Studies on syntheses and permeabilities of special polymer membranes: 30. Ultrafiltration and dialysis characteristics of cellulose nitrate-poly(vinyl pyrrolidone) polymer blend membranes

Preparation and Characterization of Polyethersulfone/Activated Carbon Composite Membranes for Water Filtration

Ultrafiltration membrane technology holds promise for wastewater treatment, but its widespread application is hindered by fouling and flux reduction issues. One effective strategy for enhancing ultrafiltration membranes involves incorporating activated carbon powder. In this study, composite polyethersulfone (PES) ultrafiltration membranes were fabricated to include activated carbon powder concentrations between 0 and 1.5 wt.%, with carbon size fixed at 200 mesh. The ultrafiltration membranes were evaluated in terms of membrane morphology, hydrophilicity, pure water flux, equilibrium water content, porosity, average pore size, protein separation, and E-coli bacteria removal. It was found that the addition of activated carbon to PES membranes resulted in improvements in some key properties. By incorporating activated carbon powder, the hydrophilicity of PES membranes was enhanced, lowering the contact angle from 60° to 47.3° for composite membranes (1.0 wt.% of activated carbon) compared to the pristine PES membrane. Water flux tests showed that the 1.0 wt.% composite membrane yielded the highest flux, with an improvement of nearly double the initial value at 2 bar, without compromising bovine serum albumin rejection or bacterial removal capabilities. This study also found that the inclusion of activated carbon had a minor impact on the membrane's porosity and equilibrium water content. Overall, these insights will be beneficial in determining the optimal concentration of activated carbon powder for PES ultrafiltration membranes.

Effect of Polyvinylpyrrolidone on Polyvinylidene Fluoride/Hydroxyapatite- Blended Nanofiltration Membranes: Characterization and Filtration Properties

INTRODUCTION

The application of polyvinylidene fluoride (PVDF) as a filtration membrane is limited due to its hydrophobicity. This paper elaborated on the fabrication process of nanofiltration PVDF membrane incorporating various quantities of hydrophilic polyvinylpyrrolidone (PVP) and hydroxyapatite (HA) using a wet phase inversion method to improve its hydrophilicity.

METHODS

The membrane was fabricated by using the wet phase inversion method. It was then characterized in terms of water permeability, water contact angle, water content, surface energy, and surface porosity. Bacteria and Fe ions filtration was conducted to investigate the membrane filtration performance.

RESULTS

The PVDF/PVP/HA-blended membrane showed the highest water permeability (6,165 LMH/Bar), water content (45.2 %), and surface energy (104.1 mN/m) when 2 wt.% of PVP was introduced into the base polymer PVDF. This fabricated membrane, labeled as PVP 2.0, also showed the lowest contact angle (64°) and the highest surface porosity (42%).

CONCLUSION

Overall, the PVP introduction patents into the polymeric membrane doping solution potentially improves membrane hydrophilicity and permeability.

Antibacterial Activity of Silver Nanoflake (SNF)-Blended Polysulfone Ultrafiltration Membrane

The aim of this research was to study the possibility of using silver nanoflakes (SNFs) as an antibacterial agent in polysulfone (PSF) membranes. SNFs at different concentrations (0.1, 0.2, 0.3 and 0.4 wt.%) were added to a PSF membrane dope solution. To investigate the effect of SNFs on membrane performance and properties, the water contact angle, protein separation, average pore size and molecular weight cutoffs were measured, and water flux and antibacterial tests were conducted. The antimicrobial activities of the SNFs were investigated using Escherichia coli taken from river water. The results showed that PSF membranes blended with 0.1 wt.% SNFs have contact angles of 55°, which is less than that of the pristine PSF membrane (81°), exhibiting the highest pure water flux. Molecular weight cutoff values of the blended membranes indicated that the presence of SNFs does not lead to enlargement of the membrane pore size. The rejection of protein (egg albumin) was improved with the addition of 0.1 wt.% SNFs. The SNFs showed antimicrobial activity against Escherichia coli, where the killing rate was dependent on the SNF concentration in the membranes. The identified bacterial colonies that appeared on the membranes decreased with increasing SNF concentration. PSF membranes blended with SNF, to a great degree, possess quality performance across several indicators, showing great potential to be employed as water filtration membranes.

High-Performance Polyurethane Nanocomposite Membranes Containing Cellulose Nanocrystals for Protein Separation

With the aim of exploring new materials and properties, we report the synthesis of a thermoplastic chain extended polyurethane membrane, with superior strength and toughness, obtained by incorporating two different concentrations of reactive cellulose nanocrystals (CNC) for potential use in kidney dialysis. Membrane nanocomposites were prepared by the phase inversion method and their structure and properties were determined. These materials were prepared from a polyurethane (PU) yielded from poly(1,4 butylene adipate) as a soft segment diol, isophorone diisocyanate (IPDI) and hexamethylenediamine (HMDA) as isocyanate and chain extender, respectively (hard segment), filled with 1 or 2% w/w CNC. Membrane preparation was made by the phase inversion method using N,N-dimethylformamide as solvent and water as nonsolvent, and subjected to dead-end microfiltration. Membranes were evaluated by their pure water flux, water content, hydraulic resistance and protein rejection. Polymers and nanocomposites were characterized by scanning electronic and optical microscopy, differential scanning calorimetry, infrared spectroscopy, strain stress testing and ¹³C solid state nuclear magnetic resonance. The most remarkable effects observed by the addition of CNCs are (i) a substantial increment in Young’s modulus to twenty-two times compared with the neat PU and (ii) a marked increase in pure water flux up to sixty times, for sample containing 1% (w/w) of CNC. We found that nanofiller has a strong affinity to soft segment diol, which crystallizes in the presence of CNCs, developing both superior mechanical and pure water flow properties, compared to neat PU. The presence of nanofiller also modifies PU intermolecular interactions and consequently the nature of membrane pores.

Study Effect of nAg Particle Size on the Properties and Antibacterial Characteristics of Polysulfone Membranes

Polysulfone ultrafiltration membranes were fabricated using various sizes (20, 40, and 90-210 nm) of silver nanoparticles (nAg) blended in a dope solution. To characterize the performance and properties of the prepared membranes, scanning electron microscopy (SEM), water contact angle, protein separation, water flux, and antibacterial tests were conducted. The characterization results revealed that when nAg particles (20 nm) were blended into the base polymer PSF, the PSF/nAg blended membrane had the lowest contact angle (58.5°) and surface energy (110.7 mN/m). When experimenting with ultrafiltration using protein solutions, bare PSF and PSF/nAg-20 blended membranes gave similar values of protein rejection: 93% of bovine serum albumin (BSA) and 70% of lysozyme rejection. Furthermore, SEM studies showed that the surface pore size was reduced by adding 20 nm nAg particles in the casting solution. Most importantly, the introduction of 40 nm nAg particles reduced the growth of bacterial colonies on the membrane surface by up to 72%. These findings revealed that nAg particles are expected to be a potential modifier for the fabrication of an ultrafiltration membrane.

Toxic metal ion separation by cellulose acetate/sulfonated poly(ether imide) blend membranes: effect of polymer composition and additive

Toxic heavy metal ion removal from industrial effluents are gaining increased visibility owing to environmental concern and saving precious materials. In this work, an attempt has been made to remove the valuable metal ions using modified ultrafiltration (UF) blend membranes based on cellulose acetate (CA) and sulfonated poly(ether imide) (SPEI) were prepared in the presence and absence of additive, poly(ethylene glycol) 600 (PEG600) in various compositions. Prepared membranes were characterized in terms of pure water flux (PWF), water content and membrane hydraulic resistance. High flux UF membranes were obtained in the range of 15-25 wt% SPEI and 2.5-10 wt% PEG600 in the polymer blend. The molecular weight cut-off (MWCO) of the blend membranes were determined using protein separation studies found to vary from 20 to greater than 69 kDa. Surface morphology of the blend membranes were analysed with scanning electron microscopy. Studies were carried out to find the rejection and permeate flux of metal ions such as Cu(II), Ni(II), Zn(II) and Cd(II) using polyethyleneimine as the chelating ligand. On increasing the composition of SPEI and PEG600, the rejection of metal ions is decreasing while the permeate flux has an increasing trend. These effects are due to the increased pore formation in the CA/SPEI blend membranes because of the hydrophilic SPEI and polymeric additive PEG600. In general, it was found that CA/SPEI blend membranes displayed higher permeate flux and lower rejection compared to pure CA membranes. The extent of separation of metal ions depends on the affinity of metal ions to polyethyleneimine to form macromolecular complexes and the stability of the formed complexes.