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Harvesting visible light for enhanced catalytic degradation of wastewater using TiO2@Fe3O4 embedded on two dimensional reduced graphene oxide nanosheets

Rajendran S, Blanco A, Gnanasekaran L, Jalil AA, Chen WH, Gracia F

Chemosphere, 2023 Dec;345:140418.
PMID: 37844702 DOI: 10.1016/j.chemosphere.2023.140418

Carbon-integrated binary metal oxide semiconductors have gained prominence in the last decade as a better material for photocatalytic wastewater treatment technology. In this regard, this research describes the investigation of the binary metal oxide TiO2@Fe3O4 embedded on reduced graphene oxide (rGO) nanosheets synthesized through a combination of sol-gel, chemical precipitation, and Hummer's processes. Besides, the catalyst is applied for the photocatalytic degradation of organic chlorophenol pollutants. The characterized diffraction results showed the peak broadening of the rGO-TiO2@Fe3O4 composite formed with tetragonal and cubic structures having small crystallite sizes. The TEM observation shows an enormous miniature of TiO2@Fe3O4 nanospheres spread on the folded 2D-rGO nanosheets with a large BET surface area. The XPS result holds the mixed phases of Fe3O4 and Fe2O3. Finally, the catalyst demonstrated a low band gap with extended light absorption towards visible light irradiation. The synergistic interactions between Fe3+ and Fe2+ improved the visible light activity due to the incorporation of rGO, and also possessed good recycling capacity. The increased mobility of electrons at the interfaces of TiO2 and Fe3O4 due to the mixing of rGO results in the separation of charge carriers by elevating the photocatalytic degradation efficiency of chlorophenol.

Matched MeSH terms: Oxides/chemistry
Fulltext Rapid adsorption of heavy metals by Fe3O4/talc nanocomposite and optimization study using response surface methodology

Kalantari K, Ahmad MB, Masoumi HR, Shameli K, Basri M, Khandanlou R

Int J Mol Sci, 2014;15(7):12913-27.
PMID: 25050784 DOI: 10.3390/ijms150712913

Fe3O4/talc nanocomposite was used for removal of Cu(II), Ni(II), and Pb(II) ions from aqueous solutions. Experiments were designed by response surface methodology (RSM) and a quadratic model was used to predict the variables. The adsorption parameters such as adsorbent dosage, removal time, and initial ion concentration were used as the independent variables and their effects on heavy metal ion removal were investigated. Analysis of variance was incorporated to judge the adequacy of the models. Optimal conditions with initial heavy metal ion concentration of 100, 92 and 270 mg/L, 120 s of removal time and 0.12 g of adsorbent amount resulted in 72.15%, 50.23%, and 91.35% removal efficiency for Cu(II), Ni(II), and Pb(II), respectively. The predictions of the model were in good agreement with experimental results and the Fe3O4/talc nanocomposite was successfully used to remove heavy metals from aqueous solutions.

Matched MeSH terms: Oxides/chemistry
Nanostructured tungsten trioxide thin films synthesized for photoelectrocatalytic water oxidation: a review

Zhu T, Chong MN, Chan ES

ChemSusChem, 2014 Nov;7(11):2974-97.
PMID: 25274424 DOI: 10.1002/cssc.201402089

The recent developments of nanostructured WO3 thin films synthesized through the electrochemical route of electrochemical anodization and cathodic electrodeposition for the application in photoelectrochemical (PEC) water splitting are reviewed. The key fundamental reaction mechanisms of electrochemical anodization and cathodic electrodeposition methods for synthesizing nanostructured WO3 thin films are explained. In addition, the effects of metal oxide precursors, electrode substrates, applied potentials and current densities, and annealing temperatures on size, composition, and thickness of the electrochemically synthesized nanostructured WO3 thin films are elucidated in detail. Finally, a summary is given for the general evaluation practices used to calculate the energy conversion efficiency of nanostructured WO3 thin films and a recommendation is provided to standardize the presentation of research results in the field to allow for easy comparison of reported PEC efficiencies in the near future.

Matched MeSH terms: Oxides/chemistry*
Kinetics and thermodynamic analysis in one-pot pyrolysis of rice hull using renewable calcium oxide based catalysts

Gan DKW, Loy ACM, Chin BLF, Yusup S, Unrean P, Rianawati E, et al.

Bioresour Technol, 2018 Oct;265:180-190.
PMID: 29894912 DOI: 10.1016/j.biortech.2018.06.003

Thermodynamic and kinetic parameters of catalytic pyrolysis of rice hull (RH) pyrolysis using two different types of renewable catalysts namely natural limestone (LS) and eggshells (ES) using thermogravimetric analysis (TG) approach at different heating rates of 10-100 K min-1 in temperature range of 323-1173 K are investigated. Catalytic pyrolysis mechanism of both catalysts had shown significant effect on the degradation of RH. Model free kinetic of iso-conversional method (Flynn-Wall-Ozawa) and multi-step reaction model (Distributed Activation Energy Model) were employed into present study. The average activation energy was found in the range of 175.4-177.7 kJ mol-1 (RH), 123.3-132.5 kJ mol-1 (RH-LS), and 96.1-100.4 kJ mol-1 (RH-ES) respectively. The syngas composition had increased from 60.05 wt% to 63.1 wt% (RH-LS) and 63.4 wt% (RH-ES). However, the CO2 content had decreased from 24.1 wt% (RH) to 20.8 wt% (RH-LS) and 19.9 wt% (RH-ES).

Matched MeSH terms: Oxides/chemistry*
Fulltext A Novel Adsorbent Magnetic Graphene Oxide Modified with Chitosan for the Simultaneous Reduction of Mycotoxins

Abbasi Pirouz A, Abedi Karjiban R, Abu Bakar F, Selamat J

Toxins (Basel), 2018 09 06;10(9).
PMID: 30200553 DOI: 10.3390/toxins10090361

A novel magnetic graphene oxide modified with chitosan (MGO-CTS) was synthesised as an adsorbent aimed to examine the simultaneous removal of mycotoxins. The composite was characterised by various procedures, namely Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and a scanning electron microscope (SEM). The adsorption evaluation was considered via pH effects, initial mycotoxin concentration, adsorption time and temperature. Adsorption isotherm data and kinetics experiments were acquired at the optimum pH 5 fit Freundlich isotherm as well as pseudo-second-order kinetic models. The thermodynamic results indicated that the adsorption of the mycotoxins was spontaneous, endothermic and favourable.

Matched MeSH terms: Oxides/chemistry*
Fulltext Exceedingly biocompatible and thin-layered reduced graphene oxide nanosheets using an eco-friendly mushroom extract strategy

Muthoosamy K, Bai RG, Abubakar IB, Sudheer SM, Lim HN, Loh HS, et al.

Int J Nanomedicine, 2015;10:1505-19.
PMID: 25759577 DOI: 10.2147/IJN.S75213

PURPOSE: A simple, one-pot strategy was used to synthesize reduced graphene oxide (RGO) nanosheets by utilizing an easily available over-the-counter medicinal and edible mushroom, Ganoderma lucidum.
METHODS: The mushroom was boiled in hot water to liberate the polysaccharides, the extract of which was then used directly for the reduction of graphene oxide. The abundance of polysaccharides present in the mushroom serves as a good reducing agent. The proposed strategy evades the use of harmful and expensive chemicals and avoids the typical tedious reaction methods.
RESULTS: More importantly, the mushroom extract can be easily separated from the product without generating any residual byproducts and can be reused at least three times with good conversion efficiency (75%). It was readily dispersible in water without the need of ultrasonication or any surfactants; whereas 5 minutes of ultrasonication with various solvents produced RGO which was stable for the tested period of 1 year. Based on electrochemical measurements, the followed method did not jeopardize RGO's electrical conductivity. Moreover, the obtained RGO was highly biocompatible to not only colon (HT-29) and brain (U87MG) cancer cells, but was also viable towards normal cells (MRC-5).
CONCLUSION: Besides being eco-friendly, this mushroom based approach is easily scalable and demonstrates remarkable RGO stability and biocompatibility, even without any form of functionalization.

Matched MeSH terms: Oxides/chemistry*
Recent trends and advancement in metal oxide nanoparticles for the degradation of dyes: synthesis, mechanism, types and its application

Senthil Rathi B, Ewe LS, S S, S S, Yew WK, R B, et al.

Nanotoxicology, 2024 May;18(3):272-298.
PMID: 38821108 DOI: 10.1080/17435390.2024.2349304

Synthetic dyes play a crucial role in our daily lives, especially in clothing, leather accessories, and furniture manufacturing. Unfortunately, these potentially carcinogenic substances are significantly impacting our water systems due to their widespread use. Dyes from various sources pose a serious environmental threat owing to their persistence and toxicity. Regulations underscore the urgency in addressing this problem. In response to this challenge, metal oxide nanoparticles such as titanium dioxide (TiO2), zinc oxide (ZnO), and iron oxide (Fe3O4) have emerged as intriguing options for dye degradation due to their unique characteristics and production methods. This paper aims to explore the types of nanoparticles suitable for dye degradation, various synthesis methods, and the properties of nanoparticles. The study elaborates on the photocatalytic and adsorption-desorption activities of metal oxide nanoparticles, elucidating their role in dye degradation and their application potential. Factors influencing degradation, including nanoparticle properties and environmental conditions, are discussed. Furthermore, the paper provides relevant case studies, practical applications in water treatment, and effluent treatment specifically in the textile sector. Challenges such as agglomeration, toxicity concerns, and cost-effectiveness are acknowledged. Future advancements in nanomaterial synthesis, their integration with other materials, and their impact on environmental regulations are potential areas for development. In conclusion, metal oxide nanoparticles possess immense potential in reducing dye pollution, and further research and development are essential to define their role in long-term environmental management.

Matched MeSH terms: Oxides/chemistry
Chromatography Scrutiny, Molecular Docking, Clarifying the Selectivities and the Mechanism of [3 + 2] Cycloloaddition Reaction between Linallol and Chlorobenzene-Nitrile-oxide

Barhoumi A, Ryachi K, Belghiti ME, Chafi M, Tounsi A, Syed A, et al.

J Fluoresc, 2024 Jul;34(4):1913-1929.
PMID: 37668770 DOI: 10.1007/s10895-023-03411-z

Employing the Molecular Electron Density Theory, [3 + 2] cycloaddition processes between 4-chlorobenzenenitrileoxide and linalool, have been applied using the DFT/B3LYP/6-311(d,p) method, activation, reaction energies and the reactivity indices are calculated. In an investigation of conceptual DFT indices, LIL-1 will contribute to this reaction as a nucleophile, whilst NOX-2 will participate as an electrophile. This cyclization is regio, chemo and stereospecific, as demonstrated by the reaction and activation energies, in clear agreement with the experiment's results, in addition, ELF analysis revealed that the mechanism for this cycloaddition occurs in two steps. Furthermore, a docking study was conducted on the products studied, and the interaction with the protein protease COVID-19 (PDB ID: 6LU7), our results indicate that the presence of the -OH group increases the affinity of these products, moreover, adsorption study by chromatography was made on silica gel as support; our outcome reveals that the -OH group creates an intramolecular hydrogen bond in the product P2, while in the product P3 will create a hydrogen bond with the silica gel which makes the two products P2 and P3 are very easy to separate by chromatography, this result is in excellent agreement with the Rf retention value. The study might provide a fundamental for developing natural anti-viral compound in promoting human health.

Matched MeSH terms: Oxides/chemistry
Fulltext Flexible and highly selective NO2 gas sensor based on direct-ink-writing of eco-friendly graphene oxide for smart wearable application

Khan J, Rezo V, Vincze T, Weis M, Momin SA, El-Atab N, et al.

Chemosphere, 2024 Nov;367:143618.
PMID: 39490758 DOI: 10.1016/j.chemosphere.2024.143618

Nitrogen dioxide (NO2) is a major cause of respiratory disorders in outdoor and indoor environments. Real-time NO2 monitoring using nonintrusive wearable devices can save lives and provide valuable health data. This study reports a room-temperature, wearable, and flexible smart NO2 gas sensor fabricated via cost-effective printing technology on a polyimide substrate. The sensor uses alkali lignin with edge-oxidised graphene oxide (EGO-AL) ink, demonstrating a sensitivity of 1.70% ppm⁻1 and a detection limit of 12.70 ppb, with excellent selectivity towards NO2. The high sensing properties are attributed to labile oxygen functional groups from GO and alkali lignin, offering abundant interacting sites for NO2 adsorption and electron transfer. The sensor fully recovers to the baseline after heat treatment at 150 °C, indicating its reusability. Integration into lab coats showcased its wearable application, utilising a flexible printed circuit board to wirelessly alert the wearer via cell phone to harmful NO2 levels (>3 ppm) in the environment. This smart sensing application underscores the potential for practical, real-time air quality monitoring, personal safety enhancement, and health management.

Matched MeSH terms: Oxides/chemistry
Synthesis and characterization of Co3O4 ultra-nanosheets and Co3O4 ultra-nanosheet-Ni(OH)2 as non-enzymatic electrochemical sensors for glucose detection

Mahmoudian MR, Basirun WJ, Woi PM, Sookhakian M, Yousefi R, Ghadimi H, et al.

Mater Sci Eng C Mater Biol Appl, 2016 Feb;59:500-508.
PMID: 26652401 DOI: 10.1016/j.msec.2015.10.055

The present study examines the synthesis of Co3O4 ultra-nanosheets (Co3O4 UNSs) and Co3O4 ultra-nanosheet-Ni(OH)2 (Co3O4 UNS-Ni(OH)2) via solvothermal process and their application as non-enzymatic electrochemical sensors for glucose detection. X-ray diffraction and transmission electron microscopy results confirmed the Co3O4 UNS deposition on Ni(OH)2 surface. The presence of Co3O4 UNSs on Ni (OH) 2 surface improved the sensitivity of glucose detection, from the increase of glucose oxidation peak current at the Co3O4 UNS-Ni(OH)2/glassy carbon electrode (current density: 2000μA·cm(-2)), compared to the Co3O4 UNSs. These results confirmed that Ni(OH)2 on glassy carbon electrode is a sensitive material for glucose detection, moreover the Co3O4 UNSs can increase the interaction and detection of glucose due to their high surface area. The estimated limit of detection (S/N=3) and limit of quantification (S/N=10) of the linear segment (5-40μM) are 1.08μM and 3.60μM respectively. The reproducibility experiments confirmed the feasibility of Co3O4 UNS-Ni(OH)2 for the quantitative detection of certain concentration ranges of glucose.

Matched MeSH terms: Hydroxides/chemistry*; Oxides/chemistry*
Fulltext Recent advances in heterogeneous photocatalytic decolorization of synthetic dyes

Muhd Julkapli N, Bagheri S, Bee Abd Hamid S

ScientificWorldJournal, 2014;2014:692307.
PMID: 25054183 DOI: 10.1155/2014/692307

During the process and operation of the dyes, the wastes produced were commonly found to contain organic and inorganic impurities leading to risks in the ecosystem and biodiversity with the resultant impact on the environment. Improper effluent disposal in aqueous ecosystems leads to reduction of sunlight penetration which in turn diminishes photosynthetic activity, resulting in acute toxic effects on the aquatic flora/fauna and dissolved oxygen concentration. Recently, photodegradation of various synthetic dyes has been studied in terms of their absorbance and the reduction of oxygen content by changes in the concentration of the dye. The advantages that make photocatalytic techniques superior to traditional methods are the ability to remove contaminates in the range of ppb, no generation of polycyclic compounds, higher speed, and lower cost. Semiconductor metal oxides, typically TiO2, ZnO, SnO, NiO, Cu2O, Fe3O4, and also CdS have been utilized as photocatalyst for their nontoxic nature, high photosensitivity, wide band gap and high stability. Various process parameters like photocatalyst dose, pH and initial dye concentrations have been varied and highlighted. Research focused on surface modification of semiconductors and mixed oxide semiconductors by doping them with noble metals (Pt, Pd, Au, and Ag) and organic matter (C, N, Cl, and F) showed enhanced dye degradation compared to corresponding native semiconductors. This paper reviews recent advances in heterogeneous photocatalytic decolorization for the removal of synthetic dyes from water and wastewater. Thus, the main core highlighted in this paper is the critical selection of semiconductors for photocatalysis based on the chemical, physical, and selective nature of the poisoning dyes.

Matched MeSH terms: Oxides/chemistry
Characterisation of micro-sized and nano-sized tungsten oxide-epoxy composites for radiation shielding of diagnostic X-rays

Azman NZ, Siddiqui SA, Low IM

Mater Sci Eng C Mater Biol Appl, 2013 Dec 1;33(8):4952-7.
PMID: 24094209 DOI: 10.1016/j.msec.2013.08.023

Characteristics of X-ray transmissions were investigated for epoxy composites filled with 2-10 vol% WO3 loadings using synchrotron X-ray absorption spectroscopy (XAS) at 10-40 keV. The results obtained were used to determine the equivalent X-ray energies for the operating X-ray tube voltages of mammography and radiology machines. The results confirmed the superior attenuation ability of nano-sized WO3-epoxy composites in the energy range of 10-25 keV when compared to their micro-sized counterparts. However, at higher synchrotron radiation energies (i.e., 30-40 keV), the X-ray transmission characteristics were similar with no apparent size effect for both nano-sized and micro-sized WO3-epoxy composites. The equivalent X-ray energies for the operating X-ray tube voltages of the mammography unit (25-49 kV) were in the range of 15-25 keV. Similarly, for a radiology unit operating at 40-60 kV, the equivalent energy range was 25-40 keV, and for operating voltages greater than 60 kV (i.e., 70-100 kV), the equivalent energy was in excess of 40 keV. The mechanical properties of epoxy composites increased initially with an increase in the filler loading but a further increase in the WO3 loading resulted in deterioration of flexural strength, modulus and hardness.

Matched MeSH terms: Oxides/chemistry*
Fulltext Infrared study of Er(3+)/Yb(3+) Co-Doped GeO(2)-PbO-Bi(2)O(3) glass

Bahari HR, Sidek HA, Adikan FR, Yunus WM, Halimah MK

Int J Mol Sci, 2012;13(7):8609-14.
PMID: 22942723 DOI: 10.3390/ijms13078609

Heavy metal oxide glasses, containing bismuth and/or lead in their glass structure are new alternatives for rare eart (RE) doped hosts. Hence, the study of the structure of these vitreous systems is of great interest for science and technology. In this research work, GeO(2)-PbO-Bi(2)O(3) glass host doped with Er(3+)/Yb(3+) ions was synthesized by a conventional melt quenching method. The Fourier transform infrared (FTIR) results showed that PbO and Bi(2)O(3) participate with PbO(4) tetragonal pyramids and strongly distort BiO(6) octahedral units in the glass network, which subsequently act as modifiers in glass structure. These results also confirmed the existence of both four and six coordination of germanium oxide in glass matrix.

Matched MeSH terms: Oxides/chemistry*
Fulltext Effect of ZnO on the physical properties and optical band gap of soda lime silicate glass

Zaid MH, Matori KA, Aziz SH, Zakaria A, Ghazali MS

Int J Mol Sci, 2012;13(6):7550-8.
PMID: 22837711 DOI: 10.3390/ijms13067550

This manuscript reports on the physical properties and optical band gap of five samples of soda lime silicate (SLS) glass combined with zinc oxide (ZnO) that were prepared by a melting and quenching process. To understand the role of ZnO in this glass structure, the density, molar volume and optical band gaps were investigated. The density and absorption spectra in the Ultra-Violet-Visible (UV-Visible) region were recorded at room temperature. The results show that the densities of the glass samples increased as the ZnO weight percentage increased. The molar volume of the glasses shows the same trend as the density: the molar volume increased as the ZnO content increased. The optical band gaps were calculated from the absorption edge, and it was found that the optical band gap decreased from 3.20 to 2.32 eV as the ZnO concentration increased.

Matched MeSH terms: Oxides/chemistry*
Fulltext Simple room-temperature preparation of high-yield large-area graphene oxide

Huang NM, Lim HN, Chia CH, Yarmo MA, Muhamad MR

Int J Nanomedicine, 2011;6:3443-8.
PMID: 22267928 DOI: 10.2147/IJN.S26812

Graphene has attracted much attention from researchers due to its interesting mechanical, electrochemical, and electronic properties. It has many potential applications such as polymer filler, sensor, energy conversion, and energy storage devices. Graphene-based nanocomposites are under an intense spotlight amongst researchers. A large amount of graphene is required for preparation of such samples. Lately, graphene-based materials have been the target for fundamental life science investigations. Despite graphene being a much sought-after raw material, the drawbacks in the preparation of graphene are that it is a challenge amongst researchers to produce this material in a scalable quantity and that there is a concern about its safety. Thus, a simple and efficient method for the preparation of graphene oxide (GO) is greatly desired to address these problems. In this work, one-pot chemical oxidation of graphite was carried out at room temperature for the preparation of large-area GO with ~100% conversion. This high-conversion preparation of large-area GO was achieved using a simplified Hummer's method from large graphite flakes (an average flake size of 500 μm). It was found that a high degree of oxidation of graphite could be realized by stirring graphite in a mixture of acids and potassium permanganate, resulting in GO with large lateral dimension and area, which could reach up to 120 μm and ~8000 μm(2), respectively. The simplified Hummer's method provides a facile approach for the preparation of large-area GO.

Matched MeSH terms: Oxides/chemistry
Fulltext Photopyroelectric spectroscopic studies of ZnO-MnO(2)-Co(3)O(4)-V(2)O(5) ceramics

Rizwan Z, Zakaria A, Ghazali MS

Int J Mol Sci, 2011;12(3):1625-32.
PMID: 21673911 DOI: 10.3390/ijms12031625

Photopyroelectric (PPE) spectroscopy is a nondestructive tool that is used to study the optical properties of the ceramics (ZnO + 0.4MnO(2) + 0.4Co(3)O(4) + xV(2)O(5)), x = 0-1 mol%. Wavelength of incident light, modulated at 10 Hz, was in the range of 300-800 nm. PPE spectrum with reference to the doping level and sintering temperature is discussed. Optical energy band-gap (E(g)) was 2.11 eV for 0.3 mol% V(2)O(5) at a sintering temperature of 1025 °C as determined from the plot (ρhυ)(2)versushυ. With a further increase in V(2)O(5), the value of E(g) was found to be 2.59 eV. Steepness factor 'σ(A)' and 'σ(B)', which characterize the slope of exponential optical absorption, is discussed with reference to the variation of E(g). XRD, SEM and EDAX are also used for characterization of the ceramic. For this ceramic, the maximum relative density and grain size was observed to be 91.8% and 9.5 μm, respectively.

Matched MeSH terms: Oxides/chemistry*
Role of calcium oxide in sludge granulation and methanogenesis for the treatment of palm oil mill effluent using UASB reactor

Ahmad A, Ghufran R, Abd Wahid Z

J Hazard Mater, 2011 Dec 30;198:40-8.
PMID: 22047724 DOI: 10.1016/j.jhazmat.2011.10.008

The granulation process in palm oil mill effluent using calcium oxide-cement kiln dust (CaO-CKD) provides an attractive and cost effective treatment option. In this study the efficiency of CaO-CKD at doses of 1.5-20 g/l was tested in batch experiments and found that 10 g of CaO/l caused the greatest degradation of VFA, butyrate and acetate. An upflow anaerobic sludge blanket (UASB) reactor was operated continuously at 35°C for 150 days to investigate the effect of CaO-CKD on sludge granulation and methanogenesis during start-up. The treatment of POME emphasized the influence of varying organic loading rates (OLR). Up to 94.9% of COD was removed when the reactor was fed with the 15.5-65.5 g-CODg/l at an OLR of 4.5-12.5 kg-COD/m(3)d, suggesting the feasibility of using CaO in an UASB process to treat POME. The ratio of volatile solids/total solids (VS/TS) and volatile fatty acids in the anaerobic sludge in the UASB reactor decreased significantly after long-term operation due to the precipitation of calcium carbonate in the granules. Granulation and methanogenesis decreased with an increase in the influent CaO-CKD concentration.

Matched MeSH terms: Oxides/chemistry*
Ab initio calculation of vibrational frequencies and Raman spectra of barium peroxide glass including comparison of tetrahedral BaO4 with GeO4 and SiO4

Rosli AN, Zabidi NA, Kassim HA, Shrivastava KN

Spectrochim Acta A Mol Biomol Spectrosc, 2011 Sep;79(5):1251-5.
PMID: 21571582 DOI: 10.1016/j.saa.2011.04.051

We have calculated the vibrational frequencies of clusters of atoms from the first principles by using the density-functional theory in the local density approximation (LDA). We are also able to calculate the electronic binding energy for all of the clusters of atoms from the optimized structure. We have made clusters of BanOm (n, m=1-6) and have determined the bond lengths, vibrational frequencies as well as intensities in each case. We find that the peroxide cluster BaO2 occurs with the O-O vibrational frequency of 836.3 cm(-1). We also find that a glass network occurs in the material which explains the vibrational frequency of 67 cm(-1). The calculated values agree with those measured from the Raman spectra of barium peroxide and Ba-B-oxide glass. We have calculated the vibrational frequencies of BaO4, GeO4 and SiO4 each in tetrahedral configuration and find that the vibrational frequencies in these systems depend on the inverse square root of the atomic mass.

Matched MeSH terms: Oxides/chemistry*
Transesterification of palm oil to methyl ester on activated carbon supported calcium oxide catalyst

Wan Z, Hameed BH

Bioresour Technol, 2011 Feb;102(3):2659-64.
PMID: 21109428 DOI: 10.1016/j.biortech.2010.10.119

In this study, methyl ester (ME) was produced by transesterification of palm oil (CPO) (cooking grade) using activated carbon supported calcium oxide as a solid base catalyst (CaO/AC). Response surface methodology (RSM) based on central composite design (CCD) was used to optimize the effect of reaction time, molar ratio of methanol to oil, reaction temperature and catalyst amount on the transesterification process. The optimum condition for CPO transesterification to methyl ester was obtained at 5.5 wt.% catalyst amount, 190°C temperature, 15:1 methanol to oil molar ratio and 1 h 21 min reaction time. At the optimum condition, the ME content was 80.98%, which is well within the predicted value of the model. Catalyst regeneration studies indicate that the catalyst performance is sustained after two cycles.

Matched MeSH terms: Oxides/chemistry*
Utilization of waste crab shell (Scylla serrata) as a catalyst in palm olein transesterification

Boey PL, Maniam GP, Hamid SA

J Oleo Sci, 2009;58(10):499-502.
PMID: 19745576

Aquaculture activity has increased the population of crab, hence increasing the generation of related wastes, particularly the shell. In addition, the number of molting process in crabs compounds further the amount of waste shell generated. As such, in the present work, the application of the waste crab shell as a source of CaO in transesterification of palm olein to biodiesel (methyl ester) was investigated. Preliminary XRD results revealed that thermally activated crab shell contains mainly CaO. Parametric study has been investigated and optimal conditions were found to be methanol/oil mass ratio, 0.5:1; catalyst amount, 4 wt. %; and reaction temperature, 338 K. As compared to laboratory CaO, the catalyst from waste crab shell performs well, thus creating another low-cost catalyst source for producing biodiesel as well as adding value to the waste crab shell. Reusability of crab shell CaO has also been studied and the outcome confirmed that the catalyst is capable to be reutilized up to 11 times, without any major deterioration.

Matched MeSH terms: Oxides/chemistry

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