Efficient Removal of Pb(II) and Cr(III) Ions from Aqueous Solutions Using Modified Cellulose Nanocrystals into the Polyamide Nanofiltration Membrane

Nowadays, discharge of toxic heavy metals through industrial, domestic, and agricultural effluents into the environment, in this study, the efficiency of thin-layer nanocomposite (TFN) nanofiltration membranes made using surface polymerization in combination with modified cellulose nanoparticles (mNC) was assessed for the removal of lead and chromium ions from aqueous solutions. In so doing, after modification of MNCSNCs, fabrication of membrane substrate and also PA selective layer, and then testing the performance of the membrane, the physical properties of the modified nanoparticles and nanocomposite membranes were also investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and zeta potential. Based on the Results obtained, the water flux of TFN2 membranes increased from 42 to 125 l/m2/h. Also, at pH = 8.5, the removal rate of Pb(II) and Cr(III) was 93% and 100%, respectively. Moreover, under these conditions, the adsorption process followed the Langmuir adsorption isotherm and the pseudo-second-order kinetic models. In general, the results showed that the synthesized nanofiltration nanocomposite membrane by embedding modified cellulose nanocrystals can be used to effectively remove Pb(II) and Cr(III) ions from aqueous solutions

Urease-carrying electrospun polyacrylonitrile mat for urea hydrolysis

Electrospinning was used to fabricate beadless microfibrous polyacrylonitrile (ePAN) mats with an average fiber diameter of 1448 ± 380 nm from a 10 wt.% PAN in dimethylformamide (DMF) dope solution at applied voltage of 18 kV and 20 cm fiber collection distance. Urease (EC 3.5.1.5) was then covalently immobilized on dispersed microfibrous ePAN mats following the chemical treatment of fibers with ethylenediamine (EDA) and glutaraldehyde (GA). The optimal concentration of GA for immobilization was 5%. The amount of loaded urease reached 157 µg/mg mat, exhibiting 54% of the free urease activity. The surface chemistry of as-spun and chemically treated fibers was examined with Fourier transform infrared (FTIR) spectroscopy. Field emission scanning electron microscopy (FESEM) was used to study the morphology and diameter of the pristine, chemically treated, and urease-immobilized microfibrous mats. Immobilized urease showed increased temperature for maximum activity (from 37 to 50 °C for free and immobilized urease, respectively) and improved storage stability (20 days). The immobilized urease was also less sensitive to the changes in pH, especially in acid conditions. In addition, nearly 70% of initial activity of the immobilized urease was retained after 15 cycles of reuse, which proved the applicability of the electrospun fibers as successful enzyme carriers

Super hydrophilic TiO2/HNT nanocomposites as a new approach for fabrication of high performance thin film nanocomposite membranes for FO application

In this work, titanium dioxide (TiO2) nanoparticles/halloysite nanotube (HNT) nanocomposites synthesized via one-step solvothermal method were used as nanofillers in the preparation of thin film nanocomposite (TFN) membranes for forward osmosis (FO) application. With respect to separation performance, it was reported that the TFN membrane incorporated with 0.05%(w/v) TiO2/HNTs (denoted as TFN0.05) exhibited the best performance due to its high water permeability and low reverse solute flux when tested using 10mM NaCl feed solution and 2.0M NaCl draw solution under two different membrane configurations. Moreover, compared to control membrane, the fabricated TFN0.05 membrane showed significantly better antifouling affinity against bovine serum albumin (BSA) as well as complete recovery of water flux after a simple water cleaning process. The results revealed that fouling in the TFN0.05 membrane is fully reversible. Overall, it can be concluded that the unique tubular structure of HNTs coupled with the excellent anti-fouling features of TiO2 have madeTiO2/HNTs a reliable material with a bright perspective in improving the antifouling affinity of conventional thin film composite membranes for FO applications. To the best of the authors' knowledge, this is the first study dedicated to the application of composite nanomaterials for the development of TFN FO membranes

Novel Polyelectrolyte-Based Draw Solute That Overcomes the Trade-Off between Forward Osmosis Performance and Ease of Regeneration

Forward osmosis (FO) is an emerging technology for seawater and brackish desalination, wastewater treatment, and other applications, such as food processing, power generation, and protein and pharmaceutical enrichment. However, choosing a draw solute (DS) that provides an appropriate driving force and, at the same time, is easy to recover, is challenging. In this study, water-soluble poly(styrene sulfonate) (PSS) was modified by a high-electrical-conductivity 3,4-ethylenedioxythiophene (EDOT) monomer to fabricate a novel draw solute (mPSS). FO tests with the CTA membrane in the active layer facing the feed solution (AL-FS) orientation, using a 50 mS/cm aqueous solution of synthesized solute and distilled water as a feed solution exhibited a water flux of 4.2 L h−1 m−2 and a corresponding reverse solute flux of 0.19 g h−1 m−2. The FO tests with the same membrane, using a 50 mS/cm NaCl control draw solution, yielded a lower water flux of 3.6 L h−1 m−2 and a reverse solute flux of 4.13 g h−1 m−2, which was more than one order of magnitude greater. More importantly, the synthesized draw solute was easily regenerated using a commercial ultrafiltration membrane (PS35), which showed over 96% rejection

Incorporation of Functionalized Halloysite Nanotubes (HNTs) into Thin-Film Nanocomposite (TFN) Nanofiltration Membranes for Water Softening

Incorporating nanoparticles (NPs) into the selective layer of thin-film composite (TFC) membranes is a common approach to improve the performance of the resulting thin-film nanocomposite (TFN) membranes. The main challenge in this approach is the leaching out of NPs during membrane operation. Halloysite nanotubes (HNTs) modified with the first generation of poly(amidoamine) (PAMAM) dendrimers (G1) have shown excellent stability in the PA layer of TFN reverse-osmosis (RO) membranes. This study explores, for the first time, using these NPs to improve the properties of TFN nanofiltration (NF) membranes. Membrane performance was evaluated in a cross-flow nanofiltration (NF) system using 3000 ppm aqueous solutions of MgCl2, Na2SO4 and NaCl, respectively, as feed at 10 bar and ambient temperature. All membranes showed high rejection of Na2SO4 (around 97–98%) and low NaCl rejection, with the corresponding water fluxes greater than 100 L m−2 h−1. The rejection of MgCl2 (ranging from 82 to 90%) was less than that for Na2SO4. However, our values are much greater than those reported in the literature for other TFN membranes. The remarkable rejection of MgCl2 is attributed to positively charged HNT-G1 nanoparticles incorporated in the selective polyamide (PA) layer of the TFN membranes

Fabrication of pore-filling cation-exchange membrane from waste polystyrene and Spunbond Meltblown Spunbond (SMS) non-woven polypropylene fabric as the substrate

Abstract Commercial ion-exchange membranes are typically thick, possessing limited mechanical strength, and have relatively high fabrication costs. In this study, we utilize a three-layer polypropylene fabric known as Spunbond Meltblown Spunbond (SMS) as the substrate. This choice ensures that the resulting membrane exhibits high strength and low thickness. SMS substrates with various area densities, including 14.5, 15, 17, 20, 25, and 30 g/m2, were coated with different concentrations of waste polystyrene solution (ranging from 5 × 104 to 9 × 104 mg/l) before undergoing sulfonation using concentrated sulfuric acid. The physicochemical and mechanical properties of the membrane were characterized and compared with those of commercial Neosepta CMX and Nafion-117 cation-exchange membranes. Remarkably, the fabricated membrane exhibited good performance compared to commercial ones. The cation-exchange capacity (2.76 meq/g) and tensile strength (37.15 MPa) were higher, and the electrical resistance (3.603Ω) and the thickness (130 μm) were lower than the commercial membranes

Hybrid forward osmosis/ultrafiltration membrane bag for water purification

In this work, a novel forward osmosis (FO)-ultrafiltration (UF) hybrid membrane is designed, constructed and its performance tested. The membrane consists of FO and UF membrane bilayer, between which highly concentrated sodium polyacrylate (SPAA) solution is sandwiched as a draw solution. When the FO side of the hybrid membrane is brought into contact with waste water, seawater or brackish water, clean water is drawn into the SPAA solution through FO membrane. The clean water is then squeezed out of the SPAA solution through the UF membrane by applying pressure, which can be either hydraulic or mechanical. Experiments were carried out to prove the validity of the design concept. Some model equations were derived to simulate the performance of the hybrid membrane and the experimental data were analyzed based on the model equations. The novel hybrid membrane is believed to allow the production of RO quality water at the UF pressure that is much lower than the pressure for RO, thus leading to significant reduction of energy consumption for water production

Synthesis of nanocomposite membrane incorporated with amino-functionalized nanocrystalline cellulose for refinery wastewater treatment

In this work, nanocomposite ultrafiltration (UF) membranes were synthesized through addition of different quantities of amino-functionalized nanocrystalline cellulose (NCs) in order to improve membrane anti-fouling resistance against oil depositions. The characterization results demonstrated that the overall porosity and hydrophilicity of the membranes were improved significantly upon addition of NCs despite a decrease in the pore size of nanocomposite membranes. The UF performance results showed that the nanocomposite membrane incorporated with 1 wt% NCs achieved an optimal water flux improvement, i.e., approximately 43% higher than the pristine membrane. Such nanocomposite membrane also exhibited promising oil rejection (>98.2%) and excellent water flux recovery rate of ˜98% and ˜85% after one and four cycles of treating 250-ppm oil-in-water emulsion solution, respectively. The desirable anti-fouling properties of nanocomposite membrane can be attributed to the existence of hydrophilic functional groups (−OH) on the surface of membrane stemming from addition of NCs that renders the membrane less vulnerable to fouling during oil-in-water emulsion treatment

Effect of air-gap length on carbon dioxide stripping performance of a surface modified polysulfone hollow fiber membrane contactor

Surface Modifying Macromolecule (SMM) blended PSf hollow fibers were spun at different air-gaps to evaluate CO2 stripping from aqueous DEA solution and water. The fabricated membranes were firstly subjected to different characterization methods such as contact angle and liquid entry pressure measurement to evaluate the membrane's hydrophobicity and wetting resistance, respectively. To determine pore size and effective porosity of the membranes, a pure helium permeation test was performed. Morphological study of the membranes was conducted by scanning electron microscopy (SEM) and atomic force microscopy (AFM). A CO2 stripping test was carried out to investigate the effects of operating variables such as liquid and gas velocity, temperature and DEA concentration on the CO2 stripping flux. It was found that the increase of liquid velocity resulted in enhanced CO2 stripping flux. On the other hand, the increase in gas velocity did not exert significant influence on the stripping flux. The increase in temperature and DEA concentration both enhanced the stripping flux. Lastly, it was concluded that the hollow fibers spun in this work at a 15 cm air-gap could achieve the best stripping flux among all the membranes fabricated so far for CO2 strippin

Carbon dioxide stripping from water through porous polysulfone hollow fiber membrane contactor

Carbon dioxide (CO2) stripping from water was conducted through the porous asymmetric polysulfone (PSf) hollow fiber membrane contactor. The effect of the liquid and gas flow rates on the stripping performance, the liquid phase CO2 concentration and the CO2 stripping efficiency of the membrane module and the effect of liquid phase temperature on CO2 stripping flux were studied. The experimental results showed that the stripping gas velocity had a minor effect on the CO2 desorption flux while the increase in the liquid velocity could enhance CO2 desorption flux in the gas stripping membrane contactor. By increasing liquid flow rate to 200 ml/min, the maximum CO2 stripping efficiency of almost 66% was achieved. Enhancement of liquid flow rate from 50 to 200 ml/min increased the CO2 flux around 482%. It was found that the CO2 stripping flux was significantly affected by the liquid phase temperature. By increasing liquid temperature from 80 to 90 °C, the CO2 stripping flux increased from 1.3 × 10−4 to 4.9 × 10−4 mol m−2 s−1 at liquid velocity of 200 ml min−1. Hence, the higher stripping efficiency can be achieved by applying the higher liquid flow rate in the membrane contactor module. As well, the liquid phase temperature is a key parameter that needs to be controlled