Key Engineering Materials Vol. 851

Abstract: Characteristics and potential of microalgae Spirulina platensis as an energy source were studied in regard to the decomposition patterns, as well as kinetic and thermodynamic parameters. The thermogravimetric analysis was performed using the TGA instrument (Mettler Toledo TG DSC 1) at a heating rate of 30 °C/min, with an atmospheric air flow-rate of 100 ml/min at the temperature range of 25-1000 °C. The kinetic was evaluated using a differential method of Arrhenius. The results showed that Spirulina platensis microalgae decomposed into three stages. The first stage is related to the evaporation of moisture, the second stage is associated with the release of volatile matter, and the final stage is the combustion stage of char. The kinetic evaluation resulted in the respective activation energy (), pre-exponential factor (log A) and reaction order (n) are 53.57 kJ/mol, 4.4 min^-1, and 1.73. It also understands from the thermodynamic analysis that the respective values of enthalpy (), Gibbs free energy ( and the entropies ( were 48.50 kJ/mol, 146,73 kJ/mol, and-174,78 J/mol.

Abstract: The investigation of Titanium dioxide (TiO₂) nanoparticles on the thermal characteristic of Tetraselmis chuii (T.Chuii) microalgae during combustion process has been carried out through a thermogravimetric (TG) analyzer. T.Chuii microalgae samples were cultured within 8 days at BBPBAP Jepara, Central Java, Indonesia. The microalgae sediment was dried at 80°C for 24 hours then was powdered by means of a mortar. Thereafter, the dried powder of microalgae was filtered with a size of 60 mesh. Titanium dioxide (TiO₂) nanoparticles were used as catalysts with the particle size of < 25 nm; these were obtained from Singapore’s Sigma Aldrich. Amount of 0.03 mg of TiO₂ and 10 mg of T.Chuii microalgae were mixed mechanically using a mortar to guarantee the homogeneous blend, and then this sample was heated up in the oven for 14 hours at 80°C. The TG experiment was performed at a temperature range 25 to 900°C with atmospheric air at a flow rate of 50 mL/min and a heating rate of 15 °C/min. Differential method of Arrhenius is applied to evaluate kinetic parameters, including reaction order (n), activation energy (E_a), and pre-exponential factor (log A) that were 0.9; 74,191 kJ/mol and 6.38 min^-1 for the stage II and 0.87; 118.47 kJ/mol and 7.29 min^-1 for stage V.

Abstract: This study aims to analyze the thermal characteristics of Tetraselmis chuii (T.Chuii) microalgae in the presence of TiO₂ (Titanium dioxide). The experiment was carried out on thermal analyzer equipment under inert condition. The blended sample has a mass ratio of microalgae and TiO₂ that was 10:0.03 (wt%). The results of the thermal analysis show that the addition of TiO₂ can change the temperature characteristics during the reaction process. The Coats-Redfern method is applied to calculate activation energy (Ea) resulted in the value of the blended fuel in the second stage that was 56.9 kJ/mol lower than that of pure microalgae that was 70.68 kJ/mol and conversely in the third stage the value of activation energy for blended fuel was 264.57 kJ/mol higher than pure microalgae that was 223.25 kJ/mol. Overall results pointed out that TiO₂ had a significant impact on the thermal characteristic of Tetraselmis chuii during the pyrolysis process.

Abstract: Vegetable oil is one of rice bran components. As triglycerides, vegetable oil can be converted to fatty acid and alkyl esters for further treatments. Synthesis of alkyl ester oil can be carried out by esterification or transesterification reaction, depending on the quality of the oil and the catalyst. The purposes of this study are 1) Rice bran oil isolation, 2) Oil esterification 3) Characterization and identification of the methyl ester that compose rice bran oil. The stages in this research are 1) Extraction of rice bran oil, 2) Synthesis of methyl ester from rice bran through esterification reaction, 3) Methyl ester characterization of rice bran oil and its potential test as biodiesel included determination of density, viscosity, refractive index, and acid number test, 4) The identification of synthesized methyl esters composition using GC-MS. The results showed that rice bran oil has a yield of 18.09%. Synthesis of methyl esters from rice bran oil through the esterification reaction with a catalyst acid yields 72.37%. The characters of the synthesized methyl ester are on the range of biodiesel quality standards, namely, the density is 0.850 g/mL, viscosity is 4.73 cSt, a refractive index is 1.45871, and an acid number is 0.76 g KOH/g methyl ester, therefore it is claimed that the synthesized methyl esters have the potential as biodiesel. The GC-MS result showed the presence of compounds methyl tetradecanoate (0.38%), methyl hexadecanoate (40.67%), methyl 9-octadecenoate (53.68%), methyl octadecanoate (5.02%), and methyl eicosanoate (0.14%).

Abstract: Natural fibers contained in bamboo are beneficial to renewable, biodegradable, abundant availability, and cheap which could be a potential substitute of synthetic materials. Tensile strength of this material is important requirements in various structural application. In this research, fiber fabrication process optimization of three types of local bamboo namely Gombong (Gigantochloa pseudoarundinacea), Haur Hejo (Bambusa tuldoides), and Tali (Gigantochloa apus) was investigated. These fibers were processed by creating a variety of the NaOH concentrations of 4 % and 6 %, immersion times of 1, 2, and 3 hours, and immersion temperatures of 25 °C and 60 °C. The process parameters and its level variations of bamboo fiber fabrication were optimized using Taguchi method. Then the contribution of each process parameter was observed using the analysis of variance (ANOVA). From Taguchi method, the optimal parameter for highest tensile strength was obtained from Tali bamboo, indicated by 4 % NaOH, 2 hours immersion time, and 60 °C immersion temperature. Meanwhile, the ANOVA revealed that the contributions for each parameter are 70 % for bamboo type, 7 % for NaOH concentration, 4 % for immersion time, and 17 % for immersion temperature with error contribution of 2 %. By using these data, it could be concluded that bamboo type selection is a critical parameter to obtain bamboo with high tensile strength. While NaOH concentration, immersion time, and immersion temperature are not critical parameters which gave flexibility in the selection process. FTIR analysis was carried in order to observe chemical bonding in bamboos. The results of FTIR on the bamboo fibers were indicated Tali bamboo has larger lignin levels decreasing than Haur Hejo and Gombong, this indicates in higher tensile strength for Tali bamboo fiber.

Abstract: Until now, used cooking oil (jelantah) has not been utilized optimally. This study seeks to convert this waste into biodiesel. Used cooking oil usually contains high concentration of free fatty acids which can be converted into methyl esters through trans-esterification by methanol. This effort is in line with the increasing need for renewable energy sources. Because the waste still contains high concentrations of free fatty acids, it is necessary to think about the right process and catalyst in converting it as biodiesel. One heterogeneous catalyst that is thought to excel in biodiesel production is ferrite-based nanocomposites, namely CaO@CoFe₂O₄ nanoparticles. The advantages of this catalyst are: it has high reactivity, thermal and chemical stability, and can be drawn by magnetic fields. This last property facilitates the catalyst isolation at the end of the process for recycling purposes. The catalytic power is expected to increase through impregnation with alkaline earth metal oxides which have a relatively high basicity, namely CaO. The purpose of this study was to synthesize and to characterize CaO@CoFe₂O₄, then to study its potential catalytic in biodiesel production from used cooking oil in various weight percent of catalyst. The main steps include: (1) synthesis of CoFe₂O₄ by coprecipitation; (2) Impregnation of CaO into CoFe₂O₄ and converted to CaO@CoFe₂O₄; (3) Characterization of the synthesized material by XRD, BET, and SEM/EDX; (4) application of CaO@CoFe₂O₄ in biodiesel production from used cooking oil; (5) characterization of biodiesel produced by viscosity measurement, yield and GC-MS analysis results. Based on the results of XRD and SEM/EDX analysis, the CaO@ CoFe₂O₄ catalyst has been successfully synthesized. Under optimal conditions, the yield of methyl ester produced with the addition of 2% of catalyst was 80.62%.

Abstract: Mercury pollution through water causes several dangerous diseases. Various efforts have been made to reduce mercury pollution. One of them is by using sorbent. Many ways to improve absorption efficiency, one of which is using magnetic sorbents. This study focused on the effect of grain size and the concentration of Mn_0.25Fe_2.75O₄@SiO₂ core-shell on mercury absorption efficiency. The synthesis of Mn_0.25Fe_2.75O₄@SiO₂ with 6 and 8 mL of TEOS was carried out through coprecipitation and sol-gel methods. The characterization using XRD, VSM, and FTIR was conducted to determine grain size, properties, and material functional groups proving that SiO₂ was successfully covered on the Fe₃O₄ surface. The percentage of absorption was found by using the AAS instrument. Diffraction data confirmed the presence of Fe₃O₄ and the amorphous SiO₂ phase. According to the Rietveld analysis of all samples demonstrated the particle size of Mn_0.25Fe_2.75O₄ around 11-12 nm. The Mn_0.25Fe_2.75O₄ core had superparamagnetic properties for magnetic separation, and the SiO₂ shell could protect the core of being oxidized or dissolved under acid condition. FTIR results showed the sample had a functional group of the main components of Fe-O and SiO₂ at a wavenumber of 420-507 cm^-1 and 801 cm^-1 (stretching) and 1078 cm^-1 (bending), respectively. The results of the mercury absorption test indicated that the smaller the grain size and the higher the concentration of TEOS, the percentage of mercury uptake would increase. In addition, the absorption percentage increased with the duration of absorption time given.

Abstract: To explore Fe minerals in Tiga Warna Beach, we investigated to assess the geochemical fraction of Fe in sediment. The samples were leached of Fe using the optimized BCR microwave method. The optimized of BCR microwave method revealed the high accuracy and precision before Fe assessment. The leached of Fe in each of fraction in sediment were measured by AAS. The same patterns of explored Fe in the geochemical fractions from the sediment fraction 1 (mobile fraction) to fraction 3 (oxidizable fraction) as stated nonresistant sediment fractions showed a lower portion of Fe compared with the Fe levels in sediment fraction 4 (residual fraction) or resistant sediment fraction. The Pollution Load Index (PLI) value and the geoaccumulation Index (I-geo) value of sediment samples in blue, green, and red waters indicating that the sediments of Tiga Warna Beach are still natural and has not been categorized as polluted.

Abstract: Plastic pollution is an environmental problem that has not resolved until now. Pyrolysis is able to be a solution to reduce plastic waste. The use of catalysts will reduce heating temperatures, speed up processing time, and increase product yield. Natural zeolite has the potency as a catalyst in pyrolysis process due to its micropore structure, high acidity and thermal stability. The purpose of this research is to determine the effect of active zeolite catalyst on the polypropylene pyrolysis. The main process of this study is pyrolysis of polypropylene (PP) plastic waste without catalysts and with natural zeolite catalysts which were non-activated and activated. Natural zeolites were activated by HF, HCl and NH₄Cl. The well result of this research is represented by the yield, viscosity, calorific value, FTIR and GC-MS analysis. Based on the results of diffractogram analysis, natural zeolites catalyst in this study is included in modernite minerals crystalline. The ratio of Si/Al in zeolite before activation was 7.07 and the acidity was 0.697 g/mmol. After the activation process, the ratio of Si/Al and zeolite acidity increased by 62.181% and 43.84%. The use of active natural zeolite catalysts in pyrolysis PP could reduce the total reaction time by 57.14%. Pyrolysis products with active zeolite catalyst compared to without catalysts had clearer color and higher heating value, compared to pirolysis without catalyst. Based on function group analysis with FTIR, the mixture of hydrolyzed compounds containing successive functional groups are-C-H (alkanes), double bond of C=C, hydroxyl-OH group which can be determined as phenol (ArOH), alcohol (ROH), and carboxylic acid (RCOOH). The GC-MS analysis showed that pyrolysis products are composed of a mixture of alkanes, cycloalkanes, alkenes, carboxylic acids with aromatic rings, and ketones. The pyrolysis products without catalysts consist of 5-11 (C5-C11) carbon atoms, whereas the range of carbon atoms of pyrolysis products with active zeolite catalysts was 6-24 (C6-C24).

Abstract: The availability of synthetic waste (SW) continuously increases, but on the contrary fossil fuels resources always decrease. The potential of SW for alternative fuel is critical to investigate for overcoming the problem generated from its overabundance and to provide its value-added. In this study, the changes of the macromolecular and the mineralogical during the SW combustion processes were investigated by Fourier Transform Infrared (FTIR) spectroscopy and x-ray diffraction (XRD), respectively. The combustion has been performed by using thermogravimetric analyzer (TGA) at a heating rate of 10 °C/min, from 25 to 1000 °C, with 100 ml/min constant flowrate of air atmosphere. According to the TGA results, the decomposition stage of the sample can be identified as a function of temperature and time. From ambient temperatures to 293 °C the sample experienced the first decomposition process that was correlated with the moisture losses and light volatile release. Macromolecular changes occurred at the temperature 293 °C where functional group of C–H in methylene was decomposed due to the removal of volatile matter. From the temperature of 293 to 485 °C the sample underwent the second stage of decomposition. The XRD result showed that mineral changes occurred at the temperature of 485 °C where the KCl compound was formed. In line with the escalating temperature, SiO₂ was decomposed at a temperature of 590 °C. The final stage occurred at the temperature 625 to 1000 °C indicated by constant of TG line. At 625 °C, XRD result indicated the significant increasing of the CaCO₃ compound.