Properties Of Nanofiltration Membranes Research Articles

Rejection Mechanism of Ionic Solute Removal by Nanofiltration Membranes: An Overview.

The toxicity of heavy metals can cause water pollution and has harmful effects on human health and the environment. Various methods are used to overcome this pressing issue and each method has its own advantages and disadvantages. Membrane filtration technology such as nanofiltration (NF) produces high quality water and has a very small footprint, which results in lower energy usage. Nanofiltration is a membrane-based separation technique based on the reverse osmosis separation process developed in the 1980s. NF membranes have a pore size of 1 nm and molecular weight cut off (MWCO) of 300 to 500 Da. The properties of NF membranes are unique since the surface charge of the membranes is dependent on the functional groups of the membrane. The rejection mechanism of NF membrane is unique as it is a combination of various rejection mechanisms such as steric hindrance, electric exclusion, dielectric effect, and hydration mechanism. However, these mechanisms have not been studied in-depth due to their complexity. There are also many factors contributing to the rejection of NF membrane. Many junior researchers would face difficulty in studying NF membrane. Therefore, this paper is designed for researchers new to the field, and will briefly review the rejection mechanisms of NF membrane by both sieving and non-sieving separation processes. This mini-review aims to provide new researchers with a general understanding of the concept of the separation process of charged membranes.

Optimizing the Surface Properties of Nanofiltration Membrane by Tailoring the Diffusion Coefficient of Amine Monomer

Optimizing the Surface Properties of Nanofiltration Membrane by Tailoring the Diffusion Coefficient of Amine Monomer

Nanofiltration-Concept and Prospects

Nanofiltration is a pressure-driven film measure for fluid stage detachments. It is employed in numerous applications due to lower energy utilization and higher motion rates. The properties of nanofiltration membranes lie between those of non-permeable reverse osmosis layers and permeable ultrafiltration layers where partition is typically thought to be because of size rejection and, sometimes, charge impacts. The improvement of nanofiltration development as a practical association over continuous years has provoked a pivotal extension in its application in different endeavours, for instance, treatment of blurring effluents from the material industries, division of medications from development stocks, demineralization in the dairy business, and metal recovery from wastewater and disease clearing

Solution Blown Nylon 6 Nanofibrous Membrane as Scaffold for Nanofiltration.

In this work, a nylon 6 nanofibrous membrane was prepared via solution blowing technology and followed hot-press as scaffold for nanofiltration. The structure and properties of the hot-pressed nylon 6 nanofibrous membrane (HNM) were studied the effect of hot-pressing parameters and areal densities. Then an ultra-thin polyamide (PA) active layer was prepared by interfacial polymerization on HNM. The effects of nanofibrous scaffolds on the surface properties of ultra-thin nanofiltration membranes and their filtration performance were studied. Results showed that the nylon 6 nanofibers prepared at a concentration of 15 wt % had a good morphology and diameter distribution and the nanofibers were stacked more tightly and significantly reduced in diameter after hot pressing at 180 °C under the pressure of 15 MPa for 10 s. When the porous scaffold was prepared, HNM with an areal density of 9.4 and 14.1 g/m2 has a better apparent structure, a smaller pore size, a higher porosity and a greater strength. At the same time, different areal densities of HNM have an important influence on the preparation and properties of nanofiltration membranes. With the increase of areal density, the uniformity of HNM increased while their surface roughness and pore size decreased, which is beneficial to the establishment of PA barrier layer. With areal density of 9.4 and 14.1 g/m2, the as-prepared nanofiltration membrane has a smoother surface and more outstanding filtration performance. The pure water flux is 13.1 L m−2 h−1 and the filtration efficiencies for NaCl and Na2SO4 are 81.3% and 85.1%, respectively.

Novel high-flux thin film composite nanofiltration membranes fabricated by the NaClO pre-oxidation of the mixed diamine monomers of PIP and BHTTM in the aqueous phase solution

Novel high-flux thin film composite (TFC) nanofiltration (NF) membranes were fabricated by the sodium hypochlorite (NaClO) pre-oxidation of the mixed diamine monomers of piperazine (PIP) and 2,2′-bis(1-hydroxyl-1-trifluoromethyl-2,2,2-triflutoethyl)-4,4′-methylenedianiline (BHTTM) in the aqueous phase solution, and via interfacial polymerization (IP) with trimesoyl chloride (TMC) on the polysulfone (PSF) ultrafiltration (UF) membrane. The chemical change of the pre-oxidation aqueous phase solution was characterized by LC-MS. By optimizing the NaClO and NaOH content in the aqueous phase solution, the pure water flux was improved greatly and the salt rejection kept on a high level (>90%). The properties of NF membranes were characterized by XPS, SEM, AFM and contact angle. Through the NaClO pre-oxidation of the mixed diamine monomers of PIP and BHTTM in the aqueous phase solution, the active layer of NF membrane became thinner and the pore size of NF membrane was enlarged. Besides, after oxidation treatment by 3000ppm active chlorine solution for 1h, the NF membrane exhibited pure water flux (PWF) with 161 (LMH) and Na2SO4 rejection of 92.1% under 0.6MPa. The molecular weight cut-off (MWCO) of the NF membrane was greater than 500, which was calculated from the carbohydrates rejection. The good performance and the satisfactory stability of the novel high-flux NF membrane demonstrated its good potential in the practical application.

Rejection of Heavy Metal Ions with Polyelectrolyte Composite Nanofiltration Membrane

Nanofiltration membrane was prepared by static layer-by-layer (LBL) self-assembly of poly (ethyleneimine) (PEI) and poly (sodium 4-styrenesulfonate) (PSS) on the modified poly-arcylonitrile ultra-filtration membrane. Study on self-assembly of polyelectrolyte membranes with changing surface charges and wettability, rejection properties of nanofiltration membrane in different conditions and pH with respect to heavy metal ions, namely Ni2+and Cd2+were investigated. The results show that the PEI/PSS membrane composed of 4 bilayers at operating pressure 0.4MPa, rejection of PAN-PEI/PSS nanofiltration membrane towards these 2 kind of heavy metal ions reached no less than 90%.

Особенности диффузии гомологов алкилпиридиния через поливинилхлоридные молекулярные сита

The process of alkylpyridinium homologous transfer through polyvinylchloride plasticized nanofiltration membranes (molecular sieves) under self-diffusion and direct current conditions. Quantitative characteristics of membrane transport: the coefficients of permeability, diffusion, the distribution coefficient, ion flux, were calculated. The dependences of the volume properties of nanofiltration membranes from the hydrocarbon radical length in the alkylpyridinium homologous in membrane solutions and pore formers were shown.

Membrane separation process for the treatment and reuse of bath dye effluents

The main purpose of this work is to study the effect of sodium chloride concentration on the removal by nanofi ltration of anionic dyes in synthetic colored wastewaters and to characterise some main performances and properties of nanofi ltration membranes of different properties. Membranes Sepa DK and NF90 were used for the study and were operated at constant transmembrane pressure. The anionic dyes, Direct Red 80 (1373 g/mol) and Acid Orange G (452 g/ mol), were used at a fi xed dye concentration for different salt concentrations. Results indicated that effects of pH, concentrations of salt have a role on the permeate fl ux and dye retention for single and mixed salt dye solution. An interesting result is that retention of Orange G is enhanced and becomes high (96%) in the presence of salt. NF 90 shows a better salt rejection than Sepa DK, for the same salt and dye concentrations. The Orange G retention increases when the pH decreases from 9 to 3. For NF90, Orange G retention is about 98%, whatever the pH. NF90 achieves the higher salt retention than Sepa DK, however, a great loss in the permeate fl uxes is observed as the concentration of NaCl increased.

A NOVEL NANOFILTRATION MEMBRANE PREPARED WITH PAMAM AND TMC (I)

A series of nanofiltration (NF) membranes were prepared with poly(amido-amine) (PAMAM) and trimesoyl chloride (TMC) via in situ interfacial polymerization. The effects of the generation number and concentration of PAMAM on the properties of NF membranes were discussed. Fourier transform infrared spectroscopy (FTIR-ATR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and contact angle measurements were employed to characterize the resulting membranes. The nanofiltration performances were evaluated with solutions of NaCl, Na2SO4, MgCl2 and MgSO4, respectively. FTIR-ATR spectra indicated that TMC reacted more sufficiently with the higher generation PAMAM. The salts rejection of the resulting membranes increased with increasing the generation number of PAMAM, which was mainly attributed to the concentration difference of terminal amino-groups among the different generation PAMAM. The MgCl2 (2000 mg/L) rejection of NF-G5 reached 90.3% under the pressure of 0.6 MPa in a cross-flow method measurement. The rejection of MgCl2 increased with increasing concentration of PAMAM. The salts rejection order of NF membranes with high rejection is MgCl2 > MgSO4 > Na2SO4 > NaCl. It was also found that the NF-Gx (x = 4, 5, 6, 7) membranes became more hydrophilic with increasing the generation number of PAMAM.