Hollow Fiber Reverse Osmosis Research Articles

The Optimized Preparation Conditions of Cellulose Triacetate Hollow Fiber Reverse Osmosis Membrane with Response Surface Methodology.

Reverse osmosis (RO) membrane materials play a key role in determining energy consumption. Currently, CTA is regarded as having one of the highest degrees of chlorine resistance among materials in the RO process. The hollow fiber membrane has the advantages of a large membrane surface area and a preparation process without any redundant processes. Herein, response surface methodology with Box-Behnken Design (BBD) was applied for optimizing the preparation conditions of the cellulose triacetate (CTA) hollow fiber RO membrane. There were four preparation parameters, including solid content, spinning temperature, post-treatment temperature, and post-treatment time, which could affect the permeability of the membrane significantly. In this study, the interaction between preparation parameters and permeability (permeate flux and salt rejection) was evaluated by regression equations. Regression equations can be applied to obtain the optimized preparation parameters of hollow fiber RO membranes and reasonably predict and optimize the permeability of the RO membranes. Finally, the optimized preparation conditions were solid content (44%), spinning temperature (167 °C), post-treatment temperature (79 °C), and post-treatment time (23 min), leading to a permeability of 12.029 (L·m-2·h-1) and salt rejection of 90.132%. This study of reinforced that CTA hollow fiber membrane may promote the transformation of the RO membrane industry.

Tannic acid reinforced interfacial polymerization fabrication of internally pressurized thin-film composite hollow fiber reverse osmosis membranes with high performance

Internally pressurized thin-film composite (TFC) hollow fiber (HF) reverse osmosis (RO) membranes have the merits of easy scaling-up and no flow dead zone, etc. In this work, we used tannic acid (TA) as a reinforced additive in m-phenylenediamine (MPD) aqueous solution to assist the interfacial polymerization process to construct a polyamide separation skin layer with high separation performance on the inner surface of polysulfone hollow fiber substrate. Due to many phenolic hydroxyl groups on tannic acid molecules, they could form hydrogen bonds with MPD molecules and thus greatly hinders MPD diffusion towards the interface, and greatly helps to manipulate the interfacial polymerization process. In this way, we obtained a TA-reinforced TFC HF RO membrane having super hydrophilicity (contact angle of merely 26.4°), much thinner skin layer (about 100 nm in thickness), as well a much smoother surface (roughness of about 35 nm) under the optimized ultra-low concentration (100 mg L−1) for tannic acid in the MPD solution. The prepared TA-reinforced membrane achieves a water permeance of 20.4 L m−2 h−1 MPa−1, which is more than 50 % higher than that of the TA-free membrane, and a NaCl rejection of about 98 % with 2000 mg L−1 NaCl solution as feed. The TA-reinforced membrane has excellent fouling resistance, chlorine resistance, as well as long-term operation stability, thus showing a broad application prospect in brackish water desalination and tap water treatment.

Defect free hollow fiber reverse osmosis membranes by combining layer-by-layer and interfacial polymerization

Hollow fibre RO membranes would be desired for many applications, but are notoriously difficult to fabricate. Here we demonstrate that combining layer-by-layer and interfacial polymerization (IP) allows straightforeward production of defect-free hollow fiber RO membranes. A polyelectrolyte multilayer (PEM) is used to fill the pores of a support membrane, to provide a controlled and smooth surface that can nevertheless act as an IP monomer reservoir. This approach is first demonstrated on a model surface, with IP layers being successfully applied on both poly(diallyldimethylammonium chloride) (PDADMAC)/poly(4-styrene sulfonate) (PSS) and poly(ethyleneimine) (PEI)/PSS PEMs. On plain hollow fiber support membranes, IP coating was found to have a success rate as low as 40%. However, by application of a PEM interlayer the success rate increases to 72% for PDADMAC/PSS and 90% for PEI/PSS. Also the separation performance of the successfully prepared IP membranes was significantly better when a PEM interlayer was applied, with higher NaCl retentions (from 94% to 97%), and better removal of organic micro-pollutants (from 96% to 98%), with just a small decrease in permeability (from 0.9 L/m2hbar to 0.7 L/m2hbar). Combining layer-by-layer and IP approaches can thus lead to the fabrication of defect free RO membranes with improved separation performance.

Analysis of reverse osmosis process in hollow fiber module with and without secondary permeate outlet

In conventional hollow fiber reverse osmosis (HF RO) modules, the lumen side has one end sealed in an epoxy resin, and the other end opened (1way RO) for permeate collection. This study investigates the effect of having both ends open (2way RO) in the HF modules. The RO experiments were conducted using de-ionized (DI) water in two ends opened HF module. The 2way RO experiments produced 10 % more permeate flow rate than 1way RO at the same average shell side pressure. This can be attributed to the building of pressure at the closed end lumen side which reached up to 1.7 bar at 1.09 L/min permeate flow rate. Further, the axial flow HF RO model was improvised to simulate the 2way RO operations. The Hagen-Poiseuille and Ergun equations were also modified to predict the pressure drop with better accuracy. Reduction in the HF inner diameter and increase in the friction factor at the lumen wall were considered to modify the Hagen-Poiseuille equation. The models based on the above factors deviated by 2 and 10 %, respectively in predicting the closed-end pressure while the generic form of Hagen-Poiseuille deviated by 67 %.

Design of robust twisted fiber bundle-reinforced cellulose triacetate hollow fiber reverse osmosis membrane with thin separation layer for seawater desalination

In general, the twisted fiber bundle with good fiber cohesion could be regarded as a new kind of supporting layer. Herein, a new type of poly(p-phenyleneterephthalamide) (PPTA) twisted fiber bundle-reinforced (FR) cellulose triacetate (CTA) hollow fiber reverse osmosis (RO) membrane was fabricated using a twin-screw spinning machine by the melt spinning method. Moreover, the morphologies, surface analysis and permeability of FR CTA hollow fiber RO membrane were investigated by scanning electron microscopy, confocal scanning microscopy and filtration performance. The CTA separation layer exhibited the favorable interfacial bonding state between CTA separation layer and PPTA twisted fiber bundle supporting layer. Especially, the advantages of FR CTA hollow fiber RO membrane could overcome the negative effect of permeability flux loss, due to the easy vulnerable to the compaction of CTA membrane when operating at moderate or high pressure process. Besides, the tensile strength increased from 9.2 to 96.8 MPa because of the higher interfacial stress transfer coefficient, which was achieved due to the interfacial bonding of FR CTA hollow fiber RO membrane. Besides, based on the filtration performance and long-term running test, FR CTA hollow fiber RO membrane with thin separation layer not only produced higher and more stable permeability flux while their salt rejection were basically the same, but also came into being smaller amount of deformation without defects than pristine CTA hollow fiber RO membranes after 200 h operation.

Development of hollow fiber reverse osmosis membranes and modules

Perspectives of the hollow fiber reverse osmosis membranes and modules development have been analysed. Comparative analysis with other types of membrane modules and tentative calculation of module’s design considering the hydrodynamic parameters of separation has been made.

Optimum operating condition of a hollow fiber reverse osmosis desalination system

A numerical simulation for an optimal operating condition of a hollow fiber reverse osmosis desalination system has been carried out by utilizing the membrane transport model based on the porous media theory. The validity of the present numerical simulation has been examined by comparing permeate salinity and flow rate obtained by the present method with the available experimental data. The three-dimensional numerical computations have revealed individual velocity and concentration distributions for brine, permeate and membrane phases in a hollow fiber reverse osmosis module containing a feeder core tube. Moreover, it has been found that optimal feed brine pressure exists in order to receive the maximum permeate flow rate under the same pumping power. The present numerical methods is useful to design a hollow fiber desalination module and find the operating conditions of a desalination system.

Numerical analysis of hollow fiber membranes for desalination

Water desalination by reverse osmosis hollow fiber membrane has been widely used to produce fresh water. This work numerically characterizes flux performance of the membrane, concentration polarization and potential fouling sites in the reverse osmosis desalination module containing hollow fiber membranes arranged in an inline and staggered configuration. Steady k-ω SST turbulence model is utilized to study membrane performance. An accurate membrane flux model, the solution-diffusion model, is employed. Hollow fiber membrane surface is treated as a functional boundary where the rate of water permeation is coupled with local concentration along the membrane surface. The rate of water permeation increases and concentration polarization decreases as the feed flow rate is increased. Hollow fiber membranes in the staggered geometry perform better than those in the inline geometry. It is proven by the present study that desalination modules containing hollow fiber membranes should be designed and optimized by careful consideration of their configurations. It is demonstrated here that flows in the hollow fiber bank becomes strongly time dependent at high flow rates and that transient effects could profoundly influence hollow fiber membrane flux performance and characterization of concentration polarization.

Regeneration efficacy of sodium chloride and sucrose binary draw solutions using hollow fine fibre reverse osmosis membrane

In this study, the regeneration performance of sodium chloride and sucrose draw solutions using a forward osmosis (FO) membrane was experimentally investigated in a FO–RO system. This efficiency was examined in terms of water flux (Jw), water recovery percentage (R%) and specific energy consumption (SEC) using a commercial RO membrane. Two sodium chloride feed solution concentrations of 9.3 g/l (osmotic pressure (OP) = 7.31 bars) and 17.9 g/l (osmotic pressure (OP) = 14.05 bars), as well as two sucrose feed solution concentrations of 150 g/l (OP = 11.21 bars) and 200 g/l (OP = 15.13 bars) were tested separately. At each experiment, feed solution is pumped to the RO membrane at different applied feed pressure values, while the flow rate and temperature of the solutions were kept constant throughout the experiments. The experimental results indicated that: water flux and water recovery percentage for sodium chloride and sucrose feed solutions in general are increased with rise in the RO feed pressure applied. Also, the SEC for sodium chloride and sucrose feed solutions decreased as the RO feed applied pressure was raised. The findings exhibit that the hollow fine fibre HR3155P RO membrane is more reliable for the regeneration of sodium chloride draw solution than sucrose draw solution. Moreover, the RO technique is not reliable to use in the regeneration of sucrose draw solution in a FO–RO system.

A Porous Media Approach for Hollow Fiber Transport Phenomena

A porous media approach based on the volume averaging theory has been proposed to investigate membrane transport processes associated with hollow fiber dialyzers and radial flow hollow fiber reverse osmosis module. A general set of macroscopic governing equations has been derived for the three individual phases, namely, the lumen side flow phase, shell side flow phase and membrane phase. Analytical and numerical solutions based on the present approach are found to agree well with available experimental data. Three-dimensional numerical models can be used for possible optimization of the hollow fiber membrane systems.

Development of Hollow Fiber Reverse Osmosis Membrane for Seawater Desalination and Actual Operating Plants

Development of Hollow Fiber Reverse Osmosis Membrane for Seawater Desalination and Actual Operating Plants

An application of the Sano–Nakayama membrane transport model in hollow fiber reverse osmosis desalination systems

The Sano–Nakayama membrane transport model recently proposed for the analysis of a countercurrent dialyzer system has been extended to describe the concentration polarization phenomena associated with hollow fiber reverse osmosis desalination systems. A set of the governing equations, namely, the continuity, momentum and concentration equations, is derived for three distinctive phases, namely, brine, permeate and membrane phases, exploiting a volume averaging approach. These equations based on the Sano–Nakayama model are coupled and subsequently reduced to three distinctive first-order ordinary equations in terms of the average velocity, pressure and salt concentration of the brine phase. These equations along with an algebraic equation for the permeate flow rate per unit volume can readily be solved to estimate permeate salinity, permeate flow rate and pressure drop in a hollow fiber reverse osmosis desalination system. Available experimental data and numerical results based on finite difference methods are found to agree well with the present analytical estimates based on the Sano–Nakayama model.

Effect of Rheological Behaviour of Cellulose Acetate Spinning Solutions on Performance of Reverse Osmosis Hollow Fiber Membranes

Kajian ini bertujuan untuk menyelidik kesan reologi semperitan terhadap membran gentian geronggang osmosis balikan. Ini dilakukan dengan penilaian reologi larutan semperitan selulosa asetat menggunakan sebuah reometer putaran dan sel optik ricih. Sifat hukum kuasa, daya normal dan profil aliran yang terjana memberi penjelasan mengenai fasa balikan dan orientasi molekul. Keputusan reologi ini kemudiannya dihubungkaitkan dengan prestasi membran gentian geronggang osmosis balikan dari segi kadar buangan dan kadar fluks. Keputusan kajian menunjukkan bahawa kadar buangan dan kadar fluks meningkat apabila kadar semperitan larutan meningkat dan ini mungkin disebabkan oleh orientasi molekul. Kata kunci: reologi semperitan; osmosis balikan; gentian geronggang; orientasi molekul Rheological assessment of cellulose acetate spinning solution using a rotational rheometer and an optical shear cell in carried out so as to study the cause and effect relationship between membrane preparation, polymer morphology and membrane performance. The power law behaviour, normal force and flow profiles generated provided clues regarding phase inversion and molecular orientation. These rheological results are then related to the separation performance of cellulose acetate reverse osmosis (RO) hollow fibers membranes; both the rejection rate and the flux rate increased with increasing dope extrusion arate, possibly due to the molecular orientation. Key words: spinning rheology; reverse osmosis; hollow fiber; molecular orientation

I111 多孔質体理論に基づく中空糸型逆浸透膜モジュールの数学モデル(OS-16: 多孔質体内の熱物質輸送と応用(1))

I111 多孔質体理論に基づく中空糸型逆浸透膜モジュールの数学モデル(OS-16: 多孔質体内の熱物質輸送と応用(1))

Pollution free techniques of membrane desalination

The polyethersulfone reverse osmosis hollow fiber module is used to desalination of brackish water. The driving force of separation is pressure difference; the non conventional source of energy, solar energy is used to create the driving force inside the hollow fiber module. To increases the life of the membranes, the brackish water first is passed to micron cartage filter and then to reverse osmosis modules of the membranes. It was found that increases in transmembrane pressure permeate flux increased and concentrated flux decreased, after few hours, it worked reversely, due to blockage of the pores of the membrane. Membrane technology is an energy saving process, Region which is come under the saline belt and problem of an electrical energy, desalination using solar membrane technology is an ecofriendly technique of separation.

The performance improvement of hollow fiber composite reverse osmosis m embranes by post-treatments

While the technology of spiral-wound reverse osmosis membrane tends to be more and more mature, the reports of hollow fiber reverse osmosis membranes are still relatively sparse. In this report, the hollow fiber composite reverse osmosis membranes were prepared by the interfacial polymerization of m-phenylenediamine (mPDA) and trimesoyl chloride (TMC) using polysulfone ultrafiltration membrane as the support. Post-treatments including with NaOCl solution and polyvinly alcohol (PVA) solution were employed to improve the performance of the membranes. The chemical composition and surface structure of the membranes obtained at the different post-treatment conditions were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and atom force microscopy (AFM). The results showed that the salt rejection of the membranes increases dramatically but the permeate flux decreases slightly after NaOCl and PVA solution treatment. The m embrane treated with 500 ppm of NaOCl solution and 20 ppm of PVA solution by turn exhibited the salt rejection of 96.3% and pure water flux of 10.9 l•m-2•h-1) at 500 ppm NaCl solution, 100 psi and 25°C.

Analysis of hollow fiber reverse osmosis membrane module of axial flow type

AbstractSeveral analyses of hollow fiber reverse osmosis (RO) modules in which permeate water flows from the outer to the inner side of the membrane have been attempted over the past 20 years. In our previous work, an FCP (Friction Concentration Polarization) model showed good agreement with a wide range of actual performance data of a hollow fiber RO membrane module of radial flow type. In this work, this analytical model was applied to axial flow type hollow fiber modules. The performance of the axial flow type module with high packing density of hollow fibers was analyzed, taking into consideration the axial concentration profile in the module. It was confirmed that this model showed good agreement with experimental data for an axial flow type RO membrane module. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Formation and structural evolution of biphenyl polyamide thin film on hollow fiber membrane during interfacial polymerization

A novel reverse osmosis hollow fiber membrane was prepared by interfacial polymerization from 3,3′,5,5′-biphenyl tetraacyl chloride and m-phenylenediamine on a polysulfone hollow fiber membrane. The structural evolution of biphenyl polyamide thin film during interfacial polymerization was monitored by attenuated total reflectance infrared, X-ray photoelectron spectroscopy and atom force microscopy. The relationship between the structure and separation properties of the membranes was investigated. Results show that the biphenyl polyamide thin film had a three-layer structure: a loose initial layer with a low cross-linked structure, a dense middle layer with a high cross-linked structure and a loose surface layer with a low cross-linked structure. The dense middle layer had an intrinsic cross-linked structure with over 86.0% amide bonds (–CONH–) and below 14.0% carboxylic groups (–COOH), mainly responsible for separation. A growth model of the biphenyl polyamide thin film was proposed to describe the structural evolution process during interfacial polymerization.

Reverse osmosis modeling with the orthogonal collocation on finite element method

A mathematical model was used to predict the performance of hollow fiber reverse osmosis membrane. The model is based on the solution-diffusion mass transfer model and takes into account the effect of the flow pattern of the permeate in the membrane. According to the flow direction inside the membrane, two types of flow can be distinguished: the co-current and counter-current flow pattern. Several studies underlined the effectiveness of the counter-current flow pattern [1]. However, no study was carried out to demonstrate this assumption. This work aims to answer clearly the question of the choice of the flow type. The parameters used in this work are the overall recovery, the average concentration of the obtained product and the final concentration of the feed rate in the closed loop processes. The resolution of the mathematical model developed for the counter-current flow pattern is subjected to the split boundary value problem. To solve this problem, a robust and efficient procedure based on orthogonal collocation on finite element method was used. Experimental data were used to verify the proposed mathematical model and accomplish the comparative study between the two flow types. The results obtained show clearly the better efficiency of the counter-current flow pattern especially in the concentrating process.

Effect of chlorine and acid injection on hollow fiber RO for SWRO

Bio-fouling results in deterioration of permeate quality and flux in reverse osmosis (RO) process. Cellulose triacetate hollow fiber membrane used for RO in SWRO has anti-chlorine property that makes technical sense compared to polyamide spiral-wound RO for overcoming bio-fouling. Mode of chlorine injection is the controlling factor of sterilization in SWRO system. This work evaluated the effects of five different modes of chlorine injecting system as well as HCl injection on the performance of HF RO system. In addition, effects of HCl and anti-scalants on anti-scale performance of HF RO system were also investigated, respectively. A brief list of chemical costs under different abovementioned operating conditions was covered in a cost analysis. The results indicated that the injecting mode that employed continuous chlorine with a relatively low concentration of 0.3–0.4 mg/L at pH 5.8–6.2 was preferable in the aspects of total bacterial count (TBC) removal, permeate flow rate, differential pressure, permeability ( P p ), performance factor (η) and chemical costs. HCl injection could improve the sterilization and prevent scaling on the membrane surface efficiently. The expense of anti-scalant (MDC220) was higher than HCl.