Fouling Issues Research Articles

Ultrahigh antifouling ultrafiltration membrane based on Ag NPs photoreduction modified PVP/BiOCl nanoflower for efficient membrane fouling removal.

Polyethersulfone (PES) is widely used as an ultrafiltration (UF) membrane material in industrial production due to its excellent performance. However, its inherent hydrophobicity leads to severe membrane fouling issues during practical operation. In this study, focusing on the fouling issues of PES UF membrane, bismuth oxychloride (BiOCl) was chosen as the main nanomaterial. Ag NPs were introduced via photoreduction into BiOCl at the optimal ratio of polyvinylpyrrolidone (PVP) and BiOCl (wt%-0.3:100), resulting in the synthesis of Ag@BiOCl nanoparticles. These nanoparticles were then blended into the PES casting solution and fabricated into composite UF membranes using the reverse thermally induced phase separation (RTIPS) method. Analysis of UV-vis characterization results revealed that the introduction of Ag NPs widened the visible light absorption range of the composite material from 414.30 nm to 508.62 nm. PL spectroscopy results indicated that Ag NPs effectively inhibited the recombination of photogenerated electron-hole pairs, significantly enhancing the photocatalytic activity of Ag@BiOCl. Additionally, the introduction of Ag NPs induced the generation of oxygen vacancies (OVs) on the surface of the composite membrane. Under visible light, the contaminated composite membrane drove the OVs in the photocatalytic material to generate hot electrons (h+-e-). These h+-e- promoted the generation of more active oxygen species, thereby improving the efficiency of membrane fouling removal. The optimal membrane in the PES/Ag@BiOCl series, AGMC5-2 exhibited a pure water flux of 3960.43 L m-2 h-1, a humic acid (HA) rejection rate of 95.00%, and a flux recovery rate of 85.98%. The antibacterial rates against E. coli and S. aureus were 79.07% and 82.33%, respectively. In this study, the PES/Ag@BiOCl composite membrane demonstrated outstanding pure water flux, excellent pollutant rejection rates, significant self-cleaning, and antibacterial properties, effectively addressing membrane fouling issues caused by the inherent hydrophobicity of PES. The successful preparation of the PES/Ag@BiOCl composite membrane lays the foundation for the application of photocatalytic membranes in the field of water treatment.

Gradient Cross‐Linking Graphene Oxide–Integrated Nanofiltration Polyvinylpyrrolidone Membrane for Polycyclic Aromatic Hydrocarbons Removal

Polycyclic aromatic hydrocarbons (PAHs) persist as organic contaminants within diverse water reservoirs, posing significant environmental and health risks. Nanofiltration (NF) membranes have emerged as effective tools for PAHs removal owing to their ability to separate based on size. However, membrane fouling and limited rejection efficiency remain as challenges. This study developed a novel gradient cross‐linking graphene oxide (GO)–integrated polyvinylpyrrolidone (PVP) NF membrane to enhance PAHs rejection while mitigating fouling issues. The gradient cross‐linking approach and GO integration are aimed at improving the membrane’s rejection performance, stability, and antifouling properties. Fourier transform spectroscopy spectra of the GO‐PVP membrane showed new peaks, indicating the GO linkage. The membrane flux increased with GO concentration due to hydrophilicity; however, membrane flux decreased for the GO‐PVP membrane at a loading of 0.5 wt% due to poor GO distribution. The results exhibited a higher membrane flux of 72.9 ± 2.9 L m−2 h−1, obtained for the GO‐PVP membrane at 0.4 wt% loading. Salt rejection decreased with GO due to the development of large pores; hence, there is always a trade‐off between membrane flux and salt rejection. GO‐PVP membrane presents a promising approach for efficiently removing PAHs from water sources. The developed membrane has the potential to be applied in various water treatment applications, contributing to improved water quality and environmental protection.

Fouling and Chemical Cleaning Strategies for Submerged Ultrafiltration Membrane: Synchronized Bench-Scale, Full-Scale, and Engineering Tests.

This study investigated membrane fouling issues associated with the operation of a submerged ultrafiltration membrane in a drinking water treatment plant (DWTP) and optimized the associated chemical cleaning strategies. By analyzing the surface components of the membrane foulant and the compositions of the membrane cleaning solution, the primary causes of membrane fouling were identified. Membrane fouling control strategies suitable for the DWTP were evaluated through chemical cleaning tests conducted for bench-scale, full-scale, and engineering cases. The results show that the membrane foulants were primarily composed of a mixture of inorganics and organics; the inorganics were mainly composed of Al and Si, while the organics were primarily humic acid (HA). Sodium citrate proved to be the most effective cleaning agent for inorganic fouling, which was mainly composed of Al, whereas sodium hypochlorite (NaClO) combined with sodium hydroxide (NaOH) showed the best removal efficiency for organic fouling, which predominantly consisted of HA and Si. However, sodium hypochlorite (NaClO) combined with sodium hydroxide (NaOH) showed the best removal efficiency for organic fouling and Si; organic fouling predominantly consisted of HA. Based on the bench-scale test results, flux recovery was verified in the full-scale system. Under a constant pressure of 30 kPa, the combined acid-alkali cleaning achieved the best flux recovery, restoring the flux from 22.8 L/(m2·h) to 66.75 L/(m2·h). In the engineering tests, combined acid-alkali cleaning yielded results consistent with those of the full-scale tests. In the practical engineering cleaning process, adopting a cleaning strategy of alkaline (NaClO + NaOH) cleaning followed by acidic (sodium citrate) cleaning can effectively solve the membrane fouling problem.

Predicting Salt Adsorption Capacity (SAC) and Membrane Fouling in Membrane Capacitive Deionization (MCDI) Using Machine Learning

Capacitive deionization (CDI) is an electrochemical technology that utilizes porous carbon electrodes to remove ionic substances. Ions from the solution are adsorbed during the charging stage and the adsorbed ions are desorbed during the discharging process, repeating the process to operate the system. To enhance ion removal capacity and prolong life of systems compared to CDI, membrane capacitive deionization (MCDI) has been developed. MCDI includes both anion and cation exchange membranes to induce the co-ion expulsion effects during the discharging stage, thereby exhibiting superior ion adsorption capacity than CDI. However, the utilization of ion exchange membranes causes a new issue of membrane fouling. Natural organic matter (NOM) serves as a common precursor to membrane fouling in nature environment. Especially, NOM could lead to the formation of fouling layers that disrupt transport phenomena across membrane systems, including ion exchange membranes used in MCDI. Numerous modeling studies have been conducted to investigate the effect of fouling on MCDI, aiming to predict fouling and evaluate the performance of MCDI in advance. Although a mathematical model was developed to predict MCDI performance under natural organic matter conditions, it had limitations of achieving high accuracy in natural environments. While a modified mathematical model showed high accuracy in predicting adsorption time reduction and capacity, it demonstrated low accuracy at points where current was applied and varied. This highlights the limitations of the modified mathematical model, as it is inadequate to consider the actual operating environment of MCDI. Therefore, this study adopted a robust machine learning model to address the limitations of the mathematical models. Electrochemical profiles and feed water conditions were used as input parameter of the model, enabling the prediction of both salt adsorption capacity and the growth of fouling layer on ion exchange membranes during operation. Consequently, this approach could improve the prediction accuracy of MCDI performance while providing detailed insights into fouling layer development, facilitating efficient operation and management of the MCDI system.

Development and Assessment of a Batch Type Ohmic Heating System for Milk Processing

This study aims to develop and assess the performance of a batch-type ohmic heating system for the thermal processing of cow and buffalo milk, particularly investigating whether the ohmic system affects the nutritional and microbial quality of the milk. An experimental setup was fabricated with a 7-liter capacity, utilizing an agitator as one electrode and the vessel surface as the other. The system was tested for heating milk from 32°C to target temperatures of 75°C and 92°C. Key processing parameters, including agitator speed and applied voltage, were optimized for both milk types. The physicochemical and microbial properties of the ohmically heated milk were evaluated, along with performance metrics such as heating rates, power consumption, and system efficiency. The developed ohmic heating system achieved heating rates of 4.29°C/min for cow milk and 2.85°C/min for buffalo milk. Cow milk demonstrated lower energy consumption, requiring less time and voltage compared to buffalo milk, with system performance coefficients of 58% for cow milk and 50% for buffalo milk. However, fouling on the agitator surface was identified as a challenge for industrial applications. Importantly, the ohmic heating process preserved the nutritional content while effectively reducing microbial load, confirming its potential for dairy processing. In conclusion, the batch-type ohmic heating system exhibited high efficiency and rapid heating capabilities for both cow and buffalo milk, indicating its viability for commercial use. Future research should focus on addressing fouling issues and further optimizing the system, enhancing the overall potential of ohmic heating technology in the dairy industry.

Novel insights into fouling mechanisms in anaerobic acidification membrane bioreactor: The leading role of pH value

Anaerobic acidification membrane bioreactors (AAMBRs) have recently emerged as effective systems for recovering volatile fatty acids (VFAs) from municipal wastewater. However, membrane fouling remains a critical challenge, with its underlying mechanisms not yet fully understood. Given its importance in inhibiting methanogenic bacteria and stabilizing VFAs production, this study explores the direct and indirect effects of pH on membrane fouling mechanisms in AAMBRs. The results demonstrated that compared to pH 7, the fouling potential of anaerobic sludge was significantly higher at pH levels of 5 and 10 owing to a decrease of sludge floc size and an increase of soluble microbial products (SMP) especially proteins. Analytical techniques such as confocal laser scanning microscopy (CLSM), fourier transform infrared spectroscopy (FTIR), and fluorescence excitation-emission matrix (F-EEM) analyses revealed a substantial increase in organic foulants particularly proteins on the membrane surface at pH levels of 5 and 10. Circular dichroism (CD) spectroscopy further indicated a significant change in protein secondary structure, specifically an increase in α-helix content under extreme pH conditions. Furthermore, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory indicated that elevated protein concentrations enhance the adhesion of sludge and SMP to membrane surfaces. Insights from the Flory-Huggins theory demonstrated that variations in protein structure significantly contribute to increased filtration resistance within the gel layer. Both experimental data and theoretical models underscore the dual role of pH in optimizing VFAs production and managing membrane fouling, offering insights for enhancing AAMBR performance and mitigating fouling issues.

Preparation of TA-O-MoS2/PES mixed matrix ultrafiltration membrane for rare earth wastewater treatment

The trade-off between permeability and selectivity, along with the issue of membrane fouling, has constrained the widespread application of ultrafiltration (UF) membranes in recycling rare earth wastewater. Here, we present the incorporation of tannic acid (TA) modified molybdenum disulfide oxide (O-MoS2) as a functional enhancer to fabricate polyethersulfone (PES) based mixed matrix membranes through a nonsolvent induced phase separation (NIPS) approach. Compared to the unmodified PES membrane, the integration of TA-O-MoS2 significantly improves the hydrophilicity, porosity in the mixed matrix membrane. By altering the concentration of TA-O-MoS2, the TA-O-MoS2/PES UF membrane achieves enhanced hydrophilicity and charge properties, resulting in a remarkable improvement in separation performance. Specifically, the optimized membrane M2 (TA-O-MoS2 addition of 0.1 wt%) exhibits a water flux of 140.98 Lm−2h−1bar−1 and a PEG 20000 rejection rate of 91.00 %, representing increases of 180 % and 120 % over the control PES membrane, respectively. Notably, membrane M2 effectively retains 91.31 % of macromolecular organic compounds in rare earth wastewater, while permitting nearly complete passage of inorganic salts, for instance CaCl2 (3.26 %) and MgSO4 (4.84 %). Moreover, the TA-O-MoS2/PES membrane demonstrates robust antifouling properties and exceptional durability, indicating its significant potential for efficient treatment and resource recovery in rare earth wastewater.

Modified PVDF ultrafiltration membrane with host–guest supramolecular trapping for efficient separation of multiple organic contaminants

In our modern lifestyle, the cocktail of organic pollutants from everyday items, such as hair dyes, cloth dyes, food colours, hair oils, cooking oils, and agricultural proteins, enters water streams through household pipelines. This unnoticed contamination, growing alarmingly, poses a serious challenge beyond the scope of conventional separation techniques, calling for a comprehensive solution. While membrane technology offers a promising solution, it grapples with persistent surface fouling issues. This study introduces a novel approach through the development of extraordinary Polyvinylidene fluoride-Montmorillonite-Cucurbit[6]uril (PVDF-M-CB[6]) mixed matrix membranes, presenting a potential breakthrough in overcoming surface fouling challenges and offering a versatile solution for the separation of an array of organic contaminants. Powered by the synergistic host–guest supramolecular complexation of CB[6] onto montmorillonite (M) clay support, these membranes demonstrate swift and selective encapsulation, leading to superior cationic dye rejection. Adding to the allure, CB[6]’s structure encourages favorable carbonyl interactions with bovine serum albumin (BSA), effectively repelling the protein away from the membrane, while also promoting seamless oil–water emulsion separation with an underwater oil contact angle of 150 ± 3°, displaying its superoleophobic nature and enhancing remarkable antifouling properties. The PV-M-CB[6] membranes showcased 2x removal of cationic dyes, 1.3x removal of anionic dyes, 1.4x oil–water emulsion separation, and 2x BSA separation compared to the pristine polyvinylidene fluoride (PVDF) membrane. These membranes displayed 98.3 % efficiency in oil–water emulsion separation and sustained a flux recovery ratio of over >75% after seven cycles. Overall, PV-M-CB[6] membranes represent an innovative solution with heightened hydrophilicity, remarkable antifouling performance, and exceptional proficiency in delivering one-stop organic foulant separation.

Innovative temperature-responsive membrane with an elastic interface for biofouling mitigation in industrial circulating cooling water treatment

To address the issues of scaling caused by heat and water evaporation in regard to circulating cooling water (CCW), TFC membrane filtration systems have been increasingly considered for terminal treatment processes because of their excellent separation performance. However, membrane biofouling phenomenon significantly hinders the widespread utilization of TFC membranes. In this study, to harness the thermal phenomenon of CCW and establish a stable and durable multifunctional antibiofouling layer, temperature-responsive Pnipam and the spectral antibacterial agent Ag were organically incorporated into commercially available TFC membranes. Biological experimental findings demonstrated that above the lower critical solution temperature (LCST), the contraction of Pnipam molecular chains facilitated the inactivation of bacteria by the antibacterial agent, resulting in an impressive sterilization efficiency of up to 99 %. XDLVO analysis revealed that below the LCST, the establishment of a hydration layer on the functional interface resulted in the creation of elevated energy barriers, effectively impeding bacterial adhesion to the membrane surface. Consequently, a high bacterial release rate of 98.4 % was achieved on the low-temperature surface. The alterations in the functional membrane surface conformation induced by temperature variations further amplified the separation between the pollutants and the membrane, creating an enhanced "elastic interface." This efficient and straightforward cleaning procedure mitigated the formation of irreversible fouling without compromising the integrity of the membrane surface. This study presents a deliberately engineered thermoresponsive antibiofouling membrane interface to address the issue of membrane fouling in membrane-based CCW treatment systems while shedding new light on the mechanisms of "inactivation" and "defense."

A Review on: Advances in Membrane Technologies for Heavy Metal Removal from contaminated Water

Abstract The contamination of water by various toxic constituents, particularly heavy metals, exerts deleterious effects on both flora and fauna, with potential repercussions for human well-being. Consequently, there exists a pressing imperative to explore methodologies aimed at the elimination of hazardous substances from polluted water. Among the array of extant approaches, membrane-based techniques emerge as notably efficacious for mitigating pollutants, specifically heavy metals, in water systems. The elimination of mineral contaminants from water holds paramount significance for fostering a hygienic environment and safeguarding human health. Polymeric membranes offer an energy-efficient approach to water purification, yet they encounter fouling issues during filtration. Surface modification of the membrane is one avenue for mitigating fouling, aiding in the maintenance of elevated water productivity levels. The present investigation undertakes a comprehensive examination of outcomes derived from diverse experiments conducted over the preceding two decades, with the objective of identifying the most pertinent membrane filtration processes, accounting for varied contaminant profiles.

Novel catalytic membrane based on γ-FeOOH@PVDF/peroxymonosulfate for efficient ammonia recovery: Self-cleaning mechanism and emerging organic contaminant degradation performance

The resolution of membrane fouling issues is crucial for the commercial application of membrane distillation (MD) ammonia recovery. The peroxymonosulfate-based advanced oxidation process (PMS-AOP) exhibited conspicuous degradation of organic pollutants, and in-situ coupling with the MD process could probably achieve desirable antifouling performance. In this research, a novel γ-FeOOH@PVDF catalytic membrane was fabricated by gas–liquid self-deposition method and fluorination treatment. The γ-FeOOH nanosheets arrayed on the substrate membrane endowed the catalytic membrane with superhydrophobicity. The MD ammonia recovery of the digestate achieved a high recovery rate (97.3%), and no membrane fouling or wetting phenomena were detected by real-time monitoring by optical coherence tomography (OCT). The batch degradation experiments of thiamphenicol (TAP) validated the γ-FeOOH@PVDF/PMS system with superior degradation performance and stability. The electron paramagnetic resonance (EPR) coordinated free radical quenching experiment determined the active substance (SO4•-, 1O2, O2•- and •OH) in the degradation process. In addition, the potential self-cleaning mechanism of the radical and non-radical pathways of γ-FeOOH@PVDF was elucidated via density functionaltheory (DFT) calculation. The quinone groups in the organic pollutants facilitated the redox of Fe(Ⅲ)/Fe(Ⅱ) and accelerated the activation of PMS. Hence, the catalytic membrane developed in this research provided a novel instructive strategy for membrane fouling control and also exhibited significant potential of coupling catalysis and membrane technology for water treatment.

Ultraviolet Grafting of Bismuth Oxide Enhances the Photocatalytic Performance of PVDF Membrane and Improves the Problem of Membrane Fouling.

Photocatalytic membranes are crucial in addressing membrane fouling issues. However, the grafting amount of the catalyst on the membrane often becomes a key factor in restricting the membrane's self-cleaning capability. To address the challenge, this manuscript proposes a method for solving membrane fouling, featuring high grafting rates of bismuth oxide (Bi2O3) and acrylic acid (AA), significant contaminant degradation capability, and reusability. A highly photocatalytic self-cleaning microfiltration membrane made of polyvinylidene fluoride bismuth oxide and acrylic acid (PVDF-g-BA) was prepared by attaching nano Bi2O3 and acrylic acid onto the polyvinylidene fluoride membrane through adsorption/deposition and UV grafting polymerization. Compared with pure membranes and pure acrylic grafted membranes (PVDF-g-AA), the modified membrane grafted with 0.5% bismuth oxide not only improves the grafting rate and filtration performance, but also has higher self-cleaning ability. Furthermore, the degradation effect of this membrane on the organic dye methyl violet 2B under visible light irradiation is very significant, with a degradation rate reaching 90% and almost complete degradation after 12 h. Finally, after repeated filtration and photocatalysis, the membrane can still significantly degrade contaminants and can be reused.

Performance of capacitive deionizing membrane distillation (CDIMD) process for the organic sewage treatment and how operating parameters can affect it

To solve the fouling issue of traditional membrane distillation (MD) technique, a newly-designed hybrid purification system integrating capacitive deionization (CDI) with MD technology was established for the organic sewage treatment in this study, namely capacitive deionizing membrane distillation (CDIMD) technology. Complexes formation via cross-linking among protein, divalent cations, and polysaccharide, an archcriminal inducing MD fouling, was remarkably alleviated in the CDIMD system considering that negatively-charged organics were clearly divided away from those divalent cations in an electric field circumstance. The CDIMD performance was deeply explored in this study focusing on the impact mechanisms of core operational parameters. An appropriate increment of feed temperature (60–65 °C) and feed flow velocity (15.72–17.82 mm/s) contributed to the anti-fouling performance of CDIMD. Considering the side reactions at voltage >1.2 v, setting working voltage at around 1.2 v seemed to be optimal for CDIMD operation. With an overall consideration of pure water production and anti-fouling performance, a properly thicker CNTs layer (40–60 μm) efficiently enhanced the fouling mitigation of CDIMD. A frequent switching of electric field direction (9/1 min) facilitated the timely regeneration of electrode and composite membranes, accordingly promoting a reliable purification of organic wastewater by CDIMD technique.

Double-drying 3D lamellar-structured aerogel membrane for efficient oil-water separation and long-lasting antibacterial activity

Conventional oil-water separation membranes are difficult to establish a trade-off between membrane flux and separation efficiency, and often result in serious secondary contamination due to their fouling issue and non-degradability. Herein, a double drying strategy was introduced through a combination of oven-drying and freeze-drying to create a super-wettable and eco-friendly oil-water separating aerogel membrane (TMAdf). Due to the regular nacre-like structures developed in the drying process and the pores formed by freeze-drying, TMAdf aerogel membrane finally develops regularly arranged porous structures. In addition, the aerogel membrane possesses excellent underwater superoleophobicity with a contact angle above 168° and antifouling properties. TMAdf aerogel membrane can effectively separate different kinds of oil-water mixtures and highly emulsified oil-water dispersions under gravity alone, achieving exceptionally high flux (3693 L·m−2·h−1) and efficiency (99 %), while being recyclable. The aerogel membrane also displays stability and universality, making it effective in removing oil droplets from water in corrosive environments such as acids, salts and alkalis. Furthermore, TMAdf aerogel membrane shows long-lasting antibacterial properties (photothermal sterilization up to 6 times) and biodegradability (completely degraded after 50 days in soil). This study presents new ideas and insights for the fabrication of multifunctional membranes for oil-water separation.

Electrochemical analysis of ion-exchange membranes fouling during electrodialysis treatment of real shale gas flowback water

Electrodialysis (ED) is considered an effective technology for desalinating shale gas flowback fluid toward environmental risk control and resource recovery. However, membrane fouling remains a significant challenge and the particular fouling behavior of ion-exchange membranes (IEMs) in real scenario remains unclear. In this study, we employed interface characterization techniques including electrochemical impedance spectroscopy (EIS) to investigate the fouling behavior of both anion-exchange membranes (AEMs) and cation-exchange membranes (CEMs) during the desalination process. Notably, a positive correlation was observed between the transmembrane electric potential (TMEP) of the target membrane and the extent of membrane fouling during ED processing. EIS data revealed the membrane bulk exhibited the most pronounced increase in modeled electrical resistance, suggesting that internal fouling more significantly inhibited mass transfer compared to external fouling. Under varying current densities, the resistance of the AEM and CEM membrane bulk increased from an initial value of 3.93–16.53 Ω cm2 and from 3.90 to 9.87 Ω cm2, respectively, corresponding to their maximum TMEP increase by factors of 6.0 and 2.0 during the ED treatment. Our results demonstrate that AEM undergone a more severe organic fouling than CEM (scaling) during desalination of real shale gas flowback fluid. Effective strategies to mitigate the fouling issue in IEMs were finally proposed. These findings provide valuable guidance on future process optimizing and fouling mitigation in the ED treatment of real shale gas flowback fluid.

Anti-fouling rotating polymer-based heat exchanger for zero liquid discharge humidification-dehumidification desalination

The objective of this investigation is to assess the performance of various heat exchangers for application in a novel solar-powered zero liquid discharge humidification-dehumidification desalination system. In this study four heat exchangers (HX) having two different flow configurations namely counter flow (cf), cross flow (cr) made up of three different materials namely high-density polyethylene (HDPE), aluminum (Al), and Polypropelyne (PP) were compared in terms of their effectiveness and overall heat transfer coefficient under varying salinity levels (up to 10%) and mixing ratios (0.22–0.45). At a mixing ratio of 0.22 and 0% salinity, PP-HXcr and Al-HXcf exhibited similar effectiveness (∼85%), surpassing that of HDPE-HXcf (∼65%). Despite PP-HXcr's lower thermal conductivity in comparison to Al-HXcf, comparable effectiveness was achieved due to the superior flow distribution in PP-HXcr. Further investigations focused on the impact of salinity on heat exchanger performance. At 3.5% salinity, all heat exchangers experienced a decline in effectiveness and heat transfer coefficient (HTC), with Al-HXcf experiencing a more pronounced decrease compared to PP-HXcr. The higher thermal conductivity of Al-HXcf led to greater salt accumulation, while PP-HXcr demonstrated minimal fouling. As the experiment progressed, fouling increased for all heat exchangers, with the Al-HXcf being practically ineffective at 10% salinity with an effectiveness below 10%. To address the issue of fouling, a rotating cross-flow heat exchanger (RPP-HXcr) was introduced. While the effectiveness of the PP-HXcr drops from 85% to approximately 60% with increasing salinity from 0% to 10%, the RPP-HXcr demonstrates only a marginal decline in effectiveness with increasing salinity. For instance, at mixing ratio of 0.22 when the salinity is increased from 0% to 10%, the effectiveness of RPP-HXcr only drops from 83% to 77%. This exceptional performance was attributed to the continuous contact between the rotating tubes and the incoming feed, effectively preventing fouling and ensuring sustained efficiency. Rotating cross-flow heat exchanger (RPP-HXcr) is introduced and validated as a potentially reliable solution for mitigating fouling, as it demonstrates sustained efficiency and minimal performance degradation across different salinity conditions.

Molecular dynamics study of the influence of electric fields on water penetration in metal confined nanochannels

Electric field regulation of water penetration in nanochannels is an important method to address membrane fouling issues. Investigating the mechanism of electric field effects on water penetration in metal-confined nanochannels is highly meaningful. This article uses molecular dynamics methods to study the characteristics of water penetration in copper nanochannels. The influence and mechanisms of different types of applied electric fields on the water penetration within the channels were analyzed. The results indicate that applying electric fields in the y and z directions can enhance water penetration efficiency within the channels. Furthermore, a sinusoidal electric field has a greater enhancing effect on water penetration compared to a uniform electric field. Particularly, with a sinusoidal electric field frequency of 50 GHz, favorable water penetration effects were observed, with maximum increases in transport rate and axial diffusion coefficient of 197.5 % and 249.7 % respectively, relative to the absence of an electric field. The sinusoidal electric field exhibited greater capability in accelerating water molecule movement, leading to a rise in system temperature, with a maximum temperature increase of 46.9 %. These findings provide microscopic evidence for the feasibility of electric field regulation of water penetration in nanochannels, offering a theoretical foundation for enhancing nanoconfined water penetration behavior within channels.

Phytic acid metal complex as precursor for fabrication of superhydrophilic membrane with photo-Fenton self-cleaning property for microalgae dewatering and oil/water emulsion separation

Membrane technology is regarded as one of the most effective approaches for microalgae dewatering in the biofuel production industrial and oil/water emulsion separation. However, it inherently suffers from the issue of membrane fouling, particularly irreversible membrane fouling, which is hard to remove by physical methods. Herein, a robust superhydrophilic membrane combined with photo-Fenton self-cleaning property was developed for microalgae dewatering and oil/water emulsion separation. Phytic acid (PA) and FeIII formed a hydrophilic PA-FeIII complex on the polyethersulfone (PES) membrane as the precursor for the in situ growth of β-FeOOH nanorods. When used for microalgae filtration, the irreversible fouling that blocked membrane pores could be degraded by the photo-Fenton reaction. Hence, the obtained PES/PA@β-FeOOH membrane possessed a flux recovery rate (FRR) of 90.2 % (within 30 min), which was significantly higher than that of the PES membrane (32.9 %). The proteins and polysaccharides (extracellular organic matter) attached on the PES/PA@β-FeOOH membrane with photo-Fenton cleaning were 11.2 and 9.1 mg/m2, which was considerably lower than that of PES after hydraulic cleaning (184.1 and 334.9 mg/m2). Moreover, due to the superhydrophilic, the prepared PES/PA@β-FeOOH membrane also exhibited excellent oil/water emulsion separation ability. This work presents a facile and mild strategy to design an anti-fouling coating with superhydrophilic and photo-Fenton activity, which can be used in membrane technology for microorganism filtration and wastewater treatment.

TiO2/CMWCNT/CaAlg composite membrane used for dye desalination and its rapid cleaning under ultraviolet light and advanced oxidation activated by monopersulfate

Membrane separation technology holds tremendous potential in treating dye wastewater. However, the widespread issue of membrane fouling leads to a significant decline in separation efficiency and lifespan. In this paper, titanium dioxide (TiO2)/carboxyl multi-walled carbon nanotube (CMWCNT)/calcium alginate (CaAlg) membranes were prepared by blending and simple cross-linking methods. The influence of TiO2 and CMWCNT concentrations on membrane performance, especially the anti-swelling performance, was explored. Additionally, the mechanical properties, filtration performance, fouling resistance, and dye/salt separation performance of the composite membrane were investigated. Notably, the rejection rate of dye molecules (Mw > 696 Da) was greater than 98 %, while the rejection rate of salt was less than 11.0 %. Furthermore, two methods for environmental-friendly cleaning membrane, photocatalytic degradation and advanced oxidation activated by monopersulfate, were performed. Finally, the photocatalytic degradation process and mechanism of Congo red (CR) were investigated by electron spin resonance (ESR).

Synergistic algal/bacterial interaction in membrane bioreactor for detoxification of 1,2-dichloroethane-rich petroleum wastewater

The study addressed the challenge of treating petroleum industry wastewater with high concentrations of 1,2-dichloroethane (1,2-DCA) ranging from 384 to 1654 mg/L, which poses a challenge for bacterial biodegradation and algal photodegradation. To overcome this, a collaborative approach using membrane bioreactors (MBRs) that combine algae and bacteria was employed. This synergistic method effectively mitigated the toxicity of 1,2-DCA and curbed MBR fouling. Two types of MBRs were tested: one (B-MBR) used bacterial cultures and the other (AB-MBR) incorporated a mix of algal and bacterial cultures. The AB-MBR significantly contributed to 1,2-DCA removal, with algae accounting for over 20% and bacteria for approximately 49.5% of the dechlorination process. 1,2-DCA metabolites, including 2-chloroethanol, 2-chloro-acetaldehyde, 2-chloroacetic acid, and acetic acid, were partially consumed as carbon sources by algae. Operational efficiency peaked at a 12-hour hydraulic retention time (HRT) in AB-MBR, enhancing enzyme activities crucial for 1,2-DCA degradation such as dehydrogenase (DH), alcohol dehydrogenase (ADH), and acetaldehyde dehydrogenase (ALDH). The microbial diversity in AB-MBR surpassed that in B-MBR, with a notable increase in Proteobacteria, Bacteroidota, Planctomycetota, and Verrucomicrobiota. Furthermore, AB-MBR showed a significant rise in the dominance of 1,2-DCA-degrading genus such as Pseudomonas and Acinetobacter. Additionally, algal-degrading phyla (e.g., Nematoda, Rotifera, and Streptophyta) were more prevalent in AB-MBR, substantially reducing the issue of membrane fouling.