Magnetic magnetite (Fe3O4) nanoparticles have attracted a great deal of attention in both fundamental research and practical applications over the past decades. Down to the nanoscale, superparamagnetic Fe3O4 nanoparticles with only a single magnetic domain exhibit high magnetic susceptibility, which provides a stronger and faster magnetic response. Their superparamagnetic properties together with other intrinsic properties such as low toxicity, high surface area-to-volume ratio and simple separation methodology, making them ideal for environmental remediation, biomedical, and agricultural applications. This review discusses three conventional wet chemical methods, including chemical co-precipitation, sol-gel synthesis and thermal decomposition for the preparation of superparamagnetic Fe3O4 nanoparticles with controlled size and magnetic properties. Nowadays, with the growing research interest in Fe3O4 nanoparticles, there is a great amount of researches reported on efficient routes to prepare size-controlled magnetic nanoparticles. Thus, this review is designed to report the recent information from synthesis to the characterization of Fe3O4 nanoparticles as well as the discussion of future perspective in this research area.
Graphene based conducting polymer composites are emerging contenders for newer optoelectronics devices like solar cells and linear / nonlinear optical devices. Beside these advanced applications, characterization approaches to analyze their liner/nonlinear optical constants, surface chemical state and structural analysis in thin film states are much needed. Herein, we reported a facile approach for the fabrication of graphene oxide (GO) and polyaniline (PANI) nano composites (PANI/GO) thin films using spin coating. Thereafter, the liner/nonlinear optical constants including first and third order nonlinear optical susceptibility were calculated using UV–vis (UV–vis) near infra-red absorption spectroscopic technique which will be an alternative to Z-scan approach and is poorly explored till now for such composites. Moreover, the increase or decrease in elemental bonding or interactions between CC, CO, COC, CN and percentage occurrence of COH, OCO, –NH2, –N+H=, and –N+H2– functionalities in PANI/GO composites were concisely explored using X-ray photoelectron spectroscopy (XPS). Addition to proving the amorphous nature of PANI/GO composites in their X-ray diffraction studies, an increase in intensity of GO peak was explored due to an increase in elemental interactions among the GO and PANI. The reduction in band gap (3.27 to 2.66 eV) and diameter of Sp2 carbon (19.62 to 15.96 nm) of PANI/GO thin films was observed with an increase in the GO concentration. The first order nonlinear optical susceptibility (X (1)) is influenced by π-π* and n- π* interaction. The third order nonlinear optical susceptibility (X (3)) was found in the range of 10−10 to 10-7 esu which can be further, optimized by changing the ratio of GO and PANI.
Omniphobic membranes have recently shown promising performance in water desalination using MD due to their ability to repel all liquid drop types and keep the membrane surface dry. This study successfully modified the surface of robust hydrophilic mullite-stainless steel hollow fibre membranes (M-SS HFMs) to omniphobic properties. The omniphobic layer was achieved through surface grafting with copper oxide (CuO) rough layer by a hydrothermal technique at different hydrothermal reaction times of 1, 2, 3, 4 and 5 h, followed by fluorination step using 1H,1H,2H,2H-perfluorode-cyltriethoxysilane (C8, 97 %). Next, the omniphobic membranes were characterized in terms of membrane morphology, roughness, mechanical strength, pore size/distribution, liquid entry pressure, contact angle and fouling accumulation. The prepared omniphobic M-SS HFMs were also tested through the DCMD system at 80 °C using a feed solution containing 35 g/L of NaCl and 10 mg/L of humic acid as a foulant agent. The results indicated that M-SS HFMs subjected to a 4 h hydrothermal reaction time, resulting in a leaf-like surface structure, exhibited superior characteristics compared to other omniphobic HFMs reported in the literature that used titania (SiO2), zinc oxide (ZnO), and cobalt (Co3O4) as roughing material. These superior features included higher roughness of 0.798 μm, liquid entry pressure of 5.40 bar, and enhanced liquid repellence and contact angles towards DI water of 167°, olive oil of 152°, and ethanol of 145°. Additionally, the M-SS HFMs at 4 h hydrothermal demonstrated remarkable performance in terms of rejection performance (99.99 %) and vapour flux stability of about 29 kg/m2.h in DCMD operations, surpassing the performance of omniphobic HFMs fabricated using mullite-ball clay, mullite-kaolinite, and alumina (Al2O3). Notably, no fouling/wetting on the membrane surface and elements leaching was observed throughout the MD operation. These findings highlight the potential of this omniphobic HFM for seawater desalination using DCMD systems, even in the presence of organic contaminants.
Eliminating phenol and other contaminants from wastewater is an essential step in addressing environmental issues. Using tailored photocatalysts is essential for the effective degradation of phenol via photocatalysis. The main objective of this study is to produce TiO2/ZnO/AgI nanocomposites employing the reflux approach in order to enhance the degradation of phenol in the presence of UV radiation. The nanocomposite incorporates TiO2 and ZnO, resulting in a narrowed band gap that enhances photocatalytic activity. The addition of AgI enhances electron transport capacities, resulting in an inclusive augmentation in performance. The physicochemical properties of the nanocomposite were extensively investigated applying an array of advanced techniques including as XRD, BET, FESEM, TEM, EDX and TGA spectroscopy practices. The combined effect of TiO2, ZnO, and AgI exhibits an approximately 100 % degradation of phenol, exceeding the individual performance of each component. The outcomes indicated that the operational parameters have a substantial impact on the photocatalytic activity, and the addition of H2O2 also improves degradation. The ideal conditions require a low concentration of H2O2 and a dose of 0.3 g/350 mL of nanocomposite. The reaction rate constant was reported as 6.96 × 10−3 min−1 under optimised conditions. The ternary nanocomposite exhibited recyclability for four successive cycles, eventually displaying ∼88 % degradation. The TiO2/ZnO/AgI nanocomposite system exhibits significant photocatalytic efficiency, which has important consequences for addressing environmental concerns caused by the persistent existence of various organic contaminants in water sources.
Since the major route of BPA exposure is via the oral route, BPA may have effects on the gastrointestinal tract, especially on the intestinal barrier, where most digestion and absorption processes occur. In this study, the effects of BPA-treated water on the small intestine (SI) and SI tight junction proteins (TJPs) of both pregnant Sprague-Dawley rats and their fetuses were investigated. Previously, hybrid photocatalytic filtration treatment by a visible light driven N-doped TiO2 membrane has successfully removed up to 81.6% of BPA in water. The effect of BPA-untreated (5.00 ± ppm) and BPA-treated water (0.9 ± ppm) after 21 days of exposure on the jejunum and ileum, as well as the expressions of claudin proteins, were investigated by Western blotting (WB) and hematoxylin and eosin (H&E) in order to investigate the potential of the photocatalytic membrane in removing the detrimental effect of BPA. The results suggest that BPA exposure altered the morphology of villi, and affected the expression level of claudin-2, -3, and -4 proteins in the jejunum and ileum of both pregnant rats and their fetuses. Interestingly, villi and claudins expressions were undisrupted in a treated-BPA water group, which indicated that the degradation of BPA via membranes effectively mitigates the effect on BPA on gastrointestinal tract.
To prevent pipe damage and lower operating costs, natural gas must be cleaned of pollutants like carbon dioxide (CO2) and hydrogen sulphide (H2S). High selectivity of the functional material in the mixed matrix membranes (MMMs) allows for a more efficient gas separation compared to traditional polymeric membranes. However, poor dispersion and compatibility between the functional material and the polymer matrix become one of the major problems of MMMs. The use of zeolite imidazole (ZIF-8) in MMMs has been explored for its ability to separate CO2/CH4 due to its versatile gas molecule diameter range and effective CO2 adsorption. In this study, the effects of ZIF-8 at various loadings were examined on the physical and chemical properties of dual layer hollow fiber MMMs and gas separation efficiency. Following the successful production of 86.25 nm ZIF-8 nanoparticles, ZIF-8-based DLHF MMMs were created. The results showed that 0.5 wt% ZIF-8 loading provided the best results, with excellent interaction between the polymer PSf and the inorganic filler ZIF-8, strong heat resistance, and chemical stability. Increased CO2 permeability and CO2/CH4 ideal selectivity by 72.5 % and 1196.2 % respectively, compared to the unmodified membrane. It was inferred through this study that minimal loading of 0.5 wt% ZIF-8 in the DLHF MMMs improved their ability to separate gases, making them a good option for capturing CO2.
Hollow fibre ceramic membranes are well-known to have unique characteristics, including superior thermal, chemical, and mechanical stabilities. The main drawback of ceramic membranes that limits their commercialisation is their high cost of raw materials. To overcome this disadvantage, a low-cost silica sand-based hollow fibre ceramic membrane (SS-HFCM) was successfully fabricated via combined phase inversion/sintering technique. Prior to fabrication, silica sand powder was first characterised using X-ray fluorescence (XRF), X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and Fourier transform infrared spectroscopy (FTIR) analyses. Furthermore, the morphology and mechanical strength were investigated using scanning electron microscopy (SEM) and three-point bending test, respectively. The effects of two major fabrication process parameters (i.e., sintering temperature and ceramic content) on the mechanical strength, morphology, pure water flux (PWF), and oily-water separation of the SS-HFCM were examined. Based on the findings, the most suitable sintering temperature was 1300 °C. Satisfactory morphological structure and strength of sponge- and finger-like voids at 55 wt% ceramic powder loading was found to be advantageous for the characteristics of the fabricated SS-HFCM. The mechanical strength of 210 MPa was obtained at the sintering temperature and content loading of 1300 °C and 57.5 wt%, respectively. The mechanical strength of SS-HFCM obtained at 1300 °C in this work is significantly higher than those reported in previous studies. Furthermore, enhanced oil-water separation performance was obtained with the highest oil rejection rate of 99.7%. This SS-HFCM has a satisfactory structure with functional inner and outer layers of separation, which can be beneficial for water treatment applications, such as microfiltration, ultrafiltration, membrane distillation, and membrane contactor.
A two-dimensional zeolitic imidazolate framework with a leaf-like structure (ZIF-L) was synthesized in aqueous solution at room temperature with a molar ratio of Zn+2/Hmim (1: 8). Various triethylamine (TEA) concentrations were also used for the rapid production of ZIF-L. Different characterization techniques like X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) were performed to investigate the effect of base type additive triethylamine (TEA) on the crystal morphology, crystallinity, particle size and thermal stability of ZIF-L particles. From the experimental results, it was found that ZIF-L with a particle size of 5.3 μm was formed at TEA/total mole ratio of 0, but particle size was decreased when TEA/total mole ratio was increased up to 0.0003. The smallest ZIF-L particles obtained were 3 μm that showed excellent thermal stability. It can be concluded that this promising synthesis method with base-type additive would provide the new insights in the development of ZIFs materials in economical ways. © 2018, Malaysian Society of Analytical Sciences.
This study assesses the effects of different polytetrafluoroethylene (PTFE) particle sizes and concentrations on the performance of dual-layer membranes in direct contact membrane distillation (DCMD). Specifically, particle sizes of 0.5 μm, 1 μm, and 6 μm were systematically evaluated at concentrations of 0 wt%, 2 wt%, 4 wt%, and 6 wt%. Comprehensive analyses, including scanning electron microscopy (SEM), liquid entry pressure (LEP), contact angle, thermogravimetric analysis (TGA), mercury intrusion porosimetry (MIP), atomic force microscopy (AFM), permeate flux, nitrogen gas permeation, and salt rejection, were employed to characterize the membranes. Under conditions of a feed temperature of 70 °C and a salt concentration of 8000 ppm for a 24 h duration, the results clearly indicated that a 0.5 μm PTFE particle size combined with a 6 wt% concentration exhibited the highest performance. This configuration achieved a permeate flux of 11 kg·m2/h and a salt rejection rate of 99.8%. The outcomes of this research have significant implications for the optimization of membranes used in DCMD applications, with potential benefits for sustainable water treatment and energy conservation.
Amine-modified mixed matrix membranes (A-Ms) have been developed with improved anti-plasticization behavior at high pressure for natural gas purification. Neat polysulfone (PSf) hollow fiber membranes and amine-modified zeolitic imidazole framework-8 (A-ZIF-8) blended PSf membranes have been prepared with the aim of purifying natural gas. The fabricated membranes have been evaluated using gas performance tests, thermogravimetric analysis (TGA), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM). When tested using pure gases, the membrane with 0.25 wt percent A-ZIF-8 demonstrated a substantial enhancement in CO2/CH4 selectivity of 50 %, 72 %, and 69 % when compared to the neat membrane, and an increase of 33 %, 78 %, and 77 % in CO2/CH4 selectivity compared to the virgin ZIF-8-based membrane at feed pressures of 6, 8, and 10 bar (g), respectively. Subsequently, the separation performance has decreased due to the increased A-ZIF-8 loading. Improved anti-plasticization behavior at high feed pressure is further demonstrated by the exceptional gas separation performance at low loading of A-ZIF-8 nanoparticles. The promising results showed the potential use of A-ZIF-8 for natural gas purification.
In this study, polyvinylidene fluoride (PVDF) hollow fibre membrane was modified by adding TiO 2 . TiO 2 presence affects the membrane structure becomes more less hydrophobic which makes the membrane less fouling. Membranes were made via dry-wet spinning method and calcined under vacuum condition by furnace (100, 300, and 500 °C). Besides, PVDF-TiO 2 uncalcined membrane were also prepared as comparison to investigated the effect of calcination on hollow fibre membrane’s functional groups. Fourier Transform Infrared (FT-IR) spectra indicated that all PVDF-TiO 2 membranes have bands of OH in the TiO 2 at ∼1600 cm −1 . Peaks of α-phase PVDF crystals appeared at ∼876, ∼876, and ∼872 cm −1 for uncalcined, 100 and 300 °C, while for 500 °C the PVDF peak only shows at 874 cm −1 . The peaks at ∼1200 cm −1 represent CF 2 groups. Peaks at ∼1400 cm −1 assigned to CH 2 groups, but it does not observed for 500 °C. Deconvolution by Fityk software that shows calcination using vacuum condition gives the compounds gradually decomposes. At high temperature calcination lead the CH 2 peak extremely lost.
This chapter introduces major developments and use of functional ceramic hollow fibre membranes, that is a membrane design consisting of a dense outer layer for separation supported on a highly porous inner catalytic substrate layer, for energy utilization in methane conversion and micro-tubular solid oxide fuel cells (SOFCs). The advantages of the dual-layer hollow fibre membrane design and the single-step co-extrusion and co-sintering process employed to achieve this membrane design are addressed. The key factors that affect the fabrication and performance of the developed membranes are discussed and future technology challenges are also outlined.
In recent years, the membrane photocatalytic reactor (MPR) systems have attracted much attention due to their promising function in treating organic pollutant and filtering clean water.Suspended photocatalyst titanium dioxide (TiO 2 ) particle always become a problematic in hybrid MPR system due to membrane fouling and TiO 2 loss.In the past few years, considerable attention has been paid to immobilize TiO 2 nanoparticles on various materials.Since ultraviolet (UV) source and TiO 2 are required for the photocatalytic reaction, thus, it is crucial to immobilize high concentration of TiO 2 on the outer surface of the polymeric membrane support.By using co-extrusion approach, a dual layer hollow fibre (DLHF) membrane was fabricated.The effect of additives on the dope polymer solutions and membrane morphologies of DLHF were investigated using of scanning electron microscopy (SEM).The SEM results showed that DLHF membranes have a good adhesion between layers with no delamination.
No abstract is provided for this article.
Long term goals need to be set to promote the country’s circular economy (CE) as well as the cleaner environment by recycling waste materials into useful products. In pursuit of controlling environmental threats of carbon-based industrial wastes, different preprocessing techniques for their conversion into other value-added materials are being put in use. This review targets the purposeful utilization of massive amount of palm oil fuel ash (POFA), generated as a waste from power plants of palm oil processing mills in the major palm oil-producing countries. Currently, unrestrained disposal of POFA captures not only precious land but also creates environmental threats and health-related issues. Present work is an attempt to establish a sustainable cleaner production (SCP) system instead of unmanaged POFA disposal. Major palm oil producer countries should address the emerging issues of POFA related unsafe environment, energy consumption and landfill spaces by adopting reuse, reduce and recycle principles. Technically, this review also focuses on the use of POFA as a promising cementitious material in concrete production. It also maps the importance of POFA in concrete production as a cement replacement by presenting various state-of-the-art chemical reactions, mode of action of POFA for its pozzolanic reactivity in cement compositions and associated technical, environmental, and economic benefits. This will provide an alternative option and a sustainable solution for the global construction industry. It is conclusively evident from an extensive literature survey of 463 published results from last 26 years that POFA can be effectively used in concrete production to replace cement without compromising on its strength, performance, and durability. Based on the till that research work on POFA applications in the cement industry and other multiple areas, a circular economic model has been presented to support the concept of zero waste and SCP. It will stimulate the technical persons and decision-makers to make policies and strategies that can spotlight the effective use of POFA in multiple applications, primarily focusing on concrete production not only for curtailing the land and water pollution but also acquiring economic benefits.
This work describes the preparation of yttria-stabilized zirconia (YSZ) hollow fibre membranes using the phase inversion and sintering process. The study aims to provide generic information on the effects of membrane preparation on the morphology and mechanical properties of YSZ hollow fibre membranes. In this work, ceramic suspensions were prepared by mixing YSZ particles, dispersant, polymer binder and organic solvent using a planetary ball milling machine. This process was followed by extrusion into a coagulation bath via an air gap, drying and sintering process at temperatures ranging from 1250°C to 1400°C. The results show that by varying the YSZ loading and YSZ/PESf ratio, different morphologies of ceramic hollow fiber membranes can be obtained due to variations in the viscosities of ceramic suspensions. Similarly, air-gap length between the spinneret and coagulant surface was found to affect the growth of the finger-like structures and sponge-like regions. Varying these parameters also gave significant effects on the mechanical strength of the ceramic membrane due to the change in membrane thickness and compactness. The sintering process had insignificant effects on the membrane morphology but the process can be used to enhance the mechanical strength of ceramic hollow fiber membranes. The optimum temperature of the sintering process was identified. It was found that increasing the sintering temperature further caused a reduction in the mechanical strength due to crack formation in the ceramic hollow fiber membrane. The preliminary performance tests showed that the ceramic hollow fiber membrane sintered at 1300°C has a pure water flux of 118.4L/m2 h. It also has a high PEG rejection with molecular weight cut off (MWCO) of 60kDa.
