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In this study, two different methods were used to introduce functionalized graphene oxide (GO) onto the surface of nanofiltration (NF) membrane to improve its performance for heavy metal removal. The first method was based on coating in which the surface of NF membrane was coated with cross-linked GO, while the second method was introducing GO into monomer solution during interfacial polymerization. The efficiency of different methods was then compared by characterizing membrane physiochemical properties, as well as separation performance. With regard to performances, the water flux of TFN-i2 membrane (with GOs incorporated into thin layer) was reported to be 95 L/m2 h compared to 75 L/m2 h found in the TFN-c2 membrane (with GOs coated on the surface) at 8 bar. Both modified membranes exhibited higher water flux than the control membrane without GO incorporation (40 L/m2 h). Although the water flux of TFN-c2 membrane was lower, it achieved higher cobalt removal (97%) than that of TFN-i2 membrane (73%) due to its higher negative surface charge that improved separation via the Donnan exclusion effect.

Graphical abstract Illustration of AA-modified TFN membrane embedded with surface-modified TNTs., Highlights • Rapid and environmentally friendly method for surface modification of thin film nanocomposite (TFN) membrane. • The developed surface-modified TFN membrane also exhibited remarkable antifouling property and flux recovery rate (>95%). • NaCl passage reduced from 2.43% to 1.50% without significantly altering pure water flux., Introduction Nanomaterials aggregation within polyamide (PA) layer of thin film nanocomposite (TFN) membrane is found to be a common issue and can negatively affect membrane filtration performance. Thus, post-treatment on the surface of TFN membrane is one of the strategies to address the problem. Objective In this study, an eco-friendly surface modification technique based on plasma enhanced chemical vapour deposition (PECVD) was used to deposit hydrophilic acrylic acid (AA) onto the PA surface of TFN membrane with the aims of simultaneously minimizing the PA surface defects caused by nanomaterials incorporation and improving the membrane surface hydrophilicity for reverse osmosis (RO) application. Methods The TFN membrane was first synthesized by incorporating 0.05 wt% of functionalized titania nanotubes (TNTs) into its PA layer. It was then subjected to 15-s plasma deposition of AA monomer to establish extremely thin hydrophilic layer atop PA nanocomposite layer. PECVD is a promising surface modification method as it offers rapid and solvent-free functionalization for the membranes. Results The findings clearly showed that the sodium chloride rejection of the plasma-modified TFN membrane was improved with salt passage reduced from 2.43% to 1.50% without significantly altering pure water flux. The AA-modified TFN membrane also exhibited a remarkable antifouling property with higher flux recovery rate (>95%, 5-h filtration using 1000 mg/L sodium alginate solution) compared to the unmodified TFN membrane (85.8%), which is mainly attributed to its enhanced hydrophilicity and smoother surface. Furthermore, the AA-modified TFN membrane also showed higher performance stability throughout 12-h filtration period. Conclusion The deposition of hydrophilic material on the TFN membrane surface via eco-friendly method is potential to develop a defect-free TFN membrane with enhanced fouling resistance for improved desalination process.

Ammonium is known to be one of the most significant pollutants in water bodies. The presence of ammonium in water is mainly originated from agricultural activities, domestic sewage and industrial effluent. This study evaluates the performance of two commercial thin film composite (TFC) membranes, i.e., NF270 and XLE from FilmTec™ for ammonium removal using synthetic wastewater and domestic sewage. The filtration experiment was conducted at different feed ammonium concentrations, humic acid concentrations, pHs and pressure. Results showed that the membrane rejection against ammonium increased dramatically with increasing ammonium concentration. However, the membrane flux was slightly compromised at higher ammonium concentration. With respect to pH, highest ammonium removal rate was able to be achieved at an optimum pH of 10. Besides, the permeation flux increased gradually with increasing feed pressure. From the results, the XLE membrane outperformed the NF270 membrane in terms of ammonium rejection. The retentate of XLE membrane filtration process was found to be useful as liquid fertiliser for plant growth. The results indicated that the TFC membrane process is not only able to produce permeate with an ammonium concentration below the acceptable limit of 10 mg/L but also able to produce retentate with enriched ammonium for plant growth.

This work aims to investigate the polyamide (PA) morphology on polysulfone (PSf) membrane supports with different morphologies. It was achieved by systematically varying the N-Methyl-2-Pyrrolidone (NMP) and Dimethylformamide (DMF) solvent composition ratios in dope solution as adapted in Tiraferri et al. The PSf membrane support was firstly synthesized via phase separation technique. Next, the PA layer of the thin film composite (TFC) membrane was synthesized via consistent interfacial polymerization parameters on the PSf membrane support. The PA layer over the resulting array of membrane supports was investigated on their surface wettability, top and cross-sectional morphologies, and performances. Result shows that with more NMP content in the dope solution produces thin and dense sponge-like top skin layer with intense extended finger-like macrovoids sublayer. Meanwhile, more DMF content in the dope solution produces thicker and dense sponge-like morphology on the top skin with finger-like pores underneath. A layer of smaller and loosen ridge-and-valley PA structures is formed on the thicker and dense sponge-like morphology. TFC membrane over support made of NMP to DMF (40:60) was observed had the highest hydrophilicity with the lowest contact angle measurement of 61.9 ± 3.1°. It also performed the highest water permeability of 4.06 LMH/bar, moderate salt rejection of 95.65% with salt permeability of 1.9 gMH.

Adsorption and photocatalytic degradation of aerobically-treated palm oil mill effluent (AT-POME), a prominent effluent across palm oil producing countries, using commercially available TiO2 P25 Degussa powder and titania nanotubes (TNT) prepared via hydrothermal technique was investigated. The as-prepared TNT exhibited tubular, open ended structure, unchanged crystallinity as compared to TiO2 and a surface area close to 200 m2/g, almost 4 folds as compared to commercial TiO2. TNT outperformed TiO2 in terms of adsorption and photodegradation of AT-POME under ultraviolet (UV) light irradiation, where TNT was able to remove up to 81% of AT-POME coloration as opposed to commercial TiO2 (69.5%) within the same experiment duration. The results indicate that TNT performs better compared to commercial TiO2 for wastewater remediation via photocatalysis.

Harvesting clean water from seawater is widely studied in thermal-driven vacuum membrane distillation (VMD) application. Although the conventional VMD promotes excellent flux due to the deaeration by means of vacuum, the external heat supply of the system suffers the heat loss during pumping high feed volume. The batch submerged VMD (S-VMD) which has internal heat supply was introduced in this work to provide uniform feed temperature in the feed tank. This simple and space-saving design makes it particularly suitable to supply water for small community with space limitation. To evaluate the energy efficiency of the S-VMD in desalinating seawater, the performance of the system had been simulated and verified with the experimental results. The effects of main operating parameters including feed temperature and its circulation rate, heat transfer coefficient, vacuum degree on permeate side, packing density of membrane and temperature polarization on the membrane permeation flux using saline water feed had been experimentally investigated. Energy efficiency in terms of gained output ratio (GOR) and thermal loss of the heat supply had also been examined. The simulated results showed that the flux enhanced with the increase of feed temperature, circulation rate, vacuum degree and packing density of membrane. The combination of feed temperature with circulation flow and packing density of membrane played dominant role to improve permeate flux and GOR of the system. This finding is important for the future implementation of S-VMD system in space-constraint remote area. The simulation results were in good agreement with experimental results, recording less than 5% error.

A green hybrid nanocomposite of rGO/ZIF-8 was successfully synthesised via multi-recycling approach by reusing unreacted reagents in mother liquor. This eco-friendly approach allows for minimal addition of fresh chemicals and thus reduces the synthesis cost. The one-pot synthesised rGO/ZIF-8 powder was recovered by filtration, and the mother liquor filtrate was reused for the next cycle of synthesis. The product yield from each cycle was evaluated by quantifying the product’s mass. Detailed characterisation studies were carried out by using XRD, TGA, FTIR, BET, SEM, and TEM. ZIF-8 nanoparticles anchored well on the surfaces of rGO without sacrificing the product yield. This approach minimises the use of organic linker and its waste product, leading to low-cost and environmentally friendly synthesis process for rGO/ZIF-8.

Enhancing the efficiency of reverse osmosis (RO) applications through the design and modification of spacer geometries for spiral wound membrane (SWM) modules remains a challenging task. In this work, four 3D feed spacer geometries with different degrees of “floating” characteristics are studied using computational fluid dynamics (CFD) simulations to investigate the mechanisms that result in shear stress and mass transfer enhancement. The modelled data reveal that the floating ratio (Rf) is not a determining factor for mass transfer enhancement, as the transport mechanism is more strongly dependent on other geometric characteristics, such as a 2- or 3-layer design. The λ2 analysis confirms our hypothesis, as the middle filament in a 3-layer design disrupts the formation of the large streamwise vortex located downstream of the intersection between the top and bottom filaments at Reh 200. This explains why 3-layer spacers (both woven and non-woven) show lower Sherwood number (Sh) than a 2-layer woven (2LW) spacer at Reh 200. However, at a smaller Reh (

There is increasing interest in the use of polyether ether ketone (PEEK) for orthopedic and dental implant applications due to its elastic modulus (close to that of bone), biocompatibility and radiolucent properties. However, PEEK is still categorized as bioinert owing to its low integration with surrounding tissues. Methods such as depositing hydroxyapatite (HA) onto the PEEK surface could increase its bioactivity. However, depositing HA without damaging the PEEK substrate is still required further investigation. Friction stir processing is a solid-state processing method that is widely used for composite substrate fabrication. In this study, a pinless tool was used to fabricate a HA/PEEK surface nanocomposite for orthopedic and dental applications. Microscopical images of the modified substrate confirmed homogenous distribution of the HA on the surface of the PEEK. The resultant HA/PEEK surface nanocomposites demonstrated improved surface hydrophilicity coupled with better apatite formation capacity (as shown in the simulated body fluid) in comparison to the pristine PEEK, making the newly developed material more suitable for biomedical application. This surface deposition method that is carried out at low temperature would not damage the PEEK substrate and thus could be a good alternative for existing commercial methods for PEEK surface modification.

The photoactivity of iron doped titania nanotubes (Fe-TNT) synthesized via facile hydrothermal technique was investigated using reactive black 5 (RB 5) as the model pollutant. The incorporation of iron (Fe) nanoparticles in titania nanotubes (TNT) structure was confirmed via x-ray diffraction while x-ray photoelectron spectroscopy analysis showed the presence of Fe3+ ions in the nanotube structure. Ultraviolet-visible spectrophotometer analysis confirmed the reduction in band gap energy, from 3.595 eV to 2.097 eV due to the interaction between Fe into TNT structure. The formation of tubular structure has also increased the specific surface area of the photocatalyst from 56.00 m2/g to between 246.23 m2/g to 142.01 m2/g for all Fe-TNT. Fe-TNT with Fe:Ti ratio of 1:3 demonstrated promising photodegradation efficiency of 90% within 120 min of visible light irradiation. The reduced band gap energy and improved visible light responsiveness imparted by incorporation of Fe nanoparticles into structure of TNT are the main factors for improved photocatalytic degradation.

Many studies indicated that phthalates, a common plasticizer, lurk silently in water bodies and can potentially harm living organisms. Therefore, removing phthalates from water sources prior to consumption is crucial. This study aims to evaluate the performance of several commercial nanofiltrations (NF) (i.e., NF3 and Duracid) and reverse osmosis (RO) membranes (i.e., SW30XLE and BW30) in removing phthalates from simulated solutions and further correlate the intrinsic properties of membranes (e.g., surface chemistry, morphology, and hydrophilicity) with the phthalates removal. Two types of phthalates, i.e., dibutyl phthalate (DBP) and butyl benzyl phthalate (BBP), were used in this work, and the effects of pH (ranging from 3 to 10) on the membrane performance were studied. The experimental findings showed that the NF3 membrane could yield the best DBP (92.5–98.8%) and BBP rejection (88.7–91.7%) regardless of pH, and these excellent results are in good agreement with the surface properties of the membrane, i.e., low water contact angle (hydrophilicity) and appropriate pore size. Moreover, the NF3 membrane with a lower polyamide cross-linking degree also exhibited significantly higher water flux compared to the RO membranes. Further investigation indicated that the surface of the NF3 membrane was severely covered by foulants after 4-h filtration of DBP solution compared to the BBP solution. This could be attributed to the high concentration of DBP presented in the feed solution owing to its high-water solubility (13 ppm) compared to BBP (2.69 ppm). Further research is still needed to study the effect of other compounds (e.g., dissolved ions and organic/inorganic matters that might be present in water) on the performance of membranes in removing phthalates.

An investigation of the effect of the molecular weight of polyethylene glycol (PEG) on thin-film composite (TFC) flat sheet polysulfone membrane performance was conducted systematically, for application in forward osmosis (FO) and pressure retarded osmosis (PRO). The TFC flat sheet PSf-modified membranes were prepared via a non-solvent phase-separation technique by introducing PEGs of different molecular weights into the dope solution. The TFC flat sheet PSf-PEG membranes were characterized by SEM, FTIR and AFM. The PSf membrane modified with PEG 600 was found to have the optimum composition. Under FO mode, this modified membrane had a water permeability of 12.30 Lm−2h−1 and a power density of 2.22 Wm−2, under a pressure of 8 bar in PRO mode, using 1 M NaCl and deionized water as the draw and feed solutions, respectively. The high water permeability and good mechanical stability of the modified TFC flat sheet PSF-PEG membrane in this study suggests that this membrane has great potential in future osmotically powered generation systems.

The effects of flipping membranes with hydrophilic/hydrophobic asymmetry are well documented in the literature, but not much is known on the impact of flipping a membrane with dense/porous layer asymmetry. In this work, the pure water flux (PWF) of a commercial polyethersulfone (PES) membrane and a ceramic ultrafiltration (UF) membrane was measured in the normal and inverted positions. Our experimental results showed that the PWF was two orders of magnitude higher when the PES membrane was flipped to the inverted position, while the increase was only two times for the ceramic membrane. The filtration experiments were also carried out using solutions of bovine serum albumin and poly(vinylpyrrolidone). A mathematical model was further developed to explain the PWF increase in the inverted position based on the Bernoulli’s rule, considering a straight cylindrical pore of small radius connected to a pore of larger radius in series. It was found by simulation that a PWF increase was indeed possible when the solid ceramic membrane was flipped, maintaining its pore geometry. The flow from a layer with larger pore size to a layer with smaller pore size occurred in the backwashing of the fouled membrane and in forward and pressure-retarded osmosis when the membrane was used with its active layer facing the draw solution (AL-DS). Therefore, this work is of practical significance for the cases where the direction of the water flow is in the inverted position of the membrane.

MIL-101(Cr), a subclass of metal–organic frameworks (MOFs), is a promising adsorbent for carbon dioxide (CO2) removal due to its large pore volume and high surface area. Solvent-free synthesis of MIL-101(Cr) was employed in this work to offer a green alternative to the current approach of synthesizing MIL-101(Cr) using a hazardous solvent. Characterization techniques including XRD, SEM, and FTIR were employed to confirm the formation of pure MIL-101(Cr) synthesized using a solvent-free method. The thermogravimetric analysis revealed that MIL-101(Cr) shows high thermal stability up to 350 °C. Among the materials synthesized, MIL-101(Cr) at the molar ratio of chromium precursor to terephthalic organic acid of 1:1 possesses the highest surface area and greatest pore volume. Its BET surface area and total pore volume are 1110 m2/g and 0.5 cm3/g, respectively. Correspondingly, its CO2 adsorption capacity at room temperature is the highest (18.8 mmol/g), suggesting it is a superior adsorbent for CO2 removal. The textural properties significantly affect the CO2 adsorption capacity, in which large pore volume and high surface area are favorable for the adsorption mechanism.

The commercial thin-film composite (TFC) nanofiltration (NF) membrane is unsuitable for engineered osmosis processes because of its thick non-woven fabric and semi-hydrophilic substrate that could lead to severe internal concentration polarization (ICP). Hence, we fabricated a new type of NF-like TFC membrane using a hydrophilic coated polyacrylonitrile/polyphenylsulfone (PAN/PPSU) substrate in the absence of non-woven fabric, aiming to improve membrane performance for water and wastewater treatment via the engineered osmosis process. Our results showed that the substrate made of a PAN/PPSU weight ratio of 1:5 could produce the TFC membrane with the highest water flux and divalent salt rejection compared to the membranes made of different PAN/PPSU substrates owing to the relatively good compatibility between PAN and PPSU at this ratio. The water flux of the TFC membrane was further improved without compromising salt rejection upon the introduction of a hydrophilic polydopamine (PDA) coating layer containing 0.5 g/L of graphene oxide (PDA/GO0.5) onto the bottom surface of the substrate. When tested using aerobically treated palm oil mill effluent (AT-POME) as a feed solution and 4 M MgCl2 as a draw solution, the best performing TFC membrane with the hydrophilic coating layer achieved a 67% and 41% higher forward osmosis (FO) and pressure retarded osmosis (PRO) water flux, respectively, compared to the TFC membrane without the coating layer. More importantly, the coated TFC membrane attained a very high color rejection (>97%) during AT-POME treatment, while its water flux and reverse solute flux were even better compared to the commercial NF90 and NF270 membranes. The promising outcomes were attributed to the excellent properties of the PAN/PPSU substrate that was coated with a hydrophilic PDA/GO coating and the elimination of the thick non-woven fabric during TFC membrane fabrication.

The usage of pharmaceutical products is becoming increasingly extensive because of the emerging ailments. Analgesic and antipyretic drugs are ranked the most used drugs worldwide. Unused or expired analgesic and antipyretic drugs are being disposed into aquatic environment which could lead to water pollution bringing adverse impacts to the living organisms which in the end cause fatality. Paracetamol, as one of the most common drug used for analgesic and antipyretic purposes to treat fever and relieve pain, was found to have much higher concentration in aquatic stream and thus need to be removed efficiently. Various technologies for paracetamol removal have been established to solve this thorny issue. This study first gives reader understanding regarding some detrimental effects of paracetamol waste towards environmental and mankind with its current disposal level and limit. Then it provides comprehensive review on the technologies to remove paracetamol effectively from aqueous stream, such as advanced oxidation process, biodegradation, adsorption, and membrane separation, which in turn inspires reader for more innovation. This review is also wrapped up with the future challenges and prospects of these techniques. By comparing all advantages and disadvantages of different technologies, advanced oxidation process is then recommended as the most practically feasible method.

The discharge of industrial effluent containing heavy metal ions would cause water pollution if such effluent is not properly treated. In this work, the performance of emerging nanofiltration (NF) like-forward osmosis (FO) membrane was evaluated for its efficiency to remove copper ion from water. Conventionally, copper ion is removed from aqueous solution via adsorption and/or ion-exchange method. The engineered osmosis method as proposed in this work considered four commercial NF membranes (i.e., NF90, DK, NDX and PFO) where their separation performances were accessed using synthetic water sample containing 100 mg·L−1 copper ion under FO and pressure retarded osmosis (PRO) orientation. The findings indicated that all membranes could achieve almost complete removal of copper regardless of membrane orientation without applying external driving force. The high removal rates were in good agreement with the outcomes of the membranes tested under pressure-driven mode at 1MPa. The use of appropriate salts as draw solutes enabled the NF membranes to be employed in engineered osmosis process, achieving a relatively low reverse solute flux. The findings showed that the best performing membrane is PFO membrane in which it achieved > 99.4% copper rejection with very minimum reverse solute flux of

This paper evaluated the effectiveness of polyester (PS)/poly(vinyl alcohol) (PVA) dynamic membrane (DM) incorporating photocatalytic zeolite/TiO2 for oil-in-water (O/W) emulsion separation. The photocatalytic zeolite/TiO2 was established onto the membrane surface via self-forming and pre-coating method with the aims of reducing membrane fouling during O/W emulsion treatment. The results obtained showed that the pre-coated composite DM could decrease support membrane fouling by improving flux recovery rate by 5.8%, while the use of the self-forming composite DM exhibited lower flux recovery rate after three filtration cycles in O/W emulsion treatment. The results were confirmed by cleaning and oil removal efficiency. The cleaning efficiency of composite DM was further enhanced by substitution of deionized water with sodium dodecyl sulfate as a cleaning agent in the treatment of O/W emulsion. Using sodium dodecyl sulfate, the pre-coated composite DM showed higher flux recovery rate (81%) than the self-forming composite DM. In addition, the photocatalytic effects of zeolite/TiO2 on the DM with respect to flux recovery rate and oil rejection under UV light source were investigated. It was found that by combining cleaning process and UV irradiation, the fouling of DM was further decreased, recording high flux recovery rate (up to 83.6%) without compromising oil rejection rate (85.3%).

In this study, the capability of a mixed matrix composite membrane (MMCM) fabricated using polyether block amide polymer PEBAX MH1657 from Arkema and in lab synthesized aminated partially reduced graphene oxide (A-prGO) nanofiller as a selective layer has been studied for gas separation. Moreover, the effects of nanofiller addition on membrane structure properties and performance were examined. The PEBAX/A-prGO membrane was fabricated as a selective layer on top of a supporting substrate layer of polysulfone 1700. MMCM was prepared in five different loadings of A-prGO nanofiller (0, 0.05, 0.1, 0.2, 0.6 (w/w)%) of the used PEBAX amount. The synthesized nanofiller and fabricated MMCM were characterized using different characterization tests (XRD, FTIR, EDX, and SEM). The optimum separation of the membrane was found when the loading of A-prGO was 0.1%. The permeability of the membrane for CO2, N2 and CH4 gases were 47.5 Barrer for CO2, 0.45 Barrer for N2 & 2 Barrer for CH4 while the selectivity of CO2/N2 and CO2/CH4 are 105.6 and 23.75, respectively. Surprisingly, the fabricated membrane performance found to be above the Robeson 2008 upper bound of permeability- selectivity relation for CO2/N2 gases separation.

This paper reports the synthesis and characterization of novel ultrafiltration (UF) electrospun nanofibrous membranes (ENMs) incorporated with iron oxide (Fe3O4) nanoparticles (NPs) for effective oily solution treatment. Three strategies were employed to improve the physiochemical properties of the resultant ENMs. Firstly, n-methyl-pyrrolidinone (NMP) was added to dimethylformamide (DMF) wherein the solvent stimulated fusion of the inter-fiber junctions was enhanced. Secondly, Fe3O4 NPs were introduced into the ENMs to improve their hydrophilicity and anti-fouling resistance against oil molecules. Thirdly, hot pressed technique was adopted to strengthen the electrospun mat, avoiding delamination of the ENMs layer during liquid filtration processes. The findings indicated that the developed Fe3O4 NPs incorporated ENMs exhibited outstanding oil elimination (94.01%) and excellent water flux recovery (79.50%) when tested with synthetic oil solution (12,000 ppm). Water productivity of over 3200 L/m2 h was achieved without forfeiting the rate of oil removal under gravity. Extraordinarily low flux declination disclosed by the proposed ENMs was attributed to their tailored surface resistance mediated oil anti-fouling character. The enhanced mechanical and oil anti-fouling traits of the prepared ENMs were established to be potential for the treatment of diverse oily effluents (especially emulsions of oil–water) in the industries.

In this study, a quantitative performance of three commercial polyamide nanofiltration (NF) membranes (i.e., NF, NF90, and NF270) for phosphorus removal under different feed conditions was investigated. The experiments were conducted at different feed phosphorus concentrations (2.5, 5, 10, and 15 mg·L−1) and elevated pHs (pH 1.5, 5, 10, and 13.5) at a constant feed pressure of 1 MPa using a dead-end filtration cell. Membrane rejection against total phosphorus generally increased with increasing phosphorus concentration regardless of membrane type. In contrast, the permeate flux for all the membranes only decreased slightly with increasing phosphorus concentration. The results also showed that the phosphorus rejections improved while water flux remained almost unchanged with increasing feed solution pH. When the three membranes were exposed to strong pHs (pH 1.5 and 13.5) for a longer duration (up to 6 weeks), it was found that the rejection capability and water flux of the membranes remained very similar throughout the duration, except for NF membrane with marginal decrement in phosphorus rejection. Adsorption study also revealed that more phosphorus was adsorbed onto the membrane structure at alkaline conditions (pH 10 and 13.5) compared to the same membranes tested at lower pHs (pH 1.5 and 5). In conclusion, NF270 membrane outperformed NF and NF90 membranes owing to its desirable performance of water flux and phosphorus rejection particularly under strong alkali solution. The NF270 membrane achieved 14.0 L·m−2·h−1 and 96.5% rejection against 10 mg·L−1 phosphorus solution with a pH value of 13.5 at the applied pressure of 1 MPa.

A literature search revealed a lack of up-to-date and detailed review articles on the use of membrane technologies for heavy metal removal. Thus, this article provides a comprehensive review of the performance and capability of different membrane processes and discusses the advantages and disadvantages of each. This review also discusses the technical challenges of existing membrane process and recommends future research to further enhance membrane performance and render it the best alternative for treating water laden with heavy metals.

Novel thin film nanocomposite (TFN) nanofiltration membrane with tunable physico-chemical properties and separation performances was fabricated by incorporating the copper benzene-1,3,5-tricarboxylate (CuBTC) nanoparticles with different concentrations (ranging from 0 to 0.75 wt.%) in the polysulfone (PSf) substrates, followed by the interfacial polymerization process of trimesoyl chloride (TMC) and piperazine (PIP) to establish top selective layer. Charaterization results show that both chemical and physical properties of poly(piperazineamide) selective layer was altered when PSf substrate was modified by CuBTC. The introduction of CuBTC nanoparticles improved the hydrophilicity of the TFN membranes (from 70.25° to 59.02°) and promoted formation of more linear structure of poly(piperazineamide) entangled with −COOH pendant groups. By incorporating 0.25 wt.% of CuBTC into the PSf substrate, the resultant membrane flux was enhanced by 22% with MgSO4 rejection remained at 97.31%. Furthermore, a notable increment of rejection against NaCl could be attained by increasing the CuBTC content in the substrate. This could be explained by the Donnan potential effect occurred on the more linear structures of poly(piperazineamide) surfaces, which results in an increase in the selectivity of monovalent salts. Moreover, the incorporation of CuBTC rendered the TFN membranes to exhibit good anti-fouling property against bovine serum albumin.

The raising oil consumption in oil and gas industries has exacerbated the disposal of oil waste into various water streams. This phenomenon has called for treatments to prevent threats to the human and environment. With some great advantages such as lower membrane fouling rate, lower energy requirement and higher water recovery rate compared to the conventional pressure-driven membrane processes, forward osmosis (FO) has been recognized as a potential candidate for oily wastewater treatment. In this study, a poly[3-(N-2-methacryloylxyethyl-N,N-dimethyl)-ammonatopropanesulfonate] (PMAPS) incorporated thin film composite (TFC) membrane with excellent anti-fouling properties was fabricated for oily wastewater through forward osmosis process. PMAPS was blended with polyethersulfone (PES) dope solution and cast into PES support layer. Interfacial polymerization (IP) technique was applied to form a thin polyamide (PA) layer atop of the PES support layer. The PMAPS incorporated TFC membranes were characterized for their morphology and surface hydrophilicity. The resultant 1% PMAPS-TFC membrane exhibited high water flux of 15.79 ± 0.3 L/m2.h and oil flux of 12.54 ± 0.8 L/m2.h when tested in FO mode for oil removal from oily wastewater using 1000 ppm emulsified oily solution as feed solution and 2 M NaCl as draw solution. The oil rejection up to 99% was also obtained. Most significantly, PMAPS incorporated TFC membrane outperformed neat TFC membrane with lower fouling propensity for oily waste treatment. When treating 10000 ppm oil emulsion, PMAPS-TFC was able to achieve average flux recovery rate of 97% while neat TFC only able to achieve 70.8% of average flux recovery rate.

In this study, polyethersulfone (PES) hollow fibre membranes incorporated with different loadings of coupled zinc–iron oxide (ZIO) (0–2 wt%) nanoparticle were fabricated and used to remove the colour of aerobically treated palm oil mill effluent (AT-POME). The ZIO nanoparticles were synthesized via solution combustion method and characterized for their physicochemical properties. A specific amount of ZIO nanoparticles was then added into the PES dope solution followed by dry/wet-jet spinning technique to produce hollow fibre membrane of negatively charge surface properties. The membranes were characterized with respect to their cross-sectional morphology, hydrophilicity, tensile strength and surface charge. The separation performance of the membranes was then evaluated using pure water and AT-POME as feed solution. Results show that the membrane incorporated with 0.5 wt% ZIO was the best performing membrane, showing pure water flux and AT-POME flux of 2.46 and 2.0 L/m2 h, respectively, when tested at 1 bar. Furthermore, this membrane also showed reasonably good rejection against colour (76.2% reduction) and improved antifouling resistance.

In this work, a new type of ultrafiltration (UF) electrospun nanofibrous membranes (ENMs) incorporating hydrous manganese dioxide (HMO) nanoparticles was fabricated with the objective of improving properties of polyethersulfone (PES)-based membrane for synthetic oily solution treatment. Two treatments were carried out to improve the mechanical property and hydrophilicity of the PES-based membrane without compromising its porosity and water permeance. The first treatment involved the use of mixed solvents – dimethylformamide and n-methyl-pyrrolidinone (DMF/NMP) in which NMP is a high vapor pressure component that could enhance the mechanical properties of the nanofibrous by improving solvent-induced fusion of inter-fiber junction points. The second treatment involved the incorporation of specific amount of HMO nanoparticles in PES dope solution to enhance membrane hydrophilicity. Heat treatment was also adopted as an effective approach to strengthen and prevent delamination of the nanofibrous mat during UF process. The HMO-incorporated ENMs exhibited an excellent oil rejection (97.98% and 94.04%) and a promising water flux recovery (89.29% and 71.10%) when used to treat a synthetic oily solution containing 5000 or 10,000 ppm oil, respectively. The best promising HMO-incorporated ENM exhibited much higher magnitude of water productivity (>7000 L/m2h) without sacrificing oil removal rate. Most importantly, this nanofillers-incorporated membrane showed significantly lower degree of flux decline as a result of improved surface resistance against oil fouling and is of potential for long-term operation with extended lifespan. The promising mechanical and anti-fouling properties of the ENMs is potentially applicable in the efficient industrial oily effluents treatment when challenged with oil-in-water emulsions.

Expansion of the aquaculture industry has been accompanied by environmental impact as the discharged effluent contains excess nutrients such as phosphorus compounds. Recovery of such nutrients is not economically feasible as it presents in trace amounts. Furthermore, brackish aquaculture effluent which contains high sodium chloride (NaCl) content makes the treated solution inappropriate for fertilizer production. Herein, this study proposed a diafiltration-nanofiltration route to perform a simultaneous phosphate concentrating and osmotion (sodium) removal from brackish aquaculture effluent. Effects of operating pressure, phosphate, and sodium content on membrane performance were first determined using Desal-5 DK membrane with three types of solutions namely (i) freshwater without NaCl, (ii) dilute brackish water with 1,500 mg/L NaCl, and (iii) brackish water with 10,000 mg/L NaCl. It was found that at 4 bar operating pressure, it could achieve higher phosphate rejection and sodium permeance. The presence of NaCl negatively influenced both phosphate rejection and concentrating factor (CF) due to the salt screening effect. It was noteworthy that negative sodium rejection (up to -16%, CF1) could be attained, indicating the concentrating effect for sodium was negligible. The concentrating process was effective to concentrate phosphate by 2-fold but less effective in removing sodium. Diafiltration was then introduced and resulted in about 76% of sodium removal. Diafiltration-nanofiltration (DF-NF) mode was shown to be a more efficient method than nanofiltration-diafiltration (NF-DF) mode as phosphate could be concentrated up to 2 factors with 99 wt% of sodium being removed from the real brackish aquaculture effluent. These findings showed that DF-NF is a feasible approach for concentrating phosphate while removing sodium ions from aquaculture effluent and the recovered nutrient solution has huge potential to be applied as liquid fertilizer for hydroponic plants.

Hazardous micropollutants (MPs) such as pharmaceutically active compounds (PhACs), pesticides and personal care products (PCPs) have emerged as a critical concern nowadays for acquiring clean and safe water resources. In the last few decades, innumerable water treatment methods involving biodegradation, adsorption and advanced oxidation process have been utilized for the removal of MPs. Of these methods, membrane technology has proven to be a promising technique for the removal of MPs due to its sustainability, high efficiency and cost-effectiveness. Herein, the aim of this article is to provide a comprehensive review regarding the MPs rejection mechanisms of reverse osmosis (RO) and nanofiltration (NF) membranes after incorporation of nanomaterials and also surface modification atop the PA layer. Size exclusion, adsorption and electrostatic charge interaction mechanisms play important roles in governing the MP removal rate. In addition, this review also discusses the state-of-the-art research on the surface modification of thin film composite (TFC) membrane and nanomaterials-incorporated thin film nanocomposite (TFN) membrane in enhancing MPs removal performance. It is hoped that this review can provide insights in modifying the physicochemical properties of NF and RO membranes to achieve better performance in water treatment process, particularly for the removal of emerging hazardous substances.