Nanofiltration Membrane Separation Research Articles

Flavonoids from Peony Seed Meal by Nanofiltration Membrane Separation

Flavonoids are polyphenolic compounds with a wide range of biological activities (antioxidation, antitumor, and immunomodulatory). The membrane separation method of flavonoids has a high recovery and biological activity, overcoming the shortcomings of traditional methods for the separation of bioactive molecules. In this study, ethanol-water ( v / v ) solution was used to extract peony seed meal. The extraction rate of total flavonoids from peony seed meal was 35.28%. Five microfiltration membranes, polypropylene (PP), polyvinylidene fluoride (PVDF), cellulose acetate (CA), polyether sulfone (PES), and polyamide (PA), were selected to pretreat the extracts, and their separation performance was investigated. A new PA-supported silicone film was prepared by sol-gel method using 1,2-bis(TRIMETHOXYSILYL)ETHANE (BTESE) as a carrier. The synthesized BTESE/PA composite membrane was applied to the purification of organic silica PSMF solution by nanofiltration process. The optimal pressure of nanofiltration operation is 0.8 MPa, and the membrane flux can reach 2.06 kg·m-2·h-1. The mass concentration of flavonoids in the retention solution was decreased to 860.56 mg·L-1, and the permeable components of PSMF were effectively separated. The total flavonoid content of the purified lyophilized powder was 146.12 mg·g-1, which was 2.4 times that before purification. The results show that PSMF can be effectively separated by BTESE/PA membrane, and the membrane solution has good antioxidant activity.

Polymer of intrinsic microporosity coated on a metal-organic framework composite membrane for highly efficient dye separation

The dyes contained in some industrial wastewater are very harmful pollutants. The application of nanofiltration membrane separation technology for dye separation has been intensively studied. In this paper, a carbon nanotube film is applied as the substrate on which to grow a dense layer of UiO-66, and a kind of polymer of intrinsic microporosity is used to coat its surface. The resulting composite membrane material exhibits an excellent separation property for various dyes, and the separation efficiency can exceed 90%. In addition, the separation mechanism of this membrane is briefly discussed, which mainly relies on a sieving effect and an electrostatic effect to achieve efficient dye separation.

Metal-phenolic network as precursor for fabrication of metal-organic framework (MOF) nanofiltration membrane for efficient desalination

A continuous and ultra-thin metal-phenolic network top layer on a polyethersulfone substrate surface was used as metal precursor for a metal-organic framework (MOF) membrane synthesis. A plant polyphenol tannic acid (TA) and Zn2+ based network top layer prepared by a layer-by-layer (LBL) self-assembly process was immersed into a 2-methylimidazole aqueous solution, and then a ZIF-8 top layer was facilely formed due to the partial self-conversion of TA-Zn2+ network to ZIF-8. The LBL process provides sufficient controllability of preparing a continuous and ultra-thin ZIF-8 top layer, which are crucial factors for nanofiltration membrane separation performance. The optimized ZIF-8 membrane exhibited a pure water permeance (PWP) of 5.1 L m−2 h−1 bar−1, a 55.2% NaCl rejection and a 93.6% Na2SO4 rejection. This is one of the few MOF membranes that possesses a divalent inorganic salt rejection higher than 90%. The novel zinc source of ZIF-8 synthesis disclosed in this study can provide a new incentive to not only MOF membrane preparation but also engineering MOFs towards a wide energy and environmental applications.

Concentration of Lipase from Aspergillus oryzae Expressing Fusarium heterosporum by Nanofiltration to Enhance Transesterification

Nanofiltration membrane separation is an energy-saving technology that was used in this study to concentrate extracellular lipase and increase its total activity for biodiesel production. Lipase was produced by recombinant Aspergillus oryzae expressing Fusarium heterosporum lipase (FHL). A sulfonated polyethersulfone nanofiltration membrane, NTR-7410, with a molecular weight cut-off of 3 kDa was used for the separation, because recombinant lipase has a molecular weight of approximately 20 kDa, which differs from commercial lipase at around 30 kDa for CalleraTM Trans L (CalT). After concentration via nanofiltration, recombinant lipase achieved a 96.8% yield of fatty acid methyl ester (FAME) from unrefined palm oil, compared to 50.2% for CalT in 24 h. Meanwhile, the initial lipase activity (32.6 U/mL) of recombinant lipase was similar to that of CalT. The composition of FAME produced from recombinant concentrated lipase, i.e., C14:1, C16:0, C18:0, C18:1 cis, and C18:2 cis were 0.79%, 34.46%, 5.41%, 45.90%, and 12.46%, respectively, after transesterification. This FAME composition, even after being subjected to nanofiltration, was not significantly different from that produced from CalT. This study reveals the applicability of a simple and scalable nanofiltration membrane technology that can enhance enzymatic biodiesel production.

Performance evaluation of integrated adsorption-nanofiltration system for emerging compounds removal: Exemplified by caffeine, diclofenac and octylphenol

Emerging pollutants introduced into surface water pose potential hazards to the safety of drinking water. In this study, the removal performance of three emerging compounds (exemplified by caffeine, diclofenac and octylphenol, with different physico-chemical properties) from synthetic water and source water by combining activated carbon (AC) adsorption and nanofiltration (NF) membrane processes was evaluated and analyzed. Results from synthetic water showed that the adsorption isotherms modeled well with the Langmuir equation. The removal performance of target compounds by AC-NF system was more remarkable than that of NF-AC combination. In the source water system, the integrated AC-NF process with coagulation pretreatment (the alum dosage of 60 mg/L) achieved satisfactory performance (the removal efficiencies of three target compounds reached > 95%). Results showed the electrostatic interaction and pollutant hydrophobicity determined the behavior and the fate of selected PPCPs/EDCs during the sequential treatment process of coagulation, activated carbon adsorption, and NF membrane separation. Finally, the AC and NF membranes were analyzed by Fourier transform infrared spectroscopy and scanning electron microscopy to understand the mechanisms, i.e. electrostatic and hydrophobic effects on the total removal process. It suggests that the integrated AC-NF process with coagulation pretreatment should be a feasible approach for removing emerging compounds in waterworks.

Optimization of ionic liquid assisted sugar conversion and nanofiltration membrane separation for 5-hydroxymethylfurfural

This paper provides complete loop of ionic liquid (IL) assisted glucose conversion to 5-hydroxymethylfurfural (HMF), nanofiltration membrane (NF) based separation and recyclability. The optimum HMF yield of 65.6% was obtained with 8wt.% catalyst loading at 125°C reaction temperature in 120min reaction time. Ea for conversion was found to be 120kJ/mol. NF was adopted first time to separate IL and HMF. The percentage of recovered HMF using NF for 1st, 2nd and 3rd batches are 94.87, 84.35 and 71.65 respectively. The structures of regenerated IL and HMF, obtained from NF and liquid–liquid extraction, were confirmed by NMR.

Effective usage of sorghum bagasse: Optimization of organosolv pretreatment using 25% 1-butanol and subsequent nanofiltration membrane separation

We investigated the use of low concentrations of butanol (<40%, all v/v) as an organosolv pretreatment to fractionate lignocellulosic biomass into cellulose, hemicellulose, and lignin. The pretreatment conditions were optimized for sorghum bagasse by focusing on four parameters: butanol concentration, sulfuric acid concentration, pretreatment temperature, and pretreatment time. A butanol concentration of 25% or higher together with 0.5% or higher acid was effective for removing lignin while retaining most of the cellulose in the solid fraction. The highest cellulose (84.9%) and low lignin (15.3%) content were obtained after pretreatment at 200 °C for 60 min. Thus, pretreatment comprising 25% butanol, 0.5% acid, 200 °C, and 60 min process time was considered optimal. Enzymatic saccharification and fermentation by Saccharomyces cerevisiae produced 61.9 g/L ethanol from 200 g/L solid fraction obtained following pretreatment, and 10.2 g/L ethanol was obtained from the liquid fraction by xylose-utilizing S. cerevisiae following membrane nanofiltration to remove butanol.

Influence of Physicochemical Parameters of Organic Solutes on the Retention and Flux in a Nanofiltration Process

AbstractA comparative study of several organic compounds (atrazine, aniline and phenol, and their derivatives, 4‐chlorophenol, 4‐nitrophenol and 4‐nitroaniline) and their removal from aqueous solutions by nanofiltration using an NF‐97 polyamide membrane is presented. The aim was to ascertain any correlation between the physicochemical parameters of the different compounds and the characteristic parameters of the nanofiltration system (permeate flux and rejection coefficient), in order to understand the behavior of the nanofiltration membrane separation processes and any relevant variables. In a previous work, the rejection coefficients and permeate flux values for phenol, 4‐chlorophenol, aniline, and atrazine were obtained. These values were used together with the new ones presented for 4‐nitroaniline and 4‐nitrophenol.

Development of nanofiltration membrane separation prediction system for binary salt solutions

AbstractThe previous studies on nanofiltration (NF) mainly focused on the work to update the existing predictive models to enhance its application in order to optimize the separation prediction. There is still lack of research which successfully creates a user-friendly system for separation process prediction optimization. In this study, a MATLAB®-based NF prediction system (NF-BIN) utilizing Donnan Steric Pore model with application of m-file programming and graphical user interface was developed specifically for binary salt solutions treatment. Prior to the prediction, locally fabricated polyethersulfone membranes with three different polymer concentrations, 19, 21, and 23%, were characterized in terms of pore radius, rp ratio of membrane thickness to porosity, Δx/Ak and effective charge density, Xd using uncharged, and charged solutes rejection data. Further the rejection prediction performance was carried out to predict the percentage contribution of ion transport mechanism of three transport modes: d...

Pretreatment of membrane separation of glyphosate mother liquor using a precipitation method

During the nanofiltration membrane separation of glyphosate mother liquor, a precipitation method was employed to remove HPO32−, which is often the cause of membrane fouling and blockage. Such removal reduces the speed of membrane flux attenuation. The purpose of the present study was to investigate the effects of precipitant quantity and type, pH value, stirring time and speed, and standing time, on the removal of HPO32−. In addition, the membrane flux separated by the nanofiltration membrane of the mother liquor post-pretreatment, was tested. Results indicated that when the initial pH was 9, the following pretreatment procedure resulted in the removal of more than 60% of the HPO32− from the glyphosate mother liquor: the addition of 0.24mol/L AlCl3·6H2O, stirring at 300r/min for 30s and 100r/min for 2.5min, followed by standing for 30min. This pretreatment–precipitation method can markedly enhance the nanofiltration membrane flux in the mother liquor and reduce the membrane flux attenuation, which facilitates nanofiltration membrane separation of the glyphosate mother liquor.

Modeling the permeate flux and rejection of nanofiltration membrane separation with high concentration uncharged aqueous solutions

In this paper, the influence of feed concentration on the performance of nanofiltration membrane separation under high concentration (0.1–0.98mol/L) of aqueous glucose is investigated using a commercial spiral-wound nanofiltration membrane. The results of the experiments show that the permeate volume flux and observed rejection at certain operating pressures are influenced seriously by concentration. In this work, the influence of concentration is studied generally based on the solution-diffusion model, from which the concentration polarization boundary resistance Rcp and mass transfer coefficient k as functions of concentrations are obtained for high concentrations. Using these relationships, the observed rejection Ro can be predicted in the case of high concentration. The good agreements between the predicted and experimental values indicate that the models proposed and modified in this work could be used to describe the behavior of nanofiltration membrane separation in a wider range of uncharged aqueous solution concentration.

Theoretical Analysis on Interacting Effect of Steric and Donnan Factors in Nanofiltration Membrane Separation System

Prestasi pemisahan sistem membran penuras nano didapati sangat bergantung kepada kesan sterik dan cas. Kajian terdahulu telah menunjukkan bahawa kombinasi yang tepat di antara saiz liang (kesan sterik) dan ketumpatan cas berkesannya (kesan Donnan) akan memberikan prestasi pemisahan yang optimum. Justeru itu, keupayaan menghasilkan membran penuras nano bersifat optimum akan memberikan pembaikan yang signifikan dari aspek prestasi membran dan pengurangan kos pemprosesan. Oleh itu, objektif utama kajian teoritikal ini ialah untuk menyelidik kesan interaktif saiz liang (rp) dan ketumpatan cas membran, (Xd) terhadap prestasi pemisahan. Dua parameter tanpa dimensi telah digunakan iaitu λ (λ = rs/rp) dan ζ(ζ = Xd/Cb). Pengangkutan elektrolit melalui membran penuras nano tersebut ditentukan dengan menggunakan model liang sterik-donnan (DSPM). Pelbagai larutan garam dengan pelbagai saiz liang dan kesan cas diuji dengan menggunakan model tersebut. Kajian menunjukkan bahawa untuk kes membran dengan kapasiti cas berkesan yang tinggi, faktor Donnan didapati lebih penting untuk membran yang longgar strukturnya. Sumbangan faktor Donnan ini berkurangan dengan peningkatan saiz liang membran. Sebaliknya, untuk membran berketumpatan cas yang rendah, kesan faktor Donnan terhadap tolakan ion boleh diabaikan, tanpa bergantung kepada saiz liang. Kata kunci: Penurasan nano, DSPM, ketumpatan caj berkesan, saiz liang, teoritikal The separation performance of NF membrane system is found to be significantly dependent on the steric and charge effects. Previous studies have shown that the right combination of membrane pore size (steric effect) and its effective charge density (donnan effect) will lead to an optimum separation performance. Hence, the ability to produce nanofiltration membranes with optimized properties will certainly provide significant improvement in terms of membrane performance and processing cost reduction. Therefore, the main objective of this theoretical study is to investigate the interactive effect of membrane pore size (rp) and membrane charge density, (Xd) towards the separation performance. Two general dimensionless parameters were used namely λ (λ = rs/rp) and ζ(ζ = Xd/Cb). The electrolyte transport through nanofiltration membranes is determined using a model based on the application of the extended Nernst–Planck equation coupled with Donnan–steric pore model (DSPM). A variety of salt solution with various pore size and charge effect was tested using the above–mentioned model. It was found that for the case of membranes with high effective charge density, the Donnan factor is more prominent for loose membranes. The contribution of the factor decreased with the increase of membrane pore size. Vice versa, for the lower charge density membrane, the effect of Donnan factor towards ion rejection could be neglected, regardless of membrane pore sizes. Key words: Nanofiltration, DSPM, membrane charge density, pore size, theoretical

Preparation of three-bore hollow fiber charged nanofiltration membrane for separation of organics and salts

Three-bore hollow fiber charged nanofiltration (NF) membrane was prepared by interfacial polymerization (IP). The results showed that the flux and rejection of NF membrane prepared in this study increased with the increasing in the operating pressure. The water flux decreased and rejection for obvious dyes increased as the solute concentration increased. The separation factor for mixture of Xylenol orange/NaCl decreased when NaCl concentration in solution increased and could reach to as high as 18. In addition, three-bore hollow fiber charged nanofiltration membrane prepared in this study has excellent stability for strong acid (pH = 3), strong alkali (pH = 11) and high temperature solution (80 °C).

Arsenate removal using a combination treatment of precipitation and nanofiltration

A combination treatment of Ca-precipitation and nanofiltration membrane was studied to remove arsenate from water. The selected nanofiltration membrane was an amphoteric charged membrane, proved by the results of ATR-FTIR spectra and zeta potential. The arsenate and calcium removal efficiencies had the lowest values at the isoelectric point of the nanofiltration membrane, attributed to the loosest steric hindrance and the weakest electrostatic repulsion. Above the isoelectric point, arsenate precipitated with calcium ion to form the low solubility compound calcium arsenate, while steric hindrance was the main mechanism of arsenate removal. In contrast, below the isoelectric point, the nanofiltration membrane with positive charges rejected calcium ion by electrostatic repulsion. The high electrostatic shielding of calcium ion prevented arsenate from coming close to the NF membrane. Either high feed arsenate concentration or high calcium oxide dose improved the removal amount of arsenate during the nanofiltration membrane separation process. In addition, the arsenate removal efficiency approached the highest value at 200 μg/L of feed arsenate concentration. The optimal transmembrane pressure was in a range of 0.5-0.7 MPa to restrict the formation of fouling cake on the nanofiltration membrane surface.

The Comprehensive Test for Geothermal Tail-Water Disposal

Geothermal reservoirs and groundwater resources in layered porous media in large sedimentary basins have enormous exploitation potential because of their extensive distribution, great quantity, and feasible temperatures and drilling depths. The discharge of geothermal wastewater (i.e. tail-water) on the surface is a serious environmental issue because of its high salinity content, so the Bureau of Geology Exploration and Mineral Resources Exploitation in Shandong Province, China called for the study of the disposal technique of the geothermal tail-water. The disposal test process is as follows: take the waste of geothermal water to make physics-chemistry preparative disposal; filtration with manganese-sand set and/or double-medium equipment; filtration with ion exchange resins; nanofiltration membrane separation; and reverse osmosis separation. After separation, the cheap, clean water can be used as a material for chemical plants. However, in the case of deeply embedded geothermal groundwater resources, connate water(buried water), or bad recharge conditions, must be dried up for a long time exploitation, causing ground depression. Therefore, it is concluded that systems utilizing reinjection, i.e. closed-circuit cycle mode injection, in sandstone reservoirs are ideal for the realization of sustainable exploitation of the geothermal groundwater resources with favorable environmental conditions on the surface.

Pilot scale nanofiltration membrane separation for waste management in textile industry

This paper presents the pilot scale membrane separation studies on dyehouse effluents of textile industry. Nanofiltration (NF) membranes which have 2 m2 of surface area were evaluated for membrane fouling on permeate flux and their suitability in separating COD, color and conductivity in relation to operating pressure and feed concentration from textile industry dyehouse effluents. Successive batch runs demonstrated that any serious membrane fouling was not experienced for NF membrane tested in treating this type of wastewater. The permeate flux was found to increase significantly with operating pressure. Flux decreased with increasing recovery rate. The overall removal efficiencies of COD, color and conductivity were found as greater than 97%. COD was lower than 10 mg/l at 12 bar pressures. Permeate COD was also increased with increasing recovery and COD was 30 mg/l with recovery of 80%. Almost complete color removal was achieved with nanofiltration membrane. Color value was also decreased from 500 Pt-Co to 10 Pt-Co unit. This significant reduction in color and COD makes possible the recycle of the permeate in the dyehouse. Permeate conductivity was decreasing with increasing pressure and retention of conductivity increases with increasing pressures. This phenomenon is expected from the analysis of conductivity mass transport model. Economical analysis have been done and the total estimated cost will be 0.81$/m3 based on 1000 m3/day of and this value is very economical for Istanbul City due to increasing industrial water supply tariffs.

Treatment of Textile Dye Plant Effluent by Nanofiltration Membrane

The study was concerned primarily with characterization of the NF45 membrane. Its pure water permeability, the mass transfer coefficient of NaCl, and the mean radius of the membrane pores were determined. Experiments run with five pure dye solutions and an industrial dye pulp solution confirmed the potential of nanofiltration membrane separation for the treatment of textile dye plant effluent. The effects of such significant parameters as initial solution concentration, transmembrane pressure, and type of dye on two fundamental characteristics of nanofiltration (flux and separation factor) were studied.

Treatment of textile desizing wastewater by pilot scale nanofiltration membrane separation

Desizing wastewaters from the bleaching and dyeing industry of Hong Kong were treated by nanofiltration (NF) membrane separation on a pilot scale in the pressure controlled region. The two brown colored wastewaters had chemical oxygen demand (COD) of 14,000 mg l −1 and 5430 mg l −1, respectively. Permeate flux and COD retention were investigated in relation to transmembrane pressure drop, temperature, and feed-solution concentration. The permeate flux was found to increase significantly with transmembrane pressure drop and to decrease with feed concentration. Higher permeate flux was found for wastewater with higher pH. A minor increase in COD retention was found for the increase in transmembrane pressure drop as well as operating temperature. The COD retention was about 95% for wastewater with pH 10.2, and 80–85% for wastewater with pH 5.5. The difference in the results obtained for the two kinds of wastewater was attributed to their compositional difference that resulted from the desizing operation. Fouling of membrane is not a big concern for the NF membrane tested in treating this type of wastewater. The quality of the permeate is all above the discharge standard for foul sewer in Hong Kong. The experimental results are consistent with the theoretical analysis.