Membrane distillation crystallization (MDCr) has emerged as a promising technology to produce inorganic crystals from various feed solutions. MDCr leverages the benefits of membrane distillation (MD), including reduced membrane fouling, operation under waste heat or solar energy while facilitating high-purity crystal formation. This study provides a comprehensive operational assessment of MDCr and the governing mechanisms. The investigation emphasized the influence of temperature gradient, membrane characteristics and feed composition on the processes of supersaturation, nucleation and crystal growth. Attention was focused on the formation of the crystals, and the polymorphs' selectivity influenced by process configuration. Practical applications are discussed across inorganic materials, food and pharmaceutical industries, where MDCr shows potential for recovery of functional crystals. Despite promising application, MDCr remains affected by membrane fouling, wetting, and energy demand, which impact fouling, supersaturation and crystal growth dynamics. The role of in-situ monitoring, modelling and process control is identified to ensure reproducibility and scale-up. The findings show that process optimization and coupling of heat and mass transfer promote the formation of tailored crystalline materials from complex feed solutions. However, this process requires standardized methods, real-time analysis and techno-economic assessment to accelerate the MDCr deployment in the current industrial operations.

With the global expansion of the photovoltaic (PV) industry, zero-liquid discharge (ZLD) is a crucial approach for sustainable wastewater management. The dynamics of dissolved organic matter (DOM) remain underexplained across the long ZLD treatment train. In this study, the DOM decomposition and distribution in a full-scale PV wastewater ZLD system were investigated via simple and engineering-feasible spectroscopic techniques and multivariate data analysis. Three DOM components were identified: the N-heterocyclic organic compound was the dominant component (accounting for 70%) and was effectively removed within the pretreatment stage. The terrestrial humic/fulvic acids were less influenced during pretreatment and were preferentially rejected in the membrane processes. The tyrosine-like and soluble microbial products were formed in the microbial and oxidation processes. The significant DOM distribution pattern was revealed in the ZLD system; the A/O, ozonation, and RO units were the hotspots for DOM transformation. Seasonal differences were also demonstrated, with the decline in biological degradation as the main driving factor. DOM is characterized by high biodegradability and autochthonous sources in summer, while exhibiting higher humification and structural stability in winter. Particularly, TN and TP were the key drivers of DOM transformation in summer, whereas membrane separation and salinity dominated in winter. This study advances the mechanistic understanding of DOM composition and distribution in a full-scale ZLD process, providing a theoretical basis for the operation optimization of PV wastewater treatment.

Achieving zero liquid discharge (ZLD) and resource recovery from industrial wastewaters requires the concentration of hypersaline brines, which remains technically challenging. Reverse osmosis (RO) technology is fundamentally limited in ZLD treatment of hypersaline wastewater due to the extremely high osmotic pressure, concentration polarization, membrane fouling, and membrane material durability issues. This review critically synthesizes recent advances in the state-of-the-art RO technologies for the concentration of hypersaline brines, with a focus on three themes: (1) the development of novel membrane materials with enhanced high-pressure tolerance, (2) the structural innovation of membrane modules aimed at improving stability under high salinity and pressure, and (3) the conceptualization, construction, and implementation of efficient RO systems and processes to avoid extensive energy input and extremely high osmotic pressure. Studies demonstrate that advanced RO systems can operate reliably at 120-160 bar, producing concentrates with total dissolved solids exceeding 150,000 mg/L. Based on a critical evaluation of diverse technological pathways, key barriers to largescale deployment are identified. Consequently, future efforts must pivot to deeper exploration of next-generation membrane materials and modules, hybrid low-energy processes, adapted membrane module and system design, and intelligent predictive controls. These advancements are pivotal for developing practical and sustainable RO technologies in high-salinity wastewater management.

The treatment of surfactant-stabilized oily saline wastewater remains a major challenge for membrane distillation (MD) due to severe oil fouling, surfactant-induced pore wetting, and high salinity. To address this, a metalbased electroactive membrane for electro-assisted membrane distillation (e-VMD) was developed by coassembling silica nanoparticles and silver nanowires (AgNWs) onto a polytetrafluoroethylene substrate. In this design, silica nanoparticles provide a hydrophobic barrier that suppresses initial oil adhesion, while AgNWs impart high electrical conductivity and improved stability in saline and surfactant-containing environments. The resulting SiO2-AgNW membrane demonstrated a water contact angle of 142.3 degrees and stable conductivity. Under an applied potential of 3 V, the SiO2-AgNW membrane achieved a high flux of 17.5 kg center dot m-2 center dot h-1 with only a 4.4% decline over 15 h, while maintaining salt rejection above 99.99%. Notably, the applied electric field altered the role of surfactants, such that instead of promoting fouling, they contributed to fouling mitigation. As an anionic surfactant, SDS absorbs oil droplets and imparts a negative charge. Under an applied electric field, the membrane cathode similarly acquires a negative surface charge, generating electrostatic repulsion that hinders the adhesion of surfactant-coated oil droplets. Mechanistic analysis and DLVO calculations indicate that the applied electric field enhances the negative charge of surfactant-coated oil droplets, leading to electrostatic repulsion with the polarized membrane that overcomes van der Waals attraction. This work provides mechanistic insights supported by DLVO analysis and fouling kinetics and suggests a potential strategy for mitigating surfactant-induced fouling in complex wastewater systems.

Industrial nickel pollution discharged into water bodies poses a serious threat to the environment and human health. Conventional biochar-based adsorbents suffer from poor mechanical strength, restricting large-scale application. Inspired by reinforced concrete, this study synthesized a high-strength hydroxyapatite nanowire (HANW) enhanced biochar hybrid aerogel (HBA). HANWs served as the reinforcing framework, while the MgCl2-modified biochar matrix provided abundant adsorption sites, synergistically boosting mechanical strength and adsorption capacity. The optimized HBA exhibited 47% higher compressive strength than conventional biochar aerogels and a notable Ni(II) adsorption capacity of 300.65 mg/g, which is 4 times more effective than conventional biochar. Comprehensive characterization confirmed Ni(II) adsorption on HBA follows a synergistic physicochemical process involving ion exchange, surface complexation, surface sedimentation, electrostatic interaction, and pore diffusion. The HANW-reinforced porous architecture not only sustains this multi-mechanistic pathway but also preserves high mass-transfer efficiency and structural stability during successive adsorption cycles. HBA further exhibited strong selectivity toward Ni(II) under competitive conditions, achieving 99.7% simultaneous removal of Ni in actual electroplating wastewater. The reinforced-concrete-like architecture offers new insights for the design of durable, recyclable, and scalable materials for heavy-metal-contaminated wastewater remediation.

Epoxy resin (EP) based composite materials, due to their advantages such as light weight, ease of processing, and mechanical properties, have been widely applied across thermal packaging field. However, the overall thermal conductivity is constrained by the interfacial thermal resistance between the filler and the substrate. Existing studies suggest that self-assembled monolayers (SAM) can enhance the interfacial thermal conductance (ITC) by forming covalent bonds. Nevertheless, limited research has focused on using SAM to form bilateral covalent bonds to regulate ITC. Therefore, SAM capable of forming bilateral covalent bonds at the EP/silicon (Si) interface were employed to enhance ITC. In this study, time-domain thermoreflectance (TDTR) experiments and molecular dynamics (MD) simulations were conducted to investigate the EP/SAM/Si system. The results demonstrate that SAM-NH2 modification, which forms bilateral covalent bonds at the EP/Si interface, increased the interfacial adhesion strength and enhanced ITC to 140%, thereby significantly promoting interfacial heat transfer. Conversely, ITC was reduced with SAM-CH3 due to the formation of single covalent bond. Subsequently, the differential effective medium (DEM) model was used to determine that the thermal conductivity of the composite modified with SAM-NH2 was improved by 11%. This study provides new insights into adjusting ITC using SAM.

The imperative to combat pollution and recover vital resources in complex industrial environments has sparked a pioneering approach — the integration of separation membranes and advanced photocatalysts. In this study, we unveil a catalyzed mass-transfer membrane to revolutionize the treatment of heavy metal salts and dyes in wastewater. Our research presents a game-changing development — the introduction of aminomalononitrile (AMN) into a polydopamine (pDA)/piperazine (PIP) selective layer, reshaping the layer's structure and significantly enhancing membrane permeance. Notably, the AMN-pDA/PIP selective layer showcases exceptional self-cleaning and anti-biofouling properties, sustaining its effectiveness over extended real-world applications. The Cu-TiO2/CuO heterojunction photocatalyst introduced a concurrent membrane modification, concomitantly diminishing Cr6+ levels during the oxidative degradation of dye species, thereby yielding impressive removal rates of Cr6+ and dye (in the context of authentic textile wastewater) approximating 70% and 100%, respectively. The mechanism underlying the exceptional photocatalytic performance was probed through comprehensive simulations and pollutant filtration tests.

This study investigates the synthesis and application of hydroxyapatite (HAp)-modified zeolite materials for efficient fluoride removal from groundwater-based drinking water. Characterization confirmed the successful incorporation of HAp onto the zeolite surface and the formation of a stable composite. EDS analysis revealed the presence of Ca and P after modification, while FTIR and XRD confirmed the structural integrity of HAp during adsorption. ZH8 exhibited the highest F-removal efficiency of 92.23% at pH 3, 30 °C, [F−] = 6 ppm and dose = 10 g/L. Meanwhile, HAp-modified zeolite showed high F-selectivity, and the competing ions had limited interference. The Langmuir model best described the adsorption process, suggesting monolayer adsorption with a maximum capacity of 39.38 mg/g for ZH8. The process followed pseudo-first-order kinetics, with equilibrium achieved within 4 h. Regeneration studies demonstrated that ZH8 maintained over 85% efficiency for three cycles, highlighting its reusability. Column studies validated the material’s practical applicability, with breakthrough times of up to 23 h under optimal conditions (flow rate: 8 cm3 min−1, bed depth: 30 cm, feed concentration: 7.5 ppm) and a maximum yield of 99% at [F−] = 5 ppm with Vb = 10.8 L. The Thomas model best described the column adsorption process, indicating chemical adsorption as the dominant mechanism. These findings demonstrate the potential of HAp-modified zeolite, particularly ZH8, as an effective adsorbent for fluoride removal in real-world applications.

Metal-organic framework (MOF) offers a promising solution to the global water crisis with atmospheric water harvesting (AWH). However, its practical application is limited by its water adsorption performance in various humidity conditions. In this work, composited MOFs (CMOFs) with hygroscopic salt were synthesized by a one- pot hydrothermal method to enhance the water uptake, and the effect of aluminum sources and dispersants was investigated. AlCl3 and Al(NO3)(3) were efficient aluminum sources that showed stable water adsorption performance, which exhibited excellent water adsorption performance with a water adsorption capacity of 0.4 g center dot g(-1) at 20 % RH for MOF-303. The crystal structure of MOF-303 will change and show a significantly low specific surface area as Al-2(SO4)(3) is used as the aluminum source, and the water adsorption capacity decreases to 0.2 g center dot g(-1) at 20 % RH because of the strong binding energy (-7.196 eV) between SO42- and MOF-303. Hygroscopic salt was incorporated in MOF successfully via the one-pot hydrothermal synthesis method, the composite ratio of salt was 0.1442, 0.1732, and 0.1607 g center dot g(-1) in MOF-303-LiOH, MOF-303-NaOH, and MOF-303-Ca(OH)(2). The new chemical state of chlorine and sodium elements demonstrate that the hygroscopic salt was adsorbed/trapped by the MOF structure. MOF-303-NaOH showed a stable water adsorption capacity of 0.22 g center dot g(-1) at 30 % RH and significantly enhanced water adsorption capacity of up to 2.05 g center dot g(-1) at 95 % RH. Meanwhile, the ratio of salts in the CMOF can be adjusted with the proportion of dispersants, the cyclic adsorption test indicated that AlFuNaOH-2 maintained the water adsorption capacity of 1.62 g center dot g(-1) without deliquesce. This work provides a new strategy for synthesizing CMOFs with excellent water adsorption performance, which can potentially promote the application of MOF in AWH.

The extensive application of ceramic membranes in wastewater treatment draws increasing attention due to their ultra-long service life. A cost-effective treatment for high-strength swine wastewater is an urgent and current need that is a worldwide challenge. A pilot-scale sequencing batch flat-sheet ceramic membrane bioreactor (ScMBR) coupled with a short-cut biological nitrogen removal (SBNR) process was developed to treat high-strength swine wastewater. The ScMBR achieved stable and excellent removal of COD (95.3%), NH4+-N (98.3%), and TN (92.7%), though temperature went down from 20 °C, to 15 °C, to 10 °C stepwise along three operational phases. The COD and NH4+-N concentrations in the effluent met with the discharge standards (GB18596-2001). Microbial community diversity was high, and the genera Pseudomonas and Comamonas were dominant in denitritation, and Nitrosomonas was dominant in nitritation. Ceramic membrane modules of this pilot-scale reactor were separated into six layers (A, B, C, D, E, F) from top to bottom. The total filtration resistance of both the top and bottom membrane modules was relatively low, and the resistance of the middle ones was high. These results indicate that the spatial distribution of the membrane fouling degree was different, related to different aeration scour intensities demonstrated by computational fluid dynamics (CFD). The results prove that the membrane fouling mechanism can be attributed to the cake layer formation of the middle modules and pore blocking of the top and bottom modules, which mainly consist of protein and carbohydrates. Therefore, different cleaning measures should be adopted for membrane modules in different positions. In this study, the efficient treatment of swine wastewater shows that the ScMBR system could be applied to high-strength wastewater. Furthermore, the spatial distribution characteristics of membrane fouling contribute to cleaning strategy formulation for further full-scale MBR applications.

Rapid advancement in aerospace technology has successfully enabled long-term life and economic activities in space, particularly in Low Earth Orbit (LEO), extending up to 2000 km from the mean sea level. However, the sustainance of the LEO Economy and its Environmental Control and Life Support System (ECLSS) still relies on a regular cargo supply of essential commodities (e.g., water, food) from Earth, for which there still is a lack of adequate and sustainable technologies. One key challenge in this context is developing water treatment technologies and standards that can perform effectively under microgravity conditions. Solving this technical challenge will be a milestone in providing a scientific basis and the necessary support mechanisms for establishing permanent bases in outer space and beyond. To identify clues towards solving this challenge, we looked back at relevant scientific research exploring novel technologies and standards for deep space exploration, also considering feedback for enhancing these technologies on land. Synthesizing our findings, we share our outlook for the future of drinking water treatment in microgravity. We also bring up a new concept for space aquatic chemistry, considering the closed environment of engineered systems operating in microgravity.

Oriented towards the pressing needs for hypersaline wastewater desalination and zero liquid discharge (ZLD), the contrasting mixed scaling of thermal-driven vacuum membrane distillation (VMD) and pressure-driven nanofiltration (NF) were investigated in this work. Bulk crystallization was the main mechanism in VMD due to the high salinity and temperature, but the time-independent resistance by the adsorption of silicate and organic matter dominated the initial scaling process. Surface crystallization and the consequent pore-blocking were the main scaling mechanisms in NF, with the high permeate drag force, hydraulic pressure, and cross-flow rate resulting in the dense scaling layer mainly composed of magnesium-silica hydrate (MSH). Silicate enhanced NF scaling with a 75% higher initial flux decline rate attributed to the MSH formation and compression, but delayed bulk crystallization in VMD. Organic matter presented an anti-scaling effect by delaying bulk crystallization in both VMD and NF, but specifically promoted CaCO3 scaling in NF. Furthermore, the incipient scaling was intensified as silicate and organic matter coexisted. The scaling mechanism shifted from surface to bulk crystallization due to the membrane concentration in both VMD and NF. This work fills the research gaps on mixed scaling mechanisms in different membrane processes, which offers insights for scaling mitigation and thereby supports the application of ZLD.

Membrane distillation (MD) has promising potential in the water purification and wastewater treatment industries; however, fouling and wetting are the main obstacles to its commercialization, and higher fluxes and energy efficiencies are essential. Magneto-responsive membranes (MagMem) with integrated magnetic nanoparticles (MNPs) enable in situ fouling mitigation and switchable separation by nano-mixing or nano-heating, triggered by external magnetic fields, in a range of membrane processes, but not yet been demonstrated in MD. This perspective discussed the potential paths of MagMem utilization in MD based on the research status and dilemmas of MD. It can be envisioned that MagMem will lead to a paradigm shift in MD, especially by in situ fouling/wetting mitigation and enhancing energy efficiency via in-place actuation and localized heating by MNPs. Moreover, remotely controllable pore tuning and specific or switchable wettability can also be anticipated. Overall, MagMem provides attractive opportunities for advanced robust and efficient MD.

The adsorption water harvesting technology can provide clean drinking water to people worldwide. This paper prepares the MOF-303(Al) by hydrothermal, investigates the effects of preparation conditions such as aqueous solvent, metal-aluminum source, reaction temperature, and dispersant type on water adsorption performance and structure topography, and the possibility of directly achieving the composite of MOF-303(Al) with inorganic salts based on hydrothermal process was explored. The results show that the aqueous solvent and dispersant have little effect on the water adsorption performance; both can achieve a water adsorption capacity of 0.4 g·g−1 and the fast adsorption kinetics of saturation adsorption can be achieved in half hour. Temperature and aluminum source will significantly affect the water adsorption performance, with a floating change of 0.3 g·g−1. Reducing the washing step of hydrothermal process can directly realize the recombination of inorganic salt and MOF-303(Al), and achieve a high adsorption capacity of 2.055 g·g−1 at 95%RH.

Exploring the vast extraterrestrial space is an inevitable trend with continuous human development. Water treatment and reuse are crucial in the limited and closed space that is available in spaceships or long-term use space bases that will be established in the foreseeable future. Dedicated water treatment technologies have experienced iterative development for more than 60 years since the first manned spaceflight was successfully launched. Herein, we briefly review the related wastewater characteristics and the history of water treatment in space stations, and we focus on future challenges and perspectives, aiming at providing insights for optimizing wastewater treatment technologies and closing the water cycle in future.

The black-odor water body restoration is an un finished business in protecting and maintaining the ecological functions of natural water systems in China. Magnetic coagulation (MC) had found a vast application prospect for its high-ef ficient separation. In this work, the performance of MC was analyzed to explore its role in natural water protection, with a focus on identi fication and removal mechanisms of the dissolved organic matters (DOM) by absorption and fluorescence spectroscopy in terms of the spectroscopic indices, two-dimensional correlation spectroscopy (2D-COS), and parallel factor analysis (PARAFAC) methods. MC presented an excellent performance for suspended and colloidal matters, phosphorus, and DOMs, and showed high adaptability in pollution interception and water restoration. Tryptophan-like, tyrosine-like, and humics were identi fied as the key components in the wastewater, which were mainly recently produced or microbial-derived. The targeted pollutants were DOMs with high molecular weight, hydrophobicity, polarity, and aromaticity for the high af finity with the hydrolyzed Al species. Polyaluminum chloride (PAC) was the key in dissolved pollutants removal, while the mix stage is crucial for DOMs with low MW or humic-like substances as PAM facilitated the flocs formation and the absorption process. However, the residual PAM and the redissolved DOMs from the recycled magnetic seeds also act as the DOM source. This work identi fied the DOM composition and removal mechanism in MC, which would promote its application in natural water protection.

Nanofiltration (NF) will play a crucial role in salt fractionation and recovery, but the complicated and severe mixed scaling is not yet fully understood. In this work, the mixed scaling patterns and mechanisms of high-pressure NF in zero-liquid discharge (ZLD) scenarios were investigated by disclosing the role of key foulants. The bulk crystallization of CaSO4 and Mg-Si complexes and the resultant pore blocking and cake formation under high pressure were the main scaling mechanisms in hypersaline desalination. The incipient scalants were Mg-Si hydrates, CaF2, CaCO3, and CaMg(CO3)2. Si deposited by adsorption and polymerization prior to and impeded Ca scaling when Mg was not added, thus pore blocking was the main mechanism. The amorphous Mg-Si hydrates contribute to dense cake formation under high hydraulic pressure and permeate drag force, causing rapid flux decline as Mg was added. Humic acid has a high affinity to Ca2+by complexation, which enhances incipient scaling by adsorption or lowers the energy barrier of nucleation but improves the interconnectivity of the foulants layer and inhibits bulk crystallization due to the chelation and directional adsorption. Bovine serum albumin promotes cake formation due to the low electrostatic repulsion and acts as a cement to particles by adsorption and bridging in bulk. This work fills the research gaps in mixed scaling of NF, which is believed to support the application of ZLD and shed light on scaling in hypersaline/ultra-hypersaline wastewater desalination applications.

Composite phase change materials with sugar alcohol as the phase change material and highly thermally conductive ceramics as the porous skeleton are widely used in various thermal storage systems. The interfacial thermal conductance (ITC) between the phase change materials under different phases and the skeleton is an important factor affecting the rate of heat storage (release) in thermal storage systems. The ITC between ceramics(AlN, SiC) and sugar alcohols (mannitol and galactitol) in the solid and liquid states is investigated by means of both time-domain thermoreflectance and molecular dynamics simulations. The results show that the ITC between phase change materials and ceramic is better in liquid state than in solid state, and that the ITC between mannitol and ceramic is better, and that the ITC betweenAlN and sugar alcohol is better. More low-frequency phonons are involved in the thermal transport of the sugar alcohols in the liquid state, with an average overlap energy of about 9.5% higher than that of the solid state and an average phonon participation rate of about 6.8% higher. It was also found that it isthe H atom in the sugar alcohol that is linked to the C atom that governs the ITC.

Membrane scaling is an enormous challenge in the desalination of hypersaline water using membrane distillation (MD). In this study, vacuum membrane distillation (VMD) was employed for brackish water treatment, with an emphasis on scaling mechanisms and mitigation strategies. Four methods, including deionized water, hydrochloric acid, and acetic acid, ultrasonication, were utilized for membrane cleaning. The cleaning efficiency was assessed through a comprehensive analysis of residual foulant layers. It was determined that mineral scaling constituted the primary fouling mechanism, and a minor amount of organic fouling was present at the interface between scaling-scaling and scale-membrane. Calcium and magnesium carbonate were the primary scaling components observed in brackish water desalination, appearing as needle-like and block crystals. Notably, CaCO3 predominantly existed as the aragonite crystal structure. Ultrasonication and deionized water demonstrated limited effectiveness due to the alkaline nature of the scaling. Conversely, the application of dynamic hydrochloric acid and acetic acid treatments resulted in a significant reduction in scaling, with acetic acid demonstrating superior efficacy in removing carbonate scaling. The results presented in this study can provide valuable theoretical guidance for the treatment of brackish water using membrane desalination techniques.

Mineral scaling is one key obstacle to membrane distillation in hypersaline wastewater desalination, but the scaling or fouling mechanism is poorly understood. Addressing this challenge required revealing the foulants layer formation process. In this work, the scaling process was deconstructed with a cascade strategy by stepwise changing the composition of the synthetic desulfurization wastewater. The flux decline curves presented a 3stage mode in vacuum membrane distillation (VMD). Heterogeneous nucleation of CaMg(CO3)2, CaF2, and CaCO3 was the main incipient scaling mechanism. Mg-Si complex was the leading foulant in 2nd-stage, during which the scaling mechanism shifted from surface to bulk crystallization. The flux decreased sharply for the formation of a thick and compacted scaling layer by the bricklaying of CaSO4 and Mg-Si-BSA complexes in the 3rd-stage. Bulk crystallization was identified as the key scaling mechanism in VMD for the high salinity and concentration multiple. The organic matter had an anti-scaling effect by changing the bulk crystallization. Humic acids (HA) and colloidal silica also contributed to incipient scaling for the high affinity to membrane, bovine serum albumin (BSA) acting as the cement of Mg-Si complexes. Mg altered the Si scaling from polymerization to Mg-Si complex formation, which significantly influence the mixed scaling mechanism. This work deconstructed the mixed scaling process and illuminated the role of main foulants, filling in the knowledge gap on the mixed scaling mechanism in VMD for hypersaline wastewater treatment and recovery.