Mixed Matrix Hollow Fiber Membranes Research Articles

Groundwater defluoridation and disinfection using carbonized bone meal impregnated polysulfone mixed matrix hollow-fiber membranes

Defluoridation and disinfection of groundwater have been attempted in this study, using carbonized bone meal (CBM) impregnated polysulfone based mixed matrix hollow fiber membrane. The membranes were characterized in terms of permeability, hydrophilicity, molecular weight cut off for different CBM concentrations. The membrane permeability was decreased from 5 × 10−10 m/Pa.s (without CBM) to 2.8 × 10-11 m/Pa.s with addition of 15 wt% CBM. Corresponding reduction in molecular weight cut off was from 85 kDa to 23 kDa. Variation of such properties were corroborated by the scanning electron micrographs of the prepared membranes that showed the membrane morphology became dense due to CBM addition in the polymer matrix. However, membrane hydrophilicity became more pronounced. In addition, the surface roughness of the prepared membranes was increased facilitating the adsorptive properties. The maximum fluoride adsorption capacity of the hollow fibers with 15 wt% CBM was observed to be 5 mg/g. Breakthrough studies were conducted for the membranes in cross flow filtration mode that showed a fresh membrane (area: 0.029 m2) can filter fluoride contaminated feed solution successfully for 24 h and 19 h, for the first and second regeneration cycles. For a real-life groundwater feed solution, the breakthrough time was observed to be 18 h. The bacterial concentration in the filtrate samples was found to be 0 CFU/ml, highlighting the antibacterial property of the prepared membranes.

Polysulfone mixed matrix hollow fiber membranes using zeolite templated carbon as a performance enhancement filler for gas separation

Zeolite-templated carbon (ZTC) was used as a new nanoporous filler to prepare mixed-matrix membranes (MMMs) with polysulfone as a continuous phase. The ZTC was prepared using a synthesized zeolite-Y template and sucrose carbon source via the impregnation method. The MMMs were fabricated through a dry-jet wet spinning technique, and the ZTC loadings were varied between 0.4–0.7wt%. The results showed that the integration of the ZTC did not change the microscopic structure of membranes. Additionally, the addition of filler did not affect the amorphous character of the polymer, while the polymer chain spacing slightly decreased. The thermal stability of MMMs improved with an increase in the glass transition temperature. The MMM at 0.4wt% loading exhibited the best separation performances as shown from the Robeson curve, with CH4, CO2, N2, O2, and H2 permeances of 5.9, 58.5, 5.0, 14.0, and 169.2 GPU, respectively. In addition, the improvements in CO2/CH4, O2/N2, H2/CH4, and CO2/N2 ideal selectivities were 290%, 117%, 272%, and 219%, respectively. On the other hand, the enhancement of the permeances and reduction in selectivities observed at 0.7wt% loading indicated that the existence of voids was a main factor in the permeation behavior of the MMMs.

Highly Propylene-Selective Mixed-Matrix Membranes by in Situ Metal–Organic Framework Formation Using a Polymer-Modification Strategy

Despite the potential of C3H6/C3H8 separation, there have been no industrial applications of zeolitic-imidazole framework-8 (ZIF-8) mixed-matrix membranes (MMMs) because of the moderate separation performances and several challenging processing issues. Herein, we present a new paradigm of MMM fabrication, named polymer-modification-enabled in situ metal-organic framework formation (PMMOF), enabling in situ formation of ZIF-8 fillers inside the 4,4-(hexafluoroisopropylidene)diphthalic anhydride 2,4,6-trimethyl-1,3-phenylenediamine polymer. PMMOF consists of four steps including hydrolysis of a polymer, ion-exchange, ligand treatment, and imidization. Each step was thoroughly analyzed and important processing parameters were identified, enabling the structural control of MMMs by PMMOF. The binary C3H6/C3H8 separation performance of the MMMs showed much higher separation factors than conventionally prepared MMMs at similar filler loadings, satisfying the commercial C3H6/C3H8 separation performance criteria. PMMOF was successfully applied for other MOFs, demonstrating that the process could be general. Finally, as a proof of concept, asymmetric mixed-matrix hollow fiber membranes (i.d. of 0.45 mm and o.d. of 0.63 mm) with ultrathin selective skin layers were prepared by PMMOF, showing C3H6 permeance of 2.17 GPU and C3H6/C3H8 separation factor of ∼20.

PES/PVP/TiO2 mixed matrix hollow fiber membrane with antifouling properties for humic acid removal

The aim of this study is to analyse the fouling behaviour of polyethersulfone (PES) / polyvinyl pyrrolidone (PVP) / titanium oxide (TiO2) mixed matrix (MM) hollow fiber (HF) membrane with varying TiO2 loadings for humic acid (HA) treatment. The MM HF membrane was fabricated using dry jet – wet phase inversion method by blending varying amount of TiO2 nanoparticles (1, 2, 3, and 4 wt. %) into the PES dope solution. The fabricated HF membrane was characterised in terms of their surface and cross section morphology, contact angle, pore size, and porosity. These characteristics can highly affect the membrane antifouling behaviour as well as membrane flux. The membrane was tested using 50 mg/L of HA solution adjusted to pH 7.7. All MM HF membranes suggested better antifouling with S2 sample at 2 wt.% TiO2 having optimal antifouling and flux performance with the lowest value for resistance by fouling and less than 5% difference from the best permeate flux and rejection values. Under this formulation, HA permeation test has registered an improved membrane flux at 23.851 kg/m2 h and HA rejection of 97.89%; an improvement of 28.9% and 3.8% respectively as compared to the neat PES membrane. HA rejection increased drastically due to higher surface hydrophilicity of TiO2 blended membranes, which repels the hydrophobic HA and prevented the adsorption of HA onto the membrane surface. This also minimize the formation of reversible and irreversible fouling by HA, which increases its antifouling abilities.

Comparison of Post-Treatment Methods on the Performance of Hollow Fiber Membranes Containing Metal Organic Framework in Gases Separation

In the current work, thermal treatment, PDMS coating, and combined thermal treatment with PDMS coating methods were applied over NH2-MIL-53(Al)/cellulose acetate (CA) hollow fiber mixed matrix membranes (HFMMM) for CO2/CH4 and CO2/N2 separation. The results showed that upon thermal treatment at 170 °C, CO2/CH4 and CO2/N2 gas pair selectivities of HFMMM were improved from 9.1 to 9.9 and 7.7 to 8.4, respectively. On the other hand, CO2/CH4 and CO2/N2 gas pair selectivities of HFMMMs were improved from 9.1 to 14.1 and 7.7 to 12.0, respectively, after thermal treatment at 220 °C. Substantial increment in gas pair selectivities of the thermally treated fibers was mainly due to polymer densification, which condensed the voids between polymer and particles. Subsequently, PDMS-coated HFMMMs exhibited gas pair selectivities of 17.0 and 16.2, respectively, which were higher compared to the untreated and thermally treated HFMMM. Highest improvement of CO2/CH4 and CO2/N2 gas pair selectivities were found for combined...

Novel polyphenylsulfone (PPSU)/nano tin oxide (SnO2) mixed matrix ultrafiltration hollow fiber membranes: Fabrication, characterization and toxic dyes removal from aqueous solutions

Novel polyphenylsulfone (PPSU)/nano tin oxide (SnO2) mixed matrix hollow fiber membranes (HFMs) were fabricated by dry-wet spinning via phase separation method. In the current research, reported the contrast between neat PPSU membrane and nanocomposite membranes (PPSU/SnO2), to determine the toxic reactive dyes namely, reactive black-5 (RB-5) and reactive orange-16 (RO-16) removal ability from the aqueous media. Scanning electron microscopy (SEM) was used to observe the HFMs cross-sectional morphological changes and surface roughness parameters of membranes were analyzed using atomic force microscopy (AFM). The surface wettability ability of HFMs was examined with a contact angle, water uptake, and porosity measurements. The cross-flow filter unit was engaged to quantify the water permeability, anti-fouling ability as well as the dye rejection ability of fabricated membranes. With increasing the SnO2 NPs wt% in PPSU polymer matrix the membrane performance was enhanced continuously, it became evident that the incorporated SnO2 NPs plays main role in membrane performance. Added, water-soluble poly (vinylpyrrolidone) (PVP) can also impact the pore morphology in membranes. At the end, PS-3 membrane exhibited lower contact angle (63.7 0), higher water uptake (74.8%), porosity (84.1%), pure water flux 362.9 L/m2 h, and high potential for dyes rejection application, of about >94% for RB-5, and >73% for RO-16 dye, respectively. From the preliminary results, it can be stated that the usage of SnO2 NPs in membrane technology become effective towards wastewater treatment.

Optimization of spinning parameters on the fabrication of NH2-MIL-53(Al)/cellulose acetate (CA) hollow fiber mixed matrix membrane for CO2 separation

The attractive features of this work lies on the optimization of spinning parameters including, take-up speed and air-gap distance on the fabrication of NH2-MIL-53(Al)/CA Hollow fiber mixed matrix membranes (HFMMMs) for gases separation. The morphology and distribution of particles in the resultant HFMMMs were characterized by using FESEM and EDX mapping, respectively. FESEM images showed that the increase in take-up speed and air-gap distance reduced the outer diameters of HFMMMs from 275.5 µm to 110.1 µm and 719.1 µm to 648.4 µm, respectively. The gas permeation results exhibited that the permeance values were reduced and ideal selectivities were improved with the increment of take-up speed. Increasing trend of ideal selectivities could be because of progression of polymer orientation, packing and mono-disperse space which suppressed the non-selective voids and Knudsen pores in the HFMMMs. However, variation of air-gap distance produced “V” and “A” pattern for permeance and ideal selectivity values, respectively, for all HFMMMs spun at different take-up speeds. The HFMMM spun at optimum spinning condition at take up speed of 12.2 m/min and air gap distances of 5.0 cm showed the highest CO2/CH4 ideal selectivity of 16.0 and CO2/N2 ideal selectivity of 12.0. Hence, optimization of spinning parameters can be considered as feasible and efficient method in order to fabricate HFMMMs with higher separation performance. The enhanced CO2 permeance and ideal selectivities demonstrated that NH2-MIL-53(Al)/CA HFMMM spun at optimum condition is potential for industrial gas separation.

Nanofiltration range desalination by high flux graphene oxide impregnated ultrafiltration hollow fiber mixed matrix membrane

In this work, a novel graphene oxide impregnated ultrafiltration grade hollow fiber membrane was prepared having capability of salt rejection in the range of nanofiltration. Sodium sulfate showed higher rejection (40%–50%) than the other salts, magnesium sulfate and sodium chloride. Charge-charge interaction is the major salt retention mechanism. Optimum operating conditions were identified as 55 kPa transmembrane pressure drop and 5 L/h cross-flow rate. Increasing the solution pH from 5 to 9 augmented the rejection of sodium sulfate from 43% to 51% at relatively high permeate flux 0.25 L/m2.h.kPa. In case of filtration of actual sea water, the permeate flux is lowered to 0.20 L/m2.h.kPa due to presence of other fouling agents. Rejection of total dissolved solids was 30% for seawater. Beyond 11 h (breakthrough time) the rejection decreases due to screening of charge effects of the membrane surface. Pretreatment by activated carbon delayed the breakthrough time to 14 h and improved permeate flux 0.22 L/m2.h.kPa. Thus, ultrafiltration grade hollow fiber mixed matrix membrane offers equivalent salt rejection of nanofiltration membrane at a much higher throughput.

Recent advances on mixed-matrix membranes for gas separation: Opportunities and engineering challenges

In the past decades, gas separation using polymeric membranes has received considerable attention and become one of the fastest growing research areas. However, existing polymeric membranes may not be able to keep up with the increasing separation needs for challenging gas mixtures such as N2/CH4 and light olefin/paraffin pairs on industrial scale due to their so-called permeability-selectivity bound. On the other hand, scaling-up issues poise huge challenges for highly permeable and highly selective inorganic membranes. Mixed-matrix membranes, composite membranes, provide an evolutionary solution to debottleneck the permeability-selectivity and scale-up issues currently faced by polymeric and inorganic membranes, respectively. Inorganic fillers in mixed-matrix membranes improve gas permeability and/or selectivity, outperforming polymeric membranes. Combined with relatively economical and simple scaling-up compared to inorganic membranes, mixed-matrix membranes could potentially be a next-generation membrane concept for gas separation applications. This review provides a brief summary on the recent progress in both flat sheet and hollow fiber mixed-matrix membranes with an emphasis on those made over the last five years. A separate section is dedicated to discussing engineering challenges transitioning from laboratory-scale to large-scale synthesis of mixed-matrix membranes. Finally, future prospects and perspectives in mixed-matrix membranes research are briefly outlined.

Membrane based direct pH parametric pumping

Membrane adsorbers have emerged as a promising alternative for classical chromatography since they have lower pressure drops and shorter diffusion paths. They are usually used in frontal flow-through configurations. Such membranes are regenerated using elution steps having the disadvantage of large dead volumes and extensive prior purification. Parametric pumping is an alternative process and is used in a variety of configurations. It uses a driving force perpendicular to fluid velocity for the adsorptive separation of mixtures utilizing a fixed adsorber bed. Here, we report a combination of a new mixed matrix hollow fiber membrane and its simultaneous use as a membrane contactor and membrane adsorber. The hollow fiber contains protein adsorbing ion exchange particles in the fiber wall. The fiber contacts the lumen-side protein containing solution with a pH-shifting gas (CO2 or NH3) on the shell side which in fact controls the pH inside the membrane wall. A silicone coating on the outside prevents a gas breakthrough from the outside. Switching between the two gasses and pH allows adsorption and desorption of proteins, enabling parametric pumping and protein recovery. As the feed flows on the inside of the hollow fiber adsorber, the dead volume can be minimized. Potentially, the solution would not even require prefiltration, as the adsorption particles are hidden and protected by the porous fiber wall.

Carboxylated Carbon Nanotubes/Polyethersulfone Hollow Fiber Mixed Matrix Membranes: Development and Characterization for Enhanced Gas Separation Performance

ABSTRACTCarboxylated carbon nanotubes (C or cCNTs) were incorporated in polyethersulfone hollow fiber membranes (P HFMs) to improve the gas separation performance, i.e., pure gas permeability and ideal gas selectivity. The developed CP HFMs showed the remarkable improvement in thermal stability and mechanical strength as compared to that of the pristine P HFMs. The pure gas permeability of CO2, CH4, O2, and N2 gases for the HFMs were measured at 3 bar feed pressure and room temperature. It was observed that the presence of cCNTs in HFMs significantly improved the CO2 and O2 permeability for CP HFMs by 10.8-and 11.7- fold, respectively, as compared to that measured for P HFMs. Furthermore, the ideal gas selectivity for CO2/CH4, O2/N2, and CO2/N2 gas pairs for CP HFMs was also remarkably enhanced by almost 8.6-, 10.7-and 9.9-times, respectively, as compared to that measured for P HFMs. CP HFMs exhibited gas separation performance better than or comparable to that of the literature-reported CNTs-based membranes. Remarkably, the gas separation performance of CP HFMs crossed Robeson’s 2008 upper bound curve for O2/N2 gas-pair and was almost closer to the upper bound curves drawn by Robeson in 2008 for CO2/CH4 and CO2/N2 gas pairs. The improved separation performance can be attributed to the presence of cCNTs in HFMs. Thus, the results obtained in this study clearly showed that the CP HFMs can potentially be used as a membrane material for the industrially relevant gas separations.

Comparison of hollow fiber and flat mixed-matrix membranes: Theory and simulation

We extend effective medium theory (EMT) to composite hollow fiber mixed matrix membranes, considering the asymmetric filler volume fraction profile arising from finite system size. This volume fraction profile leads to strong variation of the driving force (i.e. pseudo-bulk concentration gradient) in the regions adjacent to the composite ends, and to sensitivity of the effective permeability of the composite to the geometrical configuration. The new theory is validated against rigorous simulations of the transport in mixed-matrix membranes (MMMs) using both concentration-independent and concentration-dependent diffusivities in the MMM constituent phases. Both theory and simulations show that flat mixed-matrix membranes (F-MMMs) have higher effective overall permeability than hollow fiber mixed-matrix membranes (HF-MMMs), upon comparison of systems having identical operating conditions, filler phase loading and particle size. Furthermore, we show here that the sensitivity to the geometry vanishes with increase of inner radius of the hollow fiber membrane at fixed thickness, and the effective permeability of a HF-MMM is found to asymptotically approach that of a F-MMM.

Issues and Current Trends of Hollow‐Fiber Mixed‐Matrix Membranes for CO2Separation from N2and CH4

AbstractTo control CO2emission from industries, membrane technology is preferred over conventional technologies due to its numerous advantages including reliability, operational simplicity, and low capital cost. Hollow‐fiber mixed‐matrix membranes (HFMMMs) exhibit great potential for CO2separation. Various inorganic fillers were incorporated into different types of polymeric materials for fabrication of HFMMMs. This review focuses on the performance and issues of HFMMMS based on various materials for CO2/CH4and CO2/N2separation. Major features are reflected in the following three aspects: comprehensive study on the performance of HFMMMs for CO2/N2and CO2/CH4separation, issues with the fabrication of HFMMMs in CO2/N2and CO2/CH4separation, and prediction of transport models for HFMMMs in gas separation.

Aluminium fumarate metal organic framework incorporated polyacrylonitrile hollow fiber membranes: Spinning, characterization and application in fluoride removal from groundwater

Novel mixed matrix hollow fiber membranes (MMM) were prepared by phase inversion technique using polyacrylonitrile (PAN) as base polymer and aluminium fumarate (AlFu) metal organic framework (MOF) as additive. The membranes were characterized in terms of surface morphology, surface charge, permeability, molecular weight cut off, porosity, pore size and contact angle. Permeability of the membrane increased from 3.5 × 10−10 to 4.5 × 10−10 m/Pa.s with increment of MOF concentration from 0 to 10 wt%. The contact angle of the corresponding membranes decreased from 80° to 51° indicating an increase in hydrophilicity. The MH10 (10 wt% concentration) membrane sustained up to 20, 19 and 17.5 h of operation with fluoride concentration of 4, 8 and 12 mg/l, respectively, at 35 kPa transmembrane pressure and 30 l/h cross flow rate with a membrane area of 0.026 m2. Regeneration study and performance of the MMM in real life ground water samples were also investigated. Filter performance was successfully predicted by a modified model available in literature.

Treatment of methylene blue containing wastewater by a cost-effective micro-scale biochar/polysulfone mixed matrix hollow fiber membrane: Performance and mechanism studies

Dye containing wastewater has increasingly become an important contamination due to operation of various industries such as textile industry. In this study, a micro-scale biochar particles/polysulfone mixed matrix hollow fiber membrane (MMM) was applied for the removal of methylene blue from water. The static and dynamic adsorption performance was investigated. We found that the MMM exhibited a high removal efficiency of methylene blue under a wide pH range of 4–10. The adsorption process on biochar and MMM obeyed the intraparticle surface diffusion model and Langmuir isotherm model. At neutral pH, the maximum adsorption capacity was 544.459 mg/g for biochar and 165.808 mg/g for MMM. Better regeneration with a desorption rate above 92% was achieved by 1-M NaCl in 90% ethanol aqueous solution. Furthermore, the MMM displayed good performance in treating methylene blue containing wastewater through a continuous filtration mode. More importantly, the MMM showed an excellent reusability for methylene blue removal; it was able to achieve 81% of the permeate yield of the fresh MMM after three regeneration cycles. Finally, the adsorption mechanism studies indicated that the removal of methylene blue was associated with electrostatic interaction, hydrogen bonding and hydrophobic interaction.

A novel ultrafiltration grade nickel iron oxide doped hollow fiber mixed matrix membrane: Spinning, characterization and application in heavy metal removal

Abstract Nickel iron oxide nanoparticle incorporated hollow fiber mixed matrix membrane was prepared to achieve high throughput as well as high selectivity for heavy metals. The fibers were characterized in terms of their morphology, permeability, molecular weight cut off, zeta potential, surface roughness and adsorption capacity of various toxic heavy metal species. Scanning electron micrograph images showed that the tear drop-like pores in cross section of the fibers were changed into finger-like macropores on addition of nanoparticles. Porosity and pore size in the fibers increased with nanoparticle concentration. Membrane permeability increased almost twice by addition of 3 wt% nanoparticles compared to pure polysulfone membrane. Similar concentration of nanoparticles made the membrane more hydrophilic reducing its contact angle from 77° to 64° and at the same time, molecular weight cut off of the hollow fibers increased from 17 kDa to 34 kDa. Surface zeta potential of the fibers decreased with pH and the membrane with 3 wt% nanoparticles showed a surface potential about −16 mV at pH 9. The maximum adsorption capacity of membrane with 3 wt% nanoparticles was the highest for lead (52 mg/g) followed by copper (42 mg/g), zinc (35 mg/g) and cadmium (24 mg/g). Nickel (17.5 mg/g) and chromium (18 mg/g) had comparable adsorption capacity. Thus, the mixed matrix membrane developed in this study has significant potential in removal of heavy metals from aqueous solution.

Development of a novel biochar/PSF mixed matrix membrane and study of key parameters in treatment of copper and lead contaminated water

Mixed matrix membrane (MMM) has attracted increasing attentions in various applications, such as water treatment. In this study, an innovative biochar/polysulfone (PSF) mixed matrix hollow fiber membrane was fabricated by incorporating micro-sized biochar particles in the PSF matrix. It was demonstrated that the membrane was more hydrophilic than the pure PSF membrane. Higher water flux was obtained. The adsorption of copper and lead on the MMM increased as the pH was increased with the maximum adsorption capacity observed at pH > 4.5. The adsorption equilibrium was established in 7 and 12 h for lead and copper, respectively. The adsorption kinetics and isotherm followed the intraparticle surface diffusion model and Freundlich isotherm, respectively. The presence of humic acid (HA) had a little effect on the adsorption, while the ionic strength showed an adverse effect on the removal. In addition, the feed concentration and cross flow rate significantly affected the removal efficiency in a continuous filtration mode. The increase in feed concentration and cross flow rate resulted in a reduction in the volume of treated permeate that had the copper/lead concentrations below the regulated levels for drinking water. The MMM exhibited an excellent regeneration-reuse performance in the removal of both copper and lead. Finally, our mechanism studies indicated that the uptake of heavy metals was controlled by a combination of key reactions of complexation, ion-exchange and precipitation. This study indicated that the MMM can be applied as an effective and eco-friendly material for the treatment of heavy metals contaminated water.

Enhanced gas separation performance of mixed matrix hollow fiber membranes containing post-functionalized S-MIL-53

Mixed matrix hollow fiber membranes (MMHFMs) filled with metal-organic frameworks (MOFs) have great potential for energy-efficient gas separation processes, but the major hurdle is polymer/MOFs interfacial defects and membrane plasticization. Herein, lab-synthesized MIL-53 was post-functionalized by aminosilane grafting and subsequently incorporated into Ultem®1000 polymer matrix to fabricate high performance MMHFMs. SEM, DLS, XRD and TGA were performed to characterize silane-modified MIL-53 (S-MIL-53) and prepared MMHFMs. Moreover, the effect of MOFs loading was systematically investigated first; then gas separation performance of MMHFMs for pure and mixed gas was evaluated under different pressures. MMHFMs containing post-functionalized S-MIL-53 achieved remarkable gas permeation properties which was better than model predictions. Compared to pure HFMs, CO2 permeance of MMHFM loaded with 15% S-MIL-53 increased by 157% accompanying with 40% increase for CO2/N2 selectivity, which outperformed the MMHFM filled with naked MIL-53. The pure and mixed gas permeation measurements with elevated feed pressure indicated that incorporation of S-MIL-53 also increased the resistance against CO2 plasticization. This work reveals that post-modified MOFs embedded in MMHFMs facilitate the improvement of gas separation performance and suppression of membrane plasticization.

High-flux polysulfone mixed matrix hollow fiber membrane incorporating mesoporous titania nanotubes for gas separation

Abstract In this study, the gas separation performance of polysulfone (PSF) hollow fiber mixed matrix membranes (MMMs) incorporated with nanotubes derived from titania were investigated. Titania nanotubes (TNTs) were synthesized via facile hydrothermal method of different reaction times: 10 h and 48 h. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and BET analysis were conducted to scrutinize the structural morphology of the as-synthesized TNTs. TNTs produced under prolonged reaction exhibited larger tube diameters, but have rather smaller pores. No functionalizations or modifications were made regarding the surface chemistry of the TNTs prior to blending with the spinning dope. Defect-free membranes were attained up to 0.6 wt% addition of TNT10. The measured permeances for all gases tested were profoundly increased with the addition of TNTs. PSF-TNT10 0.4 wt% MMM recorded the highest permeance enhancement (about 150%), with H2, CO2, O2 permeance of 269 GPU, 120 GPU, and 26 GPU, respectively, with O2/N2, H2/CH4, CO2/CH4, and CO2/N2 selectivity remained higher than the neat membrane. TNT48 MMM demonstrated relatively lower fluxes but higher selectivity which ascribed to its smaller internal tube diameter endowing better size-exclusion capability. The TNTs formation mechanisms were discussed to justify the evolution of gas separation performance of TNT-incorporated MMMs. In light of the findings, hydrothermal method can be regarded as a versatile technique for producing TNTs of different morphologies simply by manipulating its reaction parameters. On top of that, TNTs being a low cost material, it holds enormous potential to be widely exploited in gas separation applications.

Adsorptive removal of arsenic from groundwater using chemically treated iron ore slime incorporated mixed matrix hollow fiber membrane

Abstract Iron ore slime was chemically treated and impregnated in polysulfone hollow fibers for treatment of arsenic contaminated water. Improvement of arsenic removal capacity of the treated slime was observed due to deposition of metallic hydroxide/oxyhydroxide on its surface. Successful incorporation of iron ore slime within the membrane matrix was confirmed by X-ray diffractograms. Scanning electron micrographs confirmed the blockage of pores within polysulfone membranes by the additive, resulting in decrease of porosity, permeability and molecular weight cut off. However, improved hydrophilicity, higher surface roughness and arsenic uptake capacity of prepared membranes were observed. Mechanism of arsenic removal by the mixed matrix membrane was governed by electrostatic attraction mediated adsorption. Membrane with the highest additive percentage (10 wt%) produced arsenic free water for 14 h for real life feed solution at 11.5 L/m2 h, when operated in dynamic mode. Exhausted membrane was regenerated for three cycles using synthetic solution. Breakthrough time for arsenic removal was reduced from 28 h to 22 h and 14 h after second and third cycle, respectively. Maximum interference effect on removal process is shown by dissolved sulfate ions. The membrane was also able to remove microorganisms and iron simultaneously from real life feed solution below their WHO approved permissible level.