Faktor Penyebab Nihilnya Gambar Cadas Prasejarah Di Kawasan Gunung Sewu, Jawa

In late Pleistocene to Early Holocene, the form of cultures were cave dwellings accompanied by the development of Mesolithic technology, food gathering, as well as spiritual needs in the form of burials and works of art. Gunung Sewu area is known as "Prehistoric Metropolis", with plenty of caves with high potential archaeological remains. The culture of cave dwelling is generally characterized not only by lithic, bone, and shell tools, but also the emergence of burial practices and “art” in the form of rock arts on cave walls. So far, archaeological data in the cave of the Gunung Sewu area showed that rock arts are absence. This paper tries to uncover the factors behind this absence of rock arts in Gunung Sewu. Surface survey method were being employed in this study. Various prehistoric cave sites which have been studied by previous research and proven to be containing archaeological (human and cultural) potential were re-visited. The ecosystems of these sites were also surveyed, including the nearby river systems that might provide raw material for lithics Our observations revealed that several caves have an ideal walls as a media for rock arts. Our results argued that hence there are a number of possible absent rock drawings. First, natural factors (disasters, and exfoliation of the outer layer of karst), second is the geographical position which is far from the east coast of the Sunda Shelf, the third is cultural motivational factors which did not create rock art

Preparation of alkali-activated fly ash-based geopolymer and their application in the adsorption of copper (II) and zinc (II) ions

Alkali activation of fly ash can a promising alternative of the system to improve adsorption capability of fly ash. In finding the best chemical composition of the activator solution, geopolymer has been synthesized using molar ratios of Na2O/SiO2 0.16, 0.3, and 0.5 (Gr1, Gr3, Gr5). The results indicated that the geopolymer synthesized with a ratio molar of Na2O/SiO2 0.3 (Gr3) improved the adsorption properties of fly ash substantially. Gr3 was characterized by BET, XRD, and FTIR. The batch experiment was conducted at the different duration and initial concentrations. The equilibrium sorption data were fitted for the Langmuir and Freundlich equations. The maximum sorption capacities calculated from Langmuir isotherm was 54 mg g-1 and 47 mg g-1 for Cu (II) and Zn (II) respectively. The kinetic data reveal that the pseudo-second order model was appropriate for a description of the kinetic performance

Nickel Supported on MIL-96(Al) as an Efficient Catalyst for Biodiesel and Green Diesel Production from Crude Palm Oil

In this study, a new class of heterogeneous catalyst in the form of metal-organic frameworks (MOFs), namely Material of Institute Lavoisier-96(Al), which is called MIL-96(Al), was employed for the production of biodiesel and green diesel. The synthesis of MIL-96(Al) was conducted via a hydrothermal method at 210 °C for 4 hours with dimethylformamide (DMF) as an assisting agent. The Ni was loaded into MIL-96(Al) via incipient wetness impregnation method with variations 3, 5, and 10 wt.% to form Ni/MIL-96(Al). Based on X-Ray diffraction (XRD) analysis, the obtained material has good crystallinity with characteristic peaks observed at 2? = 5.8°; 7.8°, and 9.1°. Fourier Transform Infrared (FTIR) analysis demonstrated an essential shift from 1715 cm-1 to 1666 cm-1, indicating the coordination of the carboxylate group with Al3+ metal ions. Moreover, MIL-96(Al) is stable up to 390 °C according to the thermogravimetric analysis (TGA). Based on structural and morphological analysis (using XRD, FTIR, and Scanning Electron Microscope (SEM)), the loading of Ni into MIL-96(Al) does not change the basic structure of MIL-96(Al). However, the pore diameter of MIL-96(Al) decreased from 5.7 nm to 1.4 nm after the Ni was embedded in the structure. The largest surface area was obtained from 10% Ni/MIL-96(Al) (up to 595.5 m2/g). The catalytic test exhibits that 3% Ni/MIL-96(Al) could attain an optimum yield of up to 85.24% of biodiesel, while in the case of hydrodeoxygenation (HDO) reaction, the optimum catalyst shown by 10% Ni/MIL-96(Al) with conversion and selectivity of C16 up to 90.70% and 55.22%, respectively

Preparation of alkali-activated fly ash-based geopolymer and their application in the adsorption of copper (II) and zinc (II) ions

Alkali activation of fly ash can a promising alternative of the system to improve adsorption capability of fly ash. In finding the best chemical composition of the activator solution, geopolymer has been synthesized using molar ratios of Na2O/SiO2 0.16, 0.3, and 0.5 (Gr1, Gr3, Gr5). The results indicated that the geopolymer synthesized with a ratio molar of Na2O/SiO2 0.3 (Gr3) improved the adsorption properties of fly ash substantially. Gr3 was characterized by BET, XRD, and FTIR. The batch experiment was conducted at the different duration and initial concentrations. The equilibrium sorption data were fitted for the Langmuir and Freundlich equations. The maximum sorption capacities calculated from Langmuir isotherm was 54 mg g-1 and 47 mg g-1 for Cu (II) and Zn (II) respectively. The kinetic data reveal that the pseudo-second order model was appropriate for a description of the kinetic performance

Breathable Iron-Based MIL-88 Framework as Dye Adsorbent in Aqueous Solution

Metal–organic frameworks (MOFs) have been observed to exclusively eliminate dyes confined within their respective pores. In this investigation, the synthesis of a breathable MOF structure, MIL-88B(Fe), was pursued with the objective of circumventing restrictions on pore size to enhance its adsorption capabilities. The synthesis of MIL-88B(Fe) was carried out via the assisted solvothermal method at 373 K using inexpensive yet environmentally benign FeCl3·6H2O, 1,4-benzenedicarboxylic acid, and DMF as a metal precursor, linker, and solvent, respectively. Furthermore, the MOF was subjected to extensive analytical characterisation using XRD, FT-IR spectroscopy, N2 gas sorption, TGA, and SEM. The experimental data showed that the utilisation of MIL-88B(Fe) with a dose level of 5 mg for 180 min at a pH of 9 led to the highest levels of adsorption for both dyes, with 162.82 mg g−1 for methylene blue (MB) and 144.65 mg g−1 for rhodamine B (RhB), as a result of the contrast in the molecular size between each dye. The Langmuir and Freundlich models demonstrated a correlation with isotherms, while the thermodynamic analysis demonstrated that MIL-88B(Fe) exhibits distinct endothermic and breathable properties. The efficacy of MIL-88B(Fe) adsorbent for MB and RhB in aqueous solutions indicated exceptional performance, stability, and noteworthy reusability performance

Fabrication of Graphene Oxide-Decorated Mesoporous NiFe₂O₄ as an Electrocatalyst in the Hydrogen Gas Evolution Reaction

An electrocatalyst for the hydrogen evolution reaction has been successfully synthesized from graphene oxide (GO) decorated with the mesoporous NiFe2O4. A high catalytic activity performance was reached by using the GCE surface as a conductor, and the synthesized composite contained GO/NiFe2O4. Based on the results, the as-prepared electrocatalyst exhibited a high overpotential for the HER reaction of 36 mV vs. RHE at a 10 mA current density, with an electrochemical active surface area (ECSA) of 3.18 × 10−4 cm2. Additionally, the electrocatalyst demonstrated a considerably good performance after the 9000 s stability test. It is believed that such an enhancement in electrocatalytic activity was due to the synergistic effect between the unique porosity feature of the mesoporous NiFe2O4, which may provide a more active surface, and the high conductivity of the GO

Enhancement of the Catalytic Effect on the Electrochemical Conversion of CO₂ to Formic Acid Using MXene (Ti₃C₂T_x)-Modified Boron-Doped Diamond Electrode

The rising concentration of carbon dioxide (CO2) as one of the greenhouse gases in the atmosphere is a major source of worry. Electrochemical reduction of CO2 is one of many ways to convert CO2 gas into usable compounds. An electrochemical technique was applied in this study to reduce CO2 using a boron-doped diamond (BDD) working electrode modified with MXene (Ti3C2Tx) material to improve electrode performance. MXene concentrations of 0.5 mg/mL (MXene-BDD 0.5), 1.0 mg/mL (MXene-BDD 1.0), and 2.0 mg/mL (MXene-BDD 2.0) were drop-casted onto the BDD surface. MXene was effectively deposited on top of the BDD surface, with Ti weight loads of 0.12%, 4.06%, and 7.14% on MXene-BDD 0.5, MXene-BDD 1.0, and MXene-BDD 2.0, respectively. The modified working electrode was employed for CO2 electroreduction with optimal CO2 gas aeration. The existence of the MXene substance in BDD reduced the electroreduction overpotential of CO2. For the final result, we found that the MXene-BDD 2.0 electrode effectively generated the most formic acid product with a maximum reduction potential as low as −1.3 V (vs. Ag/AgCl)