PVDF/CaCO3 composite hollow fiber membrane for CO2 absorption in gas-liquid membrane contactor

Porous hydrophobic polyvinylidene fluoride (PVDF) composite hollow fiber membranes were fabricated via phase inversion method by embedding different amounts of hydrophobic calcium carbonate (CaCO3) nano-particles in the polymer matrix. The effects of nano-particle loadings on the morphology, structure and performance of the spun membranes in gas-liquid contactors were investigated. The incorporation of hydrophobic nano-particles into the polymer network enabled the formation of more abundant and narrower finger-like pores in the composite membranes compared to plain PVDF membrane. Moreover, the addition of nano-particles enhanced the surface roughness, permeation rate, porosity and wettability resistance of the composite membranes. CO2 absorption performance of the fabricated membranes was evaluated via a gas-liquid membrane contactor system. The CO2 flux was improved to some extent by increasing the mixing ratio of CaCO3. Peak absorption performance of 1.52 × 10-3 mol m-2 s-1 at 300 ml/min absorbent flow rate was achieved when 20/100 weight ratio of CaCO3/PVDF was employed. However, further increase of the ratio resulted in a composite membrane with lower absorption performance than the other composite membranes. Moreover, a long-term stability study of the composite membrane with the best CO2 absorption flux showed no decline in performance in the initial 210 h of operation, indicating that the membrane possesses high potential for gas-liquid contactor applications

Fabrication and characterization of porous polyetherimide/montmorillonite hollow fiber mixed matrix membranes for CO2 absorption via membrane contactor

Asymmetric PEI hollow fiber mixed matrix membranes (MMMs) with improved structure and wetting resistance were fabricated via wet phase inversion method. The effects of incorporating hydrophobic MMT into polymer matrix in different loadings on the membrane properties were investigated. The membranes were characterized in terms of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), gas permeation test, hydrophobicity, wetting resistance and mechanical stability. All membranes possessed finger-like structures differing in skin layer thickness which increased with clay loading. The results revealed that the MMMs have significantly smaller pore size, higher porosity, hydrophobicity, LEPw and mechanical stability than plain PEI membrane. The membranes were further characterized by CO2 absorption test via contactor system using distilled water as absorbent and pure CO2 as solute gas. The results showed that the CO2 absorption performance increased with addition of MMT nano-clay. The membrane containing 1wt% MMT recorded the highest absorption flux of 2.35×10-3molm-2s-1 at the liquid velocity of 3ms-1, almost 135% higher than the flux of plain membrane at the same velocity. Comparatively, the flux of MMM was superior to several in-house made and commercial membranes

Experimental study on the performance and long-term stability of PVDF/montmorillonite hollow fiber mixed matrix membranes for CO2 separation process

Porous asymmetric polyvinylidene fluoride (PVDF)/montmorillonite (MMT) hollow fiber mixed matrix membranes (MMMs) with different nano-clay loadings were prepared via wet phase inversion technique and was used for membrane contactor. The fabricated MMMs were characterized in terms of morphology, structure, gas permeability, wetting resistance and mechanical stability. From morphology point of view, the fabricated membranes had a finger-like/sponge-like structure in the middle layer with a very porous thin outer skin layer and an inner skinless sponge-like structure. Atomic force microscopy (AFM) revealed an increase in surface roughness with increasing MMT loading. From gas permeation test, the surface porosity of the MMMs was higher than the plain PVDF membrane and the mean pore size of the membranes was small (34-22nm) and decreased slightly at 5wt.% MMT loading. A significant improvement in LEPw and hydrophobicity caused the prepared MMMs to show high wetting resistances. Mechanical stability test of membranes demonstrated an increase in stress at break and collapsing pressure with a slight loss in elongation with clay loading. CO2 absorption tests with water as absorbent showed that the absorption rate of the MMMs was higher than the plain membrane and increased with MMT loading. For example, at MMT loading of 5wt.% and absorbent flow rate of 0.5ms-1, the absorption flux was 1.89×10-3molm-2s-1 that was 48.7% higher than the plain PVDF membrane. Moreover, the absorption rate of the best fabricated MMM was higher than the commercial PVDF membrane. A long-term contactor test of this membrane over 350h showed that wetting did not take place and the absorption flux remained almost constant. It was concluded that, due to the higher surface hydrophobicity, wetting resistance and performance, MMMs can be a promising candidate to be used in contactor applications

Development of novel thin film nanocomposite forward osmosis membranes containing halloysite/graphitic carbon nitride nanoparticles towards enhanced desalination performance

In this study, thin film nanocomposite (TFN) membranes were fabricated by incorporating highly hydrophilic halloysite nanotubes (HNTs) and self-synthesized graphitic carbon nitride (g-C 3 N 4 ) nanoparticles into polysulfone-based substrate and interfacially polymerized polyamide top layer, respectively. The TFN membranes were evaluated for their performance in forward osmosis (FO) applications. The XRD, ATR-FTIR, FESEM and TEM results confirmed the successful synthesis of g-C 3 N 4 nanoparticles. The effects of nanomaterials incorporation were investigated in terms of membrane surface morphology, hydrophilicity and separation performance. When 0.05 wt/v% of g-C 3 N 4 was added to the polyamide layer, the membrane surface contact angle was significantly reduced from 68° in the control membrane (TFN0.0) to <10° in the TFN membrane (TFN0.05), leading to high water flux of 18.88 L/m 2 ·h (approximately 270% higher than the TFN0.0 membrane). The results have proven the predominant effect of the polyamide layer modification compared to the support modification towards FO performance enhancement. The water flux decline for the TFN0.0 and TFN0.05 membranes after a prolonged time of 1200 min was only 12% for the TFN0.05 while TFN0.0 membrane experienced 24% reduction. In addition, fouling resistance of the membranes assessed by BSA revealed that the flux of TFN0.0 has reduced by 54% after 1200 min, meanwhile TFN0.05 recorded a reduction of approximately 30%. The findings confirmed the effectiveness of g-C 3 N 4 as a promising surface modifier for polyamide layer to simultaneously contribute to flux enhancement and increased anti-fouling properties

Zeolite ZSM5-filled PVDF hollow fiber mixed matrix membranes for efficient carbon dioxide removal via membrane contactor

ZSM5 zeolite-filled PVDF mixed matrix membranes (MMMs) were wet spun and used for CO2 absorption in a contactor system. The properties of ZSM5 were analytically characterized. SEM images revealed the fully asymmetric structure of membranes, in which the creation of finger-like macrovoids was promoted with increasing filler loading. A significant increase in gas permeance was observed, which was associated with the porosity increase of the membrane surface despite the decrease in surface pore size. The surface roughness, wettability resistance, and mechanical stability of membranes were also considerably improved by filler loading. A CO2 absorption test with water revealed a higher CO2 flux of MMMs than that of the plain membrane. Peak absorption flux of 5.80 × 10-3 mol m-2 s-1 was achieved at a liquid velocity of 1.2 m s-1 for 5 wt % ZSM5/PVDF membrane (MZ5), which was nearly 177% higher than that of neat PVDF and also surpassed that of several commercial and in-house made membranes. The mass transfer resistance of the MMMs was also considerably lower than that of PVDF. (Graph Presented)

Biogas as a renewable energy fuel – A review of biogas upgrading, utilisation and storage

Biogas upgrading is a widely studied and discussed topic and its utilisation as a natural gas substitute has gained a significant attention in recent years. The production of biomethane provides a versatile application in both heat and power generation and as a vehicular fuel. This paper systematically reviews the state of the art of biogas upgrading technologies with upgrading efficiency, methane (CH4) loss, environmental effect, development and commercialisation, and challenges in terms of energy consumption and economic assessment. The market situation for biogas upgrading has changed rapidly in recent years, making the membrane separation gets significant market share with traditional biogas upgrading technologies. In addition, the potential utilisation of biogas, efficient conversion into bio-compressed natural gas (bio-CNG), and storage systems are investigated in depth. Two storing systems for bio-CNG at filling stations, namely buffer and cascade storage systems are used. The best storage system should be selected on the basis of the advantages of both systems. Also, the fuel economy and mass emissions for bio-CNG and CNG filled vehicles are studied. There is the same fuel economy and less carbon dioxide (CO2) emission for bio-CNG. Based on the results of comparisons between the technical features of upgrading technologies, various specific requirements for biogas utilisation and the relevant investment, and operating and maintenance costs, future recommendations are made for biogas upgrading

Enhanced desalination of polyamide thin film nanocomposite incorporated with acid treated multiwalled carbon nanotube-titania nanotube hybrid

Polyamide (PA) thin film nanocomposite (TFN) membrane incorporated with multiwalled carbon nanotubes-titania nanotube (MWCNT-TNT) hybrid was successfully fabricated. The hybrid was introduced to the PA selective layer during the interfacial polymerization (IP) of trimesoyl chloride (TMC) and m-phenylenediamine (MPD) monomers over porous commercial polysulfone (PS) ultrafiltration support. The resultant TFN was characterized and applied for desalination. The results revealed that the acid treated MWCNT-TNT, which act as filler in the PA membrane, improved the surface properties of the membrane in term of surface charge, surface roughness and contact angle. Consequently, the water permeability increased significantly without compromising the salt rejection performance. The highest water permeability of 0.74 L/m2 h bar was achieved for the TFN membrane containing 0.05 wt% acid treated MWCNT-TNT, which is approximately 57.45% than that of the neat PA membrane. The NaCl and Na2SO4 rejection of this membrane was 97.97% and 98.07%, respectively that is almost similar to the neat membrane

Effect of HNTs modification in nanocomposite membrane enhancement for bacterial removal by cross-flow ultrafiltration system

This study investigated the potential of silver lactate (SL)-holloysite nanotube clay (HNTs) nano-filler embedded into the polyvinylidene fluoride (PVDF) polymer matrix as an antibacterial separator. Three different nanocomposite membranes were fabricated via phase inversion technique aimed to enhance the permeation flux and fouling resistance with complete bacterial rejection. HNT has been modified by N-β-(aminoethyl)-É£-aminopropyltrimethoxy silane (AEAPTMS) aiming for immobilization of SL on the surface HNT during dope preparation. Salmonella and Enterobacter aerogenes (E. aerogenes) were considered as two types of bacteria to be removed from contaminated water in this experimental work. Nanocomposite membranes were characterized and analyzed by thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM) combined with energy dispersive X-ray (EDX), X-ray photoelectron spectroscope (XPS), atomic force microscopy (AFM), contact angle, molecular weight cut-off (MWCO) and tensile strength. Potential silver ion loss was assessed by measuring the silver content in the coagulation bath and in the UF permeate using inductive-coupled plasma mass spectrometer (ICP-MS). Moreover, antibacterial effect of the membrane was examined in terms of removal of microorganisms by filtration, Log Reduction Value (LRV) and thickness of inhibition zone. From the experimental results, the prepared nanocomposite membranes have shown more than 99% bacterial rejection, LRV of more than 3 and broad inhibition zones in the agar plate. In particular, the nanocomposite membrane consisting M-HNTs/SL/PVDF showed significant improvement in permeation flux and flux declination among all the tested membranes. It was also found that modification of HNTs resulted in reduction of silver leaching by uniform distributing of SL, which contributed to significant inhibition for both types of growth bacteria within 24 h of incubation