Natural organic matter (NOM) removal from water is getting progressively significant for water treatment plants not only to improve drinking water aesthetics such as taste and smell, but also to avoid disinfection by-products (DBPs) formed during disinfection by chlorine. This study applies the catalytic properties of the wood degrading laccase enzyme produced by white rot fungi (WRF) on breaking down and removing organic matter in drinking water. White rot fungi isolates were collected and examined for their ability to degrade humic acid (HA), a NOM model compound. Highly permeable polyethersulfone (PES) membrane was prepared following the phase inversion process and used as material to support the immobilization of the lignin-degrading enzymes extracted from Perenniporia sp. and Polyporaceae sp. for NOM degradation and removal. A 52 % humic acid removal was recorded for the Polyporaceae sp. The addition of laccase substrate 4-hydroxybenzoic acid showed a great impact on the hydrophilicity of the membranes as a decrease in contact angle measurements of <60 was achieved. Moreover, modified membrane’s immobilization yield and enzyme activity also improved. The modified membrane achieved a rejection of greater than 90 % for the model compound. Enzyme activity was a function of contact time and substrate type. The attained results revealed that catalytic membranes can be an efficient alternative for NOM removal and membrane fouling alleviation during water treatment.
Membrane bioreactor (MBRs) technology is a crucial treatment process having enhanced solid/liquid separation in the way of biological wastewater treatment. However, clogging problem in MBRs is a critical drawback. Dynamic membrane (DM) technology has recently taking more attention to eliminate the clogging problem. DM is known as a self-forming cake layer on a support layer determining the rejection properties of the system. Recently, there is a great concern and more research need to understand and model the complex structure of DM and find proper support material. This study focused on the development of an efficient DM system with different textile fabric support materials in order to treat domestic wastewater. The applicability of two textile fabrics as cotton textile fabric (TF) and metal braided one (MBTF) as support layers with ultrafiltration membrane (UF) were investigated based on the chemical oxygen demand (COD), suspended solids (SS), specific resistance to filtration (SRF), and cake depth parameters. COD and SS removal efficiencies showed that TF support layer provided better reductions.
Extraction of Acetaminophen (ACTP) using vegetable oils-based emulsion liquid membrane (ELM) was investigated. ELM consists of membrane and internal phases that form the primary water-in-oil (W/O) emulsion by using an ultrasonic probe while the external phase consists of an ACTP aqueous solution. In promoting a greener development, vegetable oil was incorporated in the formulation of ELM, replacing the hazardous conventional petroleum derivatives diluent. The potential of vegetable oil-based solvent was confirmed via a compatibility study with the carrier and surfactant whereby sunflower oil showed an auspicious potential to be employed as a diluent in ELM formulation. The effect of emulsion formulation parameters of the vegetable oil-based ELM was investigated to obtain its best formulation, by taking into consideration the ACTP extraction efficiency. The extraction study carried out using Trioctylamine (TOA) & Aliquat 336 as carrier and ammonia & sodium chloride (NaCl) as internals phase were compared. The parameters involved are emulsification time, extraction time, and the stirring speed was investigated. These works demonstrated that the ELM system was competent to successfully expel 97.73% of ACTP from aqueous solutions under optimum conditions.
This paper emphases on the preparation, characterization and application of heterogeneous cation- and anion-exchange membranes. Membranes were made by solution casting method from the blends comprises of ion-exchange resins and eco-friendly polymer binder polyvinyl alcohol (PVA). Dimensional stability of membranes in water was controlled by crosslink density of binder. Physicochemical and electrochemical characteristics of ion-exchange membranes such as ion-exchange capacity (IEC), swelling (%), water uptake (%), surface electrical resistance, and transport number have been optimized by varying the resin:binder ratio. Thermal properties of the membranes were studied using the thermogravimetric analysis and differential scanning calorimetry to evaluate the thermal degradation pattern/stability and transition temperature, i.e., Tg of ionic membranes. The morphology of membrane samples were studied using scanning electron microscope. Heterogeneous ion-exchange membranes (HIXM) prepared from the water soluble binder showed superior electrochemical properties and homogeneous morphology compared to HIXMs prepared using the organic solvent based polymer binder polyvinyl chloride (PVC) and when used for desalination in Electrodialysis stack exhibits 85.5% salt reduction.
The purpose of this study is to find the best parameters, which are the oasis waste concentration, molding pressure, and sintering temperature for the fabrication of ceramic membrane to be used in the treatment of car wash wastewater. These membranes were prepared from clay and oasis waste using the semidry-pressing process. Characterization of these membranes was done by the determination of their porosity, contact angle, and shrinkage. Following the experiments, we notice that when the oasis waste concentration goes from 8% to 22%, the membranes become more hydrophilic. The same evolution is observed when the sintering temperature and molding pressure increase from 700 to 900°C, and eight to 12 bars, respectively. Moreover, membrane porosity increases with the increase of sintering temperature and oasis waste concentration by 14.6% and 49.3%, respectively. In addition, permeate flux is proportional to the oasis waste concentration and the sintering temperature. The highest flux increase is 62.2% for the case of 15% of oasis waste concentration, while a drop of 23.8% for permeate flux is recorded with the rise of molding pressure. After determining the membrane specific volume, which complies with the Tunisian standards NT.106.002, the best experimental parameters for the membrane fabrication are found to be: (i) 22% of oasis waste concentration, (ii) 800°C for sintering temperature, and (iii) Eight bars for molding pressure. After 30 minutes of the experimentation of wastewater treatment of car wash using the best membrane, an oil rejection of 93% and permeate flux of 116× 10-6 m3/m²s could be achieved.
The linear economic model based on “take-make-dispose” has become unsustainable, revealing the necessity of shifting towards a circular economy approach, in which secondary raw materials play a key role in closing material cycles. In this context, industrial effluents with metallic content, are considered a potential secondary source for these elements, the lack of the availability of the appropriate technology being the main barrier when implementing circular economy principles at industrial scale. In this regard, supported liquid membrane systems based on facilitated transport may be decisive. Thus, the objective of this research paper is to show the potential of facilitated transport systems to foster the transition to a more sustainable management of industrial metallic effluents. To accomplish that, three different applications of supported liquid membrane systems in acidic industrial effluents will be presented: a) Zn/Fe separation, b) Ni/Cd separations and c) Removal of hexavalent Cr. Additionally, the recovery and separation of two different critical raw materials, i.e. Li and rare earth elements will be discussed. Although facilitated transport systems have been successfully applied to both, Zn/Fe and Ni/Cd separation, as well as to hexavalent Cr removal, further work should be done for the successful recovery and separation of Li and rare earths with supported liquid membrane systems, especially in terms of selectivity improvement and validation with real industrial effluents.
Global warming is a public alarming issue caused by extreme CO2 emissions. Thus, CO2 removing using TFN membranes is an effective method to improve the CO2 separation performance. Thin film nocomposite membranes composed of Pebax 1657 embedded by porous organic polymers over the porous polysulfone support used to separate CO2 from CH4 and N2 gases. Porous organic polymers were synthesized via Friedel-Crafts one-step reaction. The obtained results from field emission scanning electron microscopy and thermal gravimetric analysis revealed that the TFN membranes declared a superior compatibility between Pebax and fillers. Permeation properties of membranes were tested over various feed pressure with the range of 2–10 bar. Pure gases permeability, CO2/CH4 and CO2/N2 selectivities improved via adding porous organic polymers into the Pebax. At porous organic polymers loading of 5wt% and feed pressure of 2 bar, the CO2, CH4 and N2 permeability raised to 310.6, 27.6 and 4.5 Barrer, respectively; which exhibited a significant improvement compared to thin film composite membrane. Moreover, the CO2/CH4 and CO2/N2 selectivities also increased to 11.25 and 70.04; respectively. Obtained results reveladed that the membranes performance was enhanced as the feed gas pressure increased. TFN containing 5wt% porous organic polymers implies a CO2 permeability of 348.4 Barrer at feed pressure of 10 bar.
The wastewater discharged from the poultry slaughterhouse always contains high levels of chemical oxygen demand (COD) and biochemical oxygen demand (BOD) and thus, it requires proper treatment to minimize its negative impacts on the receiving water bodies. In this work, we presented a local case study of the full-scale implementation of membrane bioreactor (MBR) process with capacity of 144 m3/day to treat the poultry slaughterhouse wastewater. Over the 6-month monitoring period, our results showed that the permeate flow rate of the MBR process was relatively stable and only suffered from approximately 16% flux decline for the entire period with 8-h operation daily. Such flux deterioration is acceptable given the membrane was not subjected to any cleaning process. With respect to the separation efficiencies, the MBR process showed a very promising performance by meeting almost all of the parameters’ limit of the National Water Quality Standards (Class IIB Limit), except for the dissolved oxygen (DO) that displayed slightly higher value than the maximum limit. A chemical cleaning process using sodium hydrochloride as agent was found to be effective to retrieve the permeate flow rate of the fouled membrane by 99%, indicating the deposited organic foulants were mainly reversible ones. The findings from this case study clearly demonstrated the potential of MBR process for treatment of poultry slaughterhouse wastewater and played an important role to minimize the negative impacts of discharged effluents on the environment.
Hyperbranched polybenzoxazole (HBPBO) – silica hybrids were treated at different thermal protocols and their gas permselectivity were studied. Inter-chain distance and free volume of pristine HBPBO were enlarged with increasing treated temperature. Gas permeability and diffusivity of the HBPBO were considerably increased with increasing treated temperature, which was resulted from increased fractional free volume due to enlarged inter-chain distance. Gas permeability of the HBPBO was further increased by the hybridization with silica, mainly owing to the increased gas diffusivity. This fact indicated additional free volume holes were formed at the HBPBO matrix – silica interfaces. It was worth noting the HBPBO – silica hybrids had a prominent CO2/CH4 permselectivity which exceeded the upper bound, and the CO2/CH4 permselectivity was enhanced with increasing treated temperature. The notable CO2/CH4 permselectivity of the HBPBO – silica hybrids would be achieved by the synergistic effect of characteristic hyperbranched molecular structure, thermal treatment, and hybridization with silica.
In the search for more efficient gas separation membranes, blends offer a compromise between costly high-performance polymers and low-cost commercial polymers. Here, blends of the polymer of intrinsic microporosity, AO-PIM-1, and commercial Matrimid®5218 polyimide are used to prepare dense films by solution casting. The morphology of the pure polymers and their blends with 20, 40, 60 and 80 wt.% of AO-PIM-1 in Matrimid® are studied by scanning electron microscopy, and their pure gas permeability is studied as a function of the blend composition with H2, He, O2, N2, CH4 and CO2. The polymers were found only partially miscible and a two-phase structure was formed with large domains of each polymer. When necessary, the films were coated with a thin silicone layer to heal possible pinhole defects. Even small amounts of Matrimid® in AO-PIM-1 resulted in an unexpectedly strong decrease in the permeability of the PIM, whereas a small amount of the PIM led to a modest increase in permeability of Matrimid®. Due to the two-phase structure, the Maxwell model was more suitable to describe the gas permeability as a function of the blend composition than the model for miscible blends. At low Matrimid® concentrations in AO-PIM-1, all models fail to describe the experimental data due to an unexpectedly strong depression of the permeability of the PIM by Matrimid®. Time lag measurements reveal that the changes in permeability as a function of the blend composition are mostly due to changes in the diffusion coefficient.
The use of low-cost clay materials for the fabrication of ceramic membrane has attracted much interest from researchers, and the outcome would be beneficial to the industries. In this study, low-cost bentonite was used for the preparation of hollow fiber ceramic (HFC) membrane. Bentonite powder was initially characterized by field emission scanning electron microscope (FESEM) for powder surface morphology. The bentonite membrane was fabricated through dope suspension mixing, using phase inversion-based extrusion method and sintering processes. The dope suspension was prepared by mixing quantified bentonite powder, dispersant, polymer binder, and organic solvent on a planetary ball mill. This was followed by the extrusion of the dope suspension at a bore fluid rate of 10 mL/min and air gap of 5 cm and finally subjected to the sintering temperatures of 950° C, 1000° C, 1050° C, and 1100° C. FESEM images revealed that bentonite powder has a compacted interlayer order of heterogeneous surface morphology. The resulting bentonite HFC membrane surface morphologies were examined by scanning electron microscopy (SEM), and the structures exhibit asymmetric structure, which was composed of sponge-like and finger-like structures. Due to, its superhydrophilic property and pore size; the membrane contact angle and water flux performance were obtained at 1.90° and ~326 L/m2 .h, respectively. Overall, the results suggest that bentonite can be used in the fabrication of ceramic-based hollow fiber membrane and in addition, can as well be utilized in microfiltration for wastewater treatment.
The aim of this study was to find a cost-efficient leachate treatment system by comparing two MBR systems, flat sheet and hollow fiber. Data collected through continuous monitoring and laboratory analysis over the last two years has been evaluated in terms of treatment performance and economic analysis. MBR systems were found to be as effective and economical in terms of color, SS removal, and total treatment efficiency. It has been observed that the flat sheet membranes were clogged up in six weeks, while the hollow fiber membranes took 12–16 weeks to clog. Moreover, the hollow fiber module was less clogged and needed shorter washing times, resulting in lower amounts of chemical consumption. Hollow fiber membrane systems, compared to flat sheet membrane systems, have higher operational availability and lower maintenance costs. For the first time, the advantage of using submerged hollow fiber for the treatment of high-strength landfill leachate has been clearly demonstrated.
MSVMD (multi-stage vacuum membrane distillation) has recently gained attention as means of enhancing the performance of single stage configuration. The present study is aimed to analyze the impact of multi-staging in VMD (vacuum membrane distillation) on productivity and the associated temperature polarization. Another goal is to determine the point of inversion, a point after which further multi-staging is no more beneficial both in terms of permeate productivity (flux) and associated temperature polarization. After validation with the experimental data, a parametric analysis of MSVMD performance is carried out numerically. Further, the permeate productivity and associated temperature polarization phenomenon were analyzed simultaneously under varying membrane specifications. The optimum number of stages, giving the maximum possible performance of MSVMD, is estimated for variation in most prominent process variables and membrane specifications. The point of inversion was found to be above 40 stages for varying process variables, however, it remained well below 20 stages for variation in some of the prominent membrane characteristics.
In this study, a novel layered-type microfiltration (MF) ceramic membrane for advanced wastewater treatment was fabricated; composed of the support, buffer layer, and active layer. The buffer and active layers allow for the easy formation of the active layer on the support and selective permeation of the ceramic membrane, respectively. The average pore sizes of the support, buffer layer, and active layer were 2,677, 773.3, and 33.1 nm, respectively. The diameters of the active layer pores were <0.1 μm. The ceramic membrane performance and mechanical scraping effects on the membrane permeability improvement were evaluated. Mixed liquor suspended solids (MLSS) were used for the feed of an enhanced ceramic membrane filtration system, by combining the fabricated membranes and devised scrapers. The average flux recovery by scraping was 54% of the clean water flux; maintained by scraping despite the high turbidity feed. The permeation concluded within 0.2 h during scrape-off. This was not recovered despite scraping because the internal membrane pores became blocked due to the material turbidity and could not be separated at the surface of the ceramic membrane.
The innovative membrane-based technology called reverse electrodialysis (RED) is capable of producing electrical power from the controlled mixing of two aqueous streams of different salinity. There has been tremendous progress so far in the development of RED process in terms of system development, spacer design, membranes properties and operational conditions optimization. Among those, characteristics of the ion exchange membranes are found to be the critical element affecting the performances of RED process. In this respect, a brief overview of the latest developments in ion exchange membranes were presented in this review, focussing on their properties and performances in RED applications. The recent developments of nanocomposite and ion selective membranes, particularly pore filling ion exchange membranes due to their high performances and inexpensive fabrication cost were also summarized. Shortly, fouling problem for the ion exchange membranes employed in the RED system was mentioned.
The toxicity and carcinogenic effect of many drugs including antibiotics have brought up an environmental worry in the recent years. The current study examined a green emulsion liquid membrane (ELM) as an environmentally-friendly method for extracting Vancomycin antibiotic from its aqueous solutions. The main value of the idea is to reduce environmental risks of employing common unsafe organic solvents applied as diluent in the ELM process. For this purpose, the raw sunflower oil was employed to prepare ELM. An organic phase including the sunflower oil (diluents), Span 80 (emulsifier) and bis(2-ethylhexyl)phosphoric acid (D2EHPA) carrier was mixed with internal aqueous phase (stripping phase) containing NaOH. The results confirmed that almost 100% of Vancomycin was successfully extracted at the optimum conditions affecting parameters for preparing the membrane. The extraction percentage and emulsion stability was acceptable for the feeds with wide range of pH from 5-9 and NaCl concentration from 0-5 g/L. Also, a recovery percent of around 70% was achieved for the captured Vancomycin when the emulsion was broken.
This work discusses the synthesis and characterizations of the newly developed composite membranes based on chitosan/phthaloyl chitosan (Cs/PhCs) as a matrix with various compositions of multi-walled carbon nanotube/montmorillonite (MWCNT/MMT) filler. The Cs/PhCs/MWCNT/MMT composite membranes are synthesized via the solvent evaporation method and were investigated by Fourier Transform Infrared (FTIR), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS), and DMFC single cell test. The FTIR characterization result showed that all membranes have origin peaks at 3433, 2943, and 1525 cm-1 contributed to vibrations of O-H, C-H, and N-H group, respectively. Meanwhile, the composite membranes with 7.5 and 8 wt.% filler have characteristic peaks of vibration Si-O-Si, Si-OH, and Si-O at 1209, 886, and 591 cm-1 respectively. Cross-sectional micrographs of SEM and AFM revealed that the composite membrane with 7.5 wt.% filler had moderate surface roughness than the other as-fabricated membranes. As a result, this nanocomposite membrane can be an alternative polyelectrolyte membrane for DMFC applications. The resulting Cs/PhCs/MWCNT/MMT-1 composite membrane has the selectivity up to 5.13×105 S.s.cm-3 with the DMFC performance at 23.60 mW cm-2.
Most research efforts about pervaporation in the literature have focused on membrane synthesis, trying to improve the membrane properties (flux and selectivity). However, industrial applications of the pervaporation technology could become attractive if the current available membranes proved to have sufficient and stable performance in order to be integrated in the toolbox of process engineers, as a complementary separation process. In this study, the ethanol dehydration performance of commercial hybrid silica membranes (HybSi®) was assessed in a semi-pilot pervaporation unit from a process-based perspective. The aim of the study is to reveal the high potential of the process and to create a benchmark for future studies in the field. The experimental results revealed that the proposed pervaporation process can efficiently break the ethanol/water azeotrope, allowing the production of high purity ethanol. The overall assessment of the obtained pilot results showed that the proposed process is quite efficient for attracting the industrial interest.
The useful lifetime of bipolar ion exchange membranes is often limited by nucleophilic attack by hydroxide ions on the ionic groups and polymer backbone in the anion exchange layers (AELs). This is especially problematic in water treatment applications for making acid and base from salt solutions. This research investigated the effect of bulk electrolyte composition, current density, membrane thickness, ion exchange capacity, and bulk solution pH value on hydroxide ion concentrations inside the AELs of a bipolar membrane. Onedimensional Nernst-Plank equations were solved for the species Na+, Cl-, OH- and H+ within 20-100 μm thick anion and cation exchange layers with fixed charged densities ranging from 0.5-2.0 eq/L. In 1 M NaCl solutions at neutral pH values, hydroxide concentrations in the AEL reached as high as 2.2 M at a current density of 100 mA/cm2. In 1 M NaOH solutions, hydroxide ion concentrations reached as high as 3.77 M. Hydroxide concentrations in the AEL were significantly affected by the ratio of Cl- to hydroxide ions in the bulk electrolyte. Where hydroxide concentrations in the bulk electrolyte were an order of magnitude lower than chloride concentrations, membrane hydroxide concentrations were nearly proportional to the current density. Increases in ion exchange capacity and AEL thickness resulted in increased membrane hydroxide ion concentrations. Membrane concentrations of hydroxide ions can be minimized by operation at low current densities, with high background electrolyte concentrations using thin membranes with low ion exchange capacities and producing base concentrations less than 0.1 M.
Palm oil mill effluent (POME) treatment through fermentation under controlled conditions generates biogas with an equal volume of biohydrogen (H2 ) and carbon dioxide (CO2 ). The H2 can be utilised for generating renewable energy through a hydrogen fuel cell. However, the existence of CO2 at certain concentration might cause cell poisoning. Therefore, gas upgrading is required. Membrane technology has been identified as one of the best methods for gas upgrading owing to its excellent purification performance. In this study, polyvinylidene difluoride (PVDF) membrane was synthesized at various polymer concentrations of 13-18 wt% through the phase inversion method before being coated with polyethylene glycol (PEG). From the results, the surface negativity and contact angle of the synthesised PVDF membranes were increased at higher PVDF concentration, therefore leading to increase in PVDF membrane’s hydrophobicity. As there was an increase in the membrane’s hydrophobicity, the membrane’s selectivity towards H2 increased as well, with the most H2 purity noted at 85%, which was attained by PVDF18 membrane. On adding PEG on the membrane surface, hydrophobicity rose from 81° (pure PVDF) to 100.8° (PVDF-co-PEG10). Moreover, PEG coating on the surface of PVDF membranes has enhanced their selectivity with the highest value of selectivity of up to 3.3. The PVDF-co-PEG10 membrane also has the highest H2 gas purity of up to 96% in comparison to pure PVDF membrane (only 85% H2 purity). This finding proved that PVDF-co-PEG10 membrane possessed a higher preference in the H2 /CO2 separation compared to pure PVDF membrane.
