Nurasyikin Misdan

Facile modification of ZIF-8 mixed matrix membrane for CO2/CH4 separation: synthesis and preparation

Metal–organic frameworks (MOFs) possess tunable characteristics that allow various modifications to be practiced and suitability for specific applications. In this study, zeolitic imidazole framework 8 (ZIF-8) was synthesized and subjected to ammonia modification under different temperatures and ammonia solution loading. The presence of the N–H group observed after the modification indicates the successful modification of ZIF-8. The modified ZIF-8 showed notable changes with increased phase crystallinity, micropore volume and BET surface area. The unmodified and modified ZIF-8s were then dispersed into a polysulfone (PSf) matrix, and the MMMs were prepared via dry/wet phase inversion. No apparent differences in the membrane’s morphology and thermal stability were noticed between the neat PSf membrane and the MMMs. The MMMs were further subjected to pure CO2 and CH4 gas permeation experiments. CO2 permeance decreased while CO2/CH4 selectivity increased as a result of ZIF-8 modification, due to the decrease in mesopore contribution and the increase in micropore contribution to the gas permeation path. The affinity of the N–H group in the modified ZIF-8 to CO2 also contributed to the increase of CO2 permeance. For example, when the ZIF-8 modified in 25 mL ammonia solution at 60 °C (Z25c) was dispersed in the PSf matrix, the CO2/CH4 selectivity increased to 72% and CO2 permeability to 43% compared to the neat PSf membrane.

Study on the thin film composite poly(piperazine-amide) nanofiltration membranes made of different polymeric substrates: Effect of operating conditions

Three composite nanofiltration (NF) membranes made of different substrate materials—polysulfone (PSf), polyethersulfone (PES) and polyetherimide (PEI)—were successfully prepared by interfacial polymerization technique. Prior to filtration tests, the composite NF membranes were characterized using field emission scanning electron microscope (FESEM), atomic force microscope (AFM) and X-ray photoelectron spectroscope (XPS). It was observed that the surface properties of composite NF membranes were obviously altered with the use of different substrate materials. The separation performance of the prepared composite NF membranes was further evaluated by varying operating conditions, which included feed salt concentration and operating temperature. Experimental results showed that the water flux of all TFC membranes tended to decrease with increasing Na2SO4 concentration in feed solution, due to the increase in feed osmotic pressure. Of the three TFC membranes studied, PSf-based membrane demonstrated the highest salt rejection but lowest water flux owing to its highest degree of polyamide cross-linking as shown in XPS data. With respect to thermal stability, PEI-based TFC membrane outperformed the rest, overcoming the trade-off effect between permeability and rejection when the feed solution temperature was gradually increased from 30 °C to 80 °C. In addition, the relatively smoother surface of hydrophilic PEI-based membrane when compared with PSf-based membrane was found to be less susceptible to BSA foulants, leading to lower flux decline. This is because smoother surface of polyamide layer would have minimum “valley clogging,” which improves membrane anti-fouling resistance.

Physicochemical characteristics of poly(piperazine-amide) TFC nanofiltration membrane prepared at various reaction times and its relation to the performance

Abstract Poly(piperazine-amide) thin film composite (TFC) nanofiltration (NF) membranes were prepared via interfacial polymerization (IP) of trimesoyl chloride (TMC) in cyclohexane and piperazine (PIP) in water. The effect of polymerization time on the physicochemical characteristics of poly(piperazine-amide) layers and the final membrane performance was studied in detail. The morphological structures of prepared membranes were investigated using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), by contrast, was used to determine the chemical characteristics of the membranes. It is evident that the surface roughness increased with increasing polymerization time due to the formation of a supergranule-like structure over the interfacially synthesized poly(piperazine-amide) layer. Moreover, increasing the polymerization time led to a dramatic reduction of water permeability due to the significant increase of crosslinking poly(piperazine-amide) barrier layers. Experimentally determined data showed that the TFC NF membrane prepared at 10 s of polymerization time experienced 51.2 l/m2.h of water permeability with 97.02% of Na2 SO4 salt rejection at an operating pressure of 0.6 MPa.

Modified ZIF-8 mixed matrix membrane for CO2/CH4 separation

Tunability of metal–organic frameworks (MOFs) properties enables them to be tailored for specific applications. In this study, zeolitic imidazole framework 8 (ZIF-8), sub-class of MOF, underwent pre-synthesis and post-synthesis modifications. The pre-synthesis modification using GO (ZIF-8/GO) shows slight decrease in textural properties, while the post-synthesis modification using amine solution (ZIF-8/NH2) resulted in superior BET surface area and pore volume. Mixed matrix membranes (MMMs) derived from polysulfone (PSf) and the modified ZIF-8s were then prepared via dry/wet phase inversion. The polymer chain flexibility of the resulted MMMs shows rigidification, where ZIF-8/NH2 as filler resulting higher rigidification compared to ZIF-8/GO. The MMMs were further subjected to pure CO2 and CH4 gas permeation experiments. The PSf/ZIF-8/NH2 shows superior CO2/CH4 selectivity (88% increased) while sacrificing CO2 permeance due to combination of severe polymer chain rigidification and the presence of CO2-phili...

Preparation and characterisation of polyethersulfone/ hydrous ferric oxide mixed matrix membranes with improved hydrophilicity for treatment of oily waste water

The rapid growth in oil and gas industry has led to the large production of oily wastewater. The massive amount of oily wastewater derived from the industry has raised concerns in community especially its adverse impact to the environment. Membrane technology has been in the spotlight in recent advancement to treat the oily wastewater. The major obstacle regarding the membrane technology is fouling due to surfactant adsorption and/or oil droplets plugging the pore, which would lead to a severe decline of the flux and rejection rate. HFO nanoparticles are incorporated into the PES membrane matrix with the aim to improve the hydrophilicity, water permeability as well as the antifouling properties of the membrane. HFO is abundant and easily obtained making it the perfect candidate in developing economical and energy saving membrane operation. Hydrous ferric dioxide (HFO) nanoparticles were synthesised via chemical precipitation method and incorporated in polyethersulfone (PES) to fabricate nanocomposite mixed matrix membranes (MMMs) for ultrafiltration (UF). The resulting membranes were characterised by SEM, FTIR, contact angle goniometer, before further subjected to water permeation test. It was found that contact angle of membrane decreased remarkably with an increase in HMO nanoparticle loading (state the value/ percentage decrement). The pore size at the skin layer however decreased as observed by SEM. As for the UF experiments, pure water permeation rate increased remarkably with increasing nanoparticle loading.

Preparation of polyacrylnitrile (PAN)/ Manganese oxide based activated carbon nanofibers (ACNFs) for adsorption of Cadmium (II) from aqueous solution

In this work, activated carbon nanofibers (ACNFs) from precursor polyacrylnitrile (PAN) and manganese oxide (MnO2) were prepared via electrospinning process. The electrospun PAN/MnO2-based ACNFs were characterised in term of its morphological structure and specific surface area using SEM and BET analysis respectively. The comparative adsorption study of cadmium (II) ions from aqueous solution between the neat ACNFs, composite ACNFs and commercial granular activated carbon was also conducted. SEM analysis illustrated that composite ACNFs have more compact fibers with presence of MnO2 beads with smaller fiber diameter of 437.2 nm as compared to the neat ACNFs which is 575.5 nm. BET analysis elucidated specific surface area of ACNFs/MnO2 to be 67 m2/g. Under adsorption study, it was found out that Cd (II) removal by ACNFs/MnO2 was the highest (97%) followed by neat ACNFs (96%) and GAC (74%).