Commercial Polyethersulfone Research Articles

Process Performance and Nutrient Removal in Fish Processing Wastewater Using a Membrane Bioreactor (MBR) Unit for Reuse for Irrigation

This study investigated the removal of nitrogen and phosphates in fish processing wastewater through process optimization of a membrane bioreactor (MBR) treatment unit. Raw process wastewater was collected from the Makindi fish farm and was pre-filtered through a mesh of 0.8 mm. The experiment was conducted at a lab scale using commercial Polyethersulfone (PES) membranes submerged in the MBR unit. The pre-filtered wastewater sample was added into a denitrification (anoxic) tank. The process was conducted through continuous recirculation between the aeration and the anoxic tank to enhance the removal of nitrogenous compounds. The recirculation flow rate was 10L/h. A hydraulic residence time (HRT) of approximately 22-25h was maintained, and the aeration rate in the aerobic tank was 100L/min. Aluminum sulphate AI2(SO4)318H2O was added continually into the anoxic tank and with constant stirring to enhance the removal of phosphates. A removal rate of 85±2% for NH4+-N, 84±1% for NO3- -N, and 69±3% for PO43--P was obtained. The nutrient concentration in the effluent was successfully reduced to an acceptable level with both nitrogenous compounds and phosphate concentrations obtained within the range of < 30 mg/L and ≤ 5 mg/L as per the WHO guidelines for wastewater reuse for irrigation. The results showed a successful process optimization that can be applied to ensure optimized performance of the MBR unit thus improve its effectiveness for the treatment of fish processing wastewater. The study therefore recommends process optimization as a tool for effective removal of nutrients in the MBR system thus making it a potential recycling approach for treatment of fish processing wastewater for reuse for irrigation purposes.

Enhanced filtration membranes with graphene oxide and tannic acid for textile industry wastewater dye removal

ABSTRACT A novel modification technique employing a layer-by-layer (LbL) self-assembly method, integrated with a pressure-assisted filtration system, was developed for enhancing a commercial polyethersulfone (PES) microfiltration (MF) membrane. This modification involved the incorporation of tannic acid (TA) in conjunction with graphene oxide (GO) nanosheets. The effectiveness of the LbL method was confirmed through comprehensive characterization analyses, including ATR-FTIR, SEM, water contact angle (WCA), and mean pore size measurements, comparing the modified membrane with the original commercial one. Sixteen variations of PES MF membranes were superficially modified using a three-factorial design, with the deposited amount of TA and GO as key factors. The influence of these factors on the morphology and performance of the membranes was systematically investigated, focusing on parameters such as pure water permeability (PWP), blue corazol (BC) dye removal efficiency, and flux recovery rate (FRR). The membranes produced with the maximum amount of GO (0.1 mg, 0.55 wt%) and TA as the inner and outer layers demonstrated remarkable FRR and significant BC removal, exceeding 80%. Notably, there was no significant difference observed when using either 0.2 (1.11 wt%) or 0.4 mg (2.22 wt%) in the first layer, as indicated by the Tukey mean test. Furthermore, the modified membrane designated as MF/TA0.4GO0.1TA0.4 was evaluated in the filtration of a simulated dye bath wastewater, exhibiting a BC removal efficiency of 49.20% and a salt removal efficiency of 27.74%. In conclusion, the novel PES MF membrane modification proposed in this study effectively enhances the key properties of pressure-driven separation processes.

Nanofiltration Performance of Poly(p-xylylene) Nanofilms with Imidazole Side Chains.

Herein, we report the nanofiltration performance of poly(p-xylylene) thin films with imidazole side chains that were deposited onto commercial polyethersulfone ultrafiltration membranes using a chemical vapor deposition process. The resulting thin films with a few tens of nanometers exhibited water permeation under a pressure difference of 0.5 MPa and selectively rejected water-soluble organic dyes based on their molecular sizes. Additionally, thin flaky ZIF-L crystals (Zn(mim)2·(Hmim)1/2·(H2O)3/2) (Hmim = 2-methylimidazole) formed on the surface of imidazole-containing poly(p-xylylene) films, and the composite films demonstrated the ability to adsorb methylene blue molecules within the cavities of ZIF-L.

Modeling and mitigating fouling of microfiltration membranes for microalgae dewatering

Dewatering is energy-intensive for microalgae production, and microfiltration (MF) membranes are attractive because of their high energy efficiency. However, the membranes suffer from fouling by organic matter in the algae solutions, and there needs fundamental understanding of membrane fouling with actual algae solutions. Herein we thoroughly evaluate the dewatering performance of commercial polyethersulfone (PES) MF membranes using an integrated experiment and modeling approach. The effect of algae concentration, testing time, feed flow rate, and chemical cleaning on the dewatering performance and fouling-layer morphology are investigated. The fouling behavior can be successfully described using the Hermia and gel layer models with a gel concentration of 48 g/L for algae solutions. Furthermore, the PES membrane surface was grafted with hydrophilic zwitterions, which mitigated the fouling. For example, when challenged with 10 g/L algae solution in dead-end cells, the pristine and modified membrane exhibit water permeance of 80 and 170 L m−2 h−1 bar−1, respectively. Three cycles of dewatering and NaOH cleaning were performed to demonstrate the promise of the MF membranes for practical dewatering application.

Inhibition of membrane biofouling by grafting quorum sensing inhibitors onto ultrafiltration membranes

Quorum sensing inhibitors (QSIs) can inhibit biofilm formation by regulating the synthesis of extracellular polymeric substances (EPS), thus alleviating biofouling in the membrane filtration process. In this study, utilizing the adhesion ability of a mussel-inspired biomimetic material, polydopamine (PDA), natural quorum sensing inhibitors, vanillin and furanone, were modified on a commercial polyethersulfone (PES) ultrafiltration (UF) membrane to inhibit the formation of biofilm fouling. We proved that QSIs were successfully grafted onto the membrane surface without blocking the pore structure, and the pure water flux of the membrane was simultaneously improved due to hydrophilicity improvement. The vanillin-modified membrane significantly inhibited the biofilm formation of P. aeruginosa PAO1 (81.7% inhibition rate), while furanone had a certain inhibitory effect on E. coli MG1655 and PAO1. We also tested the modified membrane in the dynamic filtration of simulated wastewater, in which both modified membranes alleviated biofouling.

Assessing organic fouling of ultrafiltration membranes using partition coefficients of dissolved organic matter in aqueous two-phase systems

Organic fouling caused by dissolved organic matter (DOM) is a critical challenge for membrane technologies. In this study, prediction models for the fouling of commercial polyether sulfone (PES) and regenerated cellulose (RC) ultrafiltration membranes by DOM were established based on the hydrophobicity of DOM. The organic fouling behavior of 40 natural water samples collected from Lake Taihu was investigated. The fouling propensity of water samples on ultrafiltration membranes was evaluated using the fouling index (FI). The hydrophobicity of DOM in water samples was quantified by its partition coefficient in an aqueous two-phase system (KATPS). The FI of water samples on RC membranes was lower than that on PES membranes due to stronger repulsive Lewis acid-base interactions, which reduced DOM-membrane interactions. A significant positive correlation was found between KATPS and FI, suggesting the important role of DOM hydrophobicity in the organic fouling of ultrafiltration membranes. FI prediction models using KATPS as the variable were established using a training group containing 20 water samples for PES and RC membranes, respectively. The resulting models were then validated using the additional 20 water samples, which suggested good prediction power (RMSE = 1.65). The pH effect on the organic fouling can be adequately predicted by the same model with KATPS values measured at given pH. The results suggest that KATPS can be used as a convenient index for assessing the initial organic fouling of ultrafiltration membranes by freshwater DOM.

Biofouling-Resistant Ultrafiltration Membranes via Codeposition of Dopamine and Cetyltrimethylammonium Bromide with Retained Size Selectivity and Water Flux.

Biofouling is a serious problem in ultrafiltration (UF) membrane applications. Modifying the surface of membranes with low molecular weight, commercially available antibacterial chemistries is an excellent strategy to mitigate biofouling. Herein, we report a new strategy to impart antibacterial and anti-biofouling behavior without changing the support membrane’s size selectivity and pure water permeance (PWP). To this end, a strong antibacterial agent, cetyltrimethylammonium bromide (CTAB), was codeposited with dopamine onto commercial polyethersulfone (PES) UF membranes in the presence of nitrogen (N2) gas backflow. The PWP and pore size of the support membrane did not change with codeposition, confirming the benefit of N2 backflow in mitigating the solution intrusion phenomenon. X-ray photoelectron spectroscopy (XPS), surface ζ potentials, and contact angle measurements confirmed the successful codeposition of polydopamine (PDA) and CTAB onto the membrane. Among three different CTAB concentrations systematically investigated, the membrane functionalized with CTAB at the critical micelle concentration (CMC) provided the best anti-biofouling activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and retained its surface ζ potential after being stored in 1 M NaCl (pH = 6.8) for 3 months. Our results demonstrate the potential of using a facile, one-step approach to modify commercial UF membranes without compromising their pore size or flux, while simultaneously endowing antibacterial activity.

In situ reactive coating of porous filtration membranes with functional polymer layers to integrate boron adsorber property

The state-of-the-art reverse osmosis membranes for seawater desalination have limited competence to efficiently remove boron. One promising approach for boron removal is to integrate membrane-based separation with selective adsorption of boron in pre- or posttreatment of seawater desalination; the porous support layer of established filtration membranes, constituting the largest part of total membrane volume shall be utilized for this function. Therefore, this study focuses on performing in situ modification of commercial polyethersulfone (PES) microfiltration membranes toward reactive coating the pore surface with a boron affinity polymer-based hydrogel. Modification is carried out in two steps: 1) adsorption of an amphiphilic copolymer which contains tertiary amine groups as co-initiator for surface-selective free radical generation; 2) grafting of a hydrogel layer by using a monomer solution comprising polyol-containing monomer as boron ligand, a cross-linker monomer, and the redox initiator ammonium persulfate (APS). The entire modification process is performed under flow-through conditions. Membranes with different pore sizes were modified; modification parameters, such as molar mass of macromolecular co-initiator as well as composition of reactive monomer solution, were systematically varied. It was found that using an “integrated” initiation system with low molecular weight co-initiator N,N,N′,N′-tetraethyl ethylenediamine (TEMED) added to the reactive solution, yielded significantly higher degree of grafting and therefore superior adsorber properties. Boron binding capacity of modified membranes was evaluated in terms of boron adsorption isotherms, adsorption kinetics, break-through behavior under filtration conditions and regeneration of the adsorber. The trade-off between permeance and boron binding capacity of modified membrane was studied in order to identify promising materials with competitive overall separation performance, i.e. high permeance at a specific filter cut-off in combination with high boron binding capacity.

Biopolymer-Based Mixed Matrix Membranes (MMMs) for CO2/CH4 Separation: Experimental and Modeling Evaluation.

Alternative materials are needed to tackle the sustainability of membrane fabrication in light of the circular economy, so that membrane technology keeps playing a role as sustainable technology in CO2 separation processes. In this work, chitosan (CS)-based mixed matrix thin layers have been coated onto commercial polyethersulfone (PES) supports. The CS matrix was loaded by non-toxic 1-Ethyl-3-methylimidazolium acetate ionic liquid (IL) and/or laminar nanoporous AM-4 and UZAR-S3 silicates prepared without costly organic surfactants to improve CO2 permselectivity and mechanical robustness. The CO2/CH4 separation behavior of these membranes was evaluated experimentally at different feed gas composition (CO2/CH4 feed mixture from 20:80 to 70:30%), covering different separation applications associated with this separation. A cross-flow membrane cell model built using Aspen Custom Modeler was used to validate the process performance and relate the membrane properties with the target objectives of CO2 and CH4 recovery and purity in the permeate and retentate streams, respectively. The purely organic IL-CS and mixed matrix AM-4:IL-CS composite membranes showed the most promising results in terms of CO2 and CH4 purity and recovery. This is correlated with their higher hydrophilicity and CO2 adsorption and lower swelling degree, i.e., mechanical robustness, than UZAR-S3 loaded composite membranes. The purity and recovery of the 10 wt.% AM-4:IL-CS/PES composite membrane were close or even surpassed those of the hydrophobic commercial membrane used as reference. This work provides scope for membranes fabricated from renewable or biodegradable polymers and non-toxic fillers that show at least comparable CO2/CH4 separation as existing membranes, as well as the simultaneous feedback on membrane development by the simultaneous correlation of the process requirements with the membrane properties to achieve those process targets.

Selective separation of gold and palladium using the improved Gemini Micellar-Enhanced ultrafiltration

The aim of this study was to selectively separate precious metals such as gold and palladium from a binary solution using the Gemini micellar-enhanced ultrafiltration (GMEUF) process. The selectivity of this process was improved by adding the chelating agent ethylene diamine tetra-acetic acid (EDTA) to the solution. It means that one of these two metals can interact with the surface of Gemini micelles and reject by the membrane. The other metal must tend to bind to the ligand and enter the permeate stream. The effect of various parameters such as solution pH, operating pressure, flow rate, molar concentration ratio of the surfactant to the metal (S/M) and molar concentration ratio of the chelating agent to the metal (C/M) was investigated on the selective separation of these metals by a commercial polyethersulfone (PES) membrane and two Gemini surfactants. The rejection of gold and palladium in the optimal conditions of the above parameters reached the values of 90.2% and 21.4%, respectively, for the solutions containing N1-dodecyl-N1,N1,N2,N2-tetramethyl-N2-octylethane-1,2-diaminium bromide (CG12) micelles. In the presence of pentanediyl-1,5-bis (dimethyl cetyl ammonium bromide) (G5) micelles, these rejection values changed to 91.7% and 27.1%, respectively. The obtained results indicated a good selectivity in the separation of gold and palladium by the improved GMEUF process.

Collagen fiber membrane as multi-functional support enabled rational design of ultrahigh-flux separation membrane for the remediation of oil contamination in water

Membrane separation is a promising approach for the remediation of oil contamination in water. High-flux separation of membrane relies on the rational design of ultrathin active layer to significantly reduce mass transfer distance for achieving high separation flux, while the ultrathin active layer is usually fragile with poor mechanical strength, which has to be supported on a support. Herein, we employed collagen fiber membrane (CFM) as multi-functional support for the in-situ growth of polyacrylonitrile (PAN) layer by electrospinning to prepare the high-performance PAN/CFM composite membrane. Due to the amphiphilic nature and strong capillary effect, CFM played the role as multi-functional support to provide separation effectiveness and boosted separation flux. The PAN/CFM composite membrane enabled ultrahigh separation flux (e.g., 51751.59 L m−2 h−1 bar−1) to a variety of oil-in-water emulsion, which was one order of magnitude higher than that of commercial polyethersulfone membrane and 1.86-fold to that of cellulose acetate membrane. Furthermore, the PAN/CFM composite membrane retained high separation flux (e.g., 11046.97 L m−2 h−1 bar−1) during the 5th separation cycle, providing appreciable anti-fouling capability. Therefore, our findings provided a promising way to effectively resolve the problem of oil contamination in water.

Valorisation of sodium lignosulfonate by ultrafiltration of spent sulphite liquor using commercial polyethersulfone membrane

ABSTRACT Ultrafiltration of spent sulphite liquor, generated from a laboratory sulphite pulping using chopped stems of Prosopis juliflora, was carried out to recover sodium lignosulfonate (SLS). A commercial hydrophilised polyethersulfone flat-sheet membrane with a molecular weight cut-off of 5 kD was used for the experiments. Effects of the feed dilution factor on the permeate flux were observed, and actual solute rejection coefficients were investigated due to the formation of the concentration polarised layer on the membrane surface. In addition, flux decline and the fouling index of the membrane were determined under the present experimental conditions. SLS obtained in the reject stream was characterised following UV–VIS and nuclear magnetic resonance spectroscopy. The spectroscopic analysis confirmed the reduction of the lignin and hemicelluloses component of wood sample effectively into SLS during sulphite pulping with a considerable degree of similarity with the control sample. The results could be useful as guidelines for the scale-up of SLS production and simultaneous treatment of sulphite liquor from the paper and pulp industry.

Flux Increase Occurring When an Ultrafiltration Membrane Is Flipped from a Normal to an Inverted Position—Experiments and Theory

The effects of flipping membranes with hydrophilic/hydrophobic asymmetry are well documented in the literature, but not much is known on the impact of flipping a membrane with dense/porous layer asymmetry. In this work, the pure water flux (PWF) of a commercial polyethersulfone (PES) membrane and a ceramic ultrafiltration (UF) membrane was measured in the normal and inverted positions. Our experimental results showed that the PWF was two orders of magnitude higher when the PES membrane was flipped to the inverted position, while the increase was only two times for the ceramic membrane. The filtration experiments were also carried out using solutions of bovine serum albumin and poly(vinylpyrrolidone). A mathematical model was further developed to explain the PWF increase in the inverted position based on the Bernoulli’s rule, considering a straight cylindrical pore of small radius connected to a pore of larger radius in series. It was found by simulation that a PWF increase was indeed possible when the solid ceramic membrane was flipped, maintaining its pore geometry. The flow from a layer with larger pore size to a layer with smaller pore size occurred in the backwashing of the fouled membrane and in forward and pressure-retarded osmosis when the membrane was used with its active layer facing the draw solution (AL-DS). Therefore, this work is of practical significance for the cases where the direction of the water flow is in the inverted position of the membrane.

Membrane surface roughness promotes rapid initial cell adhesion and long term microalgal biofilm stability

In biofilm membrane photobioreactors development, conscientious works revolving around the effect of external environment factors on microalgal biofilm growth were assessed but more comparative research about the role of carrier surfaces properties such as surface roughness is necessary. Thus, commercial polyethersulfone (PES) membranes with two different molecular-weight-cut-offs (1 kDa and 30 kDa) were selected as the main representatives of surface roughness in a 20 days long-term biofilm cultivation experiment under dynamic flow condition for the biofilm evolvement of three benthic diatoms (Amphora coffeaeformis, Cylindrotheca fusiformis and Navicula incerta). Results depicted that rougher 30 kDa PES enable higher cell attachment degree for C. fusiformis (25.85 ± 2.75 × 109 cells m−2), followed by A. coffeaeformis (11.86 ± 2.76 × 109 cells m−2) and N. incerta (10.10 ± 0.65 × 109 cells m−2). Bounded extracellular polymeric substances (bEPS) gathered were relatively higher than soluble EPS (sEPS) while bEPS accumulated at least 10% higher on smooth 1 kDa PES than rough 30 kDa PES for the purpose of enhancing the biofilm disruption resistivity under liquid flow. Moreover, cell adhesion mechanism was proposed via computational fluid dynamics in parallel with EPS analysis. Copious amount of asperities and stagnant zones present on rough 30 kDa surfaces accelerated biofilm development and the consistency of the results have a great valence for interpretation of microalgal biofilm lifestyle on porous surfaces.

Physico-chemistry and adhesion kinetics of algal biofilm on polyethersulfone (PES) membrane with different surface wettability

Microalgal biofilm growth on porous substrates has recently garnered extensive attention with the advantage of high biomass productivity with low liquid culture volume. In such cultivation, the surface characteristics of supporting materials play essential role supporting biofilm growth. In view of this, a study on the membrane surface wettability of a commercial polyethersulfone (PES) membrane with two different hydrophilicities was selected in a long-term benthic biofilm cultivation experiment. Findings revealed that both soluble and bounded extracellular polymeric substances (EPS) contributed towards the formation of an adhesive gel layer onto the membrane’s surfaces. The maximum accumulated cell density was achieved by C. fusiformis around 47.64 ± 4.03 × 109 cells m−2 onto phobic PES (79.29°) and the least by N. incerta around 6.40 ± 0.49 × 109 cells m−2 onto philic PES (47.56°). The fact remained that the cell attachment rate was almost similar for both A. coffeaeformis and N. incerta but with gradual reduction after day 12 for phobic PES and day 8 for philic PES for the three benthic species. The change of adhesion ratio was well explained with their respective EPS variation. The XDLVO model employed suggested the dominance of acid-base interactions in high ionic strength liquid, leading to higher global minimum energy occurring on phobic PES. Overall, the findings indicated that biofilm formation is favored on polymer substrate having lower surface energy due to the attractive interaction of the submerged surface with those biomolecules and colloids.

Antibacterial ultrafiltration membrane with silver nanoparticle impregnation by interfacial polymerization for ballast water

AbstractInterfacial polymerization technology was employed to immobilize silver (Ag) nanoparticles on the surface of commercial polyethersulfone (PES) membrane to develop antibacterial and antifouling ultrafiltration membrane. Ag nanoparticles were prepared from the reduction of silver nitrate (AgNO3) by sodium borohydride in the presence of polyethyleneimine (PEI) as the stabilizer. The encapsulated Ag nanoparticles in the PEI solution were embedded into the PEI membrane when trimesoyl chloride solution was used to crosslink the PEI solution with the PES membrane, forming Ag‐polyamide (PA) networks through the interfacial polymerization reaction. Experimental results showed that the membrane prepared with 50 mmol/L of AgNO3 and 20 mmol/L of PEI had the optimized antibacterial effect against Escherichia coli. Bacterial concentration and species were also investigated. Exiguobacterium aestuarii and Staphylococcus aureus which are gram‐positive bacteria, needed significantly more time for the Ag‐PA/PES membrane to kill the bacteria completely when compared to E.coli and Vibrio coralliilyticus which are gram‐negative bacteria. This study showed that Ag nanoparticles impregnated in membrane surfaces were 100% effective in killing various types of marine bacteria and bacteria in the seawater collected off Sentosa Island in Singapore. These membranes exhibit excellent antibacterial and antifouling properties which can be used to kill bacteria in ballast water and seawater.

Physical and Mechanical Properties of Hollow Fiber Membranes and Technological Parameters of the Gas Separation Process.

The porous layer of composite and asymmetric hollow fiber membranes acts as a support and is exposed to strong mechanical stresses. The effect of external pressure on the polymer structure and, as a consequence, the separation characteristics of the membrane remains unsolved. Based on the solution of the Lamé approach to the calculation of the stress state of a hollow cylinder, a method of calculation was proposed for hollow fiber membranes. Calculations were based on the approximation of the isotropic nature of the physical and mechanical characteristics of the selective layer and substrate. Permissible deformation of the membrane’s selective layer was determined from the linear sector of strain-on-stress dependence, where Hooke’s law was performed. For these calculations, commercial polyethersulfone membranes were chosen with an inner and/or outer selective layer and with the following values of Young’s modulus of 2650 and 72 MPa for the selective and porous layers, respectively. The results obtained indicate that the dependence of the maximum allowable operating pressure on the substrate thickness asymptotically trends to a certain maximum value for a given membrane. Presented data showed that membranes with outer selective layer can be operated at higher working pressure. Optimal parameters for hollow fiber gas separation membrane systems should be realized, solving the optimization problem and taking into account the influence of operating, physicochemical and physicomechanical parameters on each other.

An experimental and numerical study of droplet spreading and imbibition on microporous membranes

Microporous membranes are permeable substrates primarily used for wastewater treatment and desalination. The lab-fabricated and commercial polyethersulfone (PES) microporous membranes are characterized for permeability by filtration test, cross-section thickness by SEM images, surface roughness by AFM data, and hydrophilicity by dynamic contact angle measurements. The choice of membranes of different nominal pore sizes ensures a diverse range of imbibition time scale. The hydrodynamic permeability of these membranes is calculated based on the cross-section thickness and its resistance, which is obtained from filtration test. A lubrication-based mathematical model using precursor film approximation is used to study the behavior of droplet spreading and imbibition on the membrane surface. The theoretical disjoining pressure is also shown to be related to its numerical value obtained from the mathematical model, in the case of apolar and polar interactions. The effective permeability obtained by validating the numerical predictions with contact angle experiments, is then matched to hydrodynamic permeability by introduction of lubrication ratio at the equilibrium stage.

Discolouration of contaminated water with textile dye through a combined coagulation/flocculation and membrane separation process with different natural coagulants extracted from Moringa oleifera Lam. seeds

AbstractThe removal of reactive black 5 (RB5) dye present in aqueous solution was studied by applying individual coagulation/flocculation (CF) and microfiltration (MF) processes as well as the combination of both processes (CF‐MF). In the CF process, three natural coagulants produced from Moringa oleifera Lam. seeds (MOS) were used: saline extract (ES) and the purified protein fractions of albumin (ALB) and globulin (GLO). In the MF process, a commercial polyethersulfone (PES) membrane was used. It was noticed that without the combination of both processes, the obtained RB5 removal was only 20.38% for ALB, 52.38% for GLO, and 12.50% for ES. However, when the CF process was combined with a microfiltration process, it was possible to achieve a higher textile dye removal, due to the formation of aggregates in the CF process larger than the pores of the microfiltration membrane. Especially with the ALB coagulant, the combined CF‐MF process achieved a removal greater than 95%. The results demonstrate the potential use of the purified proteins fractions of Moringa oleifera Lam. coagulant in combination with microfiltration process for water treatment.

Lignin separation from black liquor by mixed matrix polysulfone nanofiltration membrane filled with multiwalled carbon nanotubes

Carbon nanotubes (CNT)/polysulfone (PSf) mixed matrix membranes (MMM) were prepared by the non-solvent induced phase inversion method and applied in the separation of lignin from black liquor (BL). Three different type of membranes were developed to minimise the fouling phenomenon, which is one of the major concerns regarding the application of polymeric membranes for BL fractionation. The effect of CNT on the filtration and morphological properties were investigated by analyzing pure water flux, porosity, mean pore size, scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy and water contact angle. These analyses indicated that with increasing the nanotubes content (0–0.5%) resulted in an increase of ≈ 3 times in the mean pores size, water flux (14.8–132.5 Lm−2 h−1 at 15 bar), porosity (74.4–79.7%) and reduction of surface roughness of the prepared membranes. The performance of these membranes was analyzed in terms of lignin rejection and fouling resistance using standard lignoboost lignin solution at various pressures and compared with a commercial polyethersulfone membrane. It was observed that reduction in the permeate flux was lowest (~10% at 12 bar) in the 0.5% CNT-based membranes. However, in terms of lignin rejection, the highest (80–98%) and lowest (52–76%) values were achieved with the simple PSf membrane (0% CNT) and 0.1% CNT membrane, respectively. Further, fouling studies showed that through chemical cleaning, the initial flux was completely recovered for CNT-based membranes without disturbing their flux and rejection behavior. Among the 3 types of prepared membranes, 0.5% CNT membranes showed a good balance between permeate flux and lignin rejection. The application of these membranes for nanofiltration of industrial BL, pre-treated by ultrafiltration, allowed to reach 82–84% rejection for lignin and 37–42% for hemicelluloses. This suggests a significant degree of selective separation of lignin from BL using CNT-based MMM.