An enhanced water flux and anti-fouling nanocomposite ultrafiltration membrane based on quaternary ammoniumpropylated polysilsesquioxane (QAPS)/cellulose acetate (QAPS@CA) was fabricated by in situ sol-gel processing via phase inversion followed by quaternization with methyl iodide (CH3I). Membrane characterizations were performed based on the contact angle, FTIR, SEM, and TGA properties. Membrane separation performance was assessed in terms of pure water flux, rejection, and fouling resistance. The 7%QAPS@CA nanocomposite membrane showed an increased wettability (46.6° water contact angle), water uptake (113%) and a high pure water permeability of ∼370 L m-2 h-1 bar-1. Furthermore, the 7%QAPS@CA nanocomposite membrane exhibited excellent bactericidal properties (∼97.5% growth inhibition) against Escherichia coli (E. coli) compared to the bare CA membrane (0% growth inhibition). The 7%QAPS@CA nanocomposite membrane can be recommended for water treatment and biomedical applications.
There has been tremendous progress in membrane technology for gas separation, in particular oxygen separation from air in the last 20 years. It provides an alternative route to the existing conventional separation processes such as cryogenic distillation and pressure swing adsorption as well as cheaper production of oxygen with high purity. This review presents the recent advances of ceramic membranes for the separation of oxygen from air at high temperature. It covers the issues and problems with respect to the selectivity and separation performance. The paper also presents different approaches applied to overcome these challenges. The future directions of ceramic-based membranes for oxygen separation from air are also presented.
The amount of lipase from Mucor miehei adsorption on ultrafiltration polysulfone hollow fiber membrane chips has been determined using different lipase concentrations at three different temperatures, namely 30, 35, and 40 degrees C. It was experimentally shown that adsorption of lipase increases with temperature. The results were used to evaluate the constants found in the Langmuir adsorption isotherm model coupled with the Van't Hoff's relationship. A temperature dependence correlation for the amount of adsorbed lipase activity, alip,ads, and that present in the supernatant solution, alip,free was determined. The effect of varying the concentration on a cross-linking agent, namely, glutaraldehyde, to the membrane chips was also tested. It was found that, under the same operating conditions, the amount of lipase adsorbed on polysulfone membranes was increased dramatically after pre-treating the membrane with 1% Glutaraldehyde. However, increasing the concentration of the cross-linking agent has a low effect on the amount of lipase adsorbed.
The effects of different hydraulic retention time (HRT) on (RS)-MCPP utilisation was investigated by decreasing the feed flow rate in an anaerobic membrane bioreactor (AnMBR). Results showed an average COD removal efficiency of 91.4%, 96.9% and 94.4% when the reactor was operated at HRT 3, 7 and 17 d, respectively. However, when the HRT was reduced to 1d, the COD removal efficiency declined to just only 60%, confirming the AnMBR is stable to a large transient hydraulic shock loads. The (RS)-MCPP removal efficiency fluctuated from 6% to 39% at HRT 3 d, however when it was increased to 7 and 17 d, the removal efficiency increased to an average of 60% and 74.5%. In addition, (RS)-MCPP specific utilisation rates (SUR) were dependent on the HRT and gradually improved from 18 to 43 μg mg VSS(-1) d(-1) as flow rate increased.
This study explains the modeling of synthesized membranes using the Donnan Steric Pore model (DSPM) based on the Extended Nernst Planck Equation (ENP). Conventionally, structural parameters required to predict the performance of the membranes were determined through tedious experimentation, which in this study are found using a new MATLAB technique. A MATLAB program is used to determine the unknown structural parameters such as effective charge density (Xd), effective pore radius (rp), and effective membrane thickness to porosity ratio (Δx/Ak) by using the single solute rejection and permeation data. It was found that the model predicted the rejection of studied membranes accurately, with the E5C1 membrane exceeding the others (E5, E5C5) for rejection of single and divalent salt's aqueous solutions. The rejection of 100 ppm aqueous solution of NaCl for E5C1 was around 60%, whereas, for an aqueous solution of 100 ppm, CaCl2 rejection reached up to 80% at 10 bar feed pressure. The trend of salt rejection for all three membranes was found to be in the following order: E5C1 > E5C5 > E5, confirming that their structural parameters-controlled ion transport in these membranes. The structural parameters, such as effective pore radius, effective membrane thickness to porosity ratio, and effective charge density for the best performing membrane, i.e., E5C1, were determined to be 0.5 nm, 16 μm, and -6.04 mol/m3,respectively. Finally, it can be asserted that this method can be used to predict the real performance of membranes by significantly reducing the number of experiments previously required for the predictive modeling of nanofiltration-type membranes.
17α-methyltestosterone (MT) hormone is a synthetic androgenic steroid hormone utilized to induce Nile tilapia transitioning for enhanced production yield. This study specifically focuses on the removal of MT through the utilization of photocatalytic membrane reactor (PMR), which employs an in-house polyvinylidene fluoride (PVDF) ultrafiltration membrane modified with 1% nanomaterials (either TiO2 or α-Fe2O3). The molecular weight cut-off (MWCO) of the in-house membrane falls within the ultrafiltration range. Under UV95W radiation, the PMR with PVDF/TiO2 and PVDF/α-Fe2O3 membranes achieved 100% MT removal at 140 and 160 min, respectively. The MT removal by the commercial NF03 membrane was only at 50%. In contrast, without light irradiation, the MT removal by all the membranes remained unchanged after 180 min, exhibiting lower performance. The incorporation of TiO2 and α-Fe2O3 enhanced water flux and MT removal of the membrane. Notably, the catalytic activity was limited by the distribution and concentration of the catalyst at the membrane surface. The water contact angle did not correlate with the water flux for the composited membrane. The degradation of MT aligned well with Pseudo-first-order kinetic models. Thus, the in-house ultrafiltration PMR demonstrated superior removal efficiency and lower operational costs than the commercial nanofiltration membrane, attributable to its photocatalytic activities.
Guided tissue regeneration (GTR) and guided bone regeneration (GBR) are two common dental regenerative procedures used to repair periodontal defects caused by periodontitis. In both procedures, a barrier membrane is placed at the interface between the soft tissue and the periodontal defect, serving to impede the infiltration of soft tissue while creating a secluded space for periodontal regeneration. Recently, barrier membranes based on chitosan (CS) have emerged as a promising avenue for these applications. However, despite numerous studies on the development of CS-based membranes, comprehensive review articles specifically addressing their progress in GTR/GBR applications remain scarce. Herein, we review recent research and advancements in the use of CS-based membranes for periodontal GTR and GBR. The review begins by highlighting the advantageous properties of CS that make it a suitable biomaterial for GTR/GBR applications. Next, the development of composite CS-based membranes, reinforced with various compositions like bioactive fillers and therapeutic agents, is discussed in detail based on recent literature, with a focus on their enhanced efficacy in promoting periodontal regeneration. Finally, the review explores the emergence of functionally graded CS-based membranes, emphasizing their potential to address specific challenges encountered in GTR/GBR procedures.
Microalgae cultivation in open ponds requires a large footprint, while most photobioreactors need improvement in the ratio of surface to volume and energy consumption. In this study, polyethersulfone (PES) and poly(vinylidene fluoride) (PVDF) hollow fiber membranes with a large surface area were rearranged into open-ended and dead-ended configurations to improve the air-liquid interface cultivation of Navicula incerta. N. incerta were successfully grown on the porous membrane surface with the nutrients circulating inside the lumen. Fourier-transform infrared spectra showed the accumulation of polysaccharides, proteins and humic acids. Hydrophilic polysaccharides reduced water contact angles on PES and PVDF membranes to 37.2 ± 2.6° and 55.7 ± 3.3°, respectively. However, the porosity of PES (80.1 ± 1.1%) and PVDF (61.3 ± 4.5%) membranes were not significantly affected even after cultivation and harvesting of N. incerta. Scanning electron images further confirmed that N. incerta, cell debris and extracellular organic matter accumulated on the membrane. With large pores and a hydrophobic surface, PVDF hollow fiber membranes offered a greater improvement in N. incerta cell growth rate compared to PES hollow fiber membranes despite using different configurations. In the dead-ended configuration, they even attained the greatest improvement in N. incerta growth rate, up to 54.0%. However, PES hollow fiber membranes only achieved improvement in harvesting efficiency within the range of 18.7-38.0% due to weak cell adhesion. PVDF hollow fiber membranes significantly promoted the growth of microalgae N. incerta through the air-liquid interface system, leading to potential applications in wastewater treatment.
This study focuses on the development of an efficient membrane-based clarification process to enhance the performance of subsequent ultrafiltration and produce high-quality sweet lime juice. A range of casting solutions were prepared using a blend of pore-forming polymers, including polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), and cellulose acetate (CA), dissolved in dimethylformamide (DMF) solvent through the phase inversion technique. To further enhance the membrane's performance, four biopolymers poly (lactic acid) (PLA), xanthan gum, chitosan, and gelatin were incorporated, with and without clay, to refine its structure, porosity, and surface properties. The resulting membranes were characterized by FT-IR, SEM, and AFM, and their flux behaviour and fouling profiles were evaluated. The quality of the clarified juice was assessed by measuring total suspended solids (TSS), clarity, color, and apparent alcohol insoluble solids (AIS). Despite a reduction in permeate flux, the Xanthan-clay-loaded membrane enhanced juice quality and clarity. For the PLA-based membrane and the xanthan-based membrane, the fouling coefficient was lower. This membrane-based clarification technique can be applied effectively in the juice processing industries to improve product quality.
Microalgae harvesting using membrane technology is challenging because of its high fouling propensity. As an established fouling mitigation technique, efficacy of air bubbles can be improved by maximizing the impact of shear-rates in scouring foulant. In this study, it is achieved by tilting the membrane panel. We investigate the effect of tilting angle, switching period as well as aeration rate during microalgal broth filtration. Results show that higher tilting angles (up to 20°) improve permeability of up to 2.7 times of the vertical panel. In addition, operating a one-sided panel is better than a two-sided panel, in which the later involved switching mode. One-sided membrane panel only require a half of area, yet its performance is comparable with of a large-scale module. This tilted panel can lead to significant membrane cost reductions and eventually improves the competitiveness of membrane technology for microalgae harvesting application.
Membrane bioreactor (MBR) is regarded as the state-of-the-art technology in separation processes. Surface modification techniques play a critical role in improving the conventional membrane system which is mostly hydrophobic in nature. The hydrophobic nature of membranes is known to cause fouling, resulting in high maintenance costs and shorter lifespan of MBR. Thus, surface grafting aims to improve the hydrophilicity of bio-based membrane systems. This review describes the major surface grafting techniques currently used in membranes, including photo induced grafting, plasma treatment and plasma induced grafting, radiation induced grafting, thermal induced grafting and ozone induced grafting. The advantages and disadvantages of each method is discussed along with their parametric studies. The potential applications of MBR are very promising, but some integral membrane properties could be a major challenge that hinders its wider reach. The fouling issue could be resolved with the surface grafting techniques to achieve better performance of MBRs.
This paper aims to develop novel hydrophilic ionic liquid membranes using pervaporation for the recovery of biobutanol. Multiple polyvinyl alcohol (PVA) membranes based on three commercial ionic liquids with different loading were prepared for various experimental trials. The ionic liquids selected for the study include tributyl (tetradecyl) phosphonium chloride ([TBTDP][Cl]), tetrabutyl phosphonium bromide ([TBP][Br]) and tributyl methyl phosphonium methylsulphate ([TBMP][MS]). The synthesized membranes were characterized and tested in a custom-built pervaporation set-up. All ionic liquid membranes showed better results with total flux of 1.58 kg/m2h, 1.43 kg/m2h, 1.38 kg/m2h at 30% loading of [TBP][Br], [TBMP][MS] and [TBTDP][Cl] respectively. The comparison of ionic liquid membranes revealed that by incorporating [TBMP]MS to PVA matrix resulted in a maximum separation factor of 147 at 30 wt% loading combined with a relatively higher total flux of 1.43 kg/m2h. Density functional theory (DFT) calculations were also carried out to evaluate the experimental observations along with theoretical studies. The improved permeation properties make these phosphonium based ionic liquid a promising additive in PVA matrix for butanol-water separation under varying temperature conditions.
The aim of this study is to evaluate the performance and antifouling properties of polyethersulfone (PES) membrane incorporated with dual nanofiller, zinc oxide (ZnO) and multi-walled carbon nanotube (MWCNT). The synergistic effect of the these nanofillers in PES membrane is studied by blending different ratio of ZnO/MWCNT nanofiller into the PES membrane. The fabricated membranes were characterized in terms of cross-section and surface morphology, surface hydrophilicity, pore size and porosity. The filtration performance of the membranes was tested using 50 mg/L humic acid (HA) solution as model solution. SEM image and gravimetric evaluation reported that the incorporation of both MWCNT and ZnO into the PES membrane improved porosity significantly up to 46.02%. Lower water contact angle of PES membrane incorporated with equal ratio of MWCNT and ZnO (PES 3) revealed that it has neat PES membrane properties and more hydrophilic membrane surface than single filler. PES 3 outperform other membranes with excellent HA permeate flux of 40.00 L/m2.h and rejection of 88.51%. Due to hydrophilic membrane surface, PES 3 membrane demonstrate efficient antifouling properties with lower relative flux reduction (RFR) and higher flux recovery ratio (FRR). PES 3 also showed notable antibacterial properties with less bacterial attached to the membrane compared to neat PES membrane (PES 0).
Mixed matrix membranes (MMMs) were fabricated by the hydrothermal synthesis of ordered mesoporous KIT-6 type silica and incorporating in polyimide (P84). KIT-6 and MMMs were characterized to evaluate morphology, thermal stability, surface area, pore volume, and other characteristics. SEM images of synthesized MMMs and permeation data of CO2 suggested homogenous dispersion of mesoporous fillers and their adherence to the polymer matrix. The addition of KIT-6 to polymer matrix improved the permeability of CO2 due to the increase in diffusivity through porous particles. The permeability was 3.2 times higher at 30% loading of filler. However, selectivity showed a slight decrease with the increase in filler loadings. The comparison of gas permeation results of KIT-6 with the well-known MCM-41 revealed that KIT-6 based MMMs showed 14% higher permeability than that of MMMs composed of mesoporous MCM-41. The practical commercial viability of synthesized membranes was examined under different operating temperatures and mixed gas feeds. Mesoporous KIT-6 silica is an attractive additive for gas permeability enhancement without compromising the selectivity of MMMs. Graphical abstract.
Fuel cells (FCs) are a chemical fuel device which can directly convert chemical energy into electrical energy, also known as electrochemical generator. Proton exchange membrane fuel cells (PEMFCs) are one of the most appealing FC systems that have been broadly developed in recent years. Due to the poor conductivity of electrolyte membrane used in traditional PEMFC, its operation at higher temperature is greatly limited. The incorporation of ionic liquids (ILs) which is widely regarded as a greener alternative compared to traditional solvents in the proton exchange membrane electrolyte shows great potential in high temperature PEMFCs (HT-PEMFCs). This review provides insights in the latest progress of utilizing ILs as an electrochemical electrolyte in PEMFCs. Besides, electrolyte membranes that are constructed by ILs combined with polybenzimidazole (PBI) have many benefits such as better thermal stability, improved mechanical properties, and higher proton conductivity. The current review aims to investigate the newest development and existing issues of ILs research in electrolyte and material selection, system fabrication method, synthesis of ILs, and experimental techniques. The evaluation of life cycle analysis, commercialization, and greenness of ILs are also discussed. Hence, this review provides insights to material scientists and develops interest of wider community, promoting the use of ILs to meet energy challenges.
Membrane technology, especially nanofiltration (NF) has great attention to provide an imperative solution for water issues. The membrane is considered to be the heart in the separation plant. Understanding the membrane characteristics could allow predicting and optimizing the membrane performance namely flux, rejection and reduced fouling. The membrane development using biomaterials and nanomaterials provides a remarkable opportunity in the water application. This review focuses on the membrane characteristics of biomaterials and nanomaterials based nanofiltration. In this review, recent researches based on biomaterials and nanomaterials loaded membrane for salt rejection have been analyzed. Membrane fouling depends on the membrane characteristics and this review defined fouling as a ubiquitous bottleneck challenge that hampers the NF blooming applications. Fouling mitigation strategies via membrane modification using biomaterial (chitosan, curcumin and vanillin) and various other nanomaterials are critically reviewed. This review also highlights the membrane cleaning and focuses on concentrates disposal methods with zero liquid discharge system for resource recovery. Finally, the conclusion and future prospects of membrane technology are discussed. From this current review, it is apparent that the biomaterial and various other nanomaterials acquire exclusive properties that facilitate membrane advancement with improved capability for water treatment. Regardless of membrane material developments, still exist considerable difficulties in membrane commercialization. Thus, additional studies related to this field are needed to produce membranes with better performance for large‒scale applications.
Effluent originating from cheese production puts pressure onto environment due to its high organic load. Therefore, the main objective of this work was to compare the influence of different process variables (transmembrane pressure (TMP), Reynolds number and feed pH) on whey protein recovery from synthetic and industrial cheese whey using polyethersulfone (PES 30 kDa) membrane in dead-end and cross-flow modes. Analysis on the fouling mechanistic model indicates that cake layer formation is dominant as compared to other pore blocking phenomena evaluated. Among the input variables, pH of whey protein solution has the biggest influence towards membrane flux and protein rejection performances. At pH 4, electrostatic attraction experienced by whey protein molecules prompted a decline in flux. Cross-flow filtration system exhibited a whey rejection value of 0.97 with an average flux of 69.40 L/m2h and at an experimental condition of 250 kPa and 8 for TMP and pH, respectively. The dynamic behavior of whey effluent flux was modeled using machine learning (ML) tool convolutional neural networks (CNN) and recursive one-step prediction scheme was utilized. Linear and non-linear correlation indicated that CNN model (R2 - 0.99) correlated well with the dynamic flux experimental data. PES 30 kDa membrane displayed a total protein rejection coefficient of 0.96 with 55% of water recovery for the industrial cheese whey effluent. Overall, these filtration studies revealed that this dynamic whey flux data studies using the CNN modeling also has a wider scope as it can be applied in sensor tuning to monitor flux online by means of enhancing whey recovery efficiency.
Herbicides such as atrazine and humus substances such as fulvic acid are widely used in agricultural sector. They can be traced in surface and groundwater around the agriculture field at concentrations beyond the approved limit due to their mobility and persistence. Bismuth-based photocatalysts activated by visible light are potential materials for removing various organic pollutants from water bodies. These photocatalysts can also be suitable candidates for developing a hybrid membrane with anti-fouling properties. In this study, Bi2WO6 nanoparticles were synthesized via the hydrothermal method and integrated into the cellulose acetate (CA), polyetherimide (PEI), polysulfone (PSF) and polyvinylidene fluoride (PVDF) polymers via physical blending approach. The hybrid membranes were then characterized by FTIR, XPS and FESEM to confirm the chemical bonding, chemical composition and surface morphology of Bi2WO6. Thus, the pure water flux of CA (35.6 L m-2 h-1), PEI (46.56 L m-2 h-1), PSF (6.84 L m-2 h-1), and PVDF (68.47 L m-2 h-1) hybrid membranes has significantly enhanced than the pristine CA, PEI, PSF and PVDF membranes. The significant rejection of atrazine-fulvic acid was observed with hybrid membranes in the order of CA (84.1%) > PVDF (72.7%) > PEI (47.8%) > PSF (37.2%), and these membranes have shown an excellent flux recovery ratio than pristine membranes. Further, electrochemical quantification studies were performed to analyze the removal efficiency of atrazine-fulvic acid from water. In this present work, GO-modified SPE was employed for electrochemical sensing studies. The resultant CA hybrid membrane achieved removal efficiency of 84.08% for atrazine. It was observed that the Bi2WO6 established strong bonding with CA, and PVDF membranes, thus showing a significant removal efficiency and FRR than other hybrid and pristine membranes.
This research aims to evaluate the performance of PolyCera® Titan membrane for different wastewater treatment. Membrane filtration of several cycles was conducted in understanding the fouling mechanism, fouling propensity, and defouling potential of the PolyCera® Titan which had not been studied by any other researcher before. The PolyCera® Titan membrane is effective for the treatment of textile industry wastewater, palm oil mill effluent (POME), leachate, and semiconductor-industry wastewater. Rejection of methylene blue (MB) and Congo red (CR) was in the range of 78.76-86.04% and 88.89-93.71%, respectively; 94.72-96.50% NaCl, 96.07-97.62% kaolin, and 97.26-97.73% glucose were rejected from synthetic leachate indicating the removal of TDS, TSS, and COD from the leachate, respectively. Standard blocking and complete model were the best models used to explain the PolyCera® Titan membrane fouling mechanism in all types of wastewater treatment processes with a high R2 value. Physical cleaning with the use of distilled water was able to recover the permeate flux with the flux recovery ratio (FRR) value in the range of 79.2-95.22% in the first cycle, 81.20-98.16% in the second cycle, and 86.09-95.96% in the third cycle.
Discharging improperly treated oily-produced water (OPW) into the environment can have significant negative impacts on environmental sustainability. It can lead to pollution of water sources, damage to aquatic ecosystems and potential health hazards for individuals living in the affected areas. Ceramic hollow fiber membrane (CHFM) technology is one of the most effective OPW treatment methods for achieving high oil removal efficiency while maintaining membrane water permeability. In this study, low-cost calcium bentonite hollow fiber membranes (CaB-HFMs) were prepared from high-alumina calcium bentonite clay with various preparation parameters, including calcium bentonite content, sintering temperature, air gap distance and bore fluid rate. The prepared CaB-HFMs were then subjected to characterization using scanning electron microscopy (SEM), a three-point bending test, porosity, average pore size, hydraulic resistance and flux recovery ratio (FRR) analysis. Statistical analysis employing central composite design (CCD) assessed the interaction between the parameters and their effect on CaB-HFM water permeability and oil removal efficiency. Higher ceramic content and sintering temperature led to reduced porosity, smaller pore size and higher mechanical strength. In contrast, increasing the air gap distance and bore fluid rate exhibit different trends, resulting in higher porosity and pore size, along with weaker mechanical strength. Other than that, all of the CaB-HFMs displayed low hydraulic resistance (<0.01 m2 h.bar/L) and high FRR value (up to 95.2%). Based on CCD, optimal conditions for CaB-HFM were determined as follows: a calcium bentonite content of 50 wt.%, a sintering temperature of 1096 °C, an air gap distance of 5 cm and a bore fluid rate of 10 mL/min, with the desirability value of 0.937. Notably, the optimized CaB-HFMs demonstrated high oil removal efficiency of up to 99.7% with exceptional water permeability up to 535.2 L/m2.h.bar. The long-term permeation study also revealed it was capable of achieving a high average water permeation and a stable oil rejection performance of 522.15 L/m2.h.bar and 99.8%, respectively, due to their inherent hydrophilic and antifouling characteristics, making it practical for OPW treatment application.