in this study, and applied in the crude oil removal and recovery from oily sludge (OS). Based on an investigation of the SFME phase behavior and solution properties, a complete ternary phase diagram was constructed. The SFME with three-liquid phase equilibrium (Winsor III type) was selected for the treatment of OS to achieve simultaneous efficient removal (up to 95.1 %) and recovery (up to 83.2 %) of crude oil. The SFME could be reused continuously for OS treatment without purification. The removal efficiency could still keep >75.9 % after 5 times of reuse, showing high reusability. The detached crude oil could be automatically recovered based on the phase equilibrium principle without additional separation. In the washing experiments, single-factor and multi-factor orthogonal tests were applied to investigate the effects of different experimental conditions on oil removal efficiency and determine the optimal experimental scheme. The treated OS was sufficiently decontaminated according to the morphology, composition, and properties analysis by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and contact angle. The composition of the recovered crude oil was identical to that of commercial crude oil according to gas chromatography-mass spectrometry analysis, showing a high recovery value. The kinetic analysis revealed that crude oil desorption experienced three main stages: membrane diffusion, intra-particle diffusion and surface desorption, and identified the chemisorption was the main interaction between the oil-soil. Finally, the mechanism of SFME action was assessed for dissolution and activation based on ultra-low IFT.

Conjugated Microporous Polymers-Based Catalytic Membranes with Hierarchical Channels for High-Throughput Removal of Micropollutants

Engineering a catalytic membrane capable of efficiently removing emerging organic microcontaminants under ultrahigh flux conditions is of significance for water purification. Herein, drawing inspiration from the functional attributes of lymphatic vessels involved in immunosurveillance and fluid transport with minimal energy consumption, a novel hierarchical porous catalytic membrane is engineered. This membrane, based on an innovative nitrogen-rich conjugated microporous polymer (polytripheneamine, PTPA), is synthesized using an electrospinning coupled in situ polymerization approach. The resulting bioinspired membrane with hierarchical channels comprises a thin layer (≈1.7 µm) of crosslinked PTPA nanoparticles covering the interconnected electrospun nanofibers. This unique design creates an intrinsic microporous angstrom-confined system capable of activating peroxymonosulfate (PMS) to generate 98.7% singlet oxygen (1O2), enabling durable and highly efficient degradation of microcontaminants. Additionally, the presence of a thin layer of mesoporous structure between PTPA nanoparticles and macroporous channels within the interwoven nanofibers enhances mass transfer efficiency and facilitates high flux rates. Notably, the prepared hierarchical porous organic catalytic membrane demonstrates enduring high-efficiency degradation performance with a superior permeance (>95% and >2500 L m-2 h-1 bar-1) sustained over 100 h. This work introduces an innovative pathway for the design of high-performance catalytic membranes for the removal of emerging organic microcontaminants.

Single-atom catalysts activate persulfate to degrade emerging organic contaminants in aqueous environments

Single-atom catalysts (SACs) exhibit outstanding catalytic activity due to their highly dispersed metal centers. Activating persulfates (PS) with SACs can generate various reactive oxygen species (ROS) to efficiently degrade emerging organic contaminants (EOCs) in aqueous environments, offering unique advantages such as high reaction rates and excellent stability. This technique has been extensively researched and holds enormous potential applications. In this paper, we comprehensively elaborated on the synthesis methods of SACs and their limitations, and factors influencing the catalytic performance of SACs, including metal center characteristics, coordination environment, and types of substrates. We also analyzed practical considerations for application. Subsequently, we discussed the mechanism of SACs activating PS for EOCs degradation, encompassing adsorption processes, radical pathways, and non-radical pathways. Finally, we provide prospects and outline our vision for future research, aiming to guide advancements in applying this technique.

Membrane-catalysis integrated system for contaminants degradation and membrane fouling mitigation: A review

The integration of catalytic degradation and membrane separation processes not only enables continuous degradation of contaminants but also effectively alleviates inevitable membrane fouling, demonstrating fascinating practical value for efficient water purification. Such membrane-catalysis integrated system (MCIS) has attracted tremendous research interest from scientists in chemical engineering and environmental science recently. In this review, the advantages of MCIS are discussed, including the membrane structure regulation, stable catalyst loading, nano-confinement effect, and efficient natural organic matter (NOM) exclusion, highlighting the synergistic effect between membrane separation and catalytic process. Subsequently, the design considerations for the fabrication of catalytic membranes, including substrate membrane, catalytic material, and fabrication method, are comprehensively summarized. Afterward, the mechanisms and performance of MCIS based on different catalytic types, including liquid-phase oxidants/reductants involved MCIS, gas involved MCIS, photocatalysis involved MCIS, and electrocatalysis involved MCIS are reviewed in detail. Finally, the research direction and future perspectives of catalytic membranes for water purification are proposed. The current review provides an in-depth understanding of the design of catalytic membranes and facilitates their further development for practical applications in efficient water purification.

Internal Electric Field-Modulated Charge Migration Behavior in MoS2 /MIL-53(Fe) S-Scheme Heterojunction for Boosting Visible-Light-Driven Photocatalytic Chlorinated Antibiotics Degradation

Inadequate photo-generated charge separation, migration, and utilization efficiency limit the photocatalytic efficiency. Herein, a MoS2 /MIL-53(Fe) photocatalyst/activator with the S-scheme heterojunction structure is designed and the charge migration behavior is modulated by the internal electric field (IEF). The IEF intensity is enhanced to 40 mV by modulating band bending potential and the depletion layer length of MoS2 . The photo-generated electron migration process is boosted by constructing the electron migration bridge (Fe-O-S) and modulating the IEF as the driving force, confirmed by the density functional theory calculation. Compared with the pristine materials, the photocurrent density of MoS2 /MIL-53(Fe) is significantly enhanced 27.5 times. Contributed by the visible-light-driven cooperative catalytic degradation and the high-efficiency direct photo-generated electron reduction dichlorination process, satisfactory chlorinated antibiotics removal and detoxification performances are achieved. This study opens up new insights into the application of heterojunctions in photocatalytic activation of PDS in environmental remediation.

Activation of peroxymonosulfate by Fe-Mn-modified MWCNTs for selective decontamination: Formation of high-valent metal-oxo species and superoxide anion radicals

The extensive presence of organic micropollutants in complex water matrices requires the development of selective oxidation technologies. In this study, a novel selective oxidation process was developed via the conjunction of FeMn/CNTs with peroxymonosulfate and successfully used to remove micropollutants such as sulfamethoxazole (SMX) and bisphenol A from aqueous solutions. FeMn/CNTs were prepared using a facile co-precipitation method, characterized using a series of surface characterization techniques, and then tested for pollutant removal. The results showed that the FeMn/CNTs had much greater reactivity than CNTs, manganese oxide, and iron oxide. The pseudo-first-order rate constant with FeMn/CNTs was more than 2.9-5.7 times that of the other tested materials. The FeMn/CNTs had great reactivity in a wide range of pH values from 3.0 to 9.0, with the best reactivity found at pH values of 5.0 and 7.0. High-valent metal-oxo species such as Fe(IV)O and Mn(IV)O and superoxide anion radicals were determined to be the reactive species and were responsible for the oxidation of SMX. These reactive species were selective; therefore, the overall removal performance of SMX was not obviously influenced by high levels of water components including chloride ions, bicarbonates, and natural organic matters. The results from this study may promote the design and application of selective oxidation technologies for micropollutant abatement.

Removal of organophosphorus flame retardant by biochar-coated nZVI activating persulfate: Synergistic mechanism of adsorption and catalytic degradation

Triphenyl phosphate (TPhP) is a typical aromatic-based non-chlorinated organophosphorus flame retardant, which has been widely detected in a variety of environments and poses high environmental and human health risks. In this study, biochar coated nano-zero-valent iron (nZVI) was fabricated to activate persulfate (PS) to degrade TPhP from water. A range of biochars (BC400, BC500, BC600, BC700, and BC800) was prepared as potential support to coat nZVI by pyrolyzing corn stalk at 400, 500, 600, 700 and 800 °C. As outperformed other biochars in adsorption rate, adsorption capacity, and less reluctant to be influenced by environmental factors (pH, humic acid (HA), coexistence of anions), BC800 was to act as support to coat nZVI (labeled as BC800@nZVI). SEM, TEM, XRD and XPS characterization showed that nZVI was successfully supported on the BC800. Removal efficiency of 10 mg L-1 TPhP by BC800@nZVI/PS could reach to 96.9% with a high catalytic degradation kinetic rate of 0.0484 min^-1 under optimal condition. The removal efficiency remained stable in a wide pH range (3-9) and moderate concentration of HA and coexistence of anions, demonstrated the promising of using BC800@nZVI/PS system to eliminate TPhP contamination. Results from the radical scavenging and electron paramagnetic resonance (EPR) experiments demonstrated radical pathway (i.e. SO₄·^- and HO·) and non-radical pathway via ¹O₂ both play important role in TPhP degradation. The TPhP degradation pathway was proposed based on the six degradation intermediates analyzed by LC-MS. This study illustrated the synergistic mechanism of adsorption and catalytic oxidation removal of TPhP by BC800@nZVI/PS system, and provided a cost-efficient approach for TPhP remediation.

Magnetic confinement-enabled membrane reactor for enhanced removal of wide-spectrum contaminants in water: Proof of concept, synergistic decontamination mechanisms, and sustained treatment performance

Membrane chemical reactors (MCRs) have demonstrated a great potential for simultaneous removal of wide-spectrum pollutants in advanced water treatment. However, current catalyst (re)loading and catalytic reactivity limitations obstruct their practical applications. Herein, as a proof-of-concept, we report a hollow fiber membrane chemical reactor (HF-MCR) with high and sustainable catalytic reactivity, enabled by novel magnetic confinement engineering of the catalysts. Namely, the zerovalent iron (ZVI) nanocatalysts were spatially dispersed and confined to nearly parallel magnetic induction lines, forming forest-like microwire arrays in the membrane lumen. Such arrays exhibited ultrahigh hydrodynamic stability. The HF-MCR integrated sequential membrane separation and Fenton-like catalysis, thus being capable of high and synergistic wide-spectrum decontamination. The membrane separation process completely removed large nanoplastics (NPs) via size exclusion, and thus the subsequent Fenton-like catalysis process enhanced removal efficiency of otherwise permeated bisphenol A (BPA) and phosphate (P) by in situ generated reactive oxygen species (primarily ¹O₂) and iron (oxyhydr)oxides, respectively. Furthermore, highly dispersed ZVI arrays and their continuous surface depassivation driven by magnetic gradient and hydrodynamic forces conferred abundant accessible catalytic sites (i.e., Fe⁰ and Fe^II) to stimulate Fenton-like catalysis. The consequent enhancement of BPA and P removal kinetics was 3-765 and 49-492 folds those in conventional (flow-through or batch) systems, respectively. Periodic ZVI reloading ensured sustained decontamination performance of the HF-MCR. This is the first demonstration of the magnetic confinement engineering that enables efficient and unlimited catalyst (re)loading and sustainable catalytic reactivity in the MCR for water treatment, which is beyond the reach of current approaches.