Key Engineering Materials Vol. 673

Abstract: The silica extraction from palm oil mill fly ash (POMFA) using sodium hydroxide as one of viable processes for obtaining silica from agricultural waste was investigated. The effects of extraction time and temperature were closely examined to study the kinetics of the process. The fixed variables used in the present work were mass of POMFA 468.2 gram; the POMFA mass to NaOH volume ratio 0.2341 g/cm³; the concentration of NaOH 1.4 N and the stirring speed of 1065 RPM. The levels of temperature employed were 348 K, 358 K, 368 K and 378 K for different time durations up to 60 min. The mechanical fragmentation process was applied to obtain precipitated silica from the extracted silica. The precipitation conditions were: stirring speed of 1160 RPM, pH of 8.75, temperature of 303 K and precipitation time of 100 min. The shrinking core model (SCM) with intra-particle diffusion controlled mechanism and the Jander equation can satisfactorily represent the extraction process. The activation energy for silica extraction was 58.20 kJ/mol for the SCM with intra-particle diffusion and 62.22 kJ/mol for the Jander equation respectively. The precipitated silica agglomerate obtained at the time of 100 min has the median-weighed volume particle size distribution of 114.07 μm. The chemical composition and physical characteristic of precipitated silica which were analyzed with LPSA, XRF, XRD, FTIR and SEM are similar to the precipitated silica from the references.

Abstract: Recently, there has been an interest in potential of antioxidant film incorporated with natural extract. The film was produced by using chitosan in the presence of pomelo (Citrus grandis) peel extract. In this study, there were 3 different effects of parameter that had been screened by using 2-Level Factorial which were concentrations of chitosan, pomelo peel extract and glycerol. Meanwhile, the response that had been investigated which was Total Phenolic Content (TPC). The data were analyzed by using ANOVA to screen the parameters affecting the antioxidant activity of films. Factor B (concentration of pomelo peel extract) and AC (interaction between the concentration of chiotosan and glycerol) were significant parameters in this studied. Meanwhile, FTIR spectra of antioxidant film revealed that there were interaction between functional groups of chitosan with pomelo peel extract with presence of aromatic ring C=C stretch at wavelength of 1555.3 cm^-1 and 1410.7 cm^-1. These results suggested that chitosan films containing pomelo peel extract have potential as the antioxidant thin film, which can be used for development of antioxidant food packaging materials.

Abstract: Pyrolysis of rice straw using microwave irradiation with quartz glass reactor has been conducted in a 1 kW domestic microwave system having 2450 MHz frequency. The microwave was modified and was equipped with the cylindrical quartz glass reactor. There are three process parameter studied namely microwave power (watt), the amount of microwave absorber (g), and particle size (μm). The microwave absorber used in this study is char which produced from microwave assisted pyrolysis. From the study, it was found that the addition of microwave absorber had significant effects on the yields and properties of the final products. From the work done, 12.97 % of bio-oil yield was the highest amount of bio-oil produced at microwave power of 500 W, with addition of 0.5 g of microwave absorber (bio char) for the particle size of 125 μm with consistent flow of 5 L/min of nitrogen gas and constant of 10 minutes reaction time. The pH analysis of bio oil was done by using pH meter for randomly selected one reading for each parameter study where the pH of bio oil produced is acidic which is 3.11, 3.18 and 3.86. The bio-oil produced was found to contain important chemical compounds such as cyclohexanol, 2,3-dihydro-1-benzofuran, 2-methoxy-4-vinylphenol and 4-ethylphenol which analyzed by using gas chromatography.

Abstract: Over the year, agricultural establishment produced many types of waste in its daily operation. Coconut fibre for example is one of the most abundant agricultural wastes produced in Malaysia. Despite the massive amount of the waste produced, the standards of waste management in Malaysia are still poor. The main purpose of this study is to focus on the potential of coconut fibre utilization into fired clay bricks. The objectives of this study are to determine the characteristics of coconut fibre, to identify the gas emissions during firing process from coconut fibre brick and to investigate the physical and mechanical properties of from coconut fibre (1%, 3% and 5%) incorporation into fired clay brick. All the bricks were fired in a furnace up to 1050°C at 1°C/min. The gas emissions that were measured are carbon monoxide (CO), carbon dioxide (CO₂) and sulphur dioxide (SO₂). Based on the three gases, the results showed that CO₂ is the highest gas emission produced during the firing process. Physical and mechanical properties tested are total shrinkage, dry density and compressive strength. Results found that by adding different percentages of coconut fibre, most of the properties were complied with the standards except for the compressive strength of 5% of coconut fibre in clay brick. Therefore, the utilization of coconut fibre could be one of the alternative disposal methods for agriculture waste and it will also provide low-cost material for brick that produce adequate physical and mechanical properties.