Ceramic-based membranes for water and wastewater treatment

Coupled ozonation with nanofiltration and catalytic nanofiltration for the removal of micropollutants from secondary effluent

Emerging contaminants have become a global concern in recent years. Ozonation is an effective treatment for their degradation. However, it may generate toxic by-products under certain conditions. Catalytic ozonation is an option for improved contaminant oxidation, which can be enhanced by incorporating a filtering membrane, adding the advantages of retaining molecules, ions, and colloids. Recent studies have demonstrated the catalytic potential of a nanofiltration membrane functionalized with a thin layer of mesoporous maghemite (γ-Fe2O3). However, they have not tested its efficiency in real environmental matrices. In this study, the efficiency of a ceramic membrane functionalized with maghemite was tested for the removal of seven contaminants (carbamazepine, acetaminophen, sulfamethoxazole, caffeine, sodium diclofenac, diuron, and ketoprofen). The performance of ozonation and nanofiltration and the combination of both, with and without the functionalized γ-Fe2O3 layer, were compared for ultrapure water and secondary effluent with contaminants at a concentration of 0.5 mgL-1. The coupling of ozonation and functionalized membrane had around 20% higher removal for the most resistant compounds, using 70% less ozone than the configuration that used a commercial membrane. Although the initial samples did not show toxicity, there was an emergence and growth of toxicity, possibly due to the formation of toxic by-products.

Changes in the Separation Properties of Aged PVDF Ultrafiltration Membranes During Long-Term Treatment of Car Wash Wastewater

Car wash wastewater (CWW) is complex waste that may be effectively treated by the ultrafiltration (UF) process. However, one of the most important challenges in implementing this process on an industrial scale is the fouling phenomenon membrane aging. Indeed, these may lead to a reduction in UF performance possibly associated with a loss in integrity of the fouled/aged membrane. Therefore, the main aim of the current study was to provide a comprehensive investigation on the changes in the separation properties of aged FP100 ultrafiltration membranes made of polyvinylidene fluoride (PVDF) with respect to their application for long-term treatment of CWW. For this purpose, studies were conducted for new membranes and membranes previously used for over 5 years in a pilot plant. As a feed, solutions of dextran, solutions of model organism Escherichia coli and synthetic CWW were used. It has been found that PVDF membranes demonstrated poor stability when in frequent contact with chemicals periodically applied for membrane cleaning. Indeed, the aged membranes were characterised by the increased porosity. However, it is important to note that membranes aging had no significant impact on the permeate quality during the UF process of synthetic CWW. Indeed, the obtained permeate was characterised by the turbidity lower than 0.25 NTU. Likewise, with regard to the separation of E. coli, the aged PVDF membranes ensured the high process efficiency and over 99.99% bacterial retention. In the interest of the growing potential of PVDF membrane in CWW treatment, the results obtained in the current work complement the findings made in this field.

Fabrication of composite ceramic polymeric membranes for agricultural wastewater treatment

Humans have contaminated water supplies with harmful compounds, including different heavy metals. Heavy metals can interfere with human and animal vital organs and metabolic processes. They are also persistent and bioaccumulative. So, this study aimed to fabricate composite ceramic membranes (CCM) from Egyptian raw substances to eliminate heavy metals from agricultural wastewater. A ceramic supporting (CS) filter constructed from ball clay, kaolin, feldspar, and quartz using corn starch flour as a pore-developing agent. CS fired at two different temperatures and soaking times. Then, a thin polyamide 6 (PA6) coating was dip-coated over the upper layer of the support membranes. The raw materials and prepared CCM were subjected to characterization and applied to treat agricultural wastewater from the Kitchener drain in Kafr El-Sheikh Governorate, Egypt. The results showed that the CCM (M2) (membrane sintered at 1000 °C/30 min soaking time and modified with PA6) had a higher pure water permeability of 558.5 L h-1 m-2 than the membrane (M4) (membrane sintered at 1100 °C/180 min soaking time and modified with PA6). The study examined how effectively the membranes removed toxic substances from wastewater. The findings exhibited an excellent removal of > 80% and up to 97.02%, > 80% and up to 99.97% of the heavy metals, and optimum fluxes of 341.07 and 276.35 L h-1 m-2 were achieved in the cases of M2 and M4, respectively. Furthermore, with a low flux decline ratio and a high permeate recovery of 92.3% for wastewater, the modified M4 membrane demonstrated remarkable antifouling capabilities.

Pilot scale on-site demonstration and seasonality assessment of nitrogen recovery and water reclamation from pig's slurry liquid fraction

Livestock slurry has gathered significant interest as a secondary raw material for fertilisers industry due to its content on macronutrients -nitrogen, phosphorous, and potassium- and organic carbon. In this study, the performance of an on-site pilot plant composed by microfiltration, membrane-assisted stripping, and reverse osmosis for selective recovery of nitrogen as fertiliser and water reclamation was demonstrated for 2 years in a pig farm, referenced to 8 batches for seasonal assessment. Microfiltration mitigated the seasonal variation in the composition of pig slurry leading to stable process efficiency in the following steps. Membrane-assisted stripping resulted in the recovery of up to 56% of nitrogen as high-purity ammonium sulphate, and up to 42% of reclaimed water as reverse osmosis permeate. The proposed train of technologies reported proper performance and robustness during the whole demonstration period as it resulted in the production of reclaimed water and ammonium sulphate with no significant quality variations. The energy cost for both products obtained in this study was found in the average of the previous works reviewed with 12.49 kWh kg-1 NH3 produced, and 0.37 kWh m-3 of reclaimed water. The environmental assessment showed that nitrogen losses could be reduced by up to 90 kg N ha-1 d-1 by replacing manure spreading with precise fertilisation techniques, enabled by the selective recovery of nitrogen from SLF. Finally, the financial study showed that the scaling up of the proposed train of technologies would result in benefits for farms with more than 1600 pig heads.

Purification of Liquid Fraction of Digestates from Different Origins-Comparison of Polymeric and Ceramic Ultrafiltration Membranes Used for This Purpose

Circular economy, clean technologies, and renewable energy are key to climate protection and modern environmental technology. Recovering water and valuable minerals from the liquid fraction of digestate is in line with this strategy. Digestate, a byproduct of anaerobic methane fermentation in biogas plants, is a potential source of water, minerals for fertilizers, and energy rather than waste. This study examined digestate from municipal and agricultural biogas plants and highlights the need for research on both due to their differences. The use of membrane techniques for water recovery from liquid digestate offers an innovative alternative to conventional methods. This study used standalone membrane filtration and an integrated system to produce water suitable for agricultural use. Ceramic membranes with cut-offs of 1, 5, 15, and 50 kDa and polymeric membranes of polyethersulfone and regenerated cellulose with cut-offs of 10 and 30 kDa were tested. The results showed that the membrane material significantly affects the transport and separation properties. Higher cut-off values increased permeate flux across all membranes. Ceramic membranes were more susceptible to fouling in standalone ultrafiltration, but were more effective in purifying digestate than polymeric membranes. The best results were obtained with a ceramic membrane with a 1 kDa cut-off (for example, for the integrated process and the municipal digestate, the retention rates of COD, BOD5 and DOC were 69%, 62%, and 75%, respectively).

Advancements in Inorganic Membrane Filtration Coupled with Advanced Oxidation Processes for Wastewater Treatment

Membrane filtration is an effective water recycling and purification technology to remove various pollutants in water. Inorganic membrane filtration (IMF) technology has received widespread attention because of its unique high temperature and corrosion resistance. Commonly used inorganic membranes include ceramic membranes and carbon-based membranes. As novel catalytic inorganic membrane processes, IMF coupled with advanced oxidation processes (AOPs), can realize the separation and in situ degradation of pollutants, thus mitigating membrane contamination. In this paper, the types and performance of IMF are discussed. The influencing factors of inorganic membranes in practical wastewater treatment are summarized. The applications, advantages, and disadvantages of the coupled process of IMF and AOPs are summarized and outlined. Finally, the challenges and prospects of IMF and IMF coupled with AOPs are presented, respectively. This contributes to the design and development of coupled systems of membrane filtration with inorganic materials and IMF coupled with AOPs for practical wastewater treatment.

Enhancing Rubber Industry Wastewater Treatment through an Integrated AnMBR and A/O MBR System: Performance, Membrane Fouling Analysis, and Microbial Community Evolution

This study explores the effectiveness of an integrated anaerobic membrane bioreactor (AnMBR) coupled with an anoxic/oxic membrane bioreactor (A/O MBR) for the treatment of natural rubber industry wastewater with high sulfate, ammonia, and complex organic contents. This study was conducted at the lab-scale over a duration of 225 days to thoroughly investigate the efficiency and sustainability of the proposed treatment method. With a hydraulic retention time of 6 days for the total system, COD reductions were over 98%, which reduced the influent from 22,158 ± 2859 mg/L to 118 ± 74 mg/L of the effluent. The system demonstrates average NH3-N, TN, and total phosphorus (TP) removal efficiencies of 72.9 ± 5.7, 72.8 ± 5.6, and 71.3 ± 9.9, respectively. Despite an average whole biological system removal of 50.6%, the anaerobic reactor eliminated 44.9% of the raw WW sulfate. Analyses of membrane fouling revealed that organic fouling was more pronounced in the anaerobic membrane, whereas aerobic membrane fouling displayed varied profiles due to differential microbial and oxidative activities. Key bacterial genera, such as Desulfobacterota in the anaerobic stage and nitrifiers in the aerobic stage, are identified as instrumental in the biological processes. The microbial profile reveals a shift from methanogenesis to sulfide-driven autotrophic denitrification and sulfammox, with evidence of an active denitrification pathway in anaerobic/anoxic conditions. The system showcases its potential for industrial application, underpinning environmental sustainability through improved wastewater management.

Potential strategies for phytoremediation of heavy metals from wastewater with circular bioeconomy approach

Water pollution is an inextricable problem that stems from natural and human-related factors. Unfortunately, with rapid industrialization, the problem has escalated to alarming levels. The pollutants that contribute to water pollution include heavy metals (HMs), chemicals, pesticides, pharmaceuticals, and other industrial byproducts. Numerous methods are used for treating HMs in wastewater, like ion exchange, membrane filtration, chemical precipitation, adsorption, and electrochemical treatment. But the remediation through the plant, i.e., phytoremediation is the most sustainable approach to remove the contaminants from wastewater. Aquatic plants illustrate the capacity to absorb excess pollutants including organic and inorganic compounds, HMs, and pharmaceutical residues present in agricultural, residential, and industrial discharges. The extensive exploitation of these hyperaccumulator plants can be attributed to their abundance, invasive mechanisms, potential for bioaccumulation, and biomass production. Post-phytoremediation, plant biomass can be toxic to both water bodies and soil. Therefore, the circular bioeconomy approach can be applied to reuse and repurpose the toxic plant biomass into different circular bioeconomy byproducts such as biochar, biogas, bioethanol, and biodiesel is essential. In this regard, the current review highlights the potential strategies for the phytoremediation of HMs in wastewater and various strategies to efficiently reuse metal-enriched biomass material and produce commercially valuable products. The implementation of circular bioeconomy practices can help overcome significant obstacles and build a new platform for an eco-friendlier lifestyle.

Study on efficiency and mechanism of ultrasonic controlling membrane fouling in ceramic membrane bioreactors

In recent years, ceramic membranes have been increasingly used in membrane bioreactors (MBRs). However, membrane fouling was still the core issue restricting the large-scale engineering application of ceramic MBRs. As a novel and alternative technology, ultrasonic could be used to control membrane fouling. This research focused on the efficiency and mechanism of ultrasonic controlling membrane fouling in ceramic MBRs. The results showed that ultrasonic reduced the sludge concentration in MBR, and the average particle size of sludge was always in a high range. The sludge activity of the system was stable at 6-9 (mg O2·(g MLSS·h)-1), indicating that ultrasonic did not destroy the activity of microorganisms in the system. The extracellular polymer substance (EPS) of the ultrasonic group was slightly higher than that of the control group, while the soluble microbial product (SMP) content was relatively stable. The ceramic membrane of the ultrasonic group has a partial retention effect on the organic components. The application of ultrasonic slowed down the decrease of the hydrophilicity of the ceramic membrane. The main pollutants on the membrane surface exist in the form of aromatic and heteroaromatic rings, alkynes, and so forth. Ultrasonic removes the amide substances from the membrane surface. Membrane fouling resistance is mainly due to membrane pore blockage, accounting for 75.53%. PRACTITIONER POINTS: Enrich the research on the mechanism of ultrasonic technology in membrane fouling control. The MBR can still operate normally with ultrasonic applied. The time for the ceramic membrane to reach the fouling end point is 2.4 times that without ultrasonic. The main cause of membrane fouling was pore blocking, accounting for 75.53%.

Preparation and characterization of clay based ceramic porous membranes and their use for the removal of lead ions from synthetic wastewater with an insight into the removal mechanism

The present study explores the use of local clay from the United Arab Emirates (UAE) to prepare porous ceramic membranes (flat disk shape) for the purpose of removing toxic heavy metals from contaminated water. Four distinct ceramic membranes, crafted from locally sourced clay and incorporated with activated carbon and graphite, underwent careful and thorough preparation. The initial set of membranes was subjected to open-air sintering, resulting in the creation of mACA and mGrA membranes. Concurrently, a second set of meticulously prepared membranes underwent sintering under inert nitrogen conditions, yielding the formation of mACI and mGrI membranes, respectively. Prior to making the membranes, the clay material was characterized by thermogravimetric analysis (TGA), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction analysis (XRD). The clay presented the lowest weight loss compared to AC and Gr, implying that these two materials could be used as porogen agents. The X-ray fluorescence results indicated that the natural clay contained 65.5 wt% of silicon dioxide (SiO2), aluminium oxide (Al2O3), and iron (III) oxide (Fe2O3) falling within the class C category of clays according to ASTM. The FTIR analysis showed different clay regions allocated to various stretching and deformation vibrations of hydroxide, organic fraction, and (Si, Al, Fe)-O groups. The XRD analysis revealed the presence of kaolinite, illite, smectite and calcite phyllite phases in the clay mineral. The membranes were characterized using FESEM, with those containing AC (used as porogen) exhibiting large pores clearly visible on the surface, and were tested for the removal of lead (Pb2+) ions from synthetic wastewater. The removal efficiencies of the membranes were 33 %, 75.2 %, 100 % and 100 % for mACA, mACI, mGrA and mGrI respectively after 100 min operation. The wettability of the membranes was found to follow the order mACI < mACA < mGrI < mGrA, which corroborated well with water fluxes of 7, 8, 112 and 214 L h-1 m-2 recorded after 60 min duration and 1.0 bar applied pressure. The mechanisms of filtration of Pb2+ ions were adsorption for the AC-based membranes (mACA, mACI) and a combination of adsorption and size exclusion for the Gr-based membranes (mGrA, mGrI).

Application of coal fly ash based ceramic membranes in wastewater treatment: A sustainable alternative to commercial materials

The continued increase in the global population has resulted in increased water demand for domestic, agricultural, and industrial purposes. These activities have led to the generation of high volumes of wastewater, which has an impact on water quality. Consequently, more practical solutions are needed to improve the current wastewater treatment systems. The use of improved ceramic membranes for wastewater treatment holds significant prospects for advancement in water treatment and sanitation. Hence, different studies have employed ceramic membranes in wastewater treatment and the search for low-cost and environmentally friendly starting materials has continued to engender research interests. This review focuses on the application of coal fly ash in membrane technology for wastewater treatment. The processes of membrane fabrication and the various limitations of the material. Several factors that influence the properties and performance of coal fly ash ceramic membranes in wastewater treatment are also presented. Some possible solutions to the limitations are also proposed, while cost analysis of coal fly ash-based membranes is explored to evaluate its potential for large-scale applications.

Nanoparticles and nanofiltration for wastewater treatment: From polluted to fresh water

Water pollution poses significant threats to both ecosystems and human health. Mitigating this issue requires effective treatment of domestic wastewater to convert waste into bio-fertilizers and gas. Neglecting liquid waste treatment carries severe consequences for health and the environment. This review focuses on intelligent technologies for water and wastewater treatment, targeting waterborne diseases. It covers pollution prevention and purification methods, including hydrotherapy, membrane filtration, mechanical filters, reverse osmosis, ion exchange, and copper-zinc cleaning. The article also highlights domestic purification, field techniques, heavy metal removal, and emerging technologies like nanochips, graphene, nanofiltration, atmospheric water generation, and wastewater treatment plants (WWTPs)-based cleaning. Emphasizing water cleaning's significance for ecosystem protection and human health, the review discusses pollution challenges and explores the integration of wastewater treatment, coagulant processes, and nanoparticle utilization in management. It advocates collaborative efforts and innovative research for freshwater preservation and pollution mitigation. Innovative biological systems, combined with filtration, disinfection, and membranes, can elevate recovery rates by up to 90%, surpassing individual primary (<10%) or biological methods (≤50%). Advanced treatment methods can achieve up to 95% water recovery, exceeding UN goals for clean water and sanitation (Goal 6). This progress aligns with climate action objectives and safeguards vital water-rich habitats (Goal 13). The future holds promise with advanced purification techniques enhancing water quality and availability, underscoring the need for responsible water conservation and management for a sustainable future.

Artificial intelligence and structural design of inorganic hollow fiber membranes: Materials chemistry

A key challenge is to produce the uniform morphology and regular pore design of inorganic hollow fiber membranes (HFMs) due to involvement of multiple parameters including, fabrication process and materials chemistry. Inorganic HFMs required technical innovations via novel structural design and artificial intelligence (AI) to produce the uniform structure and regular pore design. Therefore, this review aims at critical analysis on the most recent and relevant approaches to tackle the issues related to tune the morphology and pore design of inorganic HFMs. Structural design and evaluation of routes towards the dope suspension, spinning, and sintering of inorganic HFMs are critically analysed. AI, driving forces and challenges involved for harnessing of materials are revealed in this review. AI programs used for the prediction of pore design and performance of HFMs have also been explained in this review. Overall, this review will provide the understanding to build the equilibrium in spinning and sintering processes to control the design of micro-channels, and structural properties of inorganic HFMs. This review has great significance to control the new design of membranes via AI programs. This review also explain the inorganic membrane efficiency as algal-bioreactor.

SiO2 Modification of Silicon Carbide Membrane via an Interfacial In Situ Sol-Gel Process for Improved Filtration Performance

Silicon carbide (SiC) membrane has emerged as a promising class of inorganic ceramic membranes with many advantageous attributes and has been used for a variety of industrial microfiltration (MF) processes. The state-of-the-art industrial manufacturing of SiC membranes based on the particle sintering method can only achieve an average pore size that ranges from 40 nm to a few micrometers, which is still unsatisfactory for ultrafiltration (UF) applications. Thus, the pore size control of SiC membranes remains a focus of continuing study. Herein, we provide an in situ sol-gel modification strategy to tailor the pore size of SiC membranes by a superficial deposition of SiO2 onto the membrane surface and membrane pore channels. Our in situ sol-gel modification method is simple and effective. Furthermore, the physical characteristics and the filtration performance of the membrane can easily be controlled by the in situ reaction time. With an optimal in situ reaction time of 30 min, the average pore size of the membrane can be reduced from macropores (400 nm) to mesopores (below 20 nm), and the retention ability for 20 nm fluorescent PS microspheres can be improved from 5% to 93%; the resultant SiC/SiO2 composite membranes are imparted with water permeance of 77 L·m-2·h-1·bar-1, improved anti-protein-fouling properties, excellent performance, and anti-acid stabilities. Therefore, modified SiC/SiO2 membranes based on the in situ sol-gel process have great potential as UF membranes for a variety of industrial processes.

A review of microplastic removal from water and wastewater by membrane technologies

Microplastics (MPs) cannot be completely removed from water/wastewater in conventional wastewater treatment plants (WWTPs) and drinking water treatment plants (DWTPs). According to the literature analysis, membrane technologies, one of the advanced treatment technologies, are the most effective and promising technologies for MP removal from water and wastewater. In this paper, firstly, the properties of MPs commonly present in WWTPs/DWTPs and the MP removal efficiency of WWTPs/DWTPs are briefly reviewed. In addition, research studies on MP removal from water/wastewater by microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), and membrane bioreactors (MBRs) are reviewed. In the next section, membrane filtration is compared with other methods used for MP removal from water/wastewater, and the advantages/disadvantages of the removal methods are discussed. Moreover, the problem of membrane fouling with MPs during filtration and the potential for MP release from polymeric membrane structure to water/wastewater are discussed. Finally, based on the studies in the literature, the current status and research deficiencies of MP removal by membrane technologies are identified, and recommendations are made for further studies.

A Combined Gas and Water Permeances Method for Revealing the Deposition Morphology of GO Grafting on Ceramic Membranes

The adhesion enhancement of a graphene oxide (GO) layer on porous ceramic substrates is a crucial step towards developing a high-performance membrane for many applications. In this work, we have achieved the chemical anchoring of GO layers on custom-made macroporous disks, fabricated in the lab by pressing α-Al₂O₃ powder. To this end, three different linkers, polydopamine (PDA), 3-Glycidoxypropyltrimethoxysilane (GPTMS) and (3-Aminopropyl) triethoxysilane (APTMS), were elaborated for their capacity to tightly bind the GO laminate on the ceramic membrane surface. The same procedure was replicated on cylindrical porous commercial ZrO₂ substrates because of their potentiality for applications on a large scale. The gas permeance properties of the membranes were studied using helium at 25 °C as a probe molecule and further scrutinized in conjunction with water permeance results. Measurements with helium at 25 °C were chosen to avoid gas adsorption and surface diffusion mechanisms. This approach allowed us to draw conclusions on the deposition morphology of the GO sheets on the ceramic support, the mode of chemical bonding with the linker and the stability of the deposited GO laminate. Specifically, considering that He permeance is mostly affected by the pore structural characteristics, an estimation was initially made of the relative change in the pore size of the developed membranes compared to the bare substrate. This was achieved by interpreting the results via the Knudsen equation, which describes the gas permeance as being analogous to the third power of the pore radius. Subsequently, the calculated relative change in the pore size was inserted into the Hagen-Poiseuille equation to predict the respective water permeance ratio of the GO membranes to the bare substrate. The reason that the experimental water permeance values may deviate from the predicted ones is related to the different surface chemistry, i.e., the hydrophilicity or hydrophobicity that the composite membranes acquire after the chemical modification. Various characterization techniques were applied to study the morphological and physicochemical properties of the materials, like FESEM, XRD, DLS and Contact Angle.

Wastewater treatment with algal based membrane bioreactor for the future: Removing emerging containments

The difficulty of developing pollutants in aquatic ecosystems and their potential effects on animals and plants have been raised. Sewage effluent can seriously harm a river's plant and animal life by reducing the water's oxygen content. Due to their increasing use and poor elimination in traditional municipal wastewater treatment plants (WWTPs), pharmaceuticals are one of the developing pollutants that have the potential to penetrate aquatic ecosystems. Due to undigested pharmaceuticals and their metabolites, which constitute a significant class of potentially hazardous aquatic pollutants. Using an algae-based membrane bioreactor (AMBR), the primary objective of this research was to eliminate emerging contaminants (ECs) identified in municipal wastewater. The first part of this research covers the basics of growing algae, an explanation of how they work, and how they remove ECs. Second, it develops the membrane in the wastewater, explains its workings, and uses the membrane to remove ECs. Finally, an algae-based membrane bioreactor for removing ECs is examined. As a result, daily algal production using AMBR technology might range from 50 to 100 mg/Liter. These kinds of machines are capable of nitrogen and phosphorus removal efficiencies of 30-97% and 46-93%, respectively.

Application of Photo-Fenton-Membrane Technology in Wastewater Treatment: A Review

Photo-Fenton coupled with membrane (photo-Fenton-membrane) technology offers great potential benefits in future wastewater treatment because it can not only degrade refractory organics, but also separate different pollutants from water; additionally, it often has a membrane-self-cleaning ability. In this review, three key factors of photo-Fenton-membrane technology, photo-Fenton catalysts, membrane materials and reactor configuration, are presented. Fe-based photo-Fenton catalysts include zero-valent iron, iron oxides, Fe-metal oxides composites and Fe-based metal-organic frameworks. Non-Fe-based photo-Fenton catalysts are related to other metallic compounds and carbon-based materials. Polymeric and ceramic membranes used in photo-Fenton-membrane technology are discussed. Additionally, two kinds of reactor configurations, immobilized reactor and suspension reactor, are introduced. Moreover, we summarize the applications of photo-Fenton-membrane technology in wastewater, such as separation and degradation of pollutants, removal of Cr(VI) and disinfection. In the last section, the future prospects of photo-Fenton-membrane technology are discussed.

The Application of Polyethersulfone Ultrafiltration Membranes for Separation of Car Wash Wastewaters: Experiments and Modelling

The wastewater generated as a result of car washes is considered a new source of water. However, recovered water must meet the required quality criteria for reuse. For this purpose, the ultrafiltration (UF) process can be successfully used. The main aim of the present work was to investigate the influence of the membrane's molecular weight cut-off (MWCO) on the UF performance in terms of the fouling phenomenon and retention degree of car wash wastewater. Moreover, for a better understanding of the fouling mechanisms, Hermia's model was used. The experimental studies were conducted with the use of two polyethersulfone (PES) membranes (MWCO of 10 kDa and 100 kDa). It has been noted that the used membranes provided a high-quality permeate and excellent turbidity removal, up to 99%. Moreover, it has been noted that the MWCO membrane has a significant impact on the fouling mechanism. Generally, a much greater intensity of fouling for the membrane with MWCO of 100 kDa was observed. Results obtained in the present study showed that both real wastewaters and the clean solutions used for washing cars cause the fouling phenomenon. It has been proven that rinsing the membranes with water is not sufficient to recover the initial membrane's performance. Hence, periodic chemical cleaning of the membranes was required. Fitting the experimental data to Hermia's model allowed us to indicate that membranes with MWCO of 100 kDa are more prone to intermediate blocking. To sum up, the findings suggest that for the UF of the car wash wastewater, the use of membranes with MWCO equal to 10 kDa is recommended.

Performance of Anaerobic Membrane Bioreactor (AnMBR) with Sugarcane Bagasse Ash-based Ceramic Membrane treating Simulated Low-strength Municipal Wastewater: Effect of Operation Conditions

This study assesses the performance of waste sugarcane bagasse ash (SBA)-based ceramic membrane in anaerobic membrane bioreactor (AnMBR) treating low-strength wastewater. The AnMBR was operated in sequential batch reactor (SBR) mode at hydraulic retention time (HRT) of 24 h, 18 h, and 10 h to understand the effect on organics removal and membrane performance. Feast-famine conditions were also examined to evaluate system performance under variable influent loadings. An average removal of >90% chemical oxygen demand (COD) was obtained at each HRT and starvation periods up to 96 days did not significantly affect removal efficiency. However, feast-famine conditions affected extracellular polymeric substances (EPS) production and consequently the membrane fouling. EPS production was high (135 mg/g MLVSS) when the system was restarted at 18 h HRT after shutdown (96 days) with corresponding high transmembrane pressure (TMP) build-up; however, the EPS content stabilized at ~60-80 mg/g MLVSS after a week of operation. Similar phenomenon of high EPS and high TMP was experienced after other shutdowns (94 and 48 days) as well. Permeate flux was 8.8±0.3, 11.2±0.1 and 18.4±3.4 L/m² h at 24 h, 18 h and 10 h HRT, respectively. Filtration-relaxation (4 min - 1 min) and backflush (up to 4 times operating flux) helped control fouling rate. Surface deposits (that significantly attributed to fouling) could be effectively removed by physical cleaning, resulting in nearly complete flux recovery. Overall, SBR-AnMBR system equipped with waste-based ceramic membrane appears promising for treatment of low-strength wastewater with disruptions in feeding.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11270-023-06173-3.

Impact of pre-coagulation on the ceramic membrane process during oil-water emulsion separation: Fouling behavior and mechanism

Coagulation has been evaluated as an economical and effective pre-treatment method for controlling membrane fouling. We investigated the influence of the pre-coagulation of oil-water (O/W) emulsions on the formation of membrane fouling in the ceramic membrane process. The results confirmed that pre-coagulation effectively mitigated the fouling formation on the ceramic membrane surface during the O/W emulsion separation. The mechanism of mitigating membrane fouling by pre-coagulation was proposed, owing to the reduction in the zeta potential value of oil droplets by pre-coagulation, resulting in weak electrostatic attraction between oil droplets and ceramic membrane surfaces, and an increase in the size of the oil droplets by pre-coagulation, leading the formation of a cake layer fouling. In addition, the decrease in the hydrophobicity of oil droplets by pre-coagulation resulted in alleviating the hydrophobic interaction between oil droplets and membrane surface. The proposed fouling mechanism was supported by the characterization of the virgin and fouled membrane surfaces and the analysis of the fouling resistance ability of the membranes. Our study could be indicative of mitigation protocols that can be used to alleviate membrane fouling on ceramic membranes during oily wastewater treatment.

New Materials and Phenomena in Membrane Distillation

In recent decades, membrane-based processes have been extensively applied to a wide range of industrial processes, including gas separation, food industry, drug purification, and wastewater treatment. Membrane distillation is a thermally driven separation process, in which only vapour molecules transfer through a microporous hydrophobic membrane. At the operational level, the performance of membrane distillation is negatively affected by wetting and temperature polarization phenomena. In order to overcome these issues, advanced membranes have been developed in recent years. This review, which focuses specifically on membrane distillation presents the basic concepts associated with the mass and heat transfer through hydrophobic membranes, membrane properties, and advances in membrane materials. Photothermal materials for solar-driven membrane distillation applications are also presented and discussed.

Recent Advanced Development of Acid-Resistant Thin-Film Composite Nanofiltration Membrane Preparation and Separation Performance in Acidic Environments

Membrane filtration technology has attracted extensive attention in academia and industry due to its advantages of eco-friendliness related to environmental protection and high efficiency. Polyamide thin-film composite nanofiltration (PA TFC NF) membranes have been widely used due to their high separation performance. Non-acid-resistant PA TFC NF membranes face tremendous challenges in an acidic environment. Novel and relatively acid-resistant polysulfonamide-based and triazine-based TFC NF membranes have been developed, but these have a serious trade-off in terms of permeability and selectivity. Hence, how to improve acid resistance of TFC NF membranes and their separation performance in acidic environments is a pivotal issue for the design and preparation of these membranes. This review first highlights current strategies for improving the acid resistance of PA TFC NF membranes by regulating the composition and structure of the separation layer of the membrane performed by manipulating and optimizing the construction method and then summarizes the separation performances of these acid-resistant TFC NF membranes in acidic environments, as studied in recent years.

Progress in alumina ceramic membranes for water purification: Status and prospects

Ceramic membranes have gained increasing attention in recent years for the removal of various contaminants from water. Alumina membrane is considered as one of the most important ceramic membranes, which plays important roles not only in separation processes such as microfiltration, ultrafiltration, and nanofiltration, but also in catalysis- and adsorption- enhanced separation applications in water purification and wastewater treatment. However, there is currently still lack of a comprehensive critical review about alumina membranes for water purification. In this review, we first discuss recent developments of alumina membranes, and then critically introduce the state-of-the-art strategies for lowering fabrication cost, improving membrane performances and mitigating membrane fouling. Especially, aiming to improve membrane performance, some emerging methods are summarized such as tailoring membrane structure, developing flexible membranes, designing nano-pores for precise separation, and enhancing multi-functionalities. In addition, engineering applications of alumina membranes for water purification are also briefly introduced. Finally, the prospects for future research on alumina membranes are proposed, such as economic preparation/application, challenging precise separation, enriching multi-functionalities, and clarifying separation mechanisms.

Membranes for Oil/Water Separation: A Review

Recent advancements in separation and membrane technologies have shown a great potential in removing oil from wastewaters effectively. In addition, the capabilities have improved to fabricate membranes with tunable properties in terms of their wettability, permeability, antifouling, and mechanical properties that govern the treatment of oily wastewaters. Herein, authors have critically reviewed the literature on membrane technology for oil/water separation with a specific focus on: 1) membrane properties and characterization, 2) development of various materials (e.g., organic, inorganic, and hybrid membranes, and innovative materials), 3) membranes design (e.g., mixed matrix nanocomposite and multilayers), and 4) membrane fabrication techniques and surface modification techniques. The current challenges and future research directions in materials and fabrication techniques for membrane technology applications in oil/water separation are also highlighted. Thus, this review provides helpful guidance toward finding more effective, practical, and scalable solutions to tackle environmental pollution by oils.

Preparation and Characterization of Low-Cost Ceramic Membrane Coated with Chitosan: Application to the Ultrafine Filtration of Cr(VI)

In this work, low-cost ceramic membranes (CMs) were prepared from ultrafine starting powders such as kaolin, clay, and starch by a dry compaction method. The ceramic membranes were sintered at different temperatures and times and were characterized by XRD, XRF, TG-DTA, SEM-EDS, N₂-BET, water absorption, compressive strength, and pure water flux. The optimal membrane, sintered at 1000 °C for 3 h, possessed water absorption of 27.27%, a compressive strength of 31.05 MPa, and pure water flux of 20.74 L/h m². Furthermore, chitosan crosslinked with glutaraldehyde was coated on the surface of the ceramic membrane by the dip coating method, and the pore size of the chitosan-coated ceramic membrane (CCCM) was 16.24 nm. Eventually, the separation performance of this membrane was assessed for the removal of chromium(VI) from aqueous solution. The ultrafine filtration of Cr(VI) was studied in the pH range of 2-7. The maximum removal of Cr(VI) was observed to be 71.25% with a pH of 3. The prepared CCCM showed good membrane properties such as mechanical stability and ultrafine structure, which have important applications for the treatment of wastewater including such heavy metals.

Electrocoagulation coupled with conductive ceramic membrane filtration for wastewater treatment: Toward membrane modification, characterization, and application

Membrane separation is an effective solution for pollutant removal, however, achieving high permeability and antifouling ability remains a pressing challenge for its widespread application. In this study, a novel method of coating flat ceramic membranes (CMs) with a conductive film (Sb-SnO₂) was developed to enhance the filtration and antifouling performance of CMs when the membrane filtration was coupled with electrocoagulation. After comparing the parameters, including the film sheet resistance and pure water flux, with those of other coating methods (i.e., gel coating and immersion hydrolysis), a well-fixed conductive coating with optimal permeability and stability was generated using spray pyrolysis with a substrate ceramic membrane surface temperature of 475 °C, precursor concentration of 0.5 M (calculate as SnO₂), and spraying amount of 50 mL (120 cm²), during membrane modification. Batch filtration experiments using wastewater from the mechanical industry demonstrated that the conductive ceramic membrane (CCM) cathode integrated with electrocoagulation at an electric field of 2.8 V/cm (3.0 mA/cm²) achieved permeate fluxes that were 0.34, 0.70, 0.75 and 1.41 times higher than those of sole CM separation after four cycles. Moreover, the membrane separation process was dominated by the standard pore-blocking model, and its correlation coefficient decreased with the exertion of the electric field, indicating that membrane filtration fouling changed from irreversible to reversible. This CCM combined with electrocoagulation exhibited significant potential for alleviating membrane fouling and widespread application, and could act as a promising technology for industrial wastewater treatment.

State-of-the-Art Organic- and Inorganic-Based Hollow Fiber Membranes in Liquid and Gas Applications: Looking Back and Beyond

The aggravation of environmental problems such as water scarcity and air pollution has called upon the need for a sustainable solution globally. Membrane technology, owing to its simplicity, sustainability, and cost-effectiveness, has emerged as one of the favorable technologies for water and air purification. Among all of the membrane configurations, hollow fiber membranes hold promise due to their outstanding packing density and ease of module assembly. Herein, this review systematically outlines the fundamentals of hollow fiber membranes, which comprise the structural analyses and phase inversion mechanism. Furthermore, illustrations of the latest advances in the fabrication of organic, inorganic, and composite hollow fiber membranes are presented. Key findings on the utilization of hollow fiber membranes in microfiltration (MF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), pervaporation, gas and vapor separation, membrane distillation, and membrane contactor are also reported. Moreover, the applications in nuclear waste treatment and biomedical fields such as hemodialysis and drug delivery are emphasized. Subsequently, the emerging R&D areas, precisely on green fabrication and modification techniques as well as sustainable materials for hollow fiber membranes, are highlighted. Last but not least, this review offers invigorating perspectives on the future directions for the design of next-generation hollow fiber membranes for various applications. As such, the comprehensive and critical insights gained in this review are anticipated to provide a new research doorway to stimulate the future development and optimization of hollow fiber membranes.

Applications of Polymeric Membranes with Carbon Nanotubes: A Review

Nanomaterials have been commonly employed to enhance the performance of polymeric membrane materials that are used in several industrial applications. Carbon nanotubes (CNTs) have gained notable attention over the years for use in membrane technology due to their anti-biofouling properties, salt rejection capability, exceptional electrical conductivity, and mechanical properties. This paper aims to discuss some of the recent applications of CNTs in membrane technology and their effect on a larger scale. The paper reviews successful case studies of incorporation of CNTs in membranes and their impact on water purification, desalination, gas separations, and energy storage, in an effort to provide a better understanding of their capabilities. Regarding the future trends of this technology, this review emphasizes improving the large-scale production processes and addressing environmental and health-related hazards of CNTs during production and usage.

Applications of Nano-Zeolite in Wastewater Treatment: An Overview

Nano-zeolite is an innovative class of materials that received recognition for its potential use in water and tertiary wastewater treatment. These applications include ion-exchange/sorption, photo-degradation, and membrane separation. The aim of this work is to summarize and analyze the current knowledge about the utilization of nano-zeolite in these applications, identify the gaps in this field, and highlight the challenges that face the wide scale applications of these materials. Within this context, an introduction to water quality, water and wastewater treatment, utilization of zeolite in contaminant removal from water was addressed and linked to its structure and the advances in zeolite preparation techniques were overviewed. To have insights into the trends of the scientific interest in this field, an in-depth analysis of the variation in annual research distribution over the last decade was performed for each application. This analysis covered the research that addressed the potential use of both zeolites and nano-zeolites. For each application, the characterization, experimental testing schemes, and theoretical analysis methodologies were overviewed. The results of the most advanced research were collected, summarized, and analyzed to allow an easy visualization and comparison of these research results. Finally, the gaps and challenges that face these applications are concluded.

Pulsed Laser Deposited Zeolite Coatings on Femtosecond Laser-Nanostructured Steel Meshes for Durable Superhydrophilic/Oleophobic Functionalities

Ultrafast laser structuring has proven to alter the wettability performance of surfaces drastically due to controlled modification of the surface roughness and energy. Surface alteration can be achieved also by coating the surfaces with functional materials with enhanced durability. On this line, robust and tunable surface wettability performance can be achieved by the synergic effects of ultrafast laser structuring and coating. In this work, femtosecond laser-structured stainless steel (SS-100) meshes were used to host the growth of NaAlSi₂O₆-H₂O zeolite films. Contact angle measurements were carried on pristine SS-100 meshes, zeolite-coated SS-100 meshes, laser-structured SS-100 meshes, and zeolite-coated laser-structured SS-100 meshes. Enhanced hydrophilic behavior was observed in the zeolite-coated SS-100 meshes (contact angle 72°) and in laser-structured SS-100 meshes (contact angle 41°). On the other hand, superior durable hydrophilic behavior was observed for the zeolite-coated laser-structured SS-100 meshes (contact angle 14°) over an extended period and reusability. In addition, the zeolite-coated laser-structured SS-100 meshes were subjected to oil-water separation tests and revealed augmented effectuation for oil-water separation.

Surface modification and effects on tribology by laser texturing in Al2O3

We investigate the surface modification by laser texturing and effects thereof on the tribological performance in Al₂O₃. By detailed observation for microstructure evolution, it has been shown that there were three distinct modification morphologies by laser treatment: dense surface microfeatures, "coral" dendritic structures, and coarse grains. X-ray diffraction (XRD) results indicated that there was no formation of metastable phases due to low supercooling in solidification in the nanosecond laser regime. The formation of AlN compounds in the laser-treated region was examined by using x-ray photoelectron spectroscopy (XPS), which led to dense surface microfeatures and randomly distributed pores formation in the laser treated region. The formation of "coral" dendritic structures on the edge of groove and coarse grains in the vicinity of the laser surface was attributed to the fast-cooling rates. Wear tests were carried out to analyze the effect of laser texturing on tribological performance. The results of coefficients of friction (COF) illustrated that laser texturing can significantly improve COFs for dry friction; however, it decreases the COFs for wet friction. The mechanism of wear was explained based on a SEM measurement for worn surfaces; the formation of surface texture can store abrasive particles and debris lead to hydrodynamic lubricant film formation and the COFs significantly reducing for wet friction.