Enhanced Mass Transfer Research Articles

Enhancing Mass Transfer of Reactive Oxygen and Nitrogen Species in Plasma‐Activated Water: A Molecular Dynamics Study on the Impact of Plasma Electric Fields

ABSTRACTThis study investigates the impact of plasma electric fields on the mass transfer characteristics of reactive oxygen and nitrogen species (RONS), specifically NO2 and O3, in water using molecular dynamics simulations. The results demonstrate that the plasma electric field significantly increases the thickness of the Gibbs Dividing Surface, reduces surface tension at the gas–liquid interface, and disrupts the hydrogen bond network. These changes lead to an enhanced solubility and self‐diffusion coefficient for both NO2 and O3. Due to stronger dipole–dipole interactions, NO2 exhibits superior mass transfer performance compared to O₃. This research provides theoretical support for the application of plasma‐activated water technology.

The Influence of Temperature on Rheological Parameters and Energy Efficiency of Digestate in a Fermenter of an Agricultural Biogas Plant

This investigation specifically aims to enhance the understanding of digestate flow and mixing behavior across typical temperatures in bioreactors in agricultural biogas plants, facilitating energy-efficient mixing. Experimental tests confirmed that digestate exhibits non-Newtonian characteristics, allowing its flow behavior to be captured by rheological models. This study validated that digestate rheology significantly varies with temperature, which influences flow resistance, mixing efficiency and overall energy requirements. Two rheological models—the Bingham and Ostwald models—were applied to characterize digestate behavior, with the Ostwald model emerging as the most effective for Computational Fluid Dynamic (CFD) simulations, given its balance between predictive accuracy and computational efficiency. Specifically, results suggest that, while three-parameter models, like the Herschel–Bulkley model, offer high precision, their computational intensity is less suitable for large-scale modeling where efficiency is paramount. The small increase in the accuracy of the shearing process description does not compensate for the significant increase in CFD calculation time. Higher temperatures were found to reduce flow resistance, which in turn enables increased flow rates and more extensive mixing zones. This enhanced mass transfer and mixing potential at elevated temperatures are especially pronounced in peripheral areas of the bioreactor, farthest from the agitators. By contributing a model for rheological behavior under realistic bioreactor conditions, this study supports the optimization of energy use in biogas production. These findings emphasize that temperature adjustments within bioreactors could serve as a reliable control strategy to maintain optimal production conditions while minimizing operational costs.

MnO2 Nanowire Thin Mesh With Enhanced Mass Transfer as Hydroxide Exchange Membrane Fuel Cell Cathode

AbstractHydroxide exchange membrane fuel cells (HEMFCs) are promising due to the potential use of nonprecious metal catalysts. However, the performance of HEMFCs based on nonprecious catalysts is still unsatisfactory, and one reason for this is hindered mass transfer in the catalyst layer. In this study, we employ a hydrothermal method to grow in situ a MnO2 nanowire thin mesh (NTM) catalytic layer on the gas diffusion electrode. The HEMFC prepared with MnO2 NTM cathode achieves a peak power density of 425 mW cm−2, surpassing the performance of the HEMFC prepared using the traditional powder catalyst spraying method by four times. High‐frequency resistance and limiting current tests indicate that the MnO2 NTM reduces ohmic resistance and improves mass transfer, thereby enhancing the HEMFC performance. Furthermore, the peak power density of the HEMFC is increased to 626 mW cm−2 by depositing additional active Co3O4 nanoparticles on the MnO2 NTM. These findings demonstrate that an interconnected and porous catalyst layer structure is beneficial for improving mass transfer properties, which in turn enhances HEMFC performance.

Fe3O4@Fe2O3 carbon aerogel particle electrodes for three-dimensional electro-Fenton oxidation: A novel mechanism promoted by non-radical pathway

Three-dimensional electro-Fenton (3D-EF) has exhibited strengths over traditional electro-Fenton (EF) process for water decontamination, but recent researches on 3D-EF are focused on the decontamination mechanism driven by the radical pathway which was environmentally sensitive and poor in anti-interference capability. This study explored the non-radical mechanism in the 3D-EF process by preparing a novel Fe3O4@Fe2O3/carbon aerogel-700 (FFCA-700) particle electrode (PE) to construct a 3D-EF system promoted by non-radical pathway. The electrodes induced electric field spontaneously polarized FFCA-700 into PEs which led to higher active surface areas of electrodes and the enhancement of mass transfer. Numerous polarized FFCA-700 served as electron donor for dissolved O2 to obtain electron to form ·O2– while the increase in positive charge of the graphitized carbon, caused by the functional group containing electron-rich oxygen, was conducive for ·O2– to transform to 1O2 thus promoting the non-radical pathway. Tetracycline (TC) was selected as the model pollutant to evaluate and compare the remediation performance of different systems. The results suggested that FFCA-700-3D-EF system performed well for pollutant removal in real wastewater. Overall, this study provided a reference for the design and optimization of CPEs and the guidance for the mechanism studies on remediation of organically contaminated wastewater by 3D-EF process.

Combining Liposomal Photocatalysts with Whole‐Cell Catalysts for One‐pot Photobiocatalysis

AbstractCooperative photobiocatalytic processes have seen extensive potentials for the synthesis of both bulk and fine chemicals owing to their versatility, eco‐friendliness, and cost‐effectiveness. Nevertheless, developing a universal and effective synthetic strategy compatible with both catalytic systems remains challenging. In this study, we explored cationic liposomes as biocompatible photocatalyst encapsulation systems and combined them with bacteria overexpressing enzymes for two‐step and three‐step cascade reactions. Specifically, the water‐soluble photocatalyst anthraquinone‐2‐sulfonate (AQS), which can oxidize benzyl alcohol, is encapsulated within the core of cationic liposomes composed of dioleoyl‐3‐trimethylammonium propane (DOTAP) and the helper lipid cholesterol. The positive charge on the liposome surface enabled electrostatic interactions with the negative charges on the membrane of Escherichia coli cells. Bacterial cells overexpressing various enzymes, such as Candida antarctica lipase B (CalB) and benzaldehyde lyase (BAL), and coated with liposomes enabled the production of added value compounds through cascade reactions with excellent production. These cascades involve CalB‐catalyzed hydrolysis, BAL‐catalyzed condensation, and AQS‐driven photo‐oxidation reactions. Therefore, the strategy offers more possibilities of combining photocatalysis with biocatalysis for recoverability, enhanced mass transfer, and enhanced compatibility in both industrial biotechnology and synthetic chemistry.

Tetracycline degradation for wastewater treatment based on ozone nanobubbles advanced oxidation processes (AOPs) – Focus on nanobubbles formation, degradation kinetics, mechanism and effects of water composition

Presence of pharmaceuticals, especially antibiotics, in industrial and domestic effluents causes serious damage to the environment. Classic wastewater treatment processes, in particular conventional biological treatment methods, are not sufficient to rapidly eliminate antibiotics. Typically, Advanced Oxidation Processes (AOPs) based on activation of hydrogen peroxide, ozone or persulfate for production of particular type of radical species or singlet oxygen are used. A one of cutting-edge technologies to increase effectiveness of AOPs based on ozone are nanobubbles based processes. Thus, this paper focuses on utilization of ozone in the form of nanobubbles for degradation of tetracycline (TC). The effects of several reaction parameters, such as antibiotic concentration, ozone intake, pH, presence of salts, were investigated. This study revealed that the presence of ozone nanobubbles had a substantial positive impact on the degradation of TC. This improvement may be attributed to the enhanced mass transfer and the production of reactive radicals that occur during the collapse of the nanobubbles. Identification of radical species revealed a significant contribution of hydroxyl radicals in the degradation of the antibiotic. AOP process based on O3 nanobubbles was most (•OH) and superoxide (O2–) effective with 100 % degradation efficiency of 100 mg/L TC within 20 min at 8 mg/L concentration of ozone. Based on identified by LC-MS intermediates a degradation mechanism has been described. Degradation of TC and intermediates transformations included methylation, hydroxylation, ring-opening steps as well as cleavage of C-N bonds. This research introduces a novel technique combining nanobubbles with advanced oxidation processes (AOPs), which is anticipated to provide enhanced efficiency and environmental sustainability.

An overlooked nanofluids effect from Fe3O4 nanoparticles enhances mass transfer in anammox granular sludge

Magnetite (Fe3O4) particles have been widely reported to enhance the anammox's activity in anammox granular sludge (AnGS), yet the underlying mechanisms remain unclear. This study demonstrates that both Fe3O4 microparticles (MPs) and nanoparticles (NPs) at a dosage of 200 mg Fe3O4/L significantly increased the specific anammox activity (SAA) of AnGS. Additionally, the transcriptional activities of the hzs and hdh genes involved in the anammox process, as well as the heme c content in AnGS, were also notably enhanced. Notably, Fe3O4 NPs were more effective than MPs in boosting anammox activity within AnGS. Mechanistically, Fe3O4 MPs released free iron, which anammox bacteria utilized to promote the synthesis of key enzymes, thereby enhancing their activity. Compared to MPs, Fe3O4 NPs not only elevated the synthesis of these key enzymes to a higher level but also induced a nanofluids effect on the surface of AnGS, improving substrate permeability and accessibility to intragranular anammox bacteria. Moreover, the nanofluids effect was identified as the primary mechanism through which Fe3O4 NPs enhanced anammox activity within AnGS. These findings provide new insights into the effects of nanoparticles on granular sludge systems, extending beyond AnGS.

Carbon dioxide capture in sodium carbonate solution: Mass transfer kinetics and DTAC surfactant enhancement mechanism

Sodium carbonate solvent absorbent has been widely studied for CO2 reduction to deal with global warming because of its green, low cost, and non-corrosive advantages. However, in the application of sodium carbonate as an absorbent for CO2 capture, there is no unified cognition of the mass transfer process, which leads to the lack of guidance for the industrial large-scale process. Moreover, the mechanism of mass transfer enhancement of surfactants, which can effectively improve the mass transfer performance, has not been effectively explored in the literature. Based on this, this paper firstly adopts the molecular dynamics method to analyze the solution characteristics after surfactant addition and optimize the surfactant. Subsequently, a classical dissolved oxygen test method was used to measure the gas-liquid mass transfer coefficient for CO2 absorption into sodium carbonate solution. And based on this mass transfer coefficient measurement method, the mass transfer process of sodium carbonate solution with surfactant was analyzed. The results showed that the sodium carbonate solution with 5 wt% concentration and 10 wt% concentration at 30 °C did not satisfy the pseudo first-order fast chemical reaction kinetics assumption. To improve CO2 absorption mass transfer rate, dodecyl trimethyl ammonium chloride (DTAC) surfactant was introduced, which was improved by 119 % compared with non-enhanced solvent at 5 wt% concentration solution, and the assumption of pseudo first order fast chemical reaction was satisfied. After the introduction of surfactant, the barrier effect decreased the liquid phase mass transfer coefficient, but the Marangoni effect happened in the 5 wt% concentration of sodium carbonate solution, which enhanced the liquid-phase mass-transfer coefficient. This finding reveals the mechanism of mass transfer promotion of sodium carbonate by the surfactant DTAC, which is of great engineering significance for the application in the field of decarbonization after the introduction of surfactant.

Evolution of Cataclysmic Variables with Binary-driven Mass Loss during Nova Eruptions

The discrepancies between observations and theoretical predictions of cataclysmic variables (CVs) suggest that there exists unknown angular-momentum-loss mechanism(s) besides magnetic braking and gravitational radiation. Mass loss due to nova eruptions belongs to the most likely candidates. While standard theory assumes that mass is lost in the form of radiation-driven, optically thick wind (fast wind), recent numerical simulations indicate that most of the mass loss is initiated and shaped by binary interaction. We explore the effect of this binary-driven mass loss (BDML) on the CV evolutions assuming a major fraction of the lost mass leaves the system from the outer Lagrangian point. Different from the traditional continuous wind picture, we consider the mass loss process to be instantaneous because the duration of nova eruptions is much shorter than the binary evolutionary timescale. Our detailed binary evolution calculations reveal the following results. (1) BDML seems able to provide extra angular momentum loss below the period gap. The mass transfer rates at a given orbital period occupy a large range, in agreement with the observed secular mass transfer rate distribution in CVs. (2) The enhanced mass transfer rates do not lead to a runaway mass transfer process and allow the white dwarfs to grow mass ≲0.1 M ☉. (3) BDML can cause both positive and negative variations in the orbital period induced by nova eruptions, in line with observations, and can potentially explain the properties of some peculiar supersoft X-ray sources likely CAL 87, 1E 0035.4−7230, and RX J0537.7−7034.

Interfacial microenvironment to construct a three-dimensional fluoride-modified cobalt oxyhydroxide/polyvinylidene fluoride for the PMS activation to remove antibiotics

The monolithic membrane reactor for purification of antibiotics-contained wastewater offers a bright means to vanquish technological challenges associated with catalyst recovery, reaction efficiency, and mass transfer typically encountered in powdered heterogeneous catalysts. Herein, a fluoride-modified cobalt oxyhydrooxide (FCO) is planted on polyvinylidene fluoride (PVDF) film via constructing a microenvironment of Co2+-F- interaction. This optimized monolithic PVDF-supported FCO (FCO-PVDF) can completely remove tetracycline, ciprofloxacin and sulfadiazine via the peroxy-monosulfate (PMS) activation within 6 min. Additionally, the FCO-PVDF maintains outstanding resistance to environmental interference and high activity stability without decay after 8 consecutive cycles. Our investigations reveal that such exceptional performance stems from the exposure of cobalt-contained active sites for PMS activation and enhanced mass transfer in 3-D structure, leading to efficient generation of active species. Experiment and characterization demonstrate 1O2 active species play the most crucial role in eliminating antibiotics, in which perform PMS decomposition at a cobalt-exposed interface of FCO-PVDF. This work underscores the significance of designing PVDF membrane integrated fluoride-modified cobalt oxyhydroxide by constructing a unique interface microenvironment for PMS activation towards antibiotics removal.

Effect of impinging angles of liquid–liquid distributor on the extraction and mass transfer performance in a rotating packed bed

Liquid-liquid extraction is a typical separation process that is widely used in various chemical processes. However, the effect of two-liquid feeding mode on the liquid–liquid Murphree efficiency (E) of rotating packed bed (RPB) remains unclear, limiting its applications. In this work, liquid–liquid distributor with different impinging angles (2θ) of two feeding liquid jets in the RPB was designed to evaluate the E, taking water as the extractant to extract benzoic acid from kerosene into the aqueous phase. The effects of operating conditions such as the 2θ, high gravity level (β), and liquid initial velocity (u0) on the E and overall volumetric mass transfer coefficient (KLa) of the RPB were studied. Experimental results revealed that both E and KLa increased with the increase of 2θ, β, and u0. In particular, when 2θ = 90°, E and KLa exhibit optimal values. At β = 49.25, u0 = 1.75 m/s, and 2θ = 90°, since the average diameter of the daughter droplets was smaller and the effective mass transfer area was larger, E reached a maximum of 64.7 % and KLa was 0.489 s−1. A correlation for predicting KLa has been established, with deviations falling within ± 20 %. This work provides theoretical basis for guiding the enhancement of mass transfer in liquid–liquid systems.

Numerical simulation and experimental study on electrochemical recovery of copper using cylindrical and conical flow reactors

This study investigates the electrochemical recovery of copper from wastewater using cylindrical and conical flow reactors. Electrochemical approaches offer advantages such as environmental compatibility, operational versatility, and energy efficiency for heavy metal remediation. However, effective recovery from dilute effluents remains challenging due to mass transfer limitations. In this work, numerical simulations were conducted to analyze the flow field and current distribution in the reactors, with a focus on the copper reduction process. Experimental results were compared with transient simulations to assess the influence of geometry and operating parameters on the performance of the reactors. The study identified that conical reactors, particularly those with a narrowing electrode gap, enhanced mass transfer rates, leading to improved copper removal efficiency. Key findings include the relationship between electrolyte flow rates, Coulombic efficiency, and copper recovery efficiency. This work contributes to the investigation of electrochemical processes for sustainable heavy metal remediation.

Electrochemical Deposition of Silver Nanoparticle Assemblies on Carbon Ultramicroelectrode Arrays.

Silver nanoparticle (AgNP) assemblies combined with electrode surfaces have a myriad of applications in electrochemical energy storage and conversion devices, (bio)sensor development, and electrocatalysis. Among various nanoparticle synthesis methods, electrochemical deposition is advantageous due to its ability to control experimental parameters, enabling the formation of low-nanoscale (<10 nm) particles with narrow size distributions. Herein, we report the electrodeposition of AgNPs on a unique electrode platform based on carbon ultramicroelectrode arrays (CUAs), exploring several experimental variables including potential, time, and silver ion concentration. Extensive scanning electron microscopy analysis revealed that more reductive deposition potentials resulted in higher counts of smaller-sized AgNPs. While previous studies have employed planar, macro-sized electrodes with millimolar silver ion concentrations and minute-long times for AgNP electrodeposition, our results demonstrate that lower Ag+ concentrations (50-100 µM) and shorter deposition times (15-30 s) are sufficient for successful AgNP formation on CUAs. These findings are attributed to enhanced mass transfer from the radial diffusion of the array-based CUAs. The quantity of deposited Ag was determined to be 1100 ± 200 nmol cm-2, consistent with AgNP-modified CUA electrocatalytic activity for hydrogen peroxide reduction. This study emphasizes the importance of carefully considering AgNP electrodeposition parameters on unconventional electrode surfaces.

Constructing interconnected hierarchical porous structures and nitrogen-doped carbon nanofibers for superior capacitive deionization

Capacitive Deionization (CDI) has emerged as a sustainable and efficient method for desalinating low-salinity water sources. However, CDI materials are often limited by insufficient surface area, slow electron/ion transport, and suboptimal electrolyte wettability, which restrict desalination capacity and rate. Herein, we simultaneously construct interconnected hierarchical porous structures and nitrogen-doping in carbon nanofibers by pyrolyzing polymer nanofiber precursors embedded with Zeolite Imidazolate Framework-8 (ZIF-8) nanoparticles. ZIF-8 nanoparticles serve not only as precise pore-forming templates but also act as a rich source of nitrogen for doping the carbon nanofibers. We optimize the pore structure and nitrogen content of the carbon nanofibers by tuning the diameter of ZIF-8 nanoparticles within the polymer nanofiber precursor, thereby achieving superior CDI performance. This unique structure not only substantially increases the specific surface area and significantly enhances mass transfer processes, but also introduces abundant nitrogen into the porous carbon fibers. This improves their hydrophilicity, adjusts their electronic structure, increases active sites, and greatly boosts the electrodes’ adsorption capacity and desalination efficiency. An electrode constructed from the optimized porous nanofibers with a larger specific surface area (LPCNF) achieves a peak desalination capacity of 68.11 mg/g. Furthermore, the electrode maintains a high salt adsorption capacity (SAC) retention of 93.4 % after 50 cycles, significantly outperforming conventional materials such as activated carbon, graphene, and carbon nanotubes. Overall, the developed method optimizes both the pore structure and enhances the nitrogen content, providing a novel strategy for developing high-performance CDI electrode materials.

Numerical investigation of thermo-electro-mechanical behavior in solid oxide fuel cells with novel traps design interconnects for enhanced mass transfer

Numerical investigation of thermo-electro-mechanical behavior in solid oxide fuel cells with novel traps design interconnects for enhanced mass transfer

Fabrication of MXene-TiO2 nanotube composite and their electrochemical study in acidic and alkaline medium

MXenes, a novel class of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, have emerged as promising electrocatalysts for the hydrogen evolution reaction (HER) due to their remarkable electrical conductivity, exceptional structural and chemical stability, and large active surface area. In this study, we synthesized a 1D/2D Ti3C2 MXene-TiO2 nanotube (TNT) composite via electrostatic self-assembly method. Field emission scanning electron microscopy (FE-SEM) confirmed the distinctive accordion-like, multilayered morphology of Ti3C2Tx MXene, while X-ray diffraction (XRD) provided the crystalline phase of the composite. High-resolution transmission electron microscopy (HR-TEM) revealed an average particle size of 38.41 nm for the MXene-TNT nanocomposite. Additionally, X-ray photoelectron spectroscopy (XPS) confirmed the composite composition, highlighting the synergistic integration of MXene and TiO2 nanotube that enhances electrical interactions and contributes to superior catalytic performance. Electrochemical performance was assessed using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) in both acidic and alkaline media. Among the composites, the MXene-TNT (1:10) loading demonstrated a low Tafel slope of 65 mV/dec in acidic media, indicative of enhanced mass transfer properties. In alkaline media, the MXene-TNT (1:5) composite exhibited a Tafel slope of 160 mV/dec for HER, with kinetic performance proving more favorable in the acidic environment. Additionally, the composite displayed a Tafel slope of 149 mV/dec for the oxygen evolution reaction (OER) in acidic media. This study demonstrates a feasible approach for developing high-performance, cost-effective electrocatalytic materials for efficient hydrogen production, utilizing MXene as a co-catalyst.

Facile construction of multifunctional Cu2O@ZnIn2S4 heterojunction with accelerated charge transfer for efficient photocatalytic treatment of tetracycline (TC) under visible light irradiation, DFT calculations

The extensive applicability and remarkable stability of nano-semiconductor photocatalysts are of paramount importance for advancing the field of efficient water treatment. This study presents, Cu2O@ZnIn2S4 photocatalytic materials with type II heterostructure were prepared by indium zinc sulfide capping technology to degrade tetracycline. Characterization results indicated that the degradation rate of tetracycline hydrochloride (TC) could achieve 99.2 % under simulated aqueous environmental conditions, maintaining a degradation rate exceeding 85 % after five cyclic stability tests. Concurrently, the constructed type-II heterojunction effectively enhanced the transient photo responsiveness of the catalyst, facilitating the rapid transfer of photogenerated electrons. Furthermore, the structural configuration of the parceled ZnIn2S4 lamellae acted as a photon trap, minimizing the reflection of incident light and augmenting light utilization efficiency. The inherent electric field of the heterojunction significantly facilitated the degradation of TC, while the nanosheet architecture and surface porosity of the catalyst contributed to enhanced mass transfer capabilities, as corroborated by density-functional theory calculations and band gap analysis. This study utilized Cu2O@ZnIn2S4 as an efficient photocatalyst for water treatment, thereby offering a viable approach for practical applications of the catalyst.

Numerical Investigation of Effects of Obstacles in Flow Channels and Depth of Flow Channels for PEMFCs

The channel is a crucial component of the polymer electrolyte membrane fuel cell (PEMFC). Since the channel can change the reactant transfer capability, water removal capability, and distribution of the reactant, it affects the performance and durability of PEMFCs. This study investigated the effects of obstacles in the serpentine-type flow channel on the performance of PEMFCs by computational fluid dynamics (CFD). The height of the obstacles was varied to analyze the electrochemical performances of the fuel cells. In addition, the depth of the flow channel was varied to compare the performances of the PEMFCs. To better represent the real-world tendency, the agglomerate model and the Forchheimer inertial effect were used. The results showed that changes in the channel depth caused greater performance improvements compared to the installation of obstacles, due to the enhanced mass transfer and improved water removal. However, the results for the installation of obstacles showed the lower non-uniformity of the current density and a reduced pressure drop compared to the changes in the channel depth, offering advantages in terms of flooding, the fuel cell life, and the operating cost.

Process intensification for low-saline water electrochemical treatment

This work tries to enhance the mass transfer and electrical properties of the electrochemical treatment in low-saline water using process intensification. Particle electrodes, turbulence promoters, electrode assembly, and bubble-induced convection are applied to the process intensification electrochemical process. The experimental and modeling results suggest that bubble-induced convection and electrode assembly structure can induce significant turbulent disturbance around the electrode surfaces. Moderate forced convection and electrode assembly structure can significantly enhance mass transfer, including convective migration and electric migration. It results in uniform concentration distribution and better electrochemical properties. The process intensification electrochemical process exhibits excellent reactor performances and pollutant removal abilities, e.g. COD and NH3-N. The dredging tail water and natural lake waters can be purified to the IV level of the environmental quality standards (GB 3838–2002) with a moderate cost. It can on-site and ready-to-use purify water using air and renewable electricity.

A pH-responsive phase-transition bi-affinity nanopolymer-assisted exosome metabolomics for early screening of osteoarthritis

Exosomes, emerging as ideal non-invasive biomarkers for disease diagnosis and monitoring, have seldom been explored based on metabolite levels. In this study, we designed and synthesized a pH-responsive phase-transition bifunctional affinity nanopolymer (pH-BiAN) that could efficiently and homogeneously separate exosomes from urine. Specifically, poly-4-vinylpyridine (P4VP) was chosen as the pH-responsive polymer and simultaneously modified with two exosome-affinity components CD63 aptamer and distearoyl phosphoethanolamine (DSPE) through a one-step amide reaction at room temperature. By utilizing two distinct but synergistic affinity mechanisms—the immune affinity between CD63 aptamer and exosomal CD63 proteins, and hydrophobic interactions between the DSPE and the exosomal lipids—pH-BiAN can enable efficient and specific exosome separation. Moreover, during the urine exosome capture procedure, the pH-BiAN outperforms conventional solid exosome separation materials by remaining soluble in the urine sample, significantly enhancing mass transfer and contact efficiency. After exosome capture, pH-BiAN can quickly aggregate and convert to solid upon pH adjustment, allowing for easy centrifugation separation. Afterwards, multiple machine learning models were established by combining liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) untargeted metabolomics for isolated exosomes, and the clinical accuracy of the training and test sets was more than 0.919, which could well distinguish early osteoarthritis patients from healthy people.