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This research studies the effect of the heating rate at calcination temperature (2°C, 5°C, 10°C, and 20°C/min) on the Ca3Co4O9 phase and crystallite size, as well as the thermal conductivity (κ) and electrical resistivity (ρ) of the material. Co(NO3)2∙6H2O and CaCO3 synthesised by sol–gel combustion technique. The Rietveld refinement technique confirmed the structure and crystal size calculations were performed using the Williamson-Hall (WH) plot. Thermogravimetric-differential thermal analysis (TGA-DTA) showed differences in the exothermic energy produced (553–683 K), which related to the reaction rate and phase transitions affecting the crystal size and thermoelectric (TE) properties as the p-type TE material. The κ and ρ values tend to increase with increasing heating rate temperature, where κ and ρ values range from 1.69 to 1.90 W/mK and 82.73 to 118.57 mΩ cm respectively. [ABSTRACT FROM AUTHOR]

Ni(II) with mixed ligand of terephthalate-pyrazine (NiTP) metal complex can form metalorganic framework (MOF) material that offer many potential applications, such as adsorbent and/or photocatalyst for dye-based wastewater treatment. Production of the NiTP by hydrothermal method in a larger scale may economically unfavorable due to it requires high temperature and long reaction time. Green synthesis of NiTP by hydrothermal method using lower temperature and shorter reaction time was investigated in this study. The synthesis was done in Ni(II):T:P mol ratio of 1:1:4 at 150 ℃ for 10 hours. The NiTP complex was characterized by infrared spectroscopy and powder-XRD. Crystallinity degree, thermal stability, band gap energy, and pore volume of the NiTP complex were compared to that of Ni(II)-terephthalate (NiT) complex, which was also made using the same condition, to study the effect of pyrazine addition on the properties of the NiTP. This study finds that the green microcrystalline NiTP complex was successfully obtained from mild reaction condition in good yield and identical to known MOF compound of [Ni(μ3-ter)(μ2-pyr)]n.(ter = terephthalate; pyr = pyrazine). Although the synthesized NiTP complex has lower crystallinity degree compared to the NiT complex, but it has better thermal stability, lower band gap energy, and bigger pore volume; therefore, it is possible to be further developed as adsorbent and/or photocatalyst for wastewater treatment. [ABSTRACT FROM AUTHOR]

The objective of this paper is to present an overview of the development of gel casting methods on synthesis techniques and the characteristics of gel casting porous ceramics and its applications. The gel casting method is a colloidal ceramic synthesis method that requires a short period for the ceramic body to develop. This review provides the latest developments in the gel casting process of synthesizing porous ceramics. At the beginning of the gel casting method development, the acrylamide (AM) system was the most commonly utilized system. Over time, the use of the AM system began to be minimized because of its toxicity. Researchers began to develop natural polymers as pore templates and natural minerals as raw materials in the gel casting method. In addition to polymers and raw materials, the gel casting process also requires additives such as gelling agents and dispersants. At the end of this review, a mapping of how to select the additives in the gel casting process, for AM systems and non-AM systems for the fabrication of porous ceramics is presented. The characteristic of porous ceramics produced by AM and non-AM systems are almost similar. Porous ceramic applications have been used as bone tissue supports, energy storage, filters, and catalyst support. This review will be a reference for future research related to the process of fabrication of advanced porous ceramics using the environmentally friendly gel casting method. [ABSTRACT FROM AUTHOR]

Previous research showed that rice husk has a high silica content so it becomes an alternative for processing rice waste. The acid leaching method is a technique to isolate silica by adding an acid solution. The research aim is to obtain the optimum silica yield and determine the chemical ash content of rice husks (rice IR-64,). Rice husks were first calcined at two various temperatures and times. The average yields obtained were 19.54% (500°C / 1 hr), 18.42% (500°C / 2 hrs), 25.03% (700°C/1 hr), and 22.4% (700°C/2 hrs). The physical appearance of ash was grains and white (700 °C/1hr), that were rinsed with 1 M HCl solution to remove impurities. Added 1 M NaOH was to form sodium silicate. The last step was to isolate silica using different concentrations of HCl and HNO3 (3 M, 2 M, and 1 M). The highest result was 99.87% of silica under HNO3 1 M solution. An infrared study supports that the isolated product was silica, with the presence of prominent peaks at 1102 cm-1 (stretching Si-O) and 471 cm-1 (bending Si-O). A unique peak at 958 cm-1 for Si-O-Ca present at the isolated silica using HCl 3 M, gives information on inosilicate type structure. X-ray diffraction analysis with QualX application showed that silica had cristobalite and wollastonite peaks, and the value of crystallinity index was about 63.91%. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is an impurity in gaseous fuels such as biogas, therefore this gas removal method is an interesting topic. The physisorption method is considered to be a simple work to be applied on a small scale. This research studies the impact of the addition of liquid triethanolamine on the porous silica on the adsorption of H2S. The silica substrate is synthesized using two-pore templates namely a mixture of polyethylene glycol (PEG)/sodium dodecyl sulfate (SDS) and the other one is pure chitosan. The silica surface was coated with triethanolamine (TEA) using the impregnation method. An H2S gas adsorption study was conducted on the synthesized silica with and without TEA. The adsorption test was carried out by flowing H2S from the reaction between FeS and HCl through the sample. The results of this study show that the TEA layer on the silica surface increases the adsorption towards H2S gas, but it is relatively small compared to similar studies. The best result of combining TEA and silica gel is shown by TEA-sil-PS which was 3.8 x 10-5 mol H2S per gram of adsorbent. [ABSTRACT FROM AUTHOR]

Chitosan-silica hybrid adsorbent has been successfully synthesized by extracting the silica of Timor Island-East Nusa Tenggara (NTT) in order to study its application to Cu2+ adsorption in water samples. This work consists of several steps which include silica extraction from Takari sand of East Nusa Tenggara, preparation of chitosan-silica hybrid, FTIR and SEM characterization, and adsorption of Cu2+. The successful extraction of silica was indicated by the existence of-OH, siloxane (Si-O-Si), Si-O in silanol (Si-OH) peaks at 3433.29 cm-1,468.70 cm-1, and 958.62 cm-1, respectively. The formation of chitosan-silica hybrid adsorbent was denoted by a peak shift of-OH in silica to3404.36 cm-1, N-H stretching vibration at 1544.98 cm-1due to an interaction between O-H in silica with N-H in chitosan, and amine (primary-NH) bending vibration at1639.49 cm-1. The surface morphology of silica changed when it was modified with chitosan from homogeneous granule to a cluster (larger particle sizes). Optimum adsorption conditions toward Cu2+ were achieved at pH 8 and contact time of 50 min, resulting in excellence adsorption efficiency of 99.3%. Adsorption of Cu2+ fitted Langmuir isotherm with the adsorption capacity of 27 mg/g. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the effect of acrylamide (AM) and methylenebicacrylamid (MBAM) ratio on the pore character of gelcasted ceramics. They were synthesized from clay by a method based on in situ polymerization of the ceramic body. The polymer amount was 40 % of the latter. The pore template was formed in the course of polymer degradation. AM and MBAM were used as a monomer and a crosslinker, correspondingly. Their ratio studied referred to 6:1; 12:1; 18:1 and 24:1. The results showed that the highest values of the surface area and the pore volume were obtained in case of 6:1 ratio (1.353 m2/g and 0.004 cc/g, respectively). The pore volume amounted to 0.001 cc/g, 0.001 cc/g and 0.002 cc/g in presence of AM : MBAM of 12:1, 18:1 and 24:1, respectively. The pore radius was found equal to 32.415 Å, 530.15 Å, 1067,622 Å and 29,174 Å at the respective ratios of 6:1; 12:1; 18:1 and 24:1. [ABSTRACT FROM AUTHOR]

The reactions of thianthrene (TA) and selenanthrene (SeA) with AlCl3 were studied in the melt phase and with liquid SO2 as solvent. From neat AlCl3 and TA, the colorless complex [AlCl3(TA)] was isolated as the main product and the dark red salt (TA)3[Al2Cl7]2 as the byproduct. The analogous solvent-free reaction of selenanthrene and AlCl3 takes a different course as colorless [Al(SeA)3][Al2Cl7]3 is formed in quantitative yield. With SO2 as solvent, both TA and SeA give the black radical salts (TA)2[AlCl4]2 and (SeA)2[AlCl4]2, respectively. In the structure of [AlCl3(TA)], thianthrene acts as a monodentate ligand and coordinates with one S atom to the pyramidal AlCl3 unit. The structure of the (TA)32+ ion is a stack of three almost planar TA molecules in parallel arrangement. [Al(SeA)3]3+ represents a tris-chelate complex ion with SeA acting as a bidentate ligand and both Se atoms binding to the octahedrally coordinated Al3+ ion. (SeA)2[AlCl4]2 consists of dimers of SeA+ radical ions, which are bound by weak intermolecular Se ···Se bonds. Tentative reaction equations are given to explain the unexpected oxidation processes that lead to the radical ions. Quantum chemical calculations were performed on the molecular fragments and on the periodical structures. The trimeric (TA)32+ ion is in the singlet state in accordance with the magnetic properties of (TA)3[Al2Cl7]2, which show a weak temperature-independent paramagnetism. The ion is bound by long-range four-center bonds between the outer two radicals. [ABSTRACT FROM AUTHOR]

The reactions of thianthrene (TA) and selenanthrene (SeA) with AlCl3 were studied in the melt phase and with liquid SO2 as solvent. From neat AlCl3 and TA, the colorless complex [AlCl3(TA)] was isolated as the main product and the dark red salt (TA)3[Al2Cl7]2 as the byproduct. The analogous solvent-free reaction of selenanthrene and AlCl3 takes a different course as colorless [Al(SeA)3][Al2Cl7]3 is formed in quantitative yield. With SO2 as solvent, both TA and SeA give the black radical salts (TA)2[AlCl4]2 and (SeA)2[AlCl4]2, respectively. In the structure of [AlCl3(TA)], thianthrene acts as a monodentate ligand and coordinates with one S atom to the pyramidal AlCl3 unit. The structure of the (TA)32+ ion is a stack of three almost planar TA molecules in parallel arrangement. [Al(SeA)3]3+ represents a tris-chelate complex ion with SeA acting as a bidentate ligand and both Se atoms binding to the octahedrally coordinated Al3+ ion. (SeA)2[AlCl4]2 consists of dimers of SeA+ radical ions, which are bound by weak intermolecular Se ···Se bonds. Tentative reaction equations are given to explain the unexpected oxidation processes that lead to the radical ions. Quantum chemical calculations were performed on the molecular fragments and on the periodical structures. The trimeric (TA)32+ ion is in the singlet state in accordance with the magnetic properties of (TA)3[Al2Cl7]2, which show a weak temperature-independent paramagnetism. The ion is bound by long-range four-center bonds between the outer two radicals. [ABSTRACT FROM AUTHOR]

The new molecularly imprinted polymer (MIP) membrane based on cassava starch—Fe3O4—was developed to detect acetaminophen and caffeine simultaneously with the differential pulse voltammetry (DPV) method. Cassava starch was reacted with sodium tripolyphosphate (STPP) as a crosslinking agent, while acetaminophen and caffeine were added as templates. The Fe3O4 nanoparticles in the composite were added to increase the sensor's sensitivity. The experimental results show that the ratio between cassava starch:STPP:acetaminophen/caffeine in the mixture for MIP membranes influences the sensitivity of the sensor obtained. MIP membranes with the best sensitivity is produced at a mixture ratio of 2:2:1. The sensor performance is also affected by the pH of the solution and the type of buffer solution used. The sensor works very well at pH 2 in PB solution. Sensors produced from GCE modified with MIP membrane from cassava starch—Fe3O4 with acetaminophen and caffeine as templates have linear range concentrations, respectively, at 50–2000 µM and 50–900 µM. Sensor sensitivity was 0.5306 A/M against acetaminophen and 0.4314 A/M against caffeine with Limit of Detection (LoD), respectively, 16 and 23 µM. Sensor selectivity and sensitivity are better than those without MIP and can be applied for the determination of the content of acetaminophen in headache medicine, with an accuracy of 96–99% and with Relative Standard Deviation (RSD) 0.9–2.56%. [ABSTRACT FROM AUTHOR]