Wan Norharyati Wan Salleh

Precursor Selection and Process Conditions in the Preparation of Carbon Membrane for Gas Separation: A Review

Carbon membranes prepared by pyrolysis/carbonization of polymeric precursors have been studied in the last few years as a promising candidate for gas separation process. As the aim of this paper, a review on polymer precursor selection and effect of pyrolysis conditions on carbon membrane characteristics and performances were discussed in detail. A number of different polymer precursors have been surveyed for their utility as materials in carbon membrane fabrication. The gas transport properties of various types of carbon membrane that produced by different researchers was summarized. Furthermore, the potential applications and future directions of carbon membrane in gas separation processes were also briefly identified.

Physicochemical properties of “green” nanocrystalline cellulose isolated from recycled newspaper

“Green” nanocrystalline cellulose (NCC) was isolated through an acid hydrolysis process from recycled newspapers and prepared via treatment with NaOH and NaClO2. Morphological characterization and physicochemical property measurements were executed using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). FTIR and chemical composition analysis demonstrated that lignin and hemicellulose structures were removed using different pretreatment steps with NaOH and NaClO2. From the SEM results, it was discovered that the size of purified cellulose fibrils reduced to a great extent, and the structure of cellulose microfibers became smoother and cleaner due to the removal of lignin with other extracts. The XRD analysis results revealed that NCC exhibits the highest crystallinity index after acid hydrolysis of bleached cellulose microfibers. TEM and AFM analysis revealed that the rod-like structure of NCC was obtained with size 5.78 ± 2.14 nm wide and 121.42 ± 32.51 nm long. The TGA results suggested that the thermal stability of the NCC was affected mainly by the dehydration reaction caused by sulphate groups. The isolated nanocrystalline cellulose attracts great interest as an inexpensive bio-based filler in polymer nanocomposites.

Incorporation of N-doped TiO2 nanorods in regenerated cellulose thin films fabricated from recycled newspaper as a green portable photocatalyst

In this work, an environmental friendly RC/N-TiO2 nanocomposite thin film was designed as a green portable photocatalyst by utilizing recycled newspaper as sustainable cellulose resource. Investigations on the influence of N-doped TiO2 nanorods incorporation on the structural and morphological properties of RC/N-TiO2 nanocomposite thin film are presented. The resulting nanocomposite thin film was characterized by FESEM, AFM, FTIR, UV-vis-NIR spectroscopy, and XPS analysis. The results suggested that there was a remarkable compatibility between cellulose and N-doped TiO2 nanorods anchored onto the surface of the RC/N-TiO2 nanocomposite thin film. Under UV and visible irradiation, the RC/N-TiO2 nanocomposite thin film showed remarkable photocatalytic activity for the degradation of methylene blue solution with degradation percentage of 96% and 78.8%, respectively. It is crucial to note that the resulting portable photocatalyst produced via an environmental and green technique in its fabrication process has good potential in the field of water and wastewater treatment application.

Regenerated cellulose membrane as bio-template for in-situ growth of visible-light driven C-modified mesoporous titania.

Visible light driven C-doped mesoporous TiO2 (C-MTiO2) nanorods have been successfully synthesized through green, low cost, and facile approach by sol-gel bio-templating method using regenerated cellulose membrane (RCM) as nanoreactor. In this study, RCM was also responsible to provide in-situ carbon sources for resultant C-MTiO2 nanorods in acidified sol at low temperatures. The composition, crystallinity, surface area, morphological structure, and optical properties of C-MTiO2 nanorods, respectively, had been characterized using FTIR, XRD, N2 adsorption/desorption, TEM, UV-vis-NIR, and XPS spectroscopy. The results suggested that the growth of C-MTiO2 nanorods was promoted by the strong interaction between the hydroxyl groups of RCMs and titanium ion. Optical and XPS analysis confirmed that carbon presence in TiO2 nanorods were responsible for band-gap narrowing, which improved the visible light absorption capability. Photocatalytic activity measurements exhibited the capability of C-MTiO2 nanorods in degradation of methyl orange in aqueous solution, with 96.6% degradation percentage under visible light irradiation.

Effect of Stabilization Condition on PEI/PVP-Based Carbon Hollow Fiber Membranes Properties

The concept of carbon membrane fabrication has attracted a great deal of attention among membrane researchers around the world in recent years. Stabilization is one of the important steps involved during the fabrication of the carbon membranes. The stabilization of PEI/PVP membrane was carried out in a tubular furnace under two types of environments (air and N2). The resulting set of experiments from thermogravimetry analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) was used to investigate the effect of stabilization environments on the properties of the prepared carbon hollow fiber membranes (CHFM)s in terms of their morphological structure, thermal property, chemical structure, and microstructure. The detailed studies with regard to the chemical reaction mechanism occurring during the heat treatment process of the PEI/PVP-based CHFMs were explored. During the heat treatment process, PEI/PVP membranes underwent various physical and chemical changes, such as coloration, shrinkage, crosslinking reaction, and random scission. Based on overall properties, the stabilization step under air environment prior to carbonization step showed the best condition for the preparation of CHFMs derived from PEI/PVP.

Effect of intermediate layer on gas separation performance of disk supported carbon membrane

ABSTRACT Porous alumina disk ceramic was decorated with various types of intermediate layers via one-step spray coating-carbonization technique. P-84 (BTDA-TDI/MDI) polymeric solution was sprayed on the alumina disk with an incorporation of intermediate layer. The membrane was carbonized at 700°C under nitrogen (N2) atmosphere with a heating rate of 3°C/min. The resultant carbon membrane was characterized in terms of its thermal stability, structural morphology, and gas permeation properties. A high-performance carbon membrane was obtained with the intermediate layer of the alumina powder, which exhibited the best selectivity of O2/N2, CO2/N2 and CO2/CH4 of 4.39, 19.89 and 58.43, respectively.

Efficient reduction of graphene oxide nanosheets using Na2C2O4 as a reducing agent

The efficient synthesis of reduced graphene oxide (RGO) nanosheets via chemical reduction process of exfoliated graphene oxide (GO) nanosheets was performed by introducing sodium oxalate (Na2C2O4) as a reducing agent. To study the effects of the reduction time on the synthesized RGO, the GO was reduced within -1/2, 1 and 2 h for RGO-1, RGO-2 and RGO-3, respectively. The C/O atomic ratio of the synthesized RGO-3 has increased from 2.16 to 6.32 after reduction as determined by X-ray photoelectron spectroscopy (XPS). The morphology analysis of the RGO-3 was determined by high-resolution transmission electron microscopy (HRTEM) almost revealed the formation of single layer. The number of RGO layers decreases as the time of the reduction increases. Based on these analysis results, sodium oxalate plays an important role in the efficient removal of the oxygen containing groups in the GO to produce high quality of RGO.

Biodegradable Gas Separation Membrane Preparation by Manipulation of Casting Parameters

Poly(lactic acid) PLA that derived from renewable resources can help our society to reduce the dependence to non-renewable fossil resources. When come to human contact, this polymer and its degradation product are neither toxic nor carcinogenic to human body. The use of poly(lactic acid) (PLA), a biodegradable polymer, as a membrane material would assist the reduction of depending to petroleum-based polymer that will assist in disposal issues on non-biodegradable polymer. This study investigated the effect of evaporation time to the gas separation performance of PLA membrane. Membrane prepared from polymer solution consists of PLA and dichloromethane (DCM) as solvent was fabricated using pneumatically controlled casting system with dry/wet phase inversion method. Permeation test was conducted using pure oxygen and nitrogen gas. The results revealed that as the evaporation time increased, the pore size and surface porosity decreased, while the skin layer thickness increased. Although the morphology of the prepared membranes showed the desirable structure, the gas separation performance of the membrane prepared with polymer concentration of 15 wt% and 60s evaporation time was found to be promising but not yet commercially ready.

Enhancement in photocatalytic degradation of methylene blue by LaFeO3-GO integrated photocatalyst-adsorbents under visible light irradiation

Perovskite LaFeO3 photocatalyst prepared by using sol-gel glucose method was assembled on graphene oxide sheets to produce integrated photocatalyst-adsorbents (IPCA) and investigated as photocatalyst for the degradation of methylene blue under visible light irradiation. The prepared photocatalyst was characterized by FTIR, XRD, FESEM, BET specific surface area measurement, TEM/HRTEM and UV-Vis spectroscopy analysis. The FTIR, FESEM and TEM analysis has suggested that the photocatalyst LaFeO3 has been successfully embedded at the surface of the graphene oxide (GO) sheets due to a strong interaction between the photocatalyst and the adsorbents matrix. Methylene blue degradation shows that IPCA possesses higher photodegradation kinetics compared to bare LaFeO3 photocatalyst. The resultant photocatalyst also possesses magnetic properties which can overcome the difficulty in recollecting and removal of photocatalyst suspension in water after photocatalytic treatment.

The effect of polymer composition on CO2/CH4 separation of supported carbon membrane

Recently, membrane technology has attracted vast attention from many scientists and engineers, particularly from the industrial area. The membrane for gas separation is favoured due to its economically feasibility and high separation performance with respect to gas permeability and selectivity. In this study, the effect of different polymer concentrations (5, 10, 13, 15 and 18 wt%) on the gas permeation properties of CO2/CH4 separation was investigated. Matrimid 5218 was chosen as the based polymer for tubular carbon membrane preparation owing to its excellent membrane properties (i.e. high mechanical and thermal stability) in order to fulfil the membrane requirement for high gas separation performance. The commercialised tubular membrane was dip-coated into Matrimid/NMP solution and then proceed with carbonisation process at the optimum condition with a heating rate of 2 K/min and under Argon gas flow rate at 200 mL/min at temperature of 1,123.15 K by using argon gas. The pure gas permeation tested for both CO2 and CH4 was carried out under room temperature at pressure controlled at 800 kPa. From the experimental results, the tubular membrane made of 15 wt % Matrimid performed the highest CO2/CH4 selectivity (87.34 %) as compared to the other membranes. The excellent performance obtained from the membrane could be attributed by the micropores formation, where the chain of the polymer had increased its packing density. Thus, membrane porosity can be increased by increasing the polymer concentration in the solution.