Fabrication of polysulfone nanocomposite membranes with silver-doped carbon nanotubes and their antifouling performance

Scale Design of Dual-Layer Polyphenylsulfone/Sulfonated Polyphenylsulfone Hollow Fiber Membranes for Nanofiltration

This study focuses on the synthesis and characterization of dual-layer sulfonated polyphenylenesulfone (SPPSu) nanocomposite hollow fiber nanofiltration membranes incorporating titanium dioxide (TiO2) nanoparticles through the phase inversion technique. Advanced tools and methods were employed to systematically evaluate the properties and performance of the newly developed membranes. The investigation primarily centered on the impact of TiO2 addition in the SPPSu inner layer on pure water permeability and salt rejection. The nanocomposite membranes exhibited a remarkable three-fold increase in pure water permeability, achieving a flux of 5.4 L/m2h.bar compared to pristine membranes. The addition of TiO2 also enhanced the mechanical properties, with an expected tensile strength increase from 2.4 to 3.9 MPa. An evaluation of salt rejection performance using a laboratory-scale filtration setup revealed a maximal rejection of 95% for Mg2SO4, indicating the effective separation capabilities of the modified dual-layer hollow fiber nanocomposite membranes for divalent ions. The successful synthesis and characterization of these membranes highlight their potential for nanofiltration processes, specifically in selectively separating divalent ions from aqueous solutions, owing to their improved pure water flux, mechanical strength, and salt rejection performance.

Nanoparticle-Enhanced PVDF Flat-Sheet Membranes for Seawater Desalination in Direct Contact Membrane Distillation

In this study, hydrophobic functionalized carbon nanotubes (fCNTs) and silica nanoparticles (fSiO₂NPs) were incorporated into polyvinylidene fluoride (PVDF) flat-sheet membranes to improve their performance in membrane distillation (MD). The performance of the as-synthesized membranes was evaluated against commercial reference polytetrafluoroethylene (PTFE) flat-sheet membranes. The water contact angle (WCA) and liquid entry pressure (LEP) of the PVDF membrane were compromised after incorporation of hydrophilic pore forming polyvinylpyrrolidone (PVP). These parameters were key in ensuring high salt rejections in MD processes. Upon incorporation of fCNTS and fSiO₂NPs, WCA and LEP improved to 103.61° and 590 kPa, respectively. Moreover, the NP additives enhanced membrane surface roughness. Thus, an increase in membrane roughness improved WCA and resistance to membrane wetting. High salt rejection (>99%) and stable fluxes (39.77 kg m^-2 h^-1) were recorded throughout a 3 h process evaluation where 3.5 wt% NaCl solution was used as feed. These findings were recorded at feed temperature of 60 ℃. Evidently, this study substantiated the necessity of high feed temperatures towards high rates of water recovery.

Fabrication and Characterisation of MWCNT/Polyvinyl (PVC) Polymer Inclusion Membrane for Zinc (II) Ion Removal from Aqueous Solution

Heavy metal pollution has prompted researchers to establish the most effective method to tackle the impacts of heavy metals on living things and the environment, which include by applying nanoparticles. An example is the employment of multi-walled carbon nanotubes (MWCNTs) as an additive in an intermediate membrane or polymer inclusion membrane (PIM). The MWCNTs were added to enhance the properties and reinforce the transport performance of zinc (II) ion (Zn2+) removal from the source phase to the receiver phase by the PIMs. The present study constructed a membrane with a poly(vinyl chloride) (PVC)-based polymer, dioctyl phthalate (DOP) plasticiser, and bis-(2-ethylhexyl) phosphate (B2EHP) carrier incorporated with different concentrations of MWCNTs. The contact angle (CA), water uptake, ion exchange capacity (IEC), and porosity of the fabricated membranes were evaluated. The membrane was also characterised by employing scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and electrochemical impedance spectroscopy (EIS). Subsequently, the fabricated PIM (W1) and mixed matrix (MM)-PIM (W2−W5) samples were assessed under different parameters to acquire the ideal membrane composition and effectiveness. Kinetic modelling of Zn2+ removal by the fabricated PIMs under similar conditions was performed to reveal the mechanisms involved. The average removal efficiency of the membranes was >99% at different parameter conditions. Nevertheless, the W3 membrane with 1.0 wt% MWCNT immersed in a 5 mg/L initial Zn2+ concentration and 1.0 M receiver solution for seven hours at pH 2 demonstrated the highest percentage of Zn2+ removal. The experimental data were best fitted to the pseudo-first-order kinetic model (PFO) in kinetic modelling, and the permeability and flux of the W3 at optimum conditions were 0.053 m s−1 and 0.0532 mol m−2 s−1, respectively. In conclusion, the transport mechanism of Zn2+ was enhanced with the addition of the MWCNTs.

A Methyl-Modified Silica Layer Supported on Porous Ceramic Membranes for the Enhanced Separation of Methyl Tert-Butyl Ether from Aqueous Solution

As a kind of volatile organic compound (VOC), methyl tert-butyl ether (MTBE) is hazardous to human health and destructive to the environment if not handled properly. MTBE should be removed before the release of wastewater. The present work supported the methyl-modified silica layer (MSL) on porous α-Al₂O₃ ceramic membranes with methyltrimethoxysilane (MTMS) as a precursor and pre-synthesized mesoporous silica microspheres as dopants by the sol-gel reaction and dip-coating method. MTMS is an environmentally friendly agent compared to fluorinated alkylsilane. The MSL-supported Al₂O₃ ceramic membranes were used for MTBE/water separation by pervaporation. The NMR spectra revealed that MTMS evolves gradually from an oligomer to a highly cross-linked methyl-modified silica species. Methyl-modified silica species and pre-synthesized mesoporous silica microspheres combine into hydrophobic mesoporous MSL. MSL makes the α-Al₂O₃ ceramic membranes transfer from amphiphilic to hydrophobic and oleophilic. The MSL-supported α-Al₂O₃ ceramic membranes (MSL-10) exhibit an MTBE/water separation factor of 27.1 and a total flux of 0.448 kg m⁻² h⁻¹, which are considerably higher than those of previously reported membranes that are modified by other alkylsilanes via the post-grafting method. The mesopores within the MSL provide a pathway for the transport of MTBE molecules across the membranes. The presence of methyl groups on the external and inner surface is responsible for the favorable separation performance and the outstanding long-term stability of the MSL-supported porous α-Al₂O₃ ceramic membranes.

Employing magnetism of Fe3O4 and hydrophilicity of ZrO2 to mitigate biofouling in magnetic MBR by Fe3O4-coated ZrO2/PAN nanocomposite membrane

The aim of this research is benefiting from the synergistic effect of the simultaneous presence of Fe₃O₄ and ZrO₂ in the form of Fe₃O₄-coated ZrO₂ (Fe₃O₄@ZrO₂) nanoparticles within the structure of PAN membrane to reduce membrane fouling. The role of Fe₃O₄ nanoparticles in increasing the pore size and magnetic saturation as well as the role of ZrO₂ in decreasing surface roughness and hydrophobicity can mitigate membrane fouling in magnetic-assisted membrane bioreactors. For this purpose, Fe₃O₄, ZrO₂, and Fe₃O₄@ZrO₂ nanoparticles were embedded into PAN membrane structure and magnetic (M _nM), hydrophilic (H _nM), and magnetic-hydrophilic (HM _nM) membranes were synthesized. H ₁M (1ZrO₂/PAN) membrane with a contact angle of 31 degrees, M ₁N (1Fe₃O₄/PAN) with a pore size of 90 nm, and H ₃M (3ZrO₂/PAN) membrane with an RMS roughness of 13.5 nm were the most hydrophilic, porous, and smoothest membranes, respectively. High sensitivity to magnetic field along with high porosity, high hydrophilicity and low surface roughness simultaneously exist within the structure of MHMs membranes, such that MH ₁M (1Fe₃O₄@ZrO₂/PAN) indicated 116% greater flux, 121% greater flux recovery, and 85% less total filtration resistance in comparison with the blank membrane in magnetic membrane bioreactor, at a magnetic field intensity of 120 mT and MLSS = 10,000 mg/l. As an overall conclusion, the output of this research was compared with other research in term of normalized flux. Results reveal that at MLSS = 10,000 mg/l, HRT = 8 h and TMP = 0.3 bar, MH ₁M membrane has normalized flux equal to 1.56 g/m² h bar which is an acceptable value compared to normalized flux reported by other researchers.

Polysulfone Composite Membranes with Carbonaceous Structure. Synthesis and Applications

The present review deals with the latest progress in the field of polysulfone composite membranes with carbon nanotubes, carbon fiber and graphene from both perspectives-synthesis and applications. These two fillers, extensively used in the last few years due to their remarkable properties, induce a high value character to the composite materials. On the other hand, polysulfone is one the most used polymers for preparing polymeric membranes due to its high versatility in a wide range of solvents and also to the properties of this remarkable polymer. All types of synthesis method were presented and also a large number of applications from industrial to biomedical were presented and discussed.