Uranium membrane separation from binary aqueous solutions of UO22+-K+ and UO22+-Ca2+ by the nanofiltration process

The performance of the nanofiltration process was investigated for uranium separation from binary aqueous solutions of UO₂²⁺-K⁺ and UO₂²⁺-Ca²⁺ containing uranium in high concentration ranges. Rejection coefficient, permeate flux, and membrane selectivity of PES-2, NF-1, and NF-2 membranes under various operational conditions of pH, pressure, and concentration of interfering cation were evaluated. In most cases, the order of metal rejections with these membranes was UO₂²⁺ > Ca²⁺ > K⁺. According to the obtained results, the nanofiltration process could be effectively used for selective uranium separation from aqueous solutions containing uranium and other monovalent and divalent cations.     

Separation performance of a nanofiltration membrane influenced by species and concentration of ions

Nanofiltration (NF), which has been largely developed over the past decade, is a promising technology for the treatment of organic and inorganic pollutants in surface and ground waters. The ESNA 1 membrane from the Nitto Denko Corporation of Japan is made of aromatic polyamide, which provides salt rejection from 50% to 90%. In this paper permeation experiments of aqueous solutions of five chlorides (NH₄Cl, NaCl, KCl, MgCl₂ and CaCl₂), three nitrates (NaNO₃, Mg(NO₃)₂ and Ca(NO₃)₂), and three sulfates (NH₄)₂SO₄, Na₂SO₄ and MgSO₄) were carried out. The effects of species and concentration of salts on the separation performance of the ESNA 1 membrane were investigated. The experimental results showed that the rejection to most salts by the ESNA 1 membrane decreased with the growth of the concentration. Then, the reflection coefficient and solute permeability of ESNA 1 membrane were calculated by the Spiegler-Kedem equation from experimental data. The reflection coefficients of the ESNA 1 membrane to salts are all above 0.95. The salt permeabilities, except for magnesium and calcium salts, increased with the growth of concentration. The sequence of rejection to anions by the ESNA 1 membrane is R(SO²⁻₄) > R(Cl⁻) > R(NO⁻₃) at the same concentration which ranges from 10 mol/m³ to 100 mol/m³. The sequence of rejection to anions by the ESNA 1 membrane can be written as follows: R(Na⁺) > R(K⁺) > R(Mg²⁺) > R(Ca²⁺) at 10 mol/m³ concentration and R(Mg²⁺) > R(Ca²⁺) > R(Na⁺) > R(K⁺) at 100 mol/m³ concentration.     

Preparation of microporous polyamide networks for carbon dioxide capture and nanofiltration

For the first time, microporous polyamide networks have been synthesized via the interfacial polymerization of piperazine and acyl chloride monomers containing tetrahedral carbon and silicon cores. These polyamides, with Brunauer–Emmett–Teller surface area between 488 and 584 m² g^?1, show a CO₂ uptake of up to 9.81 wt% and a CO₂/N₂ selectivity of up to 51 at 1 bar and 273 K, suggesting their great potential in the area of carbon capture and storage applications. We have developed the interfacial polymerization on the surface of the porous polyacrylonitrile substrate, resulting in the formation of ultrathin microporous membranes with thicknesses of about 100 nm. These nanofiltration (NF) membranes exhibited an attractive water flux of 82.8 L m^?2 h^?1 at 0.4 MPa and a high CaCl₂ (500 mg/L) rejection of 93.3%. These NF membranes follow the salt rejection sequence of CaCl₂ > NaCl > Na₂SO₄, demonstrating the positively charged character of these membranes.     

Characterization and control of foulants occurring from RO disc-tube-type, membrane treating, fluorine manufacturing, process wastewater

This study was carried out to find a way to limit fouling of disc-tube-type reverse osmosis membranes in the treatment of acid rinse wastewater from the fluorine manufacturing process as well as to pretreat the wastewater before it entered the membrane process. Experiments showed that the scale consisted of Ca²⁺, SO₄⁻² and F⁻. Complex scales were removed in a subsequent procedure where the membrane was rinsed with NaOH followed by citric acid which could consequently recover its flux up to 86%. Cleaning chemicals had to be used regularly for efficient recovery of permeate flux. Ultrasonic cleaning could also improve the recovery of permeate flux up to 83%. Calcium salts were used to remove fluoride ions. CaCl₂ removed fluoride ions up to 11% more than Ca(OH)₂ at 0.5 [Ca²⁺]/[F⁻]. At acidic pH 4-7 or alkaline pH 7 and above, residual fluoride ions increased as Ca²⁺ reacted more efficiently with Cl⁻, OH⁻ and SO₄⁻² rather than F⁻. On the other hand, fluoride ions were best removed at pH 7. Adding Ca²⁺ salt above pH 7 caused an increase of residual Ca²⁺ salt in the effluent, even if fluoride ions can be ideally removed in the form of CaF₂ at a pH over 11.     

Novel thin-film composite nanofiltration membranes fabricated via the incorporation of ssDNA for highly efficient desalination

In this work, the biomacromolecule, single-stranded deoxyribonucleic acid (ssDNA) was innovatively incorporated into the polyamide layer to tailor the permeate flux and antifouling performance of the nanofiltration (NF) membranes. With active amines groups, the ssDNA was as the aqueous phase monomers along with piperazine (PIP), and reacted with trimesoyl chloride on polyethersulfone substrate to fabricate thin-film composite (TFC) NF membranes. The NF membrane prepared under optimal ratio of ssDNA/PIP had a pure water permeability of 75.8 L m⁻² h⁻¹ (improved 58% compared to PIP NF membrane) and Na₂SO₄ rejection of 98.0% at 6.0 bar. The rejections for different inorganic salts were the order: Na₂SO₄ (98.0%) > MgSO₄ (89.2%) > MgCl₂ (72.8%) > NaCl (23.0%). Furthermore, the TFC NF membranes showed good antifouling performance in long-term running with 300 ppm bovine serum albumin and humic acid solution. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 47102.     

Positively charged loose nanofiltration membrane grafted by diallyl dimethyl ammonium chloride (DADMAC) via UV for salt and dye removal

A novel positively charged loose nanofiltration (NF) membrane was fabricated feasibly by UV-induced photografting polymerization of diallyl dimethyl ammonium chloride (DADMAC) on Polysulfone ultrafiltration membrane. A possible reaction mechanism was proposed that a linear chain structure and/or pyrrole like five-membered nitrogen heterocycles structure on the side chain were grafted to form the active barrier layer. NF membrane demonstrated a looser average pore size of 8.6 nm and positive charges surface. Owing to the nanoscale ultrathin nanoscale barrier layer and the combination of Donnan exclusion and steric hindrance, NF membrane exhibited good hydrophilicity, a high pure flux of 60 L/m² h (0.5 MPa), a good salt rejection to Mg²⁺ (90.8%), Al³⁺ (94.0%), Ca²⁺ (91.5%), and a high dye rejection to methylene blue (99.4%) and congo red (100.0%) respectively. The salts rejection of NF membrane to different salts followed the order of AlCl₃ > CaCl₂ > MgCl₂ > NaCl > LiCl > MgSO₄ > Na₂SO_4. NF membrane showed certain fouling resistance to seawater and BSA solution. The grafting polymerization kinetics were comprehensively investigated including irradiation time, monomer concentration and irradiation intensity. X-ray Photoelectron Spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurement were employed to investigate membrane chemistry, morphologies, and hydrophilicity.     

Synthesis and swelling behavior of crosslinked copolymers of neutralized maleic anhydride with other monomers

A series of novel copolymer superabsorbents based on maleic anhydride (MLN), acrylamide (AAM), hydroxyethyl methacrylate (HEMA), and N,N′‐methylenebisacrylamide (NMBA) were prepared by inverse‐suspension polymerization. The influence of the reaction parameters on the water absorption was investigated to improve the understanding and to identify the optimum reaction conditions. The water absorbences or swelling behaviors for these absorbents in various salt solutions and various alcohol solutions were studied. The tendency of the absorbency for these absorbents in salt and alcohol solutions is in the order Na⁺ > Ca²⁺ > Al³⁺ for NaCl, CaCl₂, and AlCl₃ aqueous solutions and a glycerol > glycol > methanol > ethanol solution, respectively. This article also explains the IR and SEM characterization of the water‐absorbing copolymers and their practical use in soil for water retention. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 12: 2725–2731, 2003     

Fabrication of supported carbide-derived-carbon membrane by two phases of interfacial polymerization for oil/water separation

As recovery of clean and potable water from oil contaminated produced water lies at the heart of petroleum industry, various membranes have been developed to address this challenge. Given the salient features of high thermal and chemical stabilities, ceramic membranes possess huge potential for recovering potable water from produced water. A new CDC/PA@Ceramic membrane (carbide-derived carbon/polyamide on Al₂O₃ ceramic support) was fabricated by depositing carbide derived carbon (CDC) on alumina support through two phases of interfacial polymerization using piperazine and 3,5-diaminobenzoic acid crosslinked through terephthaloyl chloride. The merits of the fabricated membrane were thoroughly characterized by several characterization techniques including Field emission scanning electron microscopy, Energy-dispersive X-ray spectroscopy, Elemental mapping, Powder X-ray diffraction and Attenuated total reflectance Fourier transform infra-red spectroscopy. The CDC/PA@Ceramic membrane showed promising performance in terms of permeate flux and separation efficiency for oil/water emulsion. The separation efficiency remained >96% for all studied emulsion-concentrations (250 ppm, 125 ppm and 67.5 ppm). The highest separation efficiency was >98% with a feed concentration of 67.5 ppm of oil/water emulsion. The highest pure water permeate flux reached 250 L/m².h at 4 bar. The long-term stability test showed that the CDC/PA@Ceramic membrane remained stable for elongated time of 720 min with constant separation efficiency of >96% and permeate flux of 58 L/m².h at 2 bars. All results were validated by visual inspection, fluorescence spectrophotometry and optical microscopy of the feed and permeate throughout the membrane performance tests. The CDC/PA@Ceramic membrane can be a potential candidate for recovering precious water from the waste produced water.     

Flux,antifouling and separation characteristics enhancement of nanocomposite polyethersulfone mixed-matrix membrane by embedding synthesized hydrophilic adipate ferroxane nanoparticles

Polyethersulfone (PES) nanofiltration (NF) membranes were prepared by blending of synthesized hydrophilic adipate ferroxane nanoparticles (AFNPs) as a novel multifunctional nanofiller via the phase inversion method. The water contact angle measurement indicated the higher hydrophilicity of the NF membranes. The water flux of the membranes improved significantly after the addition of AFNPs, from 10.4 to 32.2 kg/m²h. Antifouling characteristics of AFNPs/PES membranes were improved by increased hydrophilicity and decreased membrane surface roughness. The 0.6 wt% AFNPs/PES membrane exhibited the highest FRR (96%) and the lowest irreversible fouling resistance (6%). The nanofiltration performance of the prepared membranes was evaluated by dye removal and salt retention. The results proved the high dye removal capability of modified membranes (98% rejection) compared with the unfilled PES membrane (89% rejection). The salt retention sequence for membrane with 0.2 wt% of nanoparticles was Na₂SO₄ (70%)>MgSO₄ (60%)>NaCl (18%).     

Effects of retained natural organic matter (NOM) on NOM rejection and membrane flux decline with nanofiltration and ultrafiltration

Two natural source waters containing natural organic matter (NOM) with different physical and chemical characteristics were dead-end filtered using five types of membranes having different material and geometric properties. In this study retained dissolved organic carbon (DOC) per unit membrane area is introduced as a better parameter compared to permeate volume, time, and delivered DOC to provide a reasonable comparison of NOM rejection and flux-decline trends. Retained DOC/NOM was calculated, which influences NOM concentration polarization at the membrane interface, and transport measurements of NOM rejection and flux decline were made. Molecular weight (MW) distribution measurements (by size exclusion chromatography) were used to calculate the average MW of the NOM. This persuasively demonstrated that the nominal molecular weight cut-off (MWCO) of a membrane is not the unique predictor of rejection characteristics for NOM composites. The charge density of NOM from the source waters was measured to estimate its effects on NOM rejection and flux decline during filtration. The contact angle of the membranes was used to determine hydrophobic interactions between NOM and membrane. All filtration measurements were performed at approximately the same permeate flow rate in order to minimize artifacts from mass transfer at the membrane interface. ESNA having a nominal MWCO of 200 Daltons showed NOM rejection greater than 95% and flux decline lower than 10% under a condition of a retained DOC of 0.5 mg C/cm² for the feed source waters. The other membranes having larger membrane pores (nominal MWCOs ranging from 8,000 to 20,000 Daltons) than the ESNA showed NOM rejection ranging from 68% to 86% and flux decline ranging from 5% to 17% at the same retained DOC for the waters.     

Novel thin-film nanocomposite membrane with water-soluble polyhydroxylated fullerene for the separation of Mg2+/Li+ aqueous solution

Despite the prosperity of membrane technology, the separation efficiency for Mg²⁺/Li⁺ mixture is still far from satisfactory. Herein, a novel thin-film nanocomposite (TFN) membrane was developed by loading polyhydroxylated fullerene (PHF) via interfacial polymerization. The effects of the PHF dosages on the as-developed membranes were investigated comprehensively by XPS, SEM, AFM, contact angle measurements, as well as nanofiltration tests. The results revealed the TFN membrane containing 0.01% (w/v) PHF exhibited the optimum performances. The membrane showed a pure water flux of 6.7 L·m⁻²·h⁻¹·bar⁻¹ and salt rejections with the order of Na₂SO₄ (95.6%) > MgSO₄ (93.6%) > MgCl₂ (89.9%) > NaCl (22.6%) > LiCl (16.3%). The membrane not only presented a separation factor of 13.1 in separating Mg²⁺/Li⁺ mixtures, but also demonstrated excellent antifouling ability, which enables membrane regeneration without operation break, suggesting its great potentials in the recovery of Li⁺ from brine or seawater. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48029.     

Economical evaluation of the fluoride removal by nanofiltration

Economic evaluation was carried out for a plant of fluoride removal by nanofiltration having a capacity of 2400 m³/d (100 m³/h) corresponding to a water consumption for 50.000 capita following the Moroccan considerations in rural medium. The design of this plant was carried out for the predetermined optimized conditions corresponding to a recovery rate of 84%, a fluoride rejection of 97.8% and a pressure pump of 10 bar. The capital cost was estimated to 748,003 € and the calculated operating cost to 0.212 €/m³. These costs were briefly compared to other ones.     

Pilot plant study of an ultrafiltration membrane system fordrinking water treatment operated in the feed-and-bleed mode

A pilot plant study of a polysulfone ultrafiltration (MWCO of 30 kD) tubular membrane process was conducted for the treatment of reservoir water. The membrane separation system was operated in the cross-flow filtration mode at 4.7 m/s and the feed-and-bleed mode for a long term of 4000 h without chemical cleaning and backwashing. The results showed that the behavior of permeate flux of the membrane system operated in the feed-and-bleed mode was similar to that of membrane systems with a periodic backwashing. At the beginning of filtration, bleeding of highly concentrated retentate caused a significant increase in permeate flux by 20%. However, as filtration progressed over time, the permeate flux of the fouled membrane was almost independent of the change in concentration of retained materials by bleeding the retentate. Three distinct stages in permeate flux decline were observed as follows: (1) sharp decrease from 120 to 30 1/m²/h in 1250 h due to a rapid build-up of a fouling layer, (2) gradual decrease to 15 1/m²/h in 2800 h due to the role of tangential shear induced by cross-flow velocity, and (3) stable permeate flux until 4000 h due to the establishment of a pseudo-steady-state condition. Permeate quality was stable, regardless of concentrating and diluting retentate in each cycle and fouling for a long duration of filtration. Rejection efficiencies for ultraviolet absorbance at 260 nm (UV₂₆₀) and dissolved organic carbon (DOC) were around 58% and 49%, respectively. The measured turbidity and concentration of suspended solids in bleed water agreed with calculated values from a simple mass valance, while the measured DOC and UV₂₆₀ of bleed water were much lower than calculated values.     

Salt rejection in nanofiltration for single and binary salt mixtures in view of sulphate removal

Three commercial membranes (NF70, NF90 and TFC-SR) were firstly characterized in terms of pure water flux and the rejection of uncharged (alcohols and sugars) compounds. Subsequently, the rejection of monovalent (sodium and chloride) and divalent (calcium and sulphate) ions in single (NaCl, CaCl, and Na₂SO₄) and binary (NaCI/Na₂,SO₄ CaCl₂/CaSO₄, NaCI/CaCl₂, and Na₂SO₄/CaSO₄) salt mixtures was studied. According to the pure water permeability the TFC-SR membrane is a loosely packed NF membrane (12.3 L.m ⁻².h⁻¹.bar⁻¹), while both NF70 and NF90 are tightly packed (2.6 and 3.6 Lm⁻².h⁻¹.bar-). According to the uncharged solute rejection, the MWCO_NF70 = 60, MWCO_NF90= 200 and MWCO_TFC-SR > 500. NF70 and NF90 were equally efficient in rejecting 1-2, 1-1 and 2-1 salts (>90%), while TFC-SR showed typical negatively charged surface behaviour, i.e., R (1-2) salt > R (11) salt > R (2-1). Sulphate rejection decreased in the presence of sodium chloride more significantly than in the presence of calcium chloride due to the more efficient retention of the bivalent calcium.     

Electrokinetic property of ZrO2/cordierite composite MF membrane and its influence on the permeate flux

ZrO₂/cordierite composite microfiltration (MF) membrane was prepared by the combination of extrusion and slip casting techniques. The electrokinetic properties of as-prepared membrane were characterized by streaming potential measurements operated in tangential microfiltration mode. The influences of pH, electrolyte species and concentrations of filtered solutions on the electrokinetic properties and permeate flux were investigated. Results show that the streaming potentials are dependent on the pH, types of the electrolyte and concentrations of filtered solutions. The isoelectric point (IEP) of membranes moved from 4.2 to 5.4 with different types of 10^− 3 M electrolyte solutions. The change of ionic concentration of NaCl solution does not alter the IEP of the membranes, but does make the streaming potential tend to be zero at high salt concentration. The specific adsorption of Ca²⁺ and SO₄²⁻ ions in CaCl₂ and Na₂SO₄ solutions onto the pore wall can alter the IEP and the net charge sign of the membrane. The as-prepared ZrO₂/cordierite membrane shows a maximal permeate volume flux near the IEP.     

Humic acid fouling in the membrane distillation process

This work investigates the extent of humic acid fouling during the membrane distillation process for water treatment. The effects of pH, ionic strength, and divalent ion on fouling were studied. The experiments were performed with a 0.22-μm PVDF flat-sheet membrane in a direct contact membrane distillation unit. Flux declines were negligible (less than 6%) for the ranges of humic acid concentration, ionic strength, and pH studied. The examination of the membrane surface by SEM revealed a thin deposit layer. The addition of divalent cations (Ca²⁺) into the solution considerably reduced flux when Ca²⁺ concentration exceeded the critical coagulation concentration. Ca²⁺ affected flux by forming complexes with humic acids and resulted in coagulation on the membrane surface. The normalized flux, J/J₀, was 0.57 after 18 h of operation when the CaCl₂ concentration was 3.775 mM. However, the deposit of humic acid coagulate on the membrane surface was loosely packed, and was rather easily removed. Rinsing of the fouled membrane with clean water and a 0.1 M NaOH solution gave 100% of flux recovery.     

Superabsorbent polymeric materials. II. Swelling behavior of crosslinked poly[sodium acrylate-co-3-dimethyl(methacryloyloxyethyl) ammonium propane sulfonate] in aqueous salt solution

A series of xerogels based on sodium acrylate (SA), 3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate (DMAPS), and N,N′-methylene-bis-acrylamide (NMBA) are prepared by inverse suspension polymerization. The water absorbencies or swelling behaviors for these xerogels in water or various saline solutions respectively exhibit a value of 1435 g H₂O/g sample and 96 g H₂O/g sample of deionized water and 0.9 wt % NaCl solution at a gel containing 1.88 × 10⁻³ molar ratio of DMAPS while the extent of 1.53 × 10⁻³ molar ratio (0.25 wt % based on total monomer) of NMBA was used in the polymerization. The absorbency in the chloride salt solutions decreases with an increase in the ionic strength of salt. For the same ionic strength of various salt solutions, the swelling amount has the following tendency: Na⁺ > Fe³⁺ > A1³⁺ > Ca²⁺ for the higher ionic strength of 5 × 10⁻³ −2 × 10⁻²M and Na⁺ > Fe³⁺ > Ca²⁺ > A1³⁺ for the lower ionic strength of < 2 × 10⁻⁴M. The bound water found by DSC investigation is approximately equal to 2 g H₂O/g sample. The pH effect and thermal effect on the water absorbency for these xerogels are also investigated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1701–1712, 1997     

Salt effect of CACL2, NH4i and NAI on vapor-liquid equilibrium of ethanol + water system at 298.15 K

Salt effect on vapor-liquid equilibrium for the ethanol + waiter system was measured at 298.15 K using an experimental apparatus based on the static method. The salting-out effect of CaCl₂, NH₄I and NaI on the ethanol + water system follows the order of CaCl₂ > NaI > NH₄I. The observed experimental data were correlated by the use of a semi-empirical model proposed by Hála (1983) with an accuracy of ± 2.13%. The application of Hála's model was confirmed in the ethanol + water system to be added the salts other than CaCl₂ at 298.15 K.     

Application on to nanofiltration to water management options for oil sands operation

A membrane separation process, nanofiltration (NF), has been applied successfully for treatment of oil sandswaters, particularly to water softening and removal of toxic components. This study focused on the selection of appropriate membranes and the assessment of their performance for the removal of polyvalent ions (hardness) and naphthenic acids (NA) (the main acute toxicant in oil sands process-affected imported waters) from both imported and potential discharge waters. Experiments were carried out using a bench-scale flat sheet membrane system with several commercially available NF membranes. It was found that after membrane filtration, both water hardness and the NA concentrations were reduced significantly (>95%). A permeate flux was maintained at 15 L/m²/h or higher, with a retentate volume of about 10% of the feed volume.