Film Composite Polyamide Reverse Osmosis Research Articles

Antibacterial and Antifouling Properties of Ag‐ and Cu‐Decorated Thin Film Composite Polyamide Reverse Osmosis Membranes

AbstractIn this work, silver and copper particles of different nanoparticle precursor concentrations were decorated on the surface of thin film composite polyamide (TFC‐PA) reverse osmosis (RO) membranes by in situ method. The modified membranes were characterized by different techniques including Field emission scanning electron microscopy (FE‐SEM), X‐ray Absorption Spectroscopy (XAS), and attenuated total reflection – Fourier transforms infrared spectroscopy (ATR‐FTIR), water contact angle (WCA), and antibacterial capacity. After that, the membrane performance was compared through normalized flux and the possibility of the removal of bovine serum albumin (BSA) protein; the anti‐fouling and anti‐biofouling properties were also compared through the maintained flux ratios (%) after 5‐hour filtration. The used organic foulants were BSA protein and humic acid (HA) solutions. The results showed that, compared to the flux of the base, the flux of AgNPs‐decorated membrane can improve the separation ability up to 24% while that of CuNPs‐decorated membrane was 14%. The anti‐fouling property of decorated membranes was significantly increased compared to that of the base (from 64% for the base to over 77% for decorated membranes). Especially, the anti‐biofouling property of nanoparticles decorated membranes was also increased because of the higher maintained flux ratios (from 50% for the base to over 75% for decorated membranes). It indicates that this method can be applied to produce reverse osmosis (RO) membranes for reclamation wastewater with a high content of organic matter.

Thin Film Composite Polyamide Reverse Osmosis Membrane Technology towards a Circular Economy.

It is estimated that Reverse Osmosis (RO) desalination will produce, by 2025, more than 2,000,000 end-of-life membranes annually worldwide. This review examines the implementation of circular economy principles in RO technology through a comprehensive analysis of the RO membrane life cycle (manufacturing, usage, and end-of-life management). Future RO design should incorporate a biobased composition (biopolymers, recycled materials, and green solvents), improve the durability of the membranes (fouling and chlorine resistance), and facilitate the recyclability of the modules. Moreover, proper membrane maintenance at the usage phase, attained through the implementation of feed pre-treatment, early fouling detection, and membrane cleaning methods can help extend the service time of RO elements. Currently, end-of-life membranes are dumped in landfills, which is contrary to the waste hierarchy. This review analyses up to now developed alternative valorisation routes of end-of-life RO membranes, including reuse, direct and indirect recycling, and energy recovery, placing a special focus on emerging indirect recycling strategies. Lastly, Life Cycle Assessment is presented as a holistic methodology to evaluate the environmental and economic burdens of membrane recycling strategies. According to the European Commission’s objectives set through the Green Deal, future perspectives indicate that end-of-life membrane valorisation strategies will keep gaining increasing interest in the upcoming years.

Tailoring Polyamide Rejection Layer with Aqueous Carbonate Chemistry for Enhanced Membrane Separation: Mechanistic Insights, Chemistry-Structure-Property Relationship, and Environmental Implications.

Surface roughness and the associated nanosized voids inside the roughness structures have great influence on the separation performance of thin film composite polyamide reverse osmosis (RO) membranes. Inspired by the recent findings that these voids are formed due to the degassing of CO2 nanobubbles during interfacial polymerization, we systematically investigated the role of carbonate chemistry, particularly the solubility of CO2, in the aqueous m-phenylenediamine (MPD) solution for the first time. "Ridge-and-valley" roughness features were obtained when the pH of the MPD solution was between the two acidity constants of the carbonate system (i.e., 6.3 ≤ pH ≤ 10.3), under which condition HCO3- dominates over the other carbonate species. Increasing pH over this range led to both increased water permeability and better rejection of various solutes, thanks to the simultaneously enhanced effective filtration area and cross-linking degree of the polyamide layer. Further increase of pH to 12.5 resulted in more disparate rejection results due to membrane hydrolysis: rejection of neural solutes (B and As(III)) was compromised whereas that of charged solutes (NaCl and As(V)) was maintained. The mechanistic insights gained in the current study reveal the critical need to design RO membranes directly for end applications based on first principles.

Scaling prevention of thin film composite polyamide Reverse Osmosis membranes by Zn ions

On the West Coast of South Africa, there is an abundance of brackish groundwater. Reverse Osmosis membrane systems are used to make the borehole water fresh. Unfortunately, the salts that are removed from the water, precipitates on the membrane surface, thus, decreasing the overall process efficiency. In this study, the use of Zn2+ ions as an anti-scalant was investigated in terms of feasibility in the treatment of brackish water influent. Experimental tests were conducted on a bench scale unit, followed with a pilot plant thereafter. Three commercial membranes were exposed to natural groundwater scaling. The first, commercial anti-scalant treatment, second, anti-scalant treatment with Zn2+ ions and the third, untreated. The results, after a period of close to 5 months, showed that the flux of the membranes treated with commercial (32.78 L·m−2·h−1) and zinc (30.80 L·m−2·h−1) ions anti-scalant was higher than the untreated membrane flux (25.56 L·m−2·h−1), which decreased continuously.

Effect of surface properties of polysulfone support on the performance of thin film composite polyamide reverse osmosis membranes

ABSTRACTIn this work, influence of initial conditions and surface characteristics of porous support layer on structure and performance of a thin film composite (TFC) polyamide reverse osmosis (RO) membrane was investigated. The phase inversion method was used for casting of polysulfone (PSf) supports and interfacial polymerization was used for coating of polyamide layer over the substrates. The effect of PSf concentrations that varied between 16 wt % and 21 wt %, and kind of the solvent (DMF and NMP) used for preparation of initial casting solution were investigated on the properties of the final RO membranes. SEM imaging, surface porosity, mean pore radius, and pure water flux analysis were applied for characterization of the supports. The substrate of the membrane, which synthesized with 18 wt % of PSf showed the most porosity and the synthesized RO membrane had the lowest salt rejection. In case of the solvents, the membranes synthesized with DMF presented better separation performance that can be attributed to their lower thickness and sponge‐like structure. The best composition of support for TFC RO membranes reached 16 wt % PSf in DMF solvent. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44444.

Removal of substituted phenyl urea pesticides by reverse osmosis membranes: Laboratory scale study for field water application

Thin film composite polyamide reverse osmosis membrane prepared in laboratory was used for filtration of two phenyl urea pesticides (diuron and isoproturon) dissolved in deionized water, tap water and agriculture field water. Membrane performance in removing pesticides from water was evaluated and compared with commercial membrane data. Membrane fouling was less for diuron and the value was restricted within 11%. Membrane fouling and permeate flux decline depends on water type. For field water flux decline was maximum. The presence of mono- (Na+) and bi-valent (Ca2+) ions in feed water influences membrane performance. Isoproturon rejection for the membranes was always higher than diuron. Pesticide rejection from field water was more than 95%. The presence of humic acid in water has no significant effect on diuron and isoproturon rejection. Post filtration behavior of membranes reflects hydrophilicity change irrespective of water type. Depending upon the pesticide, membrane property influences permeate flux and water permeability.

Removal of Monoethanolamine from Wastewater by Composite Reverse Osmosis Membrane

Monoethanolamine (MEA) has been vastly used for the removal of carbon dioxide (CO2) in natural gas processing plant. However, during the absorption-desorption process and maintenance activities, a small amount of amine get carries over and discharged into the effluent wastewater stream. Due to its high Chemical Oxygen Demand (COD) and require large volume of water for dilution, therefore treatment of MEA contaminated wastewater is a major concern in most amine sweetening plants. In this research, MEA wastewater generated from PETRONAS Fertilizer Kedah Sdn. Bhd (PFK) was treated via AFC99 tubular thin film composite polyamide Reverse Osmosis (RO) membrane. The effect of operating parameter (transmembrane pressure (TMP), feed concentration and pH) towards permeate flux and MEA rejection were studied to obtain the optimum operating conditions. Experimental results showed that AFC99 membrane is able to reject MEA up to 98% when operated at TMP of 20 bars, feed concentration of 300 ppm and pH of 4. This work shows that the RO membrane was feasible and desirable to be used for removal of MEA contaminants from wastewater. Besides, the treated water fulfills the watering standards.

Elucidating the Rejection Mechanisms of PPCPs by Nanofiltration and Reverse Osmosis Membranes

In this study, the rejection mechanisms of six commonly detected pharmaceutical and personal care products (PPCPs) were systematically studied with three commercial thin film composite polyamide reverse osmosis (RO, XLE) and nanofiltration (NF, NF90, and NF270) membranes at pH 3–10. The amount of PPCP adsorption on membrane surfaces was also extracted and calculated so as to determine the contribution of adsorption mechanism on PPCP rejection using adsorption kinetics and adsorption isotherms. At low pHs, PPCP rejection was the highest for XLE followed by NF90 and NF270. As pH increased to 10, PPCP rejection increased significantly for NF90 and NF270, attributed to the enhanced electrostatic repulsion between the negatively charged membrane surface and ionized PPCPs, while being slightly increased for XLE due to the dominant mechanism of steric hindrance. The simplified charge concentration polarization model predicted well for most cases, which demonstrated the contribution of steric hindrance and electr...

Monitoring membrane biofouling via ultrasonic time-domain reflectometry enhanced by silica dosing

Detecting biofouling noninvasively in real-time has been a long-standing challenge in membrane processes. Ultrasonic Time Domain Reflectometry (UTDR) offers the potential to address this challenge when used in a ‘canary cell’ that samples a slip stream from the feed to the membrane process. However, adapting UTDR to detect biofouling is problematic owing to the small difference in acoustic properties between a biofouling layer and water or a membrane. In this study UTDR has been adapted to detect biofouling by periodic dosing of colloidal silica as an ‘acoustic enhancer’. This novel UTDR technique was applied to detect biofouling on flat sheet polyethersulfone ultrafiltration (UF) and thin film composite polyamide reverse osmosis (RO) membranes in a canary cell flow configuration. The UTDR response correlates with the transmembrane pressure and off-line measurements of the biofilm thickness via confocal laser scanning microscopy, the bacterial count, and extra-polymeric cellular substances (EPS). The acoustic enhancer was shown to have no effect on the viability of the bacteria. Hence, UTDR can be used for the noninvasive real-time detection of biofouling in high pressure membrane processes such as RO by periodic dosing of an enhancer such as colloidal silica in a canary cell.

Sorption of phenolic compounds on NF/RO membrane surfaces: Influence on membrane performance

Two commercial thin film composite polyamide reverse osmosis (BW-30) and nanofiltration (NF-90) membranes were studied for sorption of 2-nitrophenol and 2-chlorophenol. Adsorption kinetics and equilibrium on the surface of both membranes were studied. The rate of adsorption was adequately modeled by a linearized form of the pseudosecond-order kinetics in all cases. Adsorption isotherms obtained from equilibrium experiments were quite similar, except for the 2-nitrophenol/BW-30 system, which showed a higher maximum adsorption capacity. Experimental adsorption isotherms were compared with Freundlich and Langmuir models; the Langmuir model yields the best fit in all cases, suggesting the formation of a fouling monolayer onto the membrane surface. Organic deposition onto the membrane surface systematically increased hydrophobicity and diminished roughness. A strong graphical correlation was found between the relative flux decline and the organic concentration decrease in the feed. As expected, solute rejection was higher for the RO membrane (BW-30) than for the NF membrane (NF-90); the lowest rejection values were found for 2-nitrophenol. This was attributed to the increase of the solute concentration on the membrane surface due to organic sorption, which enhanced the driving force for diffusion through the membrane.

Using zwitterionic amino acid l-DOPA to modify the surface of thin film composite polyamide reverse osmosis membranes to increase their fouling resistance

Abstract This study focuses on the incorporation of redox functional amino acid 3-(3,4-dihydroxyphenyl)- l -alanine ( l -DOPA) onto commercial reverse osmosis (RO) membranes (SW 30 XLE) to create a zwitterionic surface that resists membrane fouling. The top layer of the membranes surfaces was modified by the deposition of l -DOPA from its alkaline solution. Streaming potential and contact angle measurements were conducted to characterise the membrane surface. Zeta potential data showed little or no change in the surface charge of 24-h-coated membrane relative to the original membrane. The contact angle measurements indicated that the hydrophilicity of the coated membranes was significantly improved. UV–visible spectroscopy confirmed the presence of poly DOPA film on the coated membranes. Whilst the salt rejection remained unchanged, a systematic increase in water flux was observed for the samples coated up to 12 h. Static BSA adhesion experiments revealed that l -DOPA coating has reduced the amount of BSA adsorbed to the surface. To investigate the dynamic fouling resistance of the membranes, a series of cross-flow filtration tests were carried out using bovine serum albumin (BSA) and alginic acid sodium salt solution as the feed. The modified membranes exhibited less flux decline than the original untreated membrane. Further, by water-only cleaning 98% water flux recovery ratio was achieved for the 24-h-modified membrane. The coated membranes also showed an improvement in their fouling resistance when testing with the solution containing dodecyltrimethyl ammonium bromide (DTAB), a positively charged surfactant model foulant.

Surface modification of a commercial thin film composite polyamide reverse osmosis membrane by carbodiimide-induced grafting with poly(ethylene glycol) derivatives

Based on the existing carboxylic acid groups on surface of used commercial thin film composite polyamide reverse osmosis membrane, two kinds of poly(ethylene glycol) derivatives with different chains were grafted by carbodiimide-induced method to improve the antifouling property. The membranes before and after modification were characterized by attenuated total reflectance Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and static contact angle measurement. Moreover, the water flux, NaCl rejection and fouling experiments were also conducted. The changes of chemical composition and morphology on membrane surfaces indicated the successful grafting of poly(ethylene glycol) derivatives. Compared to unmodified membrane, the modified membranes were more resistant to fouling in protein and cationic surfactant feeding solutions. The method in this study provided a new way for surface modification of commercial polyamide reverse osmosis membranes.

Effect of surface roughness on fouling of RO and NF membranes during filtration of a high organic surficial groundwater

Fouling characteristics of various thin film composite polyamide reverse osmosis (RO) and nanofiltration (NF) membranes were systematically investigated using a high organic surficial groundwater obtained from the City of Plantation, Florida. Prior to bench-scale fouling experiments, surface properties of the selected RO and NF membranes were carefully analysed in order to correlate the rate and extent of fouling to membrane surface characteristics, such as roughness, charge and hydrophobicity. More specifically, the surface roughness was characterized by atomic force microscopy, while the surface charge and hydrophobicity of the membranes were evaluated through zeta potential and contact angle measurements, respectively. The results indicated that membrane fouling became more severe with increasing surface roughness, as measured by the surface area difference, which accounts for both magnitude and frequency of surface peaks. Surface roughness was correlated to flux decline; however, surface charge was not. The limited range of hydrophobicity of the flat sheet studies prohibited conclusions regarding the correlation of flux decline and hydrophobicity.

Sodium cyanide separation and parameter estimation for reverse osmosis thin film composite polyamide membrane

Sodium cyanide separation data are obtained from synthetic binary aqueous solutions using a commercial thin film composite polyamide reverse osmosis membrane. The separation data are analyzed with the help of two membrane transport models, i.e., combined film theory–solution–diffusion (CFSD) model and combined film theory–Spiegler–Kedem (CFSK) model. The membrane transport parameters and mass transfer coefficients are estimated, simultaneously, from both the models, using a graphical method in case of CFSD model, and a nonlinear parameter estimation method for CFSK model. The new phenomena that there exists a maximum in rejection when it is plotted against product flux, which was observed previously using the same membrane for the phenol–water system, is observed in the present case too. This behavior is explained using the above said models. Though both the models predict the membrane performance reasonably, the values of CFSK model are more accurate and the mass transfer coefficients estimated from the CFSK model are comparable with the literature values.

Thin Film Composite Polyamide Membrane Parameters Estimation for Phenol-Water System by Reverse Osmosis

ABSTRACT A commercial thin film composite polyamide reverse osmosis membrane is used to separate an aqueous phenol-water binary system. The separation data are analyzed using a combined film theory-solution-diffusion (CFSD) model and a combined film theory-Spiegler-Kedem (CFSK) model. In the present investigation a new phenomenon is observed: there exists a maximum in the rejection when it is plotted against the product flux through the membrane. This behavior is explained for both models. An equation for Jv,min, which is the value of the product flux Jv at which the rejection reaches a maximum, is derived from both models. Although the parameters for both models are consistent over the range of operating conditions, the CFSK model is more accurate for the phenol-water system.