Membrane Separation Processes Research Articles

Investigation of Pretreatment of Textile Wastewater for Membrane Processes and Reuse for Washing Dyeing Machines.

The aim of this study was to investigate the best pretreatment of textile wastewater (TWW) for membrane separation processes and the previously unexplored reuse of treated TWW for washing dyeing machines. Sand filtration (SF), coagulation, coagulation/flocculation, and ultrafiltration (UF) with hollow fiber membrane (ZW1) were used for pretreatment. Pretreatment selection was based on turbidity, total organic carbon (TOC), and color. SF and ZW1 were found to be the best pretreatments. In addition, the SF and ZW1 effluents were subjected to the 5 (PT) and 50 (MW) kDa UF flat sheet membranes to test removal efficiency. ZW1-PT was better in terms of removal results and fouling. To reduce the use of drinking water for washing dyeing machines, the characteristics of ZW1-PT effluent were compared with drinking water from a textile factory. TWW treated with this hybrid process fulfils the purpose of reuse for washing dyeing machines and can be used in Galeb d.d., Croatia, or in any other textile factory, saving up to 26,000 m3 of drinking water per year. This contributes to both sustainable production and the conservation of water resources.

Design and Economic Evaluation of a Hybrid Membrane Separation Process from Multiple Refinery Gases Using a Graphic Synthesis Method

Petrochemical tail gases have various components and many separation methods, thus there are many possible design schemes, making it difficult to determine the optimal scheme. In this work, a graphic synthesis method was used to design a hybrid multi-input refinery gas separation process consisting of membranes, pressure swing adsorption (PSA), shallow condensation (SC), and distillation units for the production of valuable products which include H2, C2, LPG, and C5+. Ten refinery gases with different compositions were visualized and represented with vector couples in a triangular coordinate system. Firstly, according to the characteristics of the refinery gases, the feeds located in the same region of the triangular coordinate system were merged to simplify the number of input streams, then ten original input streams were combined into two mixed streams. Secondly, the optimal separation sequence was determined by using the unit selection rules of a graphic synthesis method. Thirdly, the process was simulated in UniSim Design and the process parameters were determined by sensitivity analysis. Finally, economic assessments were carried out, which led to an annual gross product profit of USD 38.62 × 106 and a payback period of less than 4 months.

PolyE‐IL: A polymeric Brønsted acid ionic liquid catalyst for catalytic thermo liquefaction of sugarcane bagasse into carboxylic acids

AbstractThe present study demonstrates a catalytic thermo liquefaction (CTL) process for the liquefaction of sugarcane bagasse into carboxylic acids using recyclable polymeric Brønsted acid ionic liquids (PolyE‐ILs) catalyst. A series of acid catalysts such as mineral acids, imidazole‐based ionic liquid and PolyE‐ILs with variable counter ions were tested. Of the tested catalysts, [PEI]+[HSO4]− resulted in 51.84% levulinic acid, 53.07% formic acid and 100% acetic acid yields compared with their theoretical maximum with 81.40% feedstock conversion at 210 °C for 120 min. Under 10 bar N2 pressure. The carbon‐enriched side products (CTL‐oil), catalyst and carboxylic acids were separated by integrating the adsorption and membrane separation process with >98% efficiency. The CTL‐oil with calorific a value of 25–26 MJ/kg can be explored for further energy and fuel applications. Thus, the use of a robust and recyclable catalyst at moderate operating conditions provides an efficient pathway for the valorization of sugarcane bagasse into carboxylic acids and CTL‐oil. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd

Thin-film composite membranes with programmable in-plane heterostructure for high degree-of-freedom performance control

Ultra-efficient membrane separation technologies are needed to reduce the cost of molecular separations. However, the two-dimensional isotropy of conventional selective membrane limits the freedom for deep optimization of separation process. In addition, the membrane separation properties, e.g. permeability, are difficult to be accurately pre-determined according to actual needs of applications, because membrane fabrication is largely empirical and lacks highly-controllable structure variable. Herein, we develop a novel thin-film composite membrane with high controllability, where two kinds of polyamides differing in structural and physicochemical properties are integrated into a unity according to pre-designed proportion and distribution, by generating heterogeneous polymerization interface with the help of inkjet printing. The separation performance of the heterostructure (HS) membranes show function relationships with the fabrication parameters (the essence is the ratio of different structures). The separation properties of every point (micron scale) of membrane can be individually managed. Thus, the HS design not only enables programmable, pre-determined membrane separation properties, but also opens the door to controlling their spatial distribution within membrane plane. Furthermore, the membrane with gradient permeability is proposed to solve the problem of flux imbalance within membrane elements, showing the great potential of the HS design in ultra-efficient membrane separation process.

Metal-organophosphate biphasic interfacial coordination reaction synthesizing nanofiltration membranes with the ultrathin selective layer, excellent acid-resistance and antifouling performance

Phytate as a natural strongly charged organophosphate has recently attracted much attention in diverse fields including membrane separations towards water-energy-food nexus. However, the ideal phytate-based nanofiltration membrane with defect-free and ultrathin selective layer for highly-efficient water treatment is still much challengeable due to the typical aggregation of metal ions and uncontrolled reaction between metal ion and organophosphate via conventional coating method. Herein, metal-organophosphate biphasic interfacial coordination reaction is proposed to construct ultrathin (13.4 nm) selective layer of phytate-based nanofiltration membranes with high permeance and excellent stability by controllable coordination assembly. Iron acetylacetonate (Fe(acac)3) as an organic phase monomer with powerful electron-gaining ability is exploited to avoid the aggregation of traditional Fe(III) in aqueous phase, which can also coordinate with phytic acid (PA) to ensure a defect-free ultra-thin selective layer. The architecture of the phytate-based selective layer can be well regulated by optimizing the coordination metal source, the concentration of PA and Fe(acac)3, reaction time, so as to achieve the ultrahigh permeation flux of 190 L m−2 h−1 with excellent dye rejection (99.6%). Most interestingly, our phytate-based nanofiltration membranes with plenty of hydrophilic phosphate groups on the surface and high binding energy of P–O–Fe bond (−315.1 kJ mol−1) exhibited the long-term separation stability, excellent acid-resistance and anti-pollution ability, realizing the stable membrane separation process under harsh conditions.

A Review of the Natural Gas Purification from Acid Gases by Membrane

This study aims to shed light on natural gas as an important and promising energy source. This energy source is the fastest-growing source in the world due to the increasing global demand. In this paper, the rates of growth in global demand for natural gas according to the latest reports since 1984, as well as the gas specifications required for transport and storage, acid gases, including absorption, desorption, Cryogenic and separation by membranes, are discussed with the advantages and disadvantages of each method. Focusing are presented. In addition to the primary treatment processes that take place on the gas, the most important of which is the removal of acid gases. Processes for removing on the membrane separation process as the most promising process in this field and reviewing all the research that is discussed in details of this process.

Sequential Membrane Filtration to Recover Polyphenols and Organic Acids from Red Wine Lees: The Antioxidant Properties of the Spray-Dried Concentrate

The vinification process produces a considerable amount of waste. Wine lees are the second most generated byproduct, representing around 14% of total vinification wastes. They are a valuable source of natural antioxidants, mainly polyphenols, as well as organic acids, such as tartaric acid. This paper deals with the application of an integrated, environment friendly membrane separation process to recover polyphenols and organic acids. A two-step membrane process is described, consisting of an ultra- and a nano-filtration process. The physicochemical and antioxidant properties of all the process streams were determined. High Pressure Liquid Chromatography (HPLC) was employed for identifying certain individual organic acids and polyphenols, while the antioxidant potential was determined by the 2,2′-diphenyl-1-picrylhydrazyl radical) (DPPH) radical scavenging ability and ferric reducing ability. A liquid concentrate stream containing 1351 ppm of polyphenols was produced and then spray dried. The resulting powder retained most of the polyphenols and antioxidant properties and was successfully applied to a real food system to retard lipid oxidation, followed by Thiobarbituric Acid Reactive Substances (TBARS) and the determination of oxymyoglobin content. The results show that membrane separation technology is an attractive alternative process for recovering value-added ingredients from wine lees.

Integration of Nanofiltration and Reverse Osmosis Technologies in Polyphenols Recovery Schemes from Winery and Olive Mill Wastes by Aqueous-Based Processing.

More sustainable waste management in the winery and olive oil industries has become a major challenge. Therefore, waste valorization to obtain value-added products (e.g., polyphenols) is an efficient alternative that contributes to circular approaches and sustainable environmental protection. In this work, an integration scheme was purposed based on sustainable extraction and membrane separation processes, such as nanofiltration (NF) and reverse osmosis (RO), for the recovery of polyphenols from winery and olive mill wastes. Membrane processes were evaluated in a closed-loop system and with a flat-sheet membrane configuration (NF270, NF90, and Duracid as NF membranes, and BW30LE as RO membrane). The separation and concentration efficiency were evaluated in terms of the total polyphenol content (TPC), and by polyphenol families (hydroxybenzoic acids, hydroxycinnamic acids, and flavonoids), using high-performance liquid chromatography. The water trans-membrane flux was dependent on the trans-membrane pressure for the NF and RO processes. NF90 membrane rejected around 91% of TPC for the lees filters extracts while NF270 membrane rejected about 99% of TPC for the olive pomace extracts. Otherwise, RO membranes rejected more than 99.9% of TPC for both types of agri-food wastes. Hence, NF and RO techniques could be used to obtain polyphenol-rich streams, and clean water for reuse purposes.

Surface Modification of PVDF Membrane Using Formic Acid for Enhance the Hydrophobicity for Desalination

Membrane distillation (MD) is a thermally driven membrane separation process. In recent years, MD is considered as a key technology for desalination applications. It has been proven that it has numerous advantages compared to other desalination processes such as reverse osmosis. The thermal driving force, no osmotic pressure effect on membrane fluxes are among the advantages of this MD process. Membranes fabricated from hydrophobic polymers such as polyvinylidene fluoride (PVDF) can be a great choice for MD for the desalination process. However, MD membranes are still held back by some problems, most notably due to pore wetting effects, thereby limiting their use in treating seawater for desalination propose. This study proposes the use of carboxylic acid to modify the PVDF membrane to increase its hydrophobicity as a solution to avoid wetting in MD for water desalination. As a first step, membrane produced using PVDF pellets under the phase inversion method. Then the membrane underwent modification using 5wt%, 10wt% and 15wt% of formic acid via immersion technique. The characteristics of membrane produced observed by the contact angle, Fourier-transform infrared spectroscopy (FTIR) and membrane performance test. The impact of the concentration of formic acid solution and feed temperature on the membrane was evaluated. The result showed that by modifying the membrane with formic acid resulted in the increase in contact angle from unmodified PVDF membrane, 83.03° to 100.88° when the membrane modified with formic acid with concentration was 10 wt%. It was subsequently shown through FTIR peaks that formic acid successfully modified the PVDF membranes. Highest salt rejection percentage was also obtained with 68.9% when the feed temperature is 60 °C.

Membrane distillation bioreactor (MDBR) for wastewater treatment, water reuse, and resource recovery: A review

Membrane bioreactors (MBRs) have been well established as an advanced wastewater treatment technology that combines activated sludge with a pressure-driven membrane separation process. They have been widely applied in municipal and industrial wastewater treatment systems due to their advantages over conventional activated sludge systems. However, MBRs still face major issues hindering their widespread implementation such as poor effluent quality due to low retention of trace organic contaminants, instability due to changing operating conditions, and organic membrane fouling. Membrane distillation (MD) bioreactor (MDBR) is a novel wastewater treatment technology that combines MBRs with an MD unit either separated at a side stream or submerged in the bioreactor. The concept of hybrid MDBR configuration was firstly introduced in 2007 which was followed by numerous journal articles. These studies demonstrated the MDBR potential for water, nutrients, bioenergy, and other value-added product recovery from domestic and industrial wastewater; however, there is still a lack of a comprehensive study that shows the full MDBR potential. Hence there is a need for a dedicated review that summarize and critically analyse these research findings and highlight the research gaps to provide clear path for future research. This review presents system availability and applications of hybrid MDBR. In particular, the review presents brief introduction of MBR and MD technologies followed by covering the evolution of MDBR as a novel technology for municipal and industrial wastewater treatment. Several applications of MDBR systems are reviewed with a focus on system performance and removal efficiencies. The potential of MDBR to widen wastewater reuse and achieve nutrient and biogas recovery is also presented. Finally, the main challenges that hinder the development of MDBR are discussed while recommendations on future perspectives towards MDBR commercialization are suggested.

A generalized numerical framework for solving cocurrent and counter-current membrane models for gas separation

Membrane separation has become a panacea for various scientific and engineering problems, including water treatment, gas separation, purification, hemodialysis, and drug delivery. Modeling and simulation of such systems are necessary for the design, analysis, and optimization of membrane separation processes. Despite numerous studies, an efficient numerical solution of such systems is an open problem, especially when speed and reliability matter. In this study, a generalized numerical framework for solving cocurrent and counter-current membrane models is proposed, which hinges on a straightforward and reliable Gauss-Seidel method with successive over-relaxation. The results confirm the speed and reliability of the proposed algorithm, while it is validated by the experimental data for the separation of a mixture of CH4 and CO2, as well as a mixture of He, CO2, N2, and CH4. The permeate outlet pressure estimation error can be reduced to any value as low as ∼10−14%, while the computational time on a personal laptop is not more than 4.5 s. This algorithm can be readily implemented in various programming languages and commercial software applications.

Comparison of dye wastewater treatment methods: A review

Wastewater is produced by numerous dyes producing and dye consuming industries in their process activities especially the textile industry. These effluents become toxic and harmful to the living things and the environment if not properly treated before being discharged to the environment. In recent decades dye wastewater has been becomes a growing water pollution problem because it is one of the most difficult to treat. To put an end to this problem, viable, efficient, and sustainable method of treatment of dye wastewater and color removal needs to be established. Several research papers have been done over the years on various treatment method of dye wastewater with evolving options; this paper is to bring together both the conventional and new methods. Some of the conventional and new methods researched over the years include activated sludge, coagulation, adsorption, membrane separation processes and electrochemical process etc. Although there is currently no uniform standard or method of treatment universally adopted, many countries have put in place allowable limits of composition of dischargeable wastewater. This paper seeks to explore which methods are highly efficient, produces manageable and recyclable waste and a combination/hybrid treatment option of these methods to achieve maximum color removal.

Membrane technology — the technology of scientific and technical progress

Development of effective strategies in the fi eld of scientific research and production of membrane technologies, accumulation of knowledge in this fi eld that is extremely necessary to solve urgent national economic and scientific problems. Membrane technology is a sub-branch of a new scientific and practical direction — nanotechnology. Membrane technologies in the world community have a constant increase, not less than 8 % per annum, their importance in the present and future is great in almost all sectors of the national economy of Russia. Membrane separation processes are classified by driving force. Hence their tangible diversity. Membrane technology in comparison with existing ones (filtration, etc.) currently occupy a significant place in the separation of liquid systems. The main membrane methods include: reverse osmosis, ultrafiltration, microfiltration, dialysis, electrodialysis, electroosmosis.

Recovery of Valuable Minerals from Sea Water by Membrane Separation and Adsorption Process: A Review

Recovery of Valuable Minerals from Sea Water by Membrane Separation and Adsorption Process: A Review

Molecular transformation and composition flow of dissolved organic matter in four typical concentrated leachates from the multi-stage membrane system

Concentrated leachate (CL), characterized with high content salts and compositional complexity of dissolved organic matter (DOM), is difficult to degrade. Understanding the CL from molecular insight level is the requirement for further disposal based on their components. Here, typical CL samples were collected from the multi-stage membrane separation process in a large-scale leachate plant, including nanofiltration (NF), primary ultrafiltration (PUF), secondary nanofiltration (SNF), and reverse osmosis (RO). More than 95% of DOM was removed from raw CL, of which about 3/4 flowed into PUFCL and 1/5 flowed into SNFCL. DOM with macro-molecular weight (>500 Da, 30.46%) and highly unsaturated compounds (double-bond equivalents >15) were detected in PUFCL. Nearly half of DOM was CHO-only compounds (42.04%) in SNFCL. PUFCL was abundant in heteroatom species with higher-order oxygen (O ≥ 10), which was coincident with the trend of humic substance distribution (humic substance >1/2). Based on these properties results, advanced oxidation processes, such as ozonation, might be the right process for SNFCL rich in heteroatom species with low-order oxygen (O < 10). Abundant disulfides (S2O2-6 classes, 20.19%) and monovalent salts existed in ROCL, which should be removed from the system. These findings might provide basic information for the treatment of CLs from different membranes.

Membrane Separation Process in Wastewater and Water Purification

The current scenario of increasing water scarcity and degradation of water bodies has led to the development of processes and technologies that provide more suitable treatment for both water and wastewater [...].

From sucrose to fructo-oligosaccharides: Production and purification of fructo-oligosaccharides by an integrated enzymatic catalysis and membrane separation process

Fructo-oligosaccharides (FOS) are a group of linear fructose oligomers with numerous health benefits, which can be synthesized by the transfructosylation of sucrose using fructosyltransferases (FTases). In this study, it was found that the selected FTases showed both hydrolytic and transfructosylating activities. For FOS production, the hydrolytic activities of FTases became significant when the reaction time was above 1 h. Thus, FTases needed to be inactivated or removed from the reactor after achieving the highest FOS conversion. We therefore developed an integrated ultrafiltration-diafiltration- concentration process for FTases reuse and FOS purification. Because of the 100% rejection of FTases activity and a higher average flux, a PES-10 ultrafiltration membrane was selected for FTases recovery, where the cake layer formation was the main membrane fouling mechanism. Then, a fed-batch reaction process was developed for FOS production, where the hydrolytic behavior of FTases was negligible, and the FTases dosage was reduced by 75% compared to single batch operation (four batches). Moreover, the FOS production was comparable, and 95.5% FTases was recovered by the PES10 membrane after the four fed-batches processes. Subsequently, a NF5 nanofiltration membrane was selected to further separate FOS from the FTases-free FOS solution by a constant volume diafiltration process under 45 °C, and the monosaccharides in the reaction mixture (glucose and fructose) were completely removed, increasing the FOS purity from 55.8% to 92.3%. Finally, the FOS and sucrose in the diafiltration permeate was recovered by a DL nanofiltration membrane under 60 °C. The outcome of this work offers a complete technical route for FOS production using sucrose as substrate.

Adsorption and membrane separation for removal and recovery of volatile organic compounds

Volatile organic compounds (VOCs) are a crucial kind of pollutants in the environment due to their obvious features of severe toxicity, high volatility, and poor degradability. It is particularly urgent to control the emission of VOCs due to the persistent increase of concentration and the stringent regulations. In China, clear directions and requirements for reduction of VOCs have been given in the “national plan on environmental improvement for the 13th Five-Year Plan period”. Therefore, the development of efficient technologies for removal and recovery of VOCs is of great significance. Recovery technologies are favored by researchers due to their advantages in both recycling VOCs and reducing carbon emissions. Among them, adsorption and membrane separation processes have been extensively studied due to their remarkable industrial prospects. This overview was to provide an up-to-date progress of adsorption and membrane separation for removal and recovery of VOCs. Firstly, adsorption and membrane separation were found to be the research hotspots through bibliometric analysis. Then, a comprehensive understanding of their mechanisms, factors, and current application statuses was discussed. Finally, the challenges and perspectives in this emerging field were briefly highlighted.

Preparation of hollow ceramic photocatalytic membrane grafted with silicon-doped TiO2 nanorods and conversion of high-concentration NO

A silicon-doped TiO2 nanorod (NR) graft hollow ceramic photocatalytic membrane was fabricated by a two-step hydrothermal method. The photocatalytic membranes’ surface morphology, elemental composition, group, elemental chemical valence, roughness, water contact angle and porosity were characterized by SEM-EDX, FTIR, XPS, AFM, contact-angle analysis, and mercury-injection test, respectively. The catalytic properties of the membrane surface were characterized by XRD, UV–Vis spectroscopy and PL. The catalytic separation performance of the photocatalytic membrane was evaluated by the conversion rate of NO to nitrate and the production of the intermediate NO2. Results exhibited 67.11 % higher conversion efficiency of NO (300 ppm) under UV light illumination than the individual photocatalytic system The existence of membrane structure promoted the nitrate selectivity in the photocatalytic NO process. The Si-TiO2 NR photocatalytic membrane, which coupled photocatalysis with the membrane-separation processes, showed great potential application for treatment of the high-concentration NO in thermal power plants, owing to its separation capability, good photocatalytic activity, and reusability.

Anti-fouling and anti-wetting membranes for membrane distillation

Membrane Distillation (MD) is a thermally driven membrane separation process and shows promising water recovery from diverse wastewater sources. While reverse osmosis (RO) continues to be the dominant desalination technology, opportunities exist for the development of alternate low-energy separation technologies, especially for high-salinity streams. The MD process has generated interest in the separations community as a potential alternative either as a standalone or hybrid technology with other separation technologies like RO. Development of advanced membrane materials beyond the state-of-the-art must be pursued in order to improve the energy efficiency of the process; therefore, the most notable efforts in creating improved MD membranes are reviewed in this paper. Specifically, developing anti-wetting and anti-fouling membranes are the primary areas of interest in terms of new material development. This paper reviews the recent development of MD membranes and highlights some of the challenges for practical implementation. Finally, we provide insights into some key knowledge gaps and recommend a rational approach to design MD membranes.