Preparation and characterizations of charged poly(vinyl butyral) hollow fiber ultrafiltration membranes with perfluorosulfonic acid as additive

A Comprehensive Review of Hollow-Fiber Membrane Fabrication Methods across Biomedical, Biotechnological, and Environmental Domains

This work presents methods of obtaining polymeric hollow-fiber membranes produced via the dry-wet phase inversion method that were published in renowned specialized membrane publications in the years 2010-2020. Obtaining hollow-fiber membranes, unlike flat membranes, requires the use of a special installation for their production, the most important component of which is the hollow fiber forming spinneret. This method is most often used in obtaining membranes made of polysulfone, polyethersulfone, polyurethane, cellulose acetate, and its derivatives. Many factors affect the properties of the membranes obtained. By changing the parameters of the spinning process, we change the thickness of the membranes' walls and the diameter of the hollow fibers, which causes changes in the membranes' structure and, as a consequence, changes in their transport/separation parameters. The type of bore fluid affects the porosity of the inner epidermal layer or causes its atrophy. Porogenic compounds such as polyvinylpyrrolidones and polyethylene glycols and other substances that additionally increase the membrane porosity are often added to the polymer solution. Another example is a blend of two- or multi-component membranes and dual-layer membranes that are obtained using a three-nozzle spinneret. In dual-layer membranes, one layer is the membrane scaffolding, and the other is the separation layer. Also, the temperature during the process, the humidity, and the composition of the solution in the coagulating bath have impact on the parameters of the membranes obtained.

Effect of MAX Phase Ti3ALC2 on the Ultrafiltration Membrane Properties and Performance

Membrane fouling remains a major obstacle to ultrafiltration. Due to their effectiveness and minimal energy demand, membranes have been extensively employed in water treatment. To improve the antifouling property of the PVDF membrane, a composite ultrafiltration membrane was created employing the in-situ embedment approach throughout the phase inversion process and utilizing a new 2D material, MAX phase Ti₃ALC₂. The membranes were described using FTIR (Fourier transform infrared spectroscopy), EDS (energy dispersive spectroscopy), CA (water contact angle), and porosity measurements. Additionally, atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and energy dispersive spectroscopy (EDS) were employed. Standard flux and rejection tests were applied to study the produced membranes' performance. Adding Ti₃ALC₂ reduced composite membranes' surface roughness and hydrophobicity compared to the pristine membrane. Porosity and membrane pore size increased with the addition up to 0.3% w/v, which decreased as the additive percentage increased. The mixed matric membrane with 0.7% w/v of Ti₃ALC₂ (M7) had the lowest CA. The alteration in the membranes' properties reflected well on their performance. The membrane with the highest porosity (0.1% w/v of Ti₃ALC₂, M1) achieved the highest pure water and protein solution fluxes of 182.5 and 148.7. The most hydrophilic membrane (M7) recorded the highest protein rejection and flux recovery ratio of 90.6, which was much higher than that of the pristine membrane, 26.2. MAX phase Ti₃ALC₂ is a potential material for antifouling membrane modification because of its protein permeability, improved water permeability, and outstanding antifouling characteristics.

Optimization of a polyvinyl butyral synthesis process based on response surface methodology and artificial neural network

High quality polyvinyl butyral (PVB) can be used as the intermediate film of automobile and building glass and the packaging film of photovoltaic cells. Therefore, it is necessary to optimize its synthesis process to obtain suitable products with a high acetalization degree (AD) and small particle size (d _p). In this work, a deep eutectic solvent (DES) was selected as the catalyst, and response surface methodology (RSM) and artificial neural network (ANN) were utilized to optimize the synthesis process of PVB. The concentration of polyvinyl alcohol (A), the dosage of DES (B) and n-butanal (C), and the aging temperature (D) were selected as process variables, and the comprehensive score (AD, d _p and material and energy consumption) was introduced as the response. The results showed that single-factors B, C, D, and the interactions AB, BC and CD had significant effects on the comprehensive score, and the qualified PVB products (AD > 81%, d _p = 3-3.5 μm) were obtained under the optimal conditions obtained by RSM and ANN models. ANN is a better and more precise optimization tool than RSM. Also, DES played a dual role in catalysis and dispersion in the synthesis of PVB and showed good reusability, so it has great application potential in PVB industrial production.

Fabrication of a Novel Antifouling Polysulfone Membrane with in Situ Embedment of Mxene Nanosheets

Membrane fouling is still a critical issue for the application of ultrafiltration, which has been widely used in water treatment due to its efficiency and simplicity. In order to improve the antifouling property, a new 2D material MXene was used to fabricate composite ultrafiltration membrane with the approach of in situ embedment during the phase inversion process in this study. Scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), water contact angle, bovine serum albumin rejection and porosity measurements were utilized to characterize the prepared membranes. Due to the hydrophilicity of the MXene, the composite membranes obtained higher hydrophilicity, confirmed by the decreased water contact angle. All the modified membranes had a high bovine serum albumin rejection above 90% while that of the pristine polysulfone membrane was 77.48%. The flux recovery ratio and the reversible fouling ratio of the membranes were also improved along with the increasing content of the MXene. Furthermore, the highest flux recovery ratio could also reach 76.1%. These indicated the good antifouling properties of MXene composite membranes. The enhanced water permeability and protein rejection and excellent antifouling properties make MXene a promising material for antifouling membrane modification.

Breakage and regrowth of flocs formed by sweep coagulation using additional coagulant of poly aluminium chloride and non-ionic polyacrylamide

The breakage and regrowth of flocs formed by sweep flocculation were investigated on different flocculation mechanisms using additional dosage coagulant of poly aluminium chloride (PACl) and non-ionic polyacrylamide (PAM) to explore the reversibility after floc breakage. The optimal dosage of PACl was 0.15 mM (as alum), and zeta potential exceeding 1 mV meant that sweep flocculation was dominant in the pre-flocculated process. Re-coagulation efficiency increased with additional coagulants dosing, and sedimentation rates of flocs re-formed by small additional dosage of non-ionic PAM are faster than that of flocs re-formed by additional PACl. For additional inorganic coagulant (PACl) during regrowth processes, few negatively charged particles that existed in water sample restricted the effect of charge neutralization. An amorphous aluminum hydroxide precipitation could re-activate the weaker points on the broken floc surface, but regrown flocs have loose structure indicating worse settleability. For additional non-ionic PAM dosing, lower dosage showed large values of fractal dimension and average size, probably due to that unfolded curly molecular chain and exposed amide groups of non-ionic PAM which provide superb conditions for amide group interacting with particles. The use of non-ionic PAM in flocculation has advantage of being more effective than the cationic PACl, probably because it may avoid the re-stabilization of broken flocs by polymer adsorption driven by electrostatic attraction. Hence, appropriate dosing of PAM after breakage could improve the flocs characteristics with large size and compact structure.

Performance and antifouling enhancement of polyethersulfone hollow fiber membranes incorporated with highly hydrophilic hydroxyapatite nanoparticles

Membrane fouling is one of the main drawbacks in water purification applications. The present work indicated that the fabricated HAp/PES hollow fiber membranes presented better hydrophilicity, permeation and anti-fouling performance compared to PES membranes.

The effects of hydroxyapatite nano whiskers and its synergism with polyvinylpyrrolidone on poly(vinylidene fluoride) hollow fiber ultrafiltration membranes

By introducing hydroxyapatite (HAP) nano whiskers as well as polyvinylpyrrolidone (PVP), poly(vinylidene fluoride) (PVDF)/PVP/HAP hollow fiber membranes were fabricated with the wet spinning method.

Hydrophilic modification of polyvinyl chloride hollow fiber membranes by silica with a weak in situ sol–gel method

A weak in situ sol–gel method is proposed for the hydrophilic modification of polyvinyl chloride (PVC) hollow fiber membranes by silica, which is generated by the soft hydrolysis of tetraethoxysilane (TEOS) in a deionized water bath.