Tinia Idaty Mohd Ghazi

Anaerobic digestion technology in livestock manure treatment for biogas production: A review

This article reviews the potential of anaerobic digestion (AD) for biogas production from livestock manure wastes and compares the operating and performance data for various anaerobic process configurations. It examines different kinds of manure waste treatment techniques and the influence of several parameters on biogas and methane yield. The comparison indicates that a variety of different operational conditions, various reactor configurations such as batch reactors, continuously stirred tank reactor (CSTR), plug flow reactor (PFR), up‐flow anaerobic sludge blanket (UASB), anaerobic sequencing batch reactor (ASBR), temperature phased anaerobic digestion (TPAD), and continuous one‐ and two‐stage systems, present a suitable technology for the AD of livestock manure waste. Main performance indicators are biogas and methane yield, degradation of volatile solids (VS), higher loading, and process stability with a short retention time.

Dispersion and stabilization of photocatalytic TiO 2 nanoparticles in aqueous suspension for coatings applications

To produce titanium dioxide (TiO2) nanoparticle coatings, it is desirable that the nanoparticles are dispersed into a liquid solution and remain stable for a certain period of time. Controlling the dispersion and aggregation of the nanoparticles is crucial to exploit the advantages of the nanometer-sized TiO2 particles. In this work, TiO2 nanoparticles were dispersed and stabilized in aqueous suspensions using two common dispersants which were polyacrylic acid (PAA) and ammonium polymethacrylate (Darvan C). The effect of parameters such as ultrasonication amplitude and type and amount of dispersants on the dispersibility and stability of the TiO2 aqueous suspensions were examined. Rupture followed by erosion was determined to be the main break up mechanisms when ultrasonication was employed. The addition of dispersant was found to producemore dispersed andmore stabilized aqueous suspension. 3wt.% of PAA with average molecular weight (Mw) of 2000 g/mol (PAA 2000) was determined to produce the best and most stable dispersion. The suspensions were then coated on quartz glass, whereby the photocatalytic activity of the coatings was studied via the degradation of formaldehyde gas under UV light. The coatings were demonstrated to be photocatalytically active.

Production of biogas from solid organic wastes through anaerobic digestion: a review

Anaerobic digestion treatments have often been used for biological stabilization of solid wastes. These treatment processes generate biogas which can be used as a renewable energy sources. Recently, anaerobic digestion of solid wastes has attracted more interest because of current environmental problems, most especially those concerned with global warming. Thus, laboratory-scale research on this area has increased significantly. In this review paper, the summary of the most recent research activities covering production of biogas from solid wastes according to its origin via various anaerobic technologies was presented.

Fe-Doped TiO 2 nanoparticles produced via MOCVD: synthesis, characterization, and photocatalytic activity

Iron (Fe)-doped titanium dioxide (TiO2) nanoparticles were produced via the metallorganic chemical vapour deposition (MOCVD) method at 700°C. Different amounts of ferrocene as the Fe dopant source (0.001-0.05g) were introduced inside the reactor together with the titanium precursor in order to synthesize different Fe dopant concentrations of TiO2 nanoparticles. Nitrogen (N2) adsorption results showed that increasing the Fe dopant concentration caused a slight increase in the surface area of the nanoparticles due to the decrease in nanoparticle size. The UV-diffuse reflectance spectra demonstrated an absorption shift in Fe-doped TiO2 nanoparticles to longer wavelengths, thus showing an enhancement of the absorption in the visible spectrum. Bandgap energy values determined from the UV-diffuse reflectance spectra data decreased with an increase in the Fe dopant concentrations. The photocatalytic activity of Fe-doped TiO2 nanoparticles was investigated via degradation of methylene blue under UV and fluorescent light. It was found that Fe doping reduced the photocatalytic activity of the samples. Based on X-ray photoelectron spectroscopy (XPS) results, it is believed that this is due to the unfavourable location of Fe3+ inside the interior matrix of the TiO2 nanoparticles rather than on the exterior surface, which would affect photocatalytic behaviour.

Bioenergy II: Production of Biodegradable Lubricant from Jatropha curcas and Trimethylolpropane

Jatropha oil has good potential as the renewable energy as well as lubricant feedstock. Production of Jatropha oil based lubricant was performed via a two-step process; (i) the transesterification of Jatropha oil to produce Jatropha Methyl Ester (JME) and, (ii) transesterification of JME with trimethylolpropane (TMP) under the presence of alkaline based catalyst. Transesterification of Jatropha oil was carried out at 65°C for 1 hour by using 1-2% NaOH as catalyst. While, the transesterification of JME was carried out at 150°C with pressure kept at 10mbar. The conversion of JME to jatropha biolubricant was found to be more than 80%. However, to maintain forward reaction, the amount of JME was maintained at about 4:1 ratios to TMP. The basic properties of jatropha biolubricant are found comparable to other plant based biolubricant.

Effect of postdeposition heat treatment on the crystallinity, size, and photocatalytic activity of TiO 2 nanoparticles produced via chemical vapour deposition

Titanium dioxide (TiO2) nanoparticles were produced using chemical vapour deposition (CVD) at different deposition temperatures (300-700°C). All the samples were heat treated at their respective deposition temperatures and at a fixed temperature of 400°C. A scanning electron microscope (SEM), a transmission electron microscope (TEM), and X-ray diffraction (XRD) were used to characterize the nanoparticles in terms of size and crystallinity. The photocatalytic activity was investigated via degradation of methylene blue under UV light. The effects of post deposition heat treatment are discussed in terms of crystallinity, nanoparticle size as well as photocatalytic activity. Crystallinity was found to have a much larger impact on photocatalytic activity compared to nanoparticle size. Samples having a higher degree of crystallinity were more photocatalytically active despite being relatively larger in size. Surprisingly, the photocatalytic activity of the samples reduced when heat treated at temperatures lower than the deposition temperature despite showing an improvement in crystallinity.

Temperature dependence on the synthesis of jatropha biolubricant

Jatropha oil has good potential as the renewable energy as well as lubricant feedstock. The synthesis of jatropha biolubricant was performed by transesterification of jatropha methyl ester (JME) with trimethyl-ol-propane (TMP) with sodium methoxide (NaOCH3) catalyst. The effects of temperature on the synthesis were studied at a range between 120°C and 200°C with pressure kept at 10mbar. The conversion of JME to jatropha biolubricant was found to be the highest (47%) at 200°C. However, it was suggested that the optimum temperature of the reaction is at 150°C due to insignificant improvement in biolubricant production. To maintain forward reaction, the excess amount of JME was maintained at 3.9:1 ratios to TMP. Kinetic study was done and compared. The synthesis was found to follow a second order reaction with overall rate constant of 1.49 × 10–1 (%wt/wt.min.°C)−1. The estimated activation energy was 3.94 kJ/mol. Pour point for jatropha biolubricant was at −3°C and Viscosity Index (VI) ranged from 178 to 183. The basic properties of jatropha biolubricant, pour point and viscosities are found comparable to other plant based biolubricant, namely palm oil and soybean based biolubricant.

Pretreatment of lignocellulosic biomass from animal manure as a means of enhancing biogas production

Biogas produced from lignocellulosic biomass, e.g. animal manure, has the potential to be a promising renewable energy source. Special emphasis has been placed on animal manure pretreatment in an anaerobic digestion as a means of enhancing biogas yield. Here, we review the existing pretreatment methods of anaerobic digestion with regard to their effects on the conversion of animal manure to biogas. Various methods and their challenges are highlighted. The effects of pretreatment are complex and usually depend on the animal waste characteristics and the method of choice. In general, pretreatment enhances the anaerobic digestion of the lignocellulosic content of the animal manure, by increasing the methane yield in similar operating conditions as those without the pretreatment.

3D CFD simulations of MOCVD synthesis system of titanium dioxide nanoparticles

This paper presents the 3-dimensional (3D) computational fluid dynamics (CFD) simulation study of metal organic chemical vapor deposition (MOCVD) producing photocatalytic titanium dioxide (TiO2) nanoparticles. It aims to provide better understanding of the MOCVD synthesis systeme specially of deposition process of TiO2 nanoparticles as well as fluid dynamics inside the reactor. The simulated model predicts temperature, velocity, gas streamline, mass fraction of reactants and products, kinetic rate of reaction, and surface deposition rate profiles. It was found that temperature distribution, flow pattern, and thermophoretic force considerably affected the deposition behavior of TiO2 nanoparticles. Good mixing of nitrogen (N2) carrier gas and oxygen (O2) feed gas is important to ensure uniformdeposition and the quality of the nanoparticles produced. Simulation results are verified by experiment where possible due to limited available experimental data. Good agreement between experimental and simulation results supports the reliability of simulation work.

Response Surface Methodology for Optimization of Epoxidized Trimethylolpropane Ester Synthesis from Palm Oil

To improve the oxidative stability of the palm oil-based biolubricant, the fatty acid double bonds in palm oil-based trimethylolpropane ester (TMP ester) was converted into an oxirane ring via an in-situ epoxidation method. The epoxidized TMP ester was produced from a reaction between TMP ester and peracetic acid which was prepared in-situ by reacting glacial acetic acid with hydrogen peroxide in the presence of concentrated sulphuric acid. The response surface methodology was applied using a central composite design technique to optimize the conditions of the epoxidation reaction to produce the epoxidized TMP ester. The effects of four independent variables namely concentration of acetic acid (0-2 mol), concentration of hydrogen peroxide (1.5-9.5 mol), temperature of reaction (30-110°C) and reaction time (0.5-26.5 h) on the three dependent variables; percentage of oxirane oxygen, iodine value, and hydroxyl value were studied. A second-order polynomial multiple regression model was employed to predict the three dependent variables under optimum conditions of 0.59 mol of glacial acetic acid, 7.5 mol of hydrogen peroxide concentration, at temperature of 50°C and reaction times of 7 h. The optimum values of percentage of oxirane oxygen, iodine value, and hydroxyl value were 4.01%, 1.94%, and 0.43% respectively. The analysis of variance yielded a high coefficient of determination value of 0.9395-0.9880, hence indicating the fitness of the second-order regression model to the experimental data.