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Graphene oxide (GO) membranes enabled by subnanosized diffusion channels are promising to separate small species in membrane distillation (MD). However, the challenge of effectively excluding small volatiles in MD persists due to the severe swelling and subsequent increase in GO interlamination spacing upon direct contact with the hot feed. To address this issue, we implemented a design in which a polymer is confined between the GO interlaminations, creating predominantly 2D nanochannels centered around 0.57 nm with an average membrane pore size of 0.30 nm. Compared to the virginal GO membrane, the polymer-intercalated GO membrane exhibits superior antiswelling performance, particularly at a high feed temperature of 60 °C. Remarkably, the modified membrane exhibited a high flux of approximately 52 L m–2h–1and rejection rates of about 100% for small ions and 98% for volatile phenol, with a temperature difference of 40 °C. Molecular dynamics simulations suggest that the sieving mechanisms for ions and volatiles are facilitated by the narrowed nanochannels within the polymer network situated between the 2D nanochannels of GO interlaminations. Concurrently, the unrestricted permeation of water molecules through the multinanochannel GO membrane encourages high-flux desalination of complex hypersaline wastewater.

Graphical abstract:

Hypersaline wastewater treatment using membrane distillation (MD) has gained significant attention due to its ability to completely reject nonvolatile substances. However, a critical limitation of current MD membranes is their inability to intercept volatile substances owing to their large membrane pores. Additionally, the strong interaction between volatile substances and MD membranes underwater tends to cause membrane wetting. To overcome these challenges, we developed a dual-layer thin film composite (TFC) Janus membrane through electrospinning and sequential interfacial polymerization of a polyamide (PA) layer and cross-linking a polyvinyl alcohol/polyacrylic acid (PP) layer. The resulting Janus membrane exhibited high flux (>27 L m–2h–1), salt rejection of ∼100%, phenol rejection of ∼90%, and excellent resistance to wetting and fouling. The interlayered interface between the PA and PP layer allowed the sieve of volatile substances by limiting their dissolution–diffusion, with the increasing hydrogen bond network formation preventing their transport. In contrast, small water molecules with powerful dynamics were permeable through the TFC membrane. Both experimental and molecular dynamics simulation results elucidated the sieving mechanism. Our findings demonstrate that this type of TFC Janus membrane can serve as a novel strategy to design next-generation MD membranes against volatile and non-volatile contaminants, which can have significant implications in the treatment of complex hypersaline wastewater.

Taking advantage of natural resources for freshwater production is the key to alleviating crises during maritime emergencies. Herein, we designed an asymmetrically superwettable Janus membrane for all-day freshwater harvesting; use of this membrane provided a high-quality freshwater supply with excellent solar desalination of 1.55 kg m−2h−1(daytime) and fog collection of 11.31 kg m−2h−1(nighttime).

Single oxygen-based advanced oxidation processes (1O2-AOPs) exhibit great prospects in selective degradation of organic pollutants. However, efficient production of 1O2via tailored design of catalysts to achieve selective oxidation of contaminants remains challenging. Herein, we develop a simple strategy to regulate the components and coordination of Co–N–C catalysts at the atomic level by adjusting the Zn/Co ratio of bimetallic zeolitic imidazolate frameworks (ZnxCo1-ZIFs). Zn4Co1–C demonstrates 98% selective removal of phenol in the mixed phenol/benzoic acid (phenol/BA) solutions. Density functional theory calculations and experiments reveal that more active CoN4sites are generated in Zn4Co1–C, which are beneficial to peroxymonosulfate activation to generate 1O2. Furthermore, the correlation between the origin of selectivity and well-defined catalysts is systematically investigated by the electron paramagnetic resonance test and quenching experiments. This work may provide novel insights into selective removal of target pollutants in a complicated water matrix.

Over the past two decades, persulfate-based advanced oxidation processes have attracted considerable attention because of their high efficiency and great versatility in the degradation of organic pollutants. Various radical and nonradical reactive oxygen species (ROS) with different features produced by persulfate activation have facilitated the efficient treatment of complex effluents, especially saline organic wastewater (SOW). To completely assess the advantages and shortcomings of persulfate-based advanced oxidation processes for the SOW treatment, in this review, we present the properties and verification methods of key ROS in persulfate activation and summarize the effect of anions (nitrates, halide ions, carbonates, etc.) in kinds of different catalytic systems. This review aims to provide insights into the relationship between ROS and anions to clarify the key steps in degradation processes, hence avoiding research pitfalls and empowering better investigation in SOW treatment. Finally, we propose perspectives on challenges related to accessing the selectivity of nonradical ROS to intermediates, designing targeted catalysts, coupled purification technologies, accessing the biological toxicity of intermediates and the effect of sulfates on the environment.

Clean water production calls for highly efficient and less energy-intensive technologies. Herein, a novel concept of a sequential ultrafiltration-catalysis membrane is developed by loading Co3O4/C@SiO2yolk–shell nanoreactors into the fingerlike channels of a polymeric ultrafiltration membrane. Such a sequenced structure design successfully integrates selective separation with peroxymonosulfate-based catalysis to prepare a functionalized molecular sieve membrane, which exhibits excellent decontamination performance toward multipollutants by filtering the water matrices containing humic acid (HA) and bisphenol A (BPA). In this study, 100% rejection of HA and 95% catalytic degradation of BPA were achieved under a low pressure of 0.14 MPa and an ultrahigh flux of 229 L m–2h–1, corresponding to a retention time of 3.1 s. Notably, the removal performance of multiple pollutants essentially depends on the ordered arrangement of ultrafiltration and catalysis. Moreover, the flow-through process demonstrated significant enhancement of BPA degradation kinetics, which is 21.9 times higher than that of a conventional batch reactor. This study provides a novel strategy for excellent removal of multiple pollutants in water.

Integrating pseudocapacitive materials with a conductive carbonaceous matrix is an efficient method to improve their capacitive deionization (CDI) performance. However, it remains a challenge to optimize the structure and chemical component of each part and strengthen the internal bonding between them for the further improvement of salt adsorption capacity (SAC). Herein, we report an ultrafine anatase TiO2/carbon nanocomposite confined into N-doped mesoporous carbon (TiO2/C@NMC) viaa mesostructured polydopamine (mPDA) coated MOF strategy and subsequent pyrolysis. During the pyrolysis process, the mPDA shell could construct a spatially confined environment to effectively limit the aggregation of TiO2nanoparticles and restrain their transformation into the rutile phase, contributing to the abundant faradaic active sites and strong interaction with a conductive carbon matrix. Moreover, the mPDA shell-derived N-doped mesoporous carbon provides abundant ion diffusion channels and alleviates the volume variation of the inner faradaic materials during the adsorption/desorption process. As a result, TiO2/C@NMC delivers an excellent SAC of 27.73 mg g−1and stable regeneration properties over 50 cycles, demonstrating its great potential as a superior pseudocapacitive electrode for hybrid CDI (HCDI). This work offers a promising strategy to regulate the properties of pseudocapacitive materials for designing advanced HCDI devices.

Selective removal of organic pollutants from surface water with high efficiency is crucial in water purification. Here, yolk–shell Co/C nanoreactors (YSCCNs) are facilely synthesized via pyrolysis of controllably etched ZIF-67 by tannic acid, and their degradation performance on multiple pollutants is demonstrated. To present the structure–performance relationship between the designed nanocatalyst and the selective removal of organic pollutants, bisphenol A (BPA) was selected as the targeted pollutant with coexistence of humus acid (HA). For comparison, solid and hollow ZIF-67 derived Co/C nanoparticles denoted as SCCNs and HCCNs, were also tested. The results show that YSCCNs exhibit enhanced BPA degradation rate of 0.32 min–1, which is 23.1% and 45.4% higher than that of HCCNs and SCCNs in HA (10 ppm) system. The essential improvement can be ascribed to the synergetic effects from shell layer (size-exclusion) and core/shell (confinement effect). The degradation mechanism and pathway are further confirmed by radical quenching experiments and liquid chromatography–mass spectrograph (LC–MS), respectively. In addition, some influential factors, including reaction temperature, pH value, and peroxymonosulfate (PMS) dosage are investigated in detail. This work provides a possible way to selectively remove target contaminant from multiple pollutants in complex water system.

The urgent need to efficiently and rapidly decontaminate uranium contamination in aquatic environments underscores its significance for ecological preservation and environmental restoration. Herein, a series of titanium-doped zirconium-based metal–organic frameworks were meticulously synthesized through a stepwise process. The resultant hybrid bimetallic materials, denoted as NU-Zr-n%Ti, exhibited remarkable efficiency in eliminating uranium (U (VI)) from aqueous solution. Batch experiments were executed to comprehensively assess the adsorption capabilities of NU-Zr-n%Ti. Notably, the hybrid materials exhibited a substantial increase in adsorption capacity for U (VI) compared to the parent NU-1000 framework. Remarkably, the optimized NU-Zr-15%Ti displayed a noteworthy adsorption capacity (∼118 mg g-1) along with exceptionally rapid kinetics at pH 4.0, surpassing that of pristine NU-1000 by a factor of 10. This heightened selectivity for U (VI) persisted even when diverse ions exist. The dominant mechanisms driving this high adsorption capacity were identified as the robust electrostatic attraction between the negatively charged surface of NU-Zr-15%Ti and positively charged U (VI) species as well as surface complexation. Consequently, NU-Zr-15%Ti emerges as a promising contender for addressing uranium-laden wastewater treatment and disposal due to its favorable sequestration performance.

Yolk–shell nanoparticles (YSNs) with active metal cores have shown promising applications in nanoreactors with excellent catalytic performance. In this work, Fe0@SiO2YSNs were synthesized by a sequential “two-solvents” impregnation–reduction approach. Specifically, FeSO4aqueous solution was introduced into the preformed hollow mesoporous silica spheres (HMSS), dispersed in n-hexane, via a “two-solvent” impregnation way. Subsequently, aqueous solution of sodium borohydride (NaBH4) was introduced into the cavity of HMSS by the same way, leading to the formation of Fe core inside the HMSS through the reaction between Fe2+and NaBH4. The resulting Fe0@SiO2YSNs possess distinctive structures, including active cores, accessible mesoporous channels, protective shells, and hollow cavities. To present the catalytic performance of YSNs nanoreactors, Fenton-like catalytic oxidation of phenol was chosen as the model catalysis reaction. In addition to the Fe0@SiO2YSNs, two other materials were also applied to the catalytic system for comparison, including Fe@SiO2composites with iron nanoparticles sticking on the outer shells of HMSS (Fe@SiO2-DI) and bare iron nanoparticles without HMSS (bare Fe0), respectively. The catalytic results show that Fe0@SiO2YSNs exhibit higher catalytic rate toward phenol removal at 2-fold and 4-fold as compared to that of Fe@SiO2-DI and bare Fe0, indicating the outstanding catalytic property of YSNs nanoreactors. To further clarify the relationship between catalytic properties and structural characteristics, the adsorption experiments of the three samples were also performed in the absence of H2O2. Other than catalytic results, Fe0@SiO2YSNs show slightly higher adsorption efficiency than the other two samples, indicating the accessibility of nanoreactors. This result demonstrates that the removal of phenol in the oxidation system of Fe0@SiO2YSNs may have contributed to the structure-enhanced effect of YSNs as nanoreactors.