A geochemistry study has been done in four geothermal manifestations—Ie-Seu’um, Ie-Brôuk, Ie-Jue and the Van-Heutz crater—located in the north zone of Seulawah Agam mountain (Aceh Besar District, Indonesia). The study was performed through water and gas analysis. Water analysis were done for all geothermal manifestations, but gas analysis was only done for the Ie-Jue manifestation that has fumaroles. Cation and anion contents were analyzed by ion chromatography, ICP-OES, alkalimetry titrations, and spectrophotometry, meanwhile isotopes were measured by a Liquid Water Isotope Analyzer. The resulting data were used for fluid and gas geothermometry calculations, and plotted in a FT-CO2 Cross-Plot and a CH4-CO2-H2S triangle diagram to obtain reservoir temperatures. The data were also plotted by a Cl-HCO3-SO4 triangle and Piper diagram to obtain the water type and dominant chemical composition, a Na-K-Mg triangle diagram to obtain fluid equilibria, the isotope ratio in the stable isotope plot to obtain the origin of water, and a N2-He-Ar triangle diagram to establish the origin of fumaroles. The water analysis results showed that (1) Ie-Seu’um has an average reservoir temperature of 241.9 ± 0.3 °C, a chloride water type, a dominant Na-K-Cl chemical composition, a mature water fluid equilibrium, and water of meteoric origin; (2) Ie-Brôuk has an average reservoir temperature of 321.95 ± 13.4 °C, a bicarbonate water type, a dominant Na-Ca-HCO3chemical composition, an immature water fluid equilibrium, and water of meteoric origin; (3) Ie-Jue has an average reservoir temperature of 472.4 ± 91.4 °C, a sulphate water type, a dominant Ca-SO4 chemical composition, an immature water fluid equilibrium and water of meteoric origin; and (4) the Van-Heutz crater has an average reservoir temperature of 439.3 ± 95.3 °C, a sulphate water type, a dominant Ca-SO4 chemical composition, an immature water fluid equilibrium and water of magmatic origin. The results of our gas analysis showed that Ie-Jue has an average reservoir temperature of 258.85 °C, and water of meteoric origin. Based on the reservoir temperatures, the geothermal manifestation of the north zone of Seulawah Agam mountain is considered as a high-temperature geothermal system suitable for power plant development.

In a simple and instant procedure for detecting fish freshness, a hydrogel and hydrophilic pectin matrix membrane was used successfully as an optical pH sensor by immobilizing the chromoionophore ETH 5294 (CI), which is very selective and sensitive for the membrane. The Pe/CI optical pH sensor exhibited excellent linearity between pH 5 and pH 9, with a sensor response time of 5 min and reproducibility of 1.49% relative standard deviation (RSD). The sensor showed response stability for 15 days and a response reduction of 8.6%. The sensor’s capability was demonstrated by the detection of fish freshness for 17 days at 4 °C.

Synthesis of silver nanoparticles–chitosan composite particles sphere (AgNPs-chi-spheres) has been completed and its characterization was fulfilled by UV–vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and zetasizer nano. UV–vis spectroscopy characterization showed that AgNPs-chi-spheres gave optimum absorption at a wavelength of 410 nm. The XRD spectra showed that the structure of AgNPs-chi-spheres were crystalline and spherical. Characterization by SEM showed that AgNPs-chi-spheres, with the addition of 20% of NaOH, resulted in the lowest average particle sizes of 46.91 nm. EDX analysis also showed that AgNPs-chi-spheres, with the addition of a 20% NaOH concentration, produced particles with regular spheres, a smooth and relatively nonporous structure. The analysis using zetasizer nano showed that the zeta potential value and the polydispersity index value of the AgNPs-chi-sphere tended to increase with an increased NaOH concentration. The results of the microbial activity screening showed that the AgNP-chi-Spheres with highest concentration of NaOH, produced the highest inhibition zone diameters against S. aureus, E. coli, and C. albicans, with inhibition zone diameters of 19.5, 18.56, and 12.25 nm, respectively.

In this work, calcium oxide (CaO) extracted from eggshell impregnated with magnetite (Fe 3 O 4 ) is prepared successfully and it had been applied on transesterification of palm oil off-grade. Prior experiment, the eggshells material are powdered and calcined at 900 • C then impregnated with Fe 3 O 4 and recalcined. The obtained Fe 3 O 4 /CaO catalyst is characterized using X-ray diffraction and Braunaeur-Emmet-Teller (BET) surface area. The influence of various parameters including recalcined time and temperature are investigated. The prepared catalyst is tested for transesterification of palm oil off-grade to produce biodiesel in which the optimal conditions of a methanol/palm oil off-grade molar ratio of 10:1, the catalyst weight of 6%, the reaction temperature of 70 • C, and the reaction time of 2 h. The transesterification product was analyzed using GC-MS, which showed the biodiesel yield of 90% at the recalcined temperature of 600 • C and reaction time of 2 h. It has been noted that the catalyst activity is achieved when the moderate recalcination temperature is applied and the disordered structure of the catalyst is maintained. This study also confirms that CaO impregnated with Fe 3 O 4 could be a solid catalyst for the biodiesel synthesis through transesterification reaction of palm oil off-grade.Catalysts 2020, 10, 164 2 of 13 this issue, several countries have successfully implemented some renewables from bioenergy, including biogas, biodiesel, and bioethanol [2][3][4][5]. On the other sides, some countries have also successfully generated the electrical power from renewable energy resources, such as geothermal, waves, hydro, wind, and solar energy [6][7][8][9][10]. However, there are some weak points resulted while the renewable energy is used, such as it is unstable, only available for certain periods, and therefore, its required the energy storage devices such as battery. However, the energy storage capacity of batteries is very limited, and for this reason some scientists are attempting to discover another type of energy storage materials that can store significant amount of energy [11][12][13].Calcium is one of the most abundant metals on earth. It can be mostly found as an ion in seawater [14], as well as geothermal hot springs [15][16][17][18]. It can be also found as an oxide in limestone and fossilized remnant sites [14]. However, in order to obtain the calcium from these resources is required the natural resource exploitation that is often given negative impact to environment. Considering the environmental safety, an alternative way has been used to produce calcium source, namely it produce from some renewable resources which are available abundantly in nature, such as egg shell material wastes, because the egg shell well known as a natural material contained lots of calcium oxide [19]. As fact, the eggshell waste has been an abundant wastes in environment either come from egg consumption or the food industries. The waste materials are interesting to use as eco-friendly material to produce CaO ...

Research rarely reaches the discussion of loan sharks. This study describes how intentions are influenced by service, word-of-mouth, and subjective norms, with knowledge of usury acting as a moderating variable. This quantitative study involved 150 respondents. The data collected was analyzed by using structural Equation Modeling (SEM) with SmartPLS 3 Software. According to this study, service significantly affected intention to take a loan from loan sharks but had no influence on word-of-mouth. Though it has no influence on intention, the subjective norm has a significant influence on word-of-mouth. The service on the intention is mediated by word of mouth, which has an influence on the intention. However, word-of-mouth does not act as a mediating variable between subjective norms and intentions. The intention to use the services of loan sharks is significantly moderated by knowledge about usury, which also significantly moderates word-of-mouth and subjective norms. It did not, however, moderate the influence of service on intentions. As a result, it is recommended that the government create Islamic financial institutions not only for the middle class and upper class but also for the lower economic class, which is vulnerable to loan sharks.