B.S. Ooi

Preparation and characterization of co-polyamide thin film composite membrane from piperazine and 3,5-diaminobenzoic acid

Thin film composite (TFC) co-polyamide membranes were prepared by interfacially polymerizing secondary amide and highly hydrophilic aromatic primary amide (3, 5-diaminobenzoic acid, BA). The salt rejection and flux of these membranes were measured at various feed pressures. Incorporation of the BA cause an increase in pure water permeability constant (A) and solute transport parameter (DAMkδ). The rejection ability of NaCI and Na2SO4 dropped at a higher ratio of BA and piperazine (PIP). Membrane with a higher content of BA produced a loose and defected skin layer. The reaction among the BA, PIP and trimesoyl chloride was further confirmed using Fourier transform infrared.

Characterization Methods of Thin Film Composite Nanofiltration Membranes

This review provides a comprehensive survey on the characterization methods used to study the properties and performances of thin film composite nanofiltration (NF) membranes in water separation processes. In general, the intrinsic properties of NF membranes are characterized with respect to chemical properties and physical properties using various analytical instruments. For instance, FTIR spectroscope, zeta potential analyzer, XPS, XRD, and NMR spectroscope are some of the widely used instruments to evaluate the membrane chemical properties while SEM, FESEM, TEM, AFM, contact angle goniometer, and positron annihilation spectroscopy are those that have been commonly employed to study the membrane structural properties. With respect to permeability and selectivity, NF membranes are generally characterized through filtration experiments using appropriate feed properties under specific testing conditions. Furthermore, this review also covers the characterization techniques used to study the resistance of NF membranes against chlorination, solvent, thermal, and fouling. These resistance tests can be individually conducted, depending on the practical applications of the membranes. Overall, this review attempts to give readers insights into the experimental planning and subsequent interpretation of the above-mentioned characterization techniques. It is also expected to help new researchers in the field of NF to quickly learn various NF characterization methods.

Membrane Antifouling Methods and Alternatives: Ultrasound Approach

Membranes are widely used in separation processes. Various industries use membranes as part of their production processes. However, one of the main problems in membrane separation processes is fouling. The fouling mechanism is briefly reviewed in this paper. Fouling can be controlled before it happens. Alternatively, membranes can be cleaned after fouling occurs. Several control methods such as feed pre-treatment, material selection and membrane surface modification can be applied. Cleaning methods can be categorized into several techniques: chemical, mechanical, hydrodynamic, electrical and ultrasonic cleaning methods. This paper focuses on the ultrasonic cleaning method, which is an additional force that aids filtration. The mechanism of the ultrasonic wave that reduces fouling by cavitation and acoustic streaming is reviewed. The advantages and disadvantages of ultrasound irradiation as a cleaning method are also discussed in this paper. The apparatus design and factors that influence the effectiveness of ultrasound treatments, including frequency, power intensity, feed properties, membrane properties, cross-flow velocity, temperature and pressure, are analysed. Recently, ultrasound irradiation combined with other techniques has gained increasing attention. It has been discovered that a combination of other cleaning methods with ultrasound irradiation led to the removal of the fouling layers from the membrane surface.

Preparation and characterisation of PES-ZnO mixed matrix membranes for humic acid removal

AbstractZinc oxide nanoparticles (ZnO-NPs) were incorporated into polyethersulfone (PES) matrix to prepare mixed matrix membranes. The separation performance of mixed matrix membranes with respect to humic acid (HA) removal was significantly improved through the addition of ZnO-NPs. The membranes were synthesised by dispersing various amounts of hydrophilic ZnO-NPs (0–3.75 wt.%) into a dope solution containing PES, polyvinylpyrrolidone (PVP) and dimethylacetamide in the appropriate proportions. SEM and AFM were employed to investigate the dispersion of the ZnO-NPs within the polymer matrix and characterise the surface properties of the particles. The pure water flux, HA flux and rejection rate, and the fouling resistance were investigated to evaluate the membrane performance. The characterisation results indicated that all of the PES/ZnO membranes possessed a smaller pore size than that of the pristine PES membrane. The HA rejection rates were observed to increase with the amount of added ZnO. In particul...

Effect of Hydrophilization Additive and Reaction Time on Separation Properties of Polyamide Nanofiltration Membrane

Abstract Thin film composite (TFC) nanofiltration membrane can be optimized in terms of flux and rejection by controlling the hydrophilization additive [3,5‐diaminobenzoic acid (BA)] content and reaction time in the interfacial polymerization (IP) process. By using the Donnan steric pore flow model (DSPFM), uncharged solute was passed through the membrane to determine the pore size (r p) as well as the effective thickness/porosity (Δx/A k ). The coating condition was related to the performance of NaCl permeation using the fitted r p and Δx/A k data. It was found that the pore size was reduced as reaction time was increased. Cross‐linking reduced the porosity of polypiperazinamide membrane but it was noticed that by adding a small amount of BA, the porosity was increased at longer reaction time. A small amount of BA could increase both the flux and rejection especially at higher pressure.

Characteristic and performance of polyvinylidene fluoride membranes blended with different additives in direct contact membrane distillation

AbstractMembrane distillation (MD) is a thermal-driven membrane separation process which recently garners interest from academic and industry due to its low energy requirements and the ability to integrate with renewable energy. In this work, two different additives, i.e. polyethersulfone (PES) and ethylene glycol (EG), were added into dope solutions consisting of polyvinylidene fluoride (PVDF) and 1-methyl-2-pyrrolidone (NMP) to prepare membranes for MD applications. The membranes were characterized with respect to thickness, pore size, porosity, and water contact angle using scanning electron microscope and water contact goniometer. Compared with the membranes made from pure PVDF and PVDF–EG system, it is found that PVDF–EG–PES membrane displayed improved characteristics i.e. having optimum porosity, large pore size, and thin membrane thickness coupled with finger-like structure extended from both inner and outer layers of the membrane. In addition to this, the permeate flux of PVDF–EG–PES membrane duri...

Investigation on membrane morphological and chemical properties changes at different reaction times and its effect on dye removal

Abstract The thin film composite (TFC) membranes were prepared and examined under different reaction times between piperazine and trimesoyl chloride. The physical and chemical properties of the membranes produced were investigated and related to their performance in terms of flux and rejection of methylene blue. Morphological studies were performed with Atomic Force Microscope (AFM) to determine the membrane’s surface roughness, whereas chemical properties (bonding ratio of hydroxyl and carbonyl) of the membranes were evaluated based on Fourier Transform Infrared (FTIR). It was found that the interfacial polymerization (IP) process was almost instantaneous in which the dense film layer was developed within 10 s of reaction time. Longer reaction time (10–30 s) reduced the flux through film growth, whereas 50–70 s further reduced the flux due to polymer crosslinking. The AFM images showed that the membrane roughness increased steadily with the reaction time and formed supernodules on membrane surface. The f...

Influence of ethanol as bore fluid component on the morphological structure and performance of PES hollow fiber membrane for oil in water separation

The relationships among varying bore fluid compositions containing ethanol/water were studied. The ethanol composition was varied in the ratio of 0%, 25%, 50%, 75% and 100%. The membrane dope solutions were prepared from 17.25 wt% polyethersulfone (PES), 0.75 wt% polyethylene glycol (PEG), 3 wt% silicon dioxide sol and 78.25 wt% of 1-methyl-2-pyrrolidone (NMP) via dry-jet spinning process. The membranes’ morphology as a result of varying ethanol ratio in the bore fluid composition was characterized and their effects on crude oil/water emulsion separation were evaluated. Results show that the membrane pore size and porosity decreased with increasing ethanol content in the bore fluid mixture, whereas the inner wall thickness of fibers increased. Furthermore, an increase in ethanol concentration also resulted in a slight increase in water contact angle. The use of 100/0 of ethanol/water resulted in UF membranes with the lowest performance. On the other hand, bore fluid mixture containing 25/75 ethanol/water produced membrane with the best performance for crude oil/water separation. Overall, the use of bore fluid mixture containing 25/75 ethanol/water mixture was found to be a powerful way to tune the morphological properties and performance of HF membrane.

Optimization of polyvinylidene fluoride (PVDF) membrane fabrication for protein binding using statistical experimental design

ABSTRACT Statistical experimental design was employed to optimize the preparation conditions of polyvinylidenefluoride (PVDF) membranes. Three variables considered were polymer concentration, dissolving temperature, and casting thickness, whereby the response variable was membrane-protein binding. The optimum preparation for the PVDF membrane was a polymer concentration of 16.55 wt%, a dissolving temperature of 27.5°C, and a casting thickness of 450 µm. The statistical model exhibits a deviation between the predicted and actual responses of less than 5%. Further characterization of the formed PVDF membrane showed that the morphology of the membrane was in line with the membrane-protein binding performance.

Manipulating cluster size of polyanion-stabilized Fe3O4 magnetic nanoparticle clusters via electrostatic-mediated assembly for tunable magnetophoresis behavior

We report in this article an approach for manipulating the size of magnetic nanoparticle clusters (MNCs) via electrostatic-mediated assembly technique using an electrolyte as a clustering agent. The clusters were surface-tethered with poly(sodium 4-styrenesulfonate) (PSS) through electrostatic compensation to enhance their colloidal stability. Dynamic light scattering was employed to trace the evolution of cluster size. Simultaneously, electrophoretic mobility and Fourier transform infrared spectroscopy analyses were conducted to investigate the possible schemes involved in both cluster formation and PSS grafting. Results showed that the average hydrodynamic cluster size of the PSS/MNCs and their corresponding size distributions were successfully shifted by means of manipulating the suspension pH, the ionic nature of the electrolyte, and the electrolyte concentration. More specifically, the electrokinetic behavior of the particles upon interaction with the electrolyte plays a profound role in the formation of the PSS/MNCs. Nonetheless, the solubility of the polymer in electrolyte solution and the purification of the particles from residual ions should not be omitted in determining the effectiveness of this clustering approach. The PSS adlayer makes the resultant entities highly water-dispersible and provides electrosteric stabilization to shield the PSS/MNCs from aggregation. In this study, the experimental observations were analyzed and discussed on the basis of existing fundamental colloidal theories. The strategy of cluster size manipulation proposed here is simple and convenient to implement. Furthermore, manipulating the size of the MNCs also facilitates the tuning of magnetophoresis kinetics on exposure to low magnetic field gradient, which makes this nano-entity useful for engineering applications, specifically in separation processes.Graphical Abstract