Materials Science Forum Vol. 1056

Abstract: Plastic, a non-biodegradable material has always been a concern to the environment and people. This single-use item generates waste to landfills and it persists for centuries once disposed. The urge of transforming such material into a highly valuable product has sought attention from many researchers. This study emphasizes on a nanotechnological approach to synthesize vertically-aligned carbon nanotubes (CNTs) on a substrate template using commercially available plastic bags as carbon precursor. CNTs are grown inside a hexagonally arranged nanoporous anodic alumina membranes (NAAMs). CNTs are liberated by wet chemical etching to dissolve the alumina matrix. The resulting CNTs are used as adsorption media filters for water treatment purpose. The high adsorption affinity towards heavy metals, organic matters and microbes, ability to antifouling and self-cleaning function have made CNTs a better choice over others. This article briefly discusses the catalyst-free synthesis, growth mechanism, characterization and functionalization of CNTs for water treatment application.

Abstract: Membrane distillation (MD) is a thermally driven membrane separation process. In recent years, MD is considered as a key technology for desalination applications. It has been proven that it has numerous advantages compared to other desalination processes such as reverse osmosis. The thermal driving force, no osmotic pressure effect on membrane fluxes are among the advantages of this MD process. Membranes fabricated from hydrophobic polymers such as polyvinylidene fluoride (PVDF) can be a great choice for MD for the desalination process. However, MD membranes are still held back by some problems, most notably due to pore wetting effects, thereby limiting their use in treating seawater for desalination propose. This study proposes the use of carboxylic acid to modify the PVDF membrane to increase its hydrophobicity as a solution to avoid wetting in MD for water desalination. As a first step, membrane produced using PVDF pellets under the phase inversion method. Then the membrane underwent modification using 5wt%, 10wt% and 15wt% of formic acid via immersion technique. The characteristics of membrane produced observed by the contact angle, Fourier-transform infrared spectroscopy (FTIR) and membrane performance test. The impact of the concentration of formic acid solution and feed temperature on the membrane was evaluated. The result showed that by modifying the membrane with formic acid resulted in the increase in contact angle from unmodified PVDF membrane, 83.03° to 100.88° when the membrane modified with formic acid with concentration was 10 wt%. It was subsequently shown through FTIR peaks that formic acid successfully modified the PVDF membranes. Highest salt rejection percentage was also obtained with 68.9% when the feed temperature is 60 °C.

Abstract: Biogas is one of the renewable energy alternatives. The heat of burning biogas depends on the percentage of CH₄ (methane) gas and CO₂ (carbon dioxide) gas. Biogas with high impurity gas components, such as CO₂ and H₂S (hydrogen sulfide), can cause a decrease in heating value. Therefore, purification efforts are needed. The adsorber membrane was successfully made from oil palm empty fruit bunches (OPEFB) which were pyrolyzed as physical activation. The adsorber membrane is activated to form a porous structure and a usable surface area for gas separation. This study aims to see the effect of variations in the carbon weight of OPEFB on reducing CO₂ levels in the Gunung Kupang landfill biogas. Preparation of OPEFB adsorber membrane by mixing PVA (polyvinyl alcohol) and PEG (polyethylene glycol) polymers into OPEFB with varying weights, namely 12.5, 15, and 17.5 g (grams). Membrane performance is determined based on the results of the flame test and gas chromatography test results. Based on the results of the flame test of the biogas that has been passed on the adsorber membrane, overall all samples showed a predominantly bright blue flame color. Meanwhile, the chromatographic test results showed a decrease in CO₂ levels in samples of 12.5, 15, and 17.5 g, respectively 19.6%, 32.02%, and 61.58%. The results of the flame test and gas chromatography test prove that the difference in mass weight affects the performance of the samples tested where the greater the mass of adsorber membrane used, the greater the increase in absorbed CO₂ gas content.

Abstract: Nanotechnology is receiving an intense attention these days due to its potential application in various fields including cosmeceutical and pharmaceutical. Nanoparticles encapsulating natural extract are usually characterised for their particle size and polydispersity index but zeta potential is hardly discussed. The zeta potential is the measurement that shows the aggregation behaviour, reactivity and toxicology. In this study, nanoparticle encapsulating Cymbopogon sp. have been formulated to develop a cosmeceutical product. The antioxidant properties from aqueous extract of Cymbopogon sp. was encapsulated with chitosan/alginate biopolymeric nanoparticles. Central Composite Design (CCD) of Response Surface Methodology (RSM) was employed to investigate and optimise the effects of independent variables such as pH of SA, concentration of non-ionic surfactant concentration of CaCl₂ and pH of chitosan on zeta potential and encapsulation efficiency (EE). Following the model, the optimum condition for zeta potential was selected as 6.2 of sodium alginate pH, 0.12% of non-ionic surfactant concentration, 0.05 concentration of CaCl₂ and 5.6 of chitosan pH with negative zeta potential of 18.3mV. The zeta potential obtained experimentally was close to its predicted value which is-18.09mV. The model provides a basis on the optimisation of the zeta potential on chitosan/alginate nanoparticle encapsulating Cymbopogon sp. extracts.

Abstract: Palm Fatty Acid Distillate (PFAD) consists of more than 80% of free fatty acids, primarily palmitic acid and oleic acid, which can be esterified and added to the biofuel and oleo-chemical industries as feedstock. Oleic Acid is also known as cis-9-octadecenoic acid has the chemical formula C₁₈H₃₄O₂ or (CH₃(CH₂)₇CHCH(CH₂)₇COOH). There have been numerous studies that demonstrate the nutritional value of oleic acid. The objectives of this research were to simulate the mechanism reaction design for Molecularly Imprinted Polymer (MIP) synthesis and to predict the bonding formed after synthesis by comparing the monomers and template. The mechanism and complexes formed were drawn according to the theoretical mechanism of MIP. The chemicals involved were allylthiourea as the monomer, oleic acid as the template, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, 2,2-azobisisobutyronitrile (AIBN) as the initiator, and acetonitrile as porogenic solvent. The monomer, allylthiourea was compared with the other two monomers which are vinylpyridine and acrylamide in MIP synthesis prediction. On average, when the allylthiourea was used as the monomer, the bond length was quite similar for each connection of atoms (1.316 Angstrom). However, when the vinylpyridine and acrylamide were used as the monomers, the length of the bonds was not similar to each other. On top of that, the bond angles prediction for allylthiourea-oleic acid complex agreed with the molecular geometry shape was tetrahedral due to the average angle was 109.5^o. Next, two different templates; oleic acid and palmitic acid; were compared in MIP synthesis prediction. The bond length for oleic acid was on average quite similar to each other (1.316 Angstrom) whereas for palmitic acid as the template the bond length was not similar. The palmitic acid-allylthiourea complex showed the angles reading was not synchronized to each other and quite unstable, unlike the oleic acid-allylthiourea complex. The results agree that oleic acid as the template was the best in this setting parameter for MIP synthesis.

Abstract: Water holding and release properties are important characteristics for a dressing material in wound healing. In the present study, the water holding capacity (WHC) and water release rate (WRR) of BC films produced from oil palm frond (OPF) juice were investigated. The juice was inoculated with Acetobacter xylinum in 24-well plates and incubated at 30 °C for 7 days under static conditions. The films were further dried by three different methods; air-, oven-and freeze-drying. The dried BC was characterized for its size and surface morphology by field emission-scanning electron microscopy (FE-SEM) and for its water holding and release properties. BC produced from OPF juice exhibited good WHC and WRR comparable to BC films produced from Hestrin and Schramm (HS) medium. The loosely arranged fibrils in freeze-dried BC has also resulted in highest WHC and WRR value compared to the oven-and air-dried BC. This study suggested that water holding and release properties are greatly dependent on the use of fermentation medium and drying method.

Abstract: Biofuels have been regaining popularity due to the increasing price of non-renewable fuels and the higher carbon dioxide emissions. Biofuels are manufactured from plant products and are mainly composed of lignocellulose and starch materials. This investigation aims to produce increased fermentable sugars for enhanced bioethanol production from tubers procured from northern Thailand. Varying concentrations of H₂SO₄ is used to pretreat the tubers. Before hydrolyzing with cellulase enzymes, the tubers were chopped into small pieces (1-2 cm), dried in a solar oven, powdered. The obtained results confirmed that the fermentable/ reducing sugar content of Amorphophallus spp. (suweg) tuber increased from 2.6 g/L to 19.01 g/L after enzymatic hydrolysis. The enzymes act as an excellent way to speed up the hydrolysis process. The theoretical potential of bioethanol production was calculated under ideal conditions, with the highest bioethanol concentration obtained is 9.69 ± 0.12 g/L at 0.4 % H₂SO₄ (pretreatment conc.) and 75 °C. The enhanced fermentable sugars obtained from starchy tubers may be utilized for bioethanol production to overcome depleting fossil fuels.

Abstract: Recent years have seen renewed interest in the application of ionic liquids (ILs) on extraction. Along with this grow of ionic liquids, there are significant concern over the effect of ILs on the biomass extraction. Therefore the aim of this present work was to study the inhibitory effect of synthesized ILs particularly imidazolium hydrogen sulphate [IM][HSO₄] and morpholinium tetrafluoroborate [MOR][BF₄]. Antibaterial and antifungal activities were carried out againts Bacillus cereus, Bacillus thuringiensis and Pseudallescheria boydii which are the main producer of ferulic acid (FA). Results showed that the inhibitory effects of [IM][HSO₄] againts bacteria (Bacillus cereus and Bacillus thuringiensis) and fungus (Pseudallescheria boydii) were more extensive with inhibition zone of 20.3 and 52.3 mm respectively compared to [MOR][BF₄] with 8.3 and 34.0 mm. This result represented the inhibitory effect of ILs especially on fungus as compared to bacteria tested in this present study.