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Ferrate (VI) is a unique and “green” chemical that can be utilized for oxidation, disinfection and coagulation simultaneously in a single unit without producing by-product. Herein, for the first time, we reported the integrated process of ferrate (VI) pretreatment coupled with ceramic membrane reactor for mitigating membrane fouling in natural reclaimed water treatment. Membrane fouling was effectively mitigated by ferrate pretreatment with the maximum trans-membrane pressure (TMP) reduction of 81.8% achieved at ferrate dosage of 0.15 mM. Moreover, the fouling mechanism changed from intermediate-standard blocking to cake-intermediate blocking with ferrate pretreatment and the contribution of cake layer fouling was significantly diminished with increase of ferrate dosage (≤ 0.15 mM). Statistical analysis including redundancy analysis and clustering correlation analysis showed that chemical oxygen demand (COD), dissolved organic carbon (DOC) and polysaccharide were the most important positive factors to R t with their correlation coefficients above 0.92 while SS and turbidity were the most important negative factors to R t with their correlation coefficients below − 0.87. Long-term filtration experiments also confirmed the membrane fouling control performance by ferrate with the significant extension of the onset of membrane fouling. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ceramic membrane (CM) market is growing with many full-scale applications. • CM is superior to polymeric membrane–high stability & flux, long life, low fouling. • Physicochemical processes (e.g., ozonation) are effective for fouling control. • Catalytic (nano) CMs can enhance antifouling, and pollutant removal capability. • Cost analysis of CMs, fouling control & cleaning should be evaluated at full-scale. Application of ceramic membrane technology in water and wastewater is rapidly growing. Inherent advantages of ceramic membrane including chemical/thermal stability, low fouling propensity and long lifespan make ceramic membrane technology attractive, and the ceramic membrane market is expected to achieve a compound annual growth rate of 12%. Ceramic membranes could be integrated with advanced oxidation processes such as in-situ ozonation that cannot be applied in the case of polymeric membrane due to their potential degradation during long-term exposure. In addition, the hybrid-ceramic membrane processes such as ceramic membrane bioreactor are superior to polymeric counterparts due to higher flux, higher pollutant removal, lower fouling rate and higher cleaning efficiency. Although ceramic membrane has high capital cost, life-cycle costs of ceramic and polymeric plants are comparable. Notably, full-scale ceramic membrane water/wastewater treatment plants have been installed in many countries such as Japan, USA, Singapore and United Kingdom. Given the attractiveness of this technology, performance of ceramic membrane is critically reviewed with a focus on their applications in water and wastewater treatment under mild conditions. In addition, fouling mechanisms and control strategies are elucidated and are compared with polymeric membranes. Importantly, for the first time, the status of full-scale applications and market prospects of ceramic membranes are critically analysed to show their future potential. Lastly, future research directions such as development of cost-effective ceramic membranes, understanding the biofouling evolution and economic evaluation of physicochemical processes for fouling control are proposed. [ABSTRACT FROM AUTHOR]

Herein, we developed a trimetallic CoFeCu-layered double hydroxide (LDH) assembled nanoconfined catalytic membrane, innovatively combining membrane filtration and advanced oxidation processes (AOPs). The CoFeCu-LDH nanoconfined catalytic membrane was shown to directly oxidize and mineralize micropollutants, rather than concentrating them within the brine, while also maintaining high water permeability with harmless membrane permeate. The first-order rate constant for 100% degradation of endocrine disrupting chemicals (bisphenol A), and pharmaceuticals (ranitidine, carbamazepine, oxytetracycline) (e.g., 2.40 ms−1 for ranitidine) by the CoFeCu-LDH catalytic membrane and its ultra-high water permeance of 2378.4 LMH/bar, were 1–3 orders of magnitude and 2−2000-fold higher than that of other state-of-the-art catalytic membranes, respectively. This study provides a reference for the development of sustainable and efficient catalytic membranes for water purification. [Display omitted] • CoFeCu-LDH membrane achieves 100 % removal of diverse organic pollutants. • The degradation rate is 101−3 times higher than the reported AOP systems. • CoFeCu-LDH membrane demonstrates ultra-high water permeance of 2378.4 LMH/bar. • The CoFeCu-LDH membrane/PMS system has a negative E ads value (-5.034 eV). • DFT calculations elucidate the mechanism of electron transfer and PMS activation. [ABSTRACT FROM AUTHOR]

The presence of seasonal algal blooms with harmful algae-derived organic matters threatens the performance of ultrafiltration in drinking water treatment. The hybrid process of in-situ ozonation with ceramic ultrafiltration membrane was proposed for the treatment of algal-rich water with effective removal of algal cells and mitigation of membrane fouling. The mechanism of membrane fouling mitigation with in-situ ozonation was systematically investigated from the perspective of cake layer, gel layer and membrane pore blocking. The results showed that in-situ ozonation treatment can effectively mitigate membrane fouling. For instance, transmembrane pressure was reduced by 75.8% with in-situ ozonation at 1 mg/L. In-situ ozonation resulted in the formation of a more porous and thinner cake layer due to the disintegration of extracellular organic matters that attached on the algal surface. Besides, the portion of very high molecular weight biopolymers (around 100 kDa) and the hydrophobic fraction of algae-derived organic matters, the main component intercepted by the ceramic membrane, were reduced with in-situ ozonation and thus leaded to less severe gel layer fouling. Furthermore, in-situ ozonation induced the accelerated organics degradation within the ceramic membrane pores, alleviating the membrane pore blocking. [ABSTRACT FROM AUTHOR]

For the first time in this study, CoAl-layered double hydroxide nanosheet membrane (LDH m) with abundant active sites was fabricated for peroxymonosulfate (PMS) activation with the mindset to catalytically degrade micropollutants. Depending on the catalyst loading, the developed LDH m can be driven under gravity at a permeate flux of approximately 80 L/m2 h and 210 L/m2 h at LDH loading of 0.80 mg/cm2 and 0.08 mg/cm2, respectively. Notably, the LDH m (0.63 mg) exhibited excellent PMS activation efficiency as indicated by 87.8% removal of the probe chemical (ranitidine) at 0.2 mM PMS, which was higher than that (37–44%) achieved by conventional LDH (5–20 mg)/PMS (0.2 mM) system. In addition to efficient degradation of several micropollutants, LDH m /PMS performance was not inhibited by variation in solution pH (4−8) as well as during long-term (29 h) continuous-flow operation. SO 4 •− and 1O 2 were identified as the primary reactive species in the LDH m /PMS system, while both Co and Al participated in PMS activation. This study offers a simple strategy for efficient removal of several micropollutants with significantly reduced catalyst leaching, which could be applied sustainably in water treatment. [Display omitted] • LDH m showed exceptional PMS activation efficiency as compared to LDH nanosheets. • Several micropollutants were efficiently degraded (71–97%) by the LDH m /PMS system. • PMS was activated by Co directly and Al indirectly of LDH m. • pH change (4−8) did not inhibit LDH m performance for micropollutant degradation. • Ranitidine removal remained stable after continuous (29 h) operation. [ABSTRACT FROM AUTHOR]

Nanomaterials (NMs) have received tremendous attention as emerging adsorbents for environmental applications. The ever-increasing release into aquatic systems and the potential use in water treatment processes heighten the likelihood of the interactions of NMs with aquatic dissolved organic matter (DOM). Once DOM is adsorbed on NMs, it substantially modifies the surface properties, thus altering the fate and transport of NMs, as well as their toxic effects on (micro)organisms in natural and engineered systems. The environmental consequences of DOM-NMs interaction have been widely studied in the literature. In contrast, a comprehensive understanding of DOM-NM complexes, particularly regarding the controlling factors, is still lacking, and its significance has been largely overlooked. This gap in the knowledge mainly arises from the complex and heterogeneous structures of the DOM, which prompts the urgent need to further characterize the DOM properties to deepen the understanding associated with the adsorption processes on NMs. This review aims to provide in-depth insights into the complex DOM adsorption behavior onto NMs, whether they are metal- or carbon-based materials. First, we summarize the up-to-date analytical methods to characterize the DOM to unravel the underlying adsorption mechanisms. Second, the key DOM characteristics governing the adsorption processes are discussed. Next, the environmental factors, such as the nature of adsorbents and solution chemistry, affecting the DOM-NM interactions, are identified and discussed. Finally, future studies are recommended to fully understand the chemical traits of DOM upon its adsorption onto NMs. Image 1 • Traditional and advanced analyses for DOM adsorption are fully reviewed. • Major factors to control DOM-NMs interactions are identified through literature review. • DOM properties governing DOM adsorption behaviors on NMs are highlighted. • Future studies are recommended of better understanding of DOM adsorption onto NMs. [ABSTRACT FROM AUTHOR]

• Mesoporous CuCo 2 O 4 @CNTs (M-CuCo 2 O 4 @CNTs) exhibited a long-lasting catalytic reactivity. • M-CuCo 2 O 4 @CNTs with strong surface adsorption capacity avoid the risk of cobalt-metal leaching. • E H -pH diagram revealed the evolution mechanism of M-CuCo 2 O 4 @CNTs at various pH conditions. • A new perspective for the oxidation behavior and eco-toxicity change of ranitidine (RAN) was proposed. • Theoretical calculations coupled with experiments demonstrated the mechanism of PMS activation. The sluggish redox cycle occurring during the oxidation processes and the biological toxicity caused by the leaching of dissociated cobalt ions dramatically hinder the practical application of cobalt-based catalysts. Herein, we synthesized the hydroxylated multi-walled CNTs coated with mesoporous CuCo 2 O 4 (M-CuCo 2 O 4 @CNTs) to enhance peroxymonosulfate (PMS) activation. The introduction of CNTs enabled M-CuCo 2 O 4 @CNTs with a much better thermal stability. M-CuCo 2 O 4 @CNTs with dual electron-rich active sites (≡Co and ≡Cu) exhibited a long-lasting reactivity for the rapid degradation of micropollutants under mild conditions. In the process of PMS activation, the Cu+/Cu2+ redox couple as an electron donor participated in the conversion of Co3+ to Co2+ through rapid charge transfer. More importantly, this functional material with a highly interconnected conductive network and a strong surface adsorption effect significantly limited the leaching of cobalt ions. Meanwhile, the acute toxicity (LC 50 and EC 50) and the chronic toxicity (ChV) of the intermediates of RAN were significantly reduced compared with RAN after the treatment of the M-CuCo 2 O 4 @CNTs/PMS reaction system. DFT calculations were coupled with experiments to prove that PMS molecules were more favorable to be activated at ≡Co sites compared with ≡Cu sites. Finally, this study offered a new perspective for the activation mechanism of PMS-induced heterogeneous oxidation and an attractive alternative for micropollutants elimination in water treatment. [ABSTRACT FROM AUTHOR]

Highlights • Iron pretreatment significantly mitigates ceramic membrane fouling. • Ferrate pretreatment achieves the best membrane fouling control performance. • Ferrate greatly improves the water quality of reclaimed water. • Biopolymers with the MW of 20–2000 kDa are mainly removed. • Ferrate has dual functions of chemical oxidation and coagulation. Abstract Coagulation-membrane filtration hybrid process has been widely applied in water treatment to improve water quality and alleviate membrane fouling. Herein, we systematically investigated the comparable effect of ferrate, ferrous and ferric pretreatment on fouling alleviation of ceramic membrane in reclaimed water treatment. Our results showed that the pretreatment of ferric, ferrous and ferrate remarkably alleviated membrane fouling with the fouling alleviation performance following the order: ferrate > ferrous > ferric > control. The t crit (subcritical fouling time) after which the fouling rate (dTMP/dt) became much more severe was remarkably extended from 0 (control) to 432 (ferric), 576 (ferrous) and 888 h (ferrate), respectively. Meanwhile, hydraulically reversible fouling resistance had the greatest contribution (58.3%) to the overall fouling resistance in the control case, however, hydraulically irreversible membrane fouling caused by inorganics (R ir-citrate) became more severe in long-term operation with the contribution of R ir-citrate to the total fouling resistance of 40.7%, 46.3% and 50.3% in the cases with ferric, ferrous and ferrate pretreatment, respectively. Moreover, the redundancy analysis results showed that the alleviated membrane fouling was principally owing to the sharp reduction of organic matters and the significant increase of particle size and particle concentration in influent. Compared with ferric and ferrous, ferrate had the best fouling alleviation performance, which was mainly due to its dual functions of chemical oxidation (including OH, Fe(V) and Fe(IV)) and coagulation (ferric oxyhydroxides). [ABSTRACT FROM AUTHOR]

Secondary effluent from municipal wastewater treatment plants can be used to produce reclaimed water through membrane distillation (MD), providing a potential solution to the current global water crisis. However, membrane fouling over extended periods of operation reduces the separation performance of MD systems and significantly shortens the operational life-span of the membrane. Herein, in order to overcome these limitations, a novel surface-modified PTFE membrane was fabricated by depositing polydopamine and grafting dextro (d)-tyrosine (Tyr/PDA@PTFE). This synergistic coating was designed to reduce surface hydrophobicity of the PTFE membrane and provide anti-adhesive properties for bacteria, while enhancing flux and anti-fouling performance during MD. The Tyr/PDA@PTFE membranes demonstrated enhanced MD performance and the Tyr-300/PDA@PTFE membrane (with d -tyrosine coating solution concentration of 300 μM) exhibited the best MD performance during direct contact membrane distillation (DCMD) of the secondary effluent, with the highest flux (49.1 LMH) compared with the pristine PTFE membrane (34.7 LMH), achieving a flux increase of 41.5%. Long-term DCMD operation showed that the Tyr-300/PDA@PTFE membrane exhibited improved anti-fouling performance compared with the pristine PTFE membrane, with 43.8% flux decay observed after three cycles of use, while the pristine PTFE membrane was unable to complete three cycles of use with an 87.2% decrease in flux observed by middle of the third round. The quality of permeate formed by the Tyr/PDA@PTFE membranes during MD, indicated that they could be operated stably for three cycles of use over a 40 h period, intercepting organic matter in the feed solution. The Tyr-300/PDA@PTFE membrane was especially effective for the removal of low molecular weight and humus-like substances, achieving rejection rates of 89.5% and 86.7%, respectively. Additionally, the Tyr/PDA@PTFE membrane carried the more negative charge and exhibited a high level of resistance to bio-adhesion. This study demonstrates the feasibility of use of this novel Tyr/PDA@PTFE membrane in MD, for the effective treatment of secondary effluent from wastewater treatment plants and the production of reclaimed water. [Display omitted] • Dopamine and d -tyrosine-functionalized PTFE membranes (Tyr/PDA@PTFE) were prepared. • Membrane distillation (MD) performance of Tyr/PDA@PTFE membranes was investigated. • Secondary effluent from a WWTP was selected for MD to produce reclaimed water. • The Tyr-300/PDA@PTFE membrane demonstrated the best MD performance. • Tyr/PDA@PTFE membranes showed enhanced flux and anti-fouling performance during MD. [ABSTRACT FROM AUTHOR]

• Membrane-confined catalysis for water purification is reviewed for the first time. • Fundamental understanding of nanoconfinement effect is provided. • Membrane-based nanoconfined catalysis (MNC) has unique properties. • The fabrication methods and effect of operating conditions are discussed. • A roadmap for the future research of MNC is proposed. Progress in heterogeneous advanced oxidation processes (AOPs) is hampered by several issues including mass transfer limitation, limited diffusion of short-lived reactive oxygen species (ROS), aggregation of nanocatalysts, and loss of nanocatalysts to treated water. These issues have been addressed in recent studies by executing the heterogeneous AOPs in confinement, especially in the nanopores of catalytic membranes. Under nanoconfinement (preferably at the length of less than 25 nm), the oxidant-nanocatalyst interaction, ROS-micropollutant interaction and diffusion of ROS have been observed to significantly improve, which results in enhanced ROS yield and mass transfer, improved reaction kinetics and reduced matrix effect as compared to conventional heterogenous AOP configuration. Given the significance of nanoconfinement effect, this study presents a critical review of the current status of membrane-based nanoconfined heterogeneous catalysis system for the first time. A succinct overview of the nanoconfinement concept in the context of membrane-based nanofluidic platforms is provided to elucidate the theoretical and experimental findings related to reaction kinetics, reaction mechanisms and molecule transport in membrane-based nanoconfined AOPs vs. conventional AOPs. In addition, strategies to construct membrane-based nanoconfined catalytic systems are explained along with conflicting arguments/opinions, which provides critical information on the viability of these strategies and future research directions. To show the desirability and applicability of membrane-based nanoconfined catalysis systems, performance governing factors including operating conditions and water matrix effect are particularly focused. Finally, this review presents a systematic account of the opportunities and technological constraints in the development of membrane-based nanoconfined catalytic platform to realize effective micropollutant elimination in water treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanoconfinement catalysis is implemented within Co-Cu ONS membrane nanochannels. • Co-Cu ONS membrane achieves ∼ 100% removal of organic pollutants within 86 ms. • The degradation rate is 103−5 times faster compared with the best state-of-the-art. • Oxygen vacancies facilitate electron transfer between metal cations and PMS. • DFT calculations illustrate the mechanism of nanoconfinement catalysis. Practical applications for the degradation of organic contaminants by conventional batch-mode heterogeneous advanced oxidation processes remain elusive due to mass-transfer limitations of short-lived reactive oxygen species (ROS). Nanoconfinement catalysis has received increasing attention because of enhanced reaction efficiency and mass and electron transfer. Here, we implemented the concept of nanoconfinement catalysis using a two-dimensional membrane. Ultrathin cobalt-copper oxide nanosheets (Co-Cu ONS) rich in active sites and oxygen vacancies were prepared through a facile solution reduction method. The assembled Co-Cu ONS membrane with active sites confined within membrane nanochannels spontaneously activates peroxymonosulfate and facilitates the generation of ROS and the redox cycles of metal cations. Therefore, an ultimate degradation efficiency (∼100%), ultrafast (∼86 ms) decomposition of organic pollutants, and excellent catalytic stability (greater than120 h) were achieved. The degradation rate is 103−5 times faster than the best state-of-the-art. This approach offers an attractive alternative for water purification with membrane-based nanoconfinement catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Progress in 2D nanoporous and lamellar membranes is critically reviewed. • Sub-nanoporous membranes can achieve high water permeance and rejection. • Lamellar membranes provide effective rejection of dye molecules at high water flux. • Enhanced ion rejection by lamellar membranes requires 2D material functionalisation. • Research is required on scalability, stability, fouling and pore size engineering. Wastewater contains only ∼ 1% impurities that are required to be separated precisely for water recycling and reuse applications, particularly in water scare regions. Membrane-based separation has been recognised as an environmentally-friendly and energy-efficient process for effective pollutant removal and clean water production. To further improve the selectivity and water flux of membranes, two-dimensional (2D) materials, such as graphene and those exhibiting graphene-like properties, have been intensively studied for nanoporous and lamellar membrane fabrication in the last decade. Herein, we critically review the progress in 2D membranes for water purification and uniquely discuss the performance governing factors and research gaps from the standpoint of environmental and material chemists, which are critical to realize 2D membrane commercialization. The major points of this review are: (1) among the six types of reviewed 2D membranes, graphene, graphene oxide and reduced graphene oxide membrane have been predominantly studied for water treatment. (2) atomically thin nanoporous membranes with a defined pore size can achieve excellent water permeance and selectivity but large-scale fabrication of nanoporous membranes with uniform shape and size of nanopores remains a challenge. (3) salt separation performance of the pressurized lamellar membranes may not be comparable to commercial nanofiltration membranes. (4) functionalization or crosslinking of 2D materials is inevitable to stabilize 2D membrane pore structure and/or improve molecule separation. (5) membranes fabricated using emerging 2D materials such as born nitride and MXene appear to show better stability than graphene oxide membranes. (6) several aspects, particularly membrane stability, long-term performance, and membrane fouling propensity need attention to realize commercial application of 2D membranes in water treatment. [ABSTRACT FROM AUTHOR]