Awareness on the issues associated with the development of sustainable energy and climate change has significantly improved. The fuel cell has been considered an efficient and clean alternative power source. The principle operation on proton-exchange membrane fuel cells (PEMFCs) naturally leads to the development of water as a by-product of the reaction between hydrogen and oxygen. A computational fluid dynamics (CFD) model was developed to investigate the performance of high-temperature PEMFCs and the development of water profile. The CFD model was developed using ANSYS® Fluent software, ANSYS 18.0. The model was designed as a single straight channel measuring 2.4 mm in width, 2.88 mm in height and 125 mm in length. The simulation was carried out at the temperature range of 80°C to 120°C with an operating pressure of 200 kPa. Results were presented in the form of polarisation curve and contour of the H2O mass fraction at the gas channel mid-plane at different operating temperatures. At lower operating temperature ranges, namely 80°C, the simulation results showed the higher performance of HT-PEMFC in term of current density compared to the higher operating temperature. The mass fraction of water was observed to be more concentrated at the anode gas channel compared to the cathode gas channel. The mass fraction of water at the anode and cathode gas channels increased with decreasing operating temperature from 120 °C to 80 °C that could indicate the possibility of water flooding in the HT-PEMFC components thus could affect the durability of the cell.

Keywords: HT-PEMFC; Computational fluid dynamics; Operating temperature

Butanol is the most promising alternative liquid biofuel that can substitute gasoline due to its properties which is more similar to gasoline than ethanol. In this study, butanol was produced by batch culture and repeated batch culture in acetone-butanol-ethanol fermentation (ABE) using a local strain of Clostridium acetobutylicum YM1. In batch culture using tryptone–yeast extract–acetate medium (TYA) containing 30 g/L glucose, the maximum butanol concentration was 3.78 g/L with a maximum butanol productivity of 0.08 g/L.h and the butanol yield was 0.15 g/g. Effect of some factors on the butanol production during repeated batch fermentation including drain and fill volume of medium and drain and fill time were investigated. The results of repeated batch fermentation showed that 50% (v/v) of drain and fill volume at 48 h maximized the production of butanol, productivity and yield. The highest butanol concentration was 5.12 g/L in the first cycle of repeated batch with a butanol productivity of 0.11 g/L.h and a butanol yield of 0.44 g/g. Repeated batch fermentation using free cells of Clostridium acetobutylicum YM1 eliminated the lag phase and then improved the productivity of butanol and total ABE. This study showed that repeated batch fermentation improved the efficiency of butanol production over batch culture fermentation by Clostridium acetobutylicum YM1.

Keywords: Repeated Batch Fermentation; Clostridium acetobutylicum YM1; Butanol; Biofuel.

The study of biomaterials as implants have rapidly increased over recent decades to address the issues of tissue and bone disease. The combination of graphene oxide (GO) with hydroxyapatite (HA) is expected to promote the adsorption of protein fibronectin (FN). GO was produced by Hummer’s method. Calcium hydroxide (Ca(OH)2 at 0.1, 1.0 and 2.0 M) was used as a precursor of HA for the synthesis different GO compositions (0%, 0.1% and 1.0%) through wet chemical precipitation method. The molarity of Ca(OH)2 and the composition of GO played an important role in the morphology, particle size, distribution of GO on HA surface and absorption of protein. GO and GO–HA composites were characterized using Fourier transform infrared spectroscopy, X-ray diffraction and field-emission scanning electron microscopy. Energy-dispersive X-ray spectroscopy was used to investigate protein adsorption. The average percentage yield of GO-HA composite production was highest (96.93%) at 2.0 M of Ca(OH)2. The optimum condition of GO–HA composite was 0.1 M Ca(OH)2 and 0.1% GO composition, which resulted in needle-like shape with 48.38 nm width and 201.0 nm length, well conjugation, as well as the higher distribution of GO onto the HA surface. The elemental composition of carbon (C) of GO-HA was 44% and that of uncoated HA was 33%, which confirmed the adsorption of FN. Moreover, carbon element mapping proved that the absorption of FN towards GO-HA was successful. GO-HA nanocomposite can be a promising highly biocompatible material for medical implants.

Keywords : Biomaterial; Hydroxyapatite; Graphene oxide; Fibronectin; Adsorption

Mixing in a chemical industry is a crucial as the quality of a final product depends on the mixing process. Normally, mixing in a microchannel is based on their diffusivity without turbulence flow effect which causes of its laminar flow nature in the microchannel. However, the diffusivity in the microchannel is limited by its short passage. Thus, the objective of this study is to observe the behavior of liquid-liquid mixing (acetone-water) at different condition of feed velocity; 0.01-0.10 m/s, initial concentration by volume fraction; 0.1-0.6 w/w% and design of Y-type microchannel; without and an existence of the obstacle. In this study, the Y-type microchannel is designed by SolidWorks© software and these models then are imported and meshing into AnsysCFX®. This Y-type microchannel has two inlets and one outlet with the distance from the inlets to the Y intersection point is 550 µm and the length of a straight channel is 1200 µm. From this study, it shows a well-mixed flow pattern was observed as the velocity at the inlet A is vA=0.10 m/s and inlet B is vB=0.05 m/s, with the average velocity is vo=0.075 m/s which gives the best mixing condition. Other than that, due to a severe difference on the initial concentration fed at both inlets, create the mixing process requires a longer time or lengthier channel to achieve an equilibrium mixing point due to slow molecular diffusion. Besides, the mixing behavior in the Y-type microchannel with the obstacle shows better mixing’s efficiency performance as the presence of obstacle need an extra interaction and momentum to enhances the liquid-liquid mixing.

Keywords: Mixing; Microchannel; AnsysCFX©; CFD®; Liquid-liquid interaction

Adsorption is a simple and easily operated treatment process for water and wastewater reclamation. However, the cost of activated carbon (adsorbent) is an obstacle for this process to be widely employed in developing and underdeveloped countries. Hence, a low-cost and easily available Duckweeds plant has been used as the raw material for the synthesis of low-cost activated carbon. In this study, the effect of activating agents; potassium hydroxide (KOH) and phosphoric acid (H3PO4) on the properties of the activated carbon produced from Duckweeds plants was investigated. Duckweeds plants that were impregnated with an activating agent with a ratio 1:2 were carbonized in a tube furnace for two and a half hour at 550 ºC with continuous nitrogen flow. After that, the synthesized activated carbon was used to remove methylene blue dye from aqueous solution. It was observed that activated carbon impregnated with H3PO4 possessed a more extensive exfoliated and multilayer structure, which gave rise to better adsorption performance compared to activated carbon impregnated with KOH. Furthermore, the porosity of the activated carbon impregnated with was much higher (38±6%) compared to the sample impregnated with KOH (22±4%). Indeed, the removal of dye for the former was slightly better (3-5 %) and achieved equilibrium adsorption within a shorter duration. The findings show that H3PO4 is a better activating agent to induce exfoliated and multilayer structures on the activated carbon, where both of these characteristics are important for a good adsorption process. Overall, Duckweeds plants are a feasible source for the synthesis of low-cost activated carbon. Considering that Duckweeds plants can be used to remove nutrients presence in the wastewater, the activated carbon synthesized from the plants can be incorporated into the existing wastewater treatment plant as an additional purification process.

Keywords: Activated carbon; Duckweeds; Wastewater treatment; Low-cost adsorbent; Chemical activation

5-Hydroxymethylfurfural (5-HMF) is a valuable bio-based intermediate designed from carbohydrate resources such as glucose (hexose) or fructose. In this work, direct conversion of glucose into 5-HMF was studied by analysing the activity of solid acid catalyst namely silica-supported phosphotungstic acid (H₃PW₁₂O₄₀/TEOS) as a heterogeneous catalyst. The reactions were conducted in a three-neck conical flask using dimethyl sulfoxide (DMSO) as reaction solvent under different reaction time (1, 3 and 5 hours) and temperature (100, 115 and 130 ℃). The effect of phosphotungstic acid loading was also studied in this literature (5, 12.5 and 20% H₃PW₁₂O₄₀). Thus, this paper aims to study the optimum reaction time, temperature and H₃PW₁₂O₄₀ loading to give the maximum yield of 5-HMF via direct catalytic dehydration process. The prepared catalyst 20% H₃PW₁₂O₄₀/TEOS shows promising results by displaying a yield of 5-HMF as high as 62% after 3 hours at 130 ℃ reaction temperature in the presence of DMSO solvent. Since heteropoly acid is highly soluble in DMSO, thus H₃PW₁₂O₄₀ supported in TEOS (H₃PW₁₂O₄₀/TEOS) is a promising solid catalyst for the conversion of glucose into 5-HMF. The prepared catalyst can also be recovered and recycled easily without significant loss of performance.

Keywords: 5-HMF; solid acid catalyst; supported silica catalyst; one step dehydration, selective conversion

Treatment of palm oil mill effluent (POME) with membranes can cause membrane fouling due to the presence of suspended solids and organic matters. The objective of this paper is to evaluate the performance of three types of membranes (NF270, XLE, and BW30) after the physical and chemical cleaning. Continuous chemical cleaning was conducted with NaOH and with HCl to clean the fouled membrane so as to elucidate the chemical cleaning protocols and cleaning efficiency. Flushing with ultra-pure (UP) water enabled the recovery of the fluxes of XLE and BW 30 membranes, as reflected by the mild decline (~1%) in the flux recovery for the XLE and BW 30 membranes. XLE and BW 30 membranes have exhibited consistent rejection capabilities throughout the 3-cycle filtration period. Conversely, NF 270 has failed to regain its rejection capability in the long run. Whereas, for chemical cleaning, the initial flux of NF 270 after cleaning with 0.1% NaOH rose dramatically compared to the initial flux in the first filtration cycle due to changes in the surface morphology. Conversely, NaOH cleaning had fully recovered the initial flux of the XLE and BW 30 membranes without compromise the rejection capabilities of both membranes. Based on the cleaning efficiency and permeate quality, it can be concluded that the BW 30 membrane with ultra-pure water (UP) and NaOH cleanings afforded the best and most consistent performance in the long run but HCl is not a preference for the cleaning of this membrane in the water reclamation due to the low flux recovery.

Keywords: Fouling, Membrane cleaning, Palm oil mill effluent (POME), Wastewater reclamation

In this work, mesoporous silica (MSN) was synthesized and tested for ammonia adsorption. The synthesized MSN was characterized using the Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Brunauer–Emmett–Teller (BET). In the ammonia adsorption experimental, the mass of MSN was varied at 0.5, 1.0, 1.5, 2.0 and 2. 5 g. The data of ammonia uptake by MSN was plotted using Langmuir and Freundlich isotherms, while the kinetic adsorptions were determined using pseudo-first order and pseudo-second order kinetics. The results showed the MSN structural was hexagonal form and particle size of 70 to 150 nm. Characterization using FTIR shows the MSN contained various chemical functional groups. The adsorption of ammonia rest resulted with a high percentage of ammonia removal. At 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 g of MSN, the highest adsorption uptake at 5 minutes were 0.79, 0.42, 0.31, 0.21, 0.17 and 0.12 mg/g, respectively. The adsorption data were fitted to the isotherm and kinetic models to predict the mechanism and kinetic characteristics of the adsorption process. The Freundlich isotherm model shows the highest correlation with the Freunclidh (KF) and adsorption constant (n) of 6.78 and 0.39 mg/g, respectively. For the kinetic modeling, the data of ammonia adsorption process were well fitted to the pseudo-second order with coefficient determination (R2) value of 0.9992. These results indicated the potential for a new application of MSN as an effective adsorbent for ammonia removal and it can be applied in the water treatment processes.

Keywords: Mesoporous silica; Ammonia adsorption; Water treatment; Isotherms model; Kinetic model

Chemical composition of lignocellulosic biomass (LCB) is an important parameter to be determined in order to identify the chemical potential in LCB. The compositional analysis of LCB is the first analysis performed prior to any LCB conversion process to produce high value-added products. LCB composition is generally characterized according to Laboratory Analytical Procedures (LAPs) published by National Renewable Energy Laboratory (NREL), USA. Major chemical components determined are glucan, xylan, arabinan, galactan, mannan, ash, extractives and lignin. The mathematical parts performed manually in the compositional analysis are tedious, complex and repetitive due to the interrelation of calculations within each chemical component. These manual calculations for each chemical component should be performed carefully and systematically to avoid errors in the final results of LCB composition. Therefore, this research work developed a computerized method to perform automatic LCB composition calculation system using Visual Basic (VB) software integrating its Graphical User Interface (GUI) concept to help users in performing the LCB composition calculation specifically for biomass-based research use.

Keyword : Lignocellulosic Biomass; Compositional Analysis, Graphical User Interface

Water-based drilling fluids (WBDF) are widely applied in oil and gas industry due to its environmental compatibility. However, the issues regarding on the fluid loss control is still a major concern in drilling fluid industry. Therefore, the introduction of nanomaterials in drilling fluids is one of the advanced approaches to solve the problems. Nanomaterials possess inherent physico-chemical properties compared to micro or macro-sized particles due to its large surface area. In this study, nanosilica particles have been selected as fluid loss control additive due to its high stability and functionality. The nanosilica particles were synthesized via sol-gel technique and the average size obtained was 70±7 nm. The nanosilica was then modified using Sodium Dodecyl Sulphate (SDS) in order to produce hydrophobic particles. It was done in order to produce hydrophobic layer that can prevent fluid inflow-outflow in order to stabilize the wellbore during drilling operation by producing a filtration layer on the wall of the wellbore which overcome the fluid loss. A ratio of 50 wt% SDS/SiO2 was used and the contact angle obtained was 100±8.13°. The hydrophobic nanosilica was added in the drilling fluid formulation and the performance was evaluated in terms of filter cake thickness and filtrate volume. The filter cake thickness was found less than 1 mm and the fluid loss reduction percentage was 44 % for drilling fluid with hydrophobic nanosilica. Besides, the drilling fluids with hydrophobic nanosilica presented a good rheological behaviour, thermal stability and a high methylene blue capacity while the filtrates exhibited low alkalinity, low chloride ion concentration and total hardness lower than 500 mg/L.

Keywords: Drilling fluids; Nanoparticles; Water-based; Hydrophobic, Additives

In this study, oil palm biomass of empty fruit bunch (EFB) fibers was used as lignocellulosic-based material models for wastewater remediation. EFB fibers were improvised by enhancing its surface functionalization for the removal of the color in the actual effluent from the textile industry. Briefly, EFB fibers were modified using polyethyleneimine (PEI) and ethylenediaminetetraacetic acid (EDTA) to produce cationic and anionic adsorbents, respectively. The modified fibers (PEI-EFB and EDTA-EFB) were used to study the efficiency in removing anionic and cationic ions from the effluents at different pHs, temperatures and initial dye concentrations. The optimum pH and temperature were investigated to be at pH 3 and 20 ºC whereas the adsorption occurred efficiently. The comparison between the modified adsorbent shows higher adsorption capacity by cationic functionalization. The charge of the PEI-EFB was positive over the entire pH range, which suggests the successful modification of the EFB fibers by PEI. In the kinetics study, the adsorption capacity of PEI-EFB fibers in the removal of color can be up to 572.3 mg/g, which improved by ~five times of the adsorption capacity of the raw EFB fibers. Whereas, based on the experimental work and adsorption models fitting, PEI-EFB fitted on the Pseudo First-Order in comparison with the Pseudo Second-Order. Additionally, the isotherm model was fitted with the Freundlich model, contrary with the Langmuir model, its mechanism suggesting a monolayer and heterogeneous adsorption behavior of the adsorption processes.

Keywords: Adsorption; EFB; Chemical treatment; Dyes; Textile effluent