Recent advancements in the application of new monomers and membrane modification techniques for the fabrication of thin film composite membranes: A review

Thin film composite (TFC) membranes have been experiencing significant modifications recently aiming to improve their structure, properties and separation efficiency. One of the promising modifications to tailor the membranes more efficient is changing the materials used. m-phenylene diamine (MPD), piperazine (PIP), and trimesoyl chloride (TMC) are the most common monomers used to fabricate TFC membranes. Recent studies have introduced several alternatives to these traditional monomers showing significant contribution of these monomers to the physicochemical properties of the membranes (e.g., surface roughness, hydrophilicity, cross-linking density, chemical structure) as well as membranes\u27 separation efficiency. Emergence of more favorable functional groups such as carboxylic and amine groups due to the new materials integration facilitates the polymerization process and is beneficial to the membrane properties. Here, a critical review on the new interfacial polymerization monomers applied for reverse osmosis (RO) and nanofiltration (NF) membranes fabrication is presented. The membrane molecular structure and fabrication mechanism are investigated in details. This is followed by a review of the recent surface modification methods including grafting, coating and additive incorporating into the thin layer of membranes. The application of alternative monomers to MPD, PIP and TMC are investigated and the benefits of using these monomers or co-monomers are discussed

A Study for Water Purification Using Reverse Osmosis Membrane Modified with Carbon Nanotube

Water desalination systems is among the methods used to produce potable water to be used for domestic, agricultural and industrial applications.  Reverse osmosis is a common methods  employed for desalination facilities, mainly because of its low energy consumption, and high efficiency for permeate production. The main aim of this research is to use nanocomposite containing carbon nanotubes to improve membrane wall performance. in addition, the increase in the flux as a result of decreased clogging surface on the membrane was also studied.  To accomplish the objective of the study, the synthesized polyamid reverse osmosis nanocomposite membrane were used for purification of brackish water with the characteristic of having the electroconductivity of 4000 µs/cm. The modified raw-multi walled carbon nanotubes membrane was embedded through polymerization method in order to increase porosities and hydrophilicity. Analysis of Contact angle, SEM, FTIR and AFM were done for recognizing the compounds which were created on the surface of membranes and membranes hydrophilicity. Three sets of samples were prepared for testing in the membrane cell synthesis analysis. Water flux and rejection rates were assessed every 30 minutes. Results of this study showed that the membranes have soft hydrophil surfaces and by increasing nanocomposite concentrations with specified measure, the water flux increased up to 30.8 L/m2h which was noticeable compared to the simple polyamide membranes. Our results also showed that fouling reduced considerably and the clogging condition was reduced by nanocomposite membranes, and the rejection rate was higher than 97 percent for all synthesized membranes with pyrrol

Improving the performance of polyamide Nano-filtration membrane in acidic media by incorporation of modified multi-walled carbon nanotubes

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Optimization of Coagulation-Flocculation Process in Efficient Arsenic Removal from Highly Contaminated Groundwater by Response Surface Methodology

Elevated arsenic (As) contamination in water, especially groundwater, has been recognized as a major problem of catastrophic proportions. This work explores As(V) removal via the coagulation-flocculation process by use of ferric chloride coagulant and polyacrylamide k16 co-coagulant as a first time. The effects of major operating variables such as coagulant dosing (50, 125 and 200 mg/L), co-coagulant dosing (5, 12.5 and 20 mg/L), pH (6, 7and 8), fast mixing time (1, 2 and 3 min), and fast mixing speed (110, 200 and 300 rpm) on As(V) removal efficiency were investigated by a Box-Behnken statistical experiment design (BBD) and response surface methodology (RSM). According to factors F values, coagulant dosing, rapid mixing speed, pH, and co-coagulant dosing showed the most effect on As(V) removal efficiency, and the rapid mixing time factor indicated the slightest effect. The proposed quadratic model was significant with a p value R2 and adjusted R2 values of 0.9855 and 0.9738, respectively. Predicted model optimal conditions with target of complete As(V) removal were coagulant dosing = 197.63 ppm, co-coagulant dosing = 19.55 ppm, pH = 7.37, fast mixing time = 1.43 min and fast mixing speed = 286.77 rpm. The treatment of Nazarabad well water sample with an initial As(V) concentration of 5 mg/L under the optimal conditions removed 100% As(V) with the volume of produced sludge of 10.7 mL/200 mL. Increasing coagulant dosing, co-coagulant dosing, fast mixing time and fast mixing speed operation parameters from low-level to high-level values indicated 78%, 20%, 10.52% and 9.47% increases in volume of the produced sludge, respectively. However, a reduction of 13.63% in volume of the produced sludge resulted via pH increases

Improvement in flux and antifouling properties of PVC ultrafiltration membranes by incorporation of zinc oxide (ZnO) nanoparticles

In this study, modification of polyvinyl chloride (PVC) ultrafiltration membranes with zinc oxide (ZnO) nanoparticle addition was taken into consideration. The ZnO at five different weights was added to the polymeric solution, and the membranes were fabricated by the phase inversion method using water as a nonsolvent and PEG 6 kDa as a pore former additive. The results showed that the pure water flux of the modified membranes increased up to 3 wt% ZnO addition, which was the optimized amount of the nanoparticle addition in this study. Also, at 3 wt% ZnO addition, flux recovery ratio reached from 69% to above 90%, indicated that the nanocomposite membranes were less susceptible to be fouled. BSA rejection of the membranes also enhanced up to 97% by 3 wt% ZnO addition. The membranes were further characterized by SEM images and remarkable changes in their morphologies were observed, and they became more porous with higher interconnectivity between the pores. Furthermore, EDAX analysis was applied to study ZnO dispersion in the membrane structure and except for 4 wt% ZnO addition which particles aggregation was noticeable, ZnO was dispersed finely in the membrane structure. In addition, the modified membranes had higher hydrophilicity and lower contact angle that was effective to obtain higher water flux

Fouling reduction of emulsion polyvinylchloride ultrafiltration membranes blended by PEG: the effect of additive concentration and coagulation bath temperature

In the present work, ultrafiltration membranes were prepared using emulsion polyvinyl chloride (EPVC) with the addition of various concentrations of polyethylene glycol (PEG) to investigate the morphological structure and separation properties. The effects of polymer concentration, coagulation bath temperature (CBT), and PEG (6\ua0kDa) concentrations—a pore former hydrophilic additive—were studied. Through the phase inversion, the membranes—which were induced by immersion precipitation in a water coagulation bath—were fabricated through dissolving EPVC in N-methyl-pyrrolidinone, a polymer solvent. Morphological features of the membranes were characterized through scanning electron microscopy, pore size and porosity, and contact angle measurements. Water and bovine serum albumin (BSA) were used in order to study the separation and permeation performance of the fabricated membranes at 3\ua0bar, which is operating pressure. The results which were obtained from contact angle test indicated an increment in the membranes hydrophilicity with an increase in PEG concentrations, and then it decreased again. Increasing the CBT led to macrovoid formation in the membrane structure and the appreciation of both membrane permeability and BSA rejection. The addition of PEG resulted in a more porous structure and a higher water flux for those membranes, which were prepared with 13\ua0wt.% EPVC; while, for those which were fabricated with 15\ua0wt.% polymer, an opposite trend was observed

Preparation and characterization of novel nanoporous SBA-16-COOH embedded polysulfone ultrafiltration membrane for protein separation

Polysulfone ultrafiltration membrane was modified by novel nanoporous SBA-16-COOH during the membrane preparation via the phase inversion. The pure water flux and bovine serum albumin (BSA, as the foulant) flux were measured at 2 bar and the membranes’ antifouling behavior were analyzed. The membranes showed higher water flux after SBA-16-COOH addition up to 2 wt% and after that the flux slightly decreased which is attributed to the aggregation of SBA-16-COOH particles at the higher concentrations. SBA-16-COOH addition improved the surface hydrophilicity and led to elongated finger-like pores within the membranes cross section structure. The water flux after BSA flux was still higher than the one before BSA, thereby SBA-16-COOH addition resulted in better antifouling properties. In terms of BSA rejection, the nanocomposite SBA-16-COOH-based membranes outperform the pristine PSf membrane with rejection values up to 98.9%. The water contact angle confirmed the enhanced hydrophilicity of the membranes’ surface due to [sbnd]COOH functional groups of the nanomaterials which led to a higher permeability and an enhanced fouling resistance

Fabrication of thin-film nanocomposite nanofiltration membranes incorporated with aromatic amine-functionalized multiwalled carbon nanotubes. Rejection performance of inorganic pollutants from groundwater with improved acid and chlorine resistance

A thin-film nanocomposite nanofiltration (TFN-NF) membrane was fabricated through blending a novel aromatic amine-functionalized multiwalled carbon nanotubes (AAF-MWCNTs) and an aliphatic amine-functionalized multiwalled carbon nanotubes (AF-MWCNTs). The polyamide layer was synthesised by interfacial polymerisation (IP) between piperazine and trimesoyl chloride monomers. The improved resistance of NF membranes to chlorine and acid were characterised by X-ray photoelectron spectroscopy (XPS), field emission-scanning electron microscopy, atomic force microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, contact angle, and zeta potential measurements. XPS analysis confirmed chlorine and acid resistance properties, as well as an improvement in the polyamide network cross-linking degree of the new nanofiltration membranes incorporated with AAF-MWCNTs (AAF–NF). The membrane transport properties and the performance on the rejection of HAsO4-2, NO3-, and NH4+ from solutions mimicking polluted groundwater were evaluated. Membrane performance to the target pollutants were determined by the solution-electro-diffusion (SED) model coupled with reactive transport. The results showed that AAF–NF membranes, with long-lifetimes, could be applied for the removal of As(V) from polluted groundwater. Water permeate flux and the arsenic rejection of the AAF–NF membrane increased by 15% when it is compared with a typical commercial semi-aromatic polyamide nanofiltration membranes (Desal DL).Peer ReviewedPostprint (author's final draft