Water transport properties of boron nitride nanosheets incorporated thin film nanocomposite membrane for salt removal

This work has focused on the fabrication of thin film composite (TFC) and thin film nanocomposite (TFN) membranes for reverse osmosis (RO) application. Raw boron nitride (BN) and chemically activated boron nitride (A-BN) were used as nanofillers in polysulfone support layer and trimesoyl chloride (TMC) to improve the membrane performance. Different concentrations of BN and A-BN (ranging from 0 to 1 wt %) were added to the polysulfone (PSf) microporous support and polyamide layer was formed on top of PSf support through interfacial polymerization of 1,3-Phenylendiamine and trimesoyl chloride. The fabricated TFN membranes were characterized in terms of membranes structure, contact angle, separation properties, as well as RO performance. According to AFM and SEM images, TFN membranes showed larger average pore size and higher surface roughness as compared with TFC membrane. Thus, TFN membrane showed higher pure water flux but lower NaCl rejection. The addition of BN led to increase in pore size of membrane without increase the selectivity of membrane. The addition of both BN and A-BN into polyamide layer does not aid to improve the properties of membrane. In conclusion, BN nanoparticles showed the potential to be used as nanofillers that aid in formation of larger pore size

Synthesis and characterization of two-stage curing reactive bio-based polymers

Two-stage curing reactive bio-based polymers network namely, poly(octanediol-co-dodecanedioate-co-citrate-co-itaconate) (PODCI) were successfully synthesized using 1,8-octanediol, citric acid, itaconic acid and 1,12-dodecanedioic acid. In the first curing stage, a prepolymer of PODCI was thermally crosslinked. At a later time, a second curing was completed thru photo-initiated free-radical polymerization. Here, we discovered that permanent shape of the thermally crosslinked PODCI was successfully reconfigured by application of second stage curing. The molar ratio of itaconic acid (IA) to citric acid (CA) and time of photo-curing was varied. Based on XRD analysis, the polymer crystallinity of the bio-based polymer decreased with time of photo-curing. The swelling ratio of bio-based polymer decreased from 2750 % to 250 % as soon as completion of second stage curing. PODCI existed as a semi-crystalline polymer with a melting transition temperature of 40.2 ℃. Also, PODCI exhibited excellent shape memory properties with shape recovery by nearly 100%

Synthesis and characterization of graphene derived from rice husks

Graphene was successfully synthesized by activating rice husk ash (RHA) using potassium hydroxide (KOH) at 800 oC with 1:2 impregnation ratio. Raman spectroscopy analysis confirmed the presence of graphitic structure. The demonstrated methodology utilizes RHA as carbon source and used as sacrifice to prevent oxidation during synthesis process on the mixture of KOH and RHA against air at high temperature. The novelty of this synthesis methodology use environmentally-friendly biomass resource as a starting material, does not utilize catalysts, and prove that graphene can be synthesized at a relatively low synthesis temperature

Enhanced gas separation performance of polysulfone membrane by incorporation of zeolite-templated carbon

The zeolite-templated carbon (ZTC) with a unique structure was utilized as a new porous filler for preparing mixed matrix membrane (MMM). The zeolite-Y used as template was synthesized via hydrothermal method. The ZTC was prepared by impregnation of sucrose into the pore of zeolite-Y, followed by carbonization and template removal. The obtained ZTC was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2 isotherm analysis. Results showed that the ZTC was amorphous and possess specific surface area of 1254 m2/g and 0.95 cm3/g for total pore volume. The MMM was fabricated by adding 0.4 wt% ZTC via dry/wet spinning process with polysulfone (PSF) as the matrix. The fabricated membranes were analyzed using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM),and thermal gravimetric analysis (TGA), whereas the gas permeation properties weretested using single gases (CO2, O2, N2, CH4, and H2). The SEM results showed that incorporation of the ZTC was found to be similar as the morphological structure (dense layer and finger-like structure) of neat PSF membrane and the thermal stability was observed to be enhanced. In comparison to neat PSF membrane, uncoated PSF/ZTC MMM exhibited selectivities improvement for CO2/CH4 (290%), O2/N2 (117%), CO2/N2(219%) and H2/CH4 (272%), while coated PSF/ZTC MMM showed enhancement up to 1110%, 368%, 838%, and 802%, respectively with acceptable permeances. Compared to neat PSF membrane, profound selectivities enhancement could be achieved even with low ZTC loading inside the MMM

Asymmetric polysulfone-cloisite 15A® nanocomposite membrane for gas separation

Defect-free asymmetric Polysulfone (PSF)-Cloisite 15A® nanocomposite membrane was fabricated with the intention to investigate the gas permeation behavior of the resulting material combination. Various weights of Cloisite 15A® organoclay were added into PSF matrices by solution intercalation method assisted by sonication dispersion. The gas permeation properties of the PSF-Cloisite 15A® nanocomposite membranes were evaluated by pure gases: nitrogen, methane, and carbon dioxide. The distribution of Cloisite 15A® particles in PSF matrices was analyzed by SEM. The gas flux of the PSF-Cloisite 15A® nanocomposite membranes declined as the Cloisite 15A® weight loading increased. The CO2/CH4 and CO2/N2 pure gas selectivity of PSF nanocomposite with 0.5 wt. % of Cloisite 15A® loading exceeded that of neat PSF membrane. The decrease in flux followed by the increase in pure gas selectivity was related to the way in which the clay layers were dispersed in the PSF matrices. Considerable improvement in CO2 selectivity was attainable even by incorporating low amount of such layered structure nanoparticle which can be attractive in producing robust materials for CO2-removal membranes from CO2-containing gas streams such as post-combustion and natural gas stream

The role of layered silicate loadings and their dispersion states on the gas separation performance of mixed matrix membrane

Mixed matrix membranes (MMMs) embodying different types of organoclays, namely Cloisite® 5, Cloisite® 15A and Cloisite® 30B as the disperse phase for gas separation membranes, were prepared. Polysulfone (PSF) has been used as host matrix to prepare asymmetric membranes attained by the dry-wet phase inversion casting process. FESEM analysis has revealed that defect-free asymmetric MMM morphology with no issues pertaining to non-ideal organic-inorganic interphase was fabricated. The effects of organoclay types and loadings on gas permeation properties were characterized by constant pressure and the variable volume method. From the gas permeation experiment, all nanocomposites exhibited significant reduction in the gas permeation rate even with the addition of very low clay loadings (less than 1wt%). The results suggested that the clay particle loading dictated the extent at which the organoclays were dispersed in the polymer matrix as well as their gas discrimination ability. The information on the degree of clay dispersion, aspect ratio, and the number of clay stacks per tactoid unit was gleaned by making use of the famous phenomenological models derived by Nielsen and Cussler[U+05F3]s group. PSF-C15A membranes with the loading of 0.05wt% were found to be comprised of exfoliated clay nanoplatelet (confirmed by XRD and TEM analysis) with calculated aspect ratio of more than 500 giving rise to striking selectivity (CO2/CH4 ideal selectivity=52.67 for PSF-C15A0.05) well above the recognized intrinsic selectivity for PSF membrane

Antifouling property of oppositely charged titania nanosheet assembled on thin film composite reverse osmosis membrane for highly concentrated oily saline water treatment

With the blooming of oil and gas industries, oily saline wastewater treatment becomes a viable option to resolve the oily water disposal issue and to provide a source of water for beneficial use. Reverse osmosis (RO) has been touted as a promising technology for oily saline wastewater treatment. However, one great challenge of RO membrane is fouling phenomena, which is caused by the presence of hydrocarbon contents in the oily saline wastewater. This study focuses on the fabrication of antifouling RO membrane for accomplishing simultaneous separation of salt and oil. Thin film nanocomposite (TFN) RO membrane was formed by the layer by layer (LbL) assembly of positively charged TNS (pTNS) and negatively charged TNS (nTNS) on the surface of thin film composite (TFC) membrane. The unique features, rendered by hydrophilic TNS bilayer assembled on TFC membrane in the formation of a hydration layer to enhance the fouling resistance by high concentration oily saline water while maintaining the salt rejection, were discussed in this study. The characterization findings revealed that the surface properties of membrane were improved in terms of surface hydrophilicity, surface roughness, and polyamide(PA) cross-linking. The TFC RO membrane coated with 2-bilayer of TNS achieved >99% and >98% for oil and salt rejection, respectively. During the long-term study, the 2TNS-PA TFN membrane outperformed the pristine TFC membrane by exhibiting high permeability and much lower fouling propensity for low to high concentration of oily saline water concentration (1000 ppm, 5000 ppm and 10,000 ppm) over a 960 min operation. Meanwhile, the average permeability of uncoated TFC membrane could only be recovered by 95.7%, 89.1% and 82.9% for 1000 ppm, 5000 ppm and 10,000 ppm of the oily saline feedwater, respectively. The 2TNS-PA TFN membrane achieved almost 100% flux recovery for three cycles by hydraulic washing

A kinetic and mechanistic study of adsorptive removal of metal ions by imidazole-functionalized polymer graft banana fiber

Chemically modified fibrous bio-adsorbent extracted from banana trunk was synthesized for potential application in adsorption of heavy metal from wastewater. Glycidyl methacrylate (GMA) polymer graft was first introduced onto the fiber through electron beam irradiation technique. GMA-grafted fiber was subsequently functionalized with imidazole (IMI) group through epoxide ring-opening reaction where amine density of 2.00 mmol/g was achieved. The adsorbent was characterized with Scanning Electron Microscopy (SEM), Fourier Transformed Infrared Spectroscopy (ATR-FTIR), and Thermogravimetric Analyzer (TGA). An extensive kinetic and mechanistic study on the adsorptive removal of metal ions (Cu2+, Pb2+ and Zn2+) by IMI-functionalized GMA-grafted banana fiber is presented. The effects of pH and initial concentration on adsorption capacity were investigated. The adsorption data were correlated with pseudo-first and second order model and the isotherms were analyzed with Langmuir and Freundlich model in order to explain the kinetics and adsorption mechanisms of different metal ions. The thermodynamic studies revealed that the adsorption process for metal ions was exothermic. We also demonstrated that the IMI-GMA-grafted fiber can be regenerated using dilute HNO3 solution, and can be recycled up to 10 times while maintaining satisfactory adsorption performance. Lastly, the chemically modified bio-sorbent was used to treat a local domestic sewage water

Thin Film Composite Membrane for Oily Waste Water Treatment: Recent Advances and Challenges

Oily wastewater discharge from various industry processes and activities have caused dramatic impacts on the human and environment. Treatment of oily wastewater using membrane technology has gained worldwide attention due to its efficiency in removing the amount and concentration of oil and grease as well as other specific pollutants in order to be reused or to fulfill stringent discharge standard. The application of thin film composite (TFC) membrane in reverse osmosis (RO) and forward osmosis (FO) for oily wastewater treatment is an emerging and exciting alternative in this field. This review presents the recent and distinctive development of TFC membranes to address the issues related to oily wastewater treatment. The recent advances in terms of TFC membrane design and separation performance evaluation are reviewed. This article aims to provide useful information and strategies, in both scientific knowledge advancement and practical implementation point of view, for the application TFC membrane for oily wastewater treatment

Adsorption studies of packed bed column for the removal of dyes using amine functionalized radiation induced grafted fiber

In this paper, the adsorption performance of packed bed column with amine functionalized radiation-induced grafted fibers (AFF) for the removal of acid blue 80 (AB 80) was investigated. Pretreated banana fibers were grafted with glycidyl methacrylate (GMA) with the assistance of electron beam irradiation and subsequently functionalized with imidazole, which was used as the precursor of anionic dye adsorption. The effect of flow rate, bed height and inlet concentration on the breakthrough curves were analyzed in terms of AFF adsorption performance. The experiment revealed that the increase in bed height and inlet concentration promoted the adsorption efficacy, whereas reduction was observed when the flow rate increased. The highest bed capacity obtained was 194.45 mg/g at adsorption condition of 5 ml/min flow rate, 100 mg/l inlet concentration and 50 mm of bed height. In order to determine the optimum operational parameters, the data were collected via the experiment fitted into Yoon and Nelson, and Thomas and Bed Depth Service Time (BDST) mathematical models. At various conditions, Thomas model closely defined the behaviors of the breakthrough curves. The maximum adsorption capacity calculated from Yoon–Nelson and Thomas models increased with the increase in flow rate and inlet concentration. However, a reduction was observed with the increase in bed height. Meanwhile, the BDST model exhibited good agreement with the experimental data as well as high correlation coefficient value r2 ~ 0.99, which indicated the validity of BSDT model for the column adsorption system with AFF. The experimental results attained had suggested that developed AFF is quite effective as a biosorbent for the removal of the dyes