Hasil Pencarian  ::  Simpan CSV :: Kembali

"This book focuses on a group of new materials labeled "graphene oxides." It provides a comprehensive overview of graphene oxide-based nanomaterials in terms of their synthesis, structures, properties, and extensive applications in catalysis, separation, filtration, energy storage, and conversion. The book also covers emerging research on graphite oxides and the impact of the research on fundamental and applied sciences. "

"Saat ini tantalum dan niobium yang merupakan salah satu dari empat belas unsur kritis di dunia telah mengalami defisit pasokan sejak tahun 2015. Oleh karena itu perlu dilakukan usaha untuk mendapatkan sumber lain dalam rangka memenuhi kebutuhan tantalum dan niobium di berbagai segmen industri yang semakin meningkat. Salah satu sumber alternatif untuk memenuhi kebutuhan tantalum dan niobium tersebut adalah terak timah Bangka (TTB) yang mengandung Ta2O5 0,33 % berat dan Nb2O5 0,64 % berat. Tinjauan pada terak timah Bangka yang telah dilakukan oleh peneliti sebelumnya menyatakan bahwa perolehan nilai rasio pengayaan yang rendah disebabkan kurang efektifnya proses pelindian, baik melalui rute asam-basa maupun basa-asam. Oleh karena itu, kebaruan penelitian ini difokuskan pada penggunaan proses roastingquenching (pemanggangan diikuti dengan pencelupan secara cepat ke dalam air) sebagai pre-treatment proses pelindian dengan lima rute berbeda. Dengan proses roasting-quenching tersebut diharapkan akan terjadi peretakan panas (thermal cracking), reduksi ukuran partikel yang akhirnya memperluas area pembasahan. Dengan lebih luasnya area pembasahan akan memudahkan terjadinya reaksi antara oksida berharga maupun oksida lain dengan larutan pelindi dan pada akhirnya diharapkan akan meningkatkan rasio pengayaan tantalum oksida dan niobium oksida dalam TTB tersebut. TTB yang telah mengalami pemanggangan pada suhu 900⁰C diikuti dengan pencelupan secara cepat ke dalam air dan pengayakan, hasil prosesnya disingkat TTB-TPP.Pada studi ini TTB-PPP dilakukan pelindian dengan 5 rute variasi pelarut dan variasi konsentrasi pelarut. Adapun 5 rute variasi pelarut adalah: (i) HF; (ii) HCl; dilanjutkan ke dalam NaOH; (iii) NaOH dilanjutkan ke dalam HClO4; (iv) NaOH dilanjutkan ke dalam H3PO4 dan (v) NaOH dilanjutkan ke dalam HClO4 terakhir H2SO4. Hasil karakterisasi menggunakan X-Ray Fluorescence (XRF), Scanning Electron Microscope-Energy Dispersive X-ray Analysis (SEM-EDAX), Atomic Absorption Spectroscopy (AAS) dan Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) yang dilakukan terhadap TTB, TTB-PPP, residu dan filtrate hasil pelindian ditemukan bahwa TTB-PPP yang dilakukan pelindian dengan larutan NaOH 8 M (2 jam), dilanjutkan pelindian dengan larutan HClO4 0,8 M (2 jam), dan terakhir dilakukan pelindian dengan larutan H2SO4 0,8 M (2 jam), menghasilkan rasio pengayaan paling optimum yaitu 4,09 untuk tantalum oksida dan 3,34 untuk niobium oksida. Sedangkan pelindian TTB-PPP dengan NaOH 8 M (2 jam) dilanjutkan dengan H3PO4 1,5 M (2 jam) menghasilkan rasio pengayaan tantalum oksida 3,7 dan niobium oksida 3,02.

---

Currently tantalum and niobium which are one of the fourteen critical elements in the world has experienced supply deficits since 2015. Therefore, efforts are needed to obtain alternative sources in order to meet the supplies of tantalum and niobium in various industry segments that are increased. One alternative source to meet the needs of tantalum and niobium is Bangka tin slag (BTS) containing Ta2O5 0.33 % wt and Nb2O5 0.64 % wt. A review of the Bangka tin slag that has been performed by previous researchers stated that low enrichment ratio values are due to ineffective leaching processes, both acid-base and acid-base routes. Therefore, the novelty of this research is focused on the use of roasting-quenching process (roasting followed by rapid quenching into water) as pre-treatment of leaching process with five different routes. With the roastingquenching process it is expected to provide thermal cracking, reduction of particle size which eventually expanded the wetting area. With a wider area of the wetting will facilitate the reaction between the precious oxide and other oxides with the leachate solution and ultimately it is expected to increase the ratio of enrichment of tantalum oxide and niobium oxide in tin slag Bangka. In the 900⁰C roasted BTS followed by a rapid quenching into the water and sieving, the result of the process is abbreviated as BTS-RQS.In this study, BTS-RQS leached with 5 routes of solvent variation and variation of solvent concentration. The 5 routes of solvent variation are: (i) HF; (ii) HCl is continued into NaOH; (iii) NaOH is continued into HClO4; (iv) NaOH is continued into H3PO4 and (v) NaOH is continued into HClO4 and the final into H2SO4. The results of characterization using X-Ray Fluorescence (XRF), Scanning Electron Microscope-Energy Dispersive X-ray Analysis (SEM-EDAX), Atomic Absorption Spectroscopy (AAS) and Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) performed on BTS, BTS-RQS, leaching residues and leaching filtrates found that BTS-RQS leached by 8 M NaOH solution (2 h), followed by leaching with HClO4 0.8 M (2 h), and lastly leached with a solution of H2SO4 0.8 M (2 h), yielding the most optimum enrichment ratio of 4.09 for Ta2O5 and 3.34 for Nb2O5. While BTS-RQS leaching with 8 M NaOH (2 h) followed by 1.5 M H3PO4 (2 h) resulted in an enrichment ratio of 3.7 for Ta2O5 and 3.02 for Nb2O5."

"Grafena merupakan material komposit yang memiliki karakteristik mekanik, optik, dan konduktivitas yang baik. Dibutuhkan alternatif untuk menurunkan cost dalam proses fabrikasinya, salah satu upayanya adalah mengganti bahan baku menjadi limbah biomassa, digunakan limbah kulit singkong. Metode yang digunakan dalam pembutan grafena adalah mereduksi grafena oksida. Grafena oksida dibuat menggunakan metode Hummers termodifikasi. Metode reduksi kimia adalah metode yang umum digunakan, tetapi memiliki residu yang berbahaya bagi lingkungan. Oleh karena itu, digunakan metode  alternatif yaitu reduksi laser. Proses reduksi dilakukan dalam 4 variasi waktu, yaitu 1, 2, 3, dan 4 jam. Dilakukan beberapa pengujian, diantaranya SEM, FTIR, UV-Vis, dan XRD. Hasil UV-Vis dari proses reduksi grafena oksida didapatkan puncak pada 237 nm untuk 1 jam, 245 untuk 2 jam, dan optimum 3 jam pada 261 nm menunjukkan adanya transisi orbital C=C. Setelah 3 jam, puncak menghilang mengindikasikan terbentuk cacat. Hasil FTIR menunjukkan hilangnya puncak gugus oksigen dan hidroksil. Pengamatan SEM menunjukkan morfologi lembaran tipis dan menggulung serta hasil XRD yang mengalami pergeseran puncak ke daerah 25,7°.

---

Graphene is a composite material that has good mechanical, optical and conductivity characteristics. Alternative is needed to reduce costs in the fabrication process, one of the efforts is to replace the raw material to biomass waste  used cassava peel. The method used in making graphene is by reducing graphene oxide. Graphene oxide synthesized using a modified Hummers method. The chemical reduction method is the most commonly used method, but it has residues that are harmful to the environment. Therefore, an alternative method is used, namely laser reduction. Laser reduction used various reduction time range from 1, 2, 3, and 4 hours. Several characterization techniques were utilized, including SEM, FTIR, UV-Vis, and XRD. The UV-Vis results from the process reduction of graphene oxide showed peaks at 237 nm for 1 hour, 245 for 2 hours, and an optimum for 3 hours at 261 nm indicating a C=C orbital transition. After 3 hours, the peaks disappeared indicating defect formed. FTIR results also show the loss of the hydroxyl group peaks, indicating a successful reduction process. SEM observations showed the morphology of thin and rolled sheets. Finally, XRD results or rGO displayed a peak shift back to region 25,7°."

"Pada studi ini, tiga persentase massa dari perak ditambahkan ke nanokomposit oksidanikel dan oksida cerium dengan tiga rasio molar berbeda dari kedua oksida.Nanokomposit telah disintesis menggunakan metode ultrasonic-assisted. Lima teknikkarakterisasi digunakan untuk mengevaluasi bahan, X-ray diffraction (XRD), X-rayfluorescence (XRF), UV-Vis diffuse reflectance, Raman Spectroscopy, danAdsorpsi/Desorpsi Nitrogen. Dua sumber radiasi, cahaya tampak UV digunakan untukmendegradasi metilen biru sebagai objek polutan untuk aktivitas fotokatalitik. Katalisnanokomposit dengan persentase massa Ag sebanyak 20 wt.% menunjukkan aktivitasfotokatalitik tertinggi. Dalam proses degradasi metilen biru dengan katalis nanokompositelektron scavenger merupakan spesies aktif utama pada proses degradasi

---

In this study, three different weight percentages of silver were added to the nickel oxide

and cerium oxide nanocomposites with three different molar ratios of the two oxides.

These nanocomposites were synthesized using ultrasonic-assisted techniques. Five

characterization techniques were carried out to evaluate the materials, X-ray diffraction

(XRD), X-ray fluorescence (XRF), UV-Vis diffuse reflectance, Raman Spectroscopy,

and Nitrogen Adsorption/Desorption. Two radiation sources, visible and ultraviolet, were

used to degrade methylene blue as a pollutant object for photocatalytic activities. The

nanocomposite catalyst with twenty weight percentages of silver showed the highest

photocatalytic activity. In the degradation process of methylene blue with these

nanocomposite catalyst that electrons becomes the main active species in the process."

"ABSTRAKBased on the content of the galangal's essential oil which can be used as antimicroorganism, analgesic, and antiseptic characterized with inhibiting and destructing microorganism life process, it is predicted that there is a possibility of essential oil can be used for anti-inflammatory agent. Nitric-oxide (NO) is an unstable gas produced by cell such as macrophage and has the function as antimicroorganism. The aim of this study was to investigate whether essential oil of galangal components has an effect to the macrophage NO production, which stimulated by LPS E. coli.The both curative and preventive analysis using ANOVA showed that the NO productions differences were significant (p< 0,01). This study showed that the NO levels produced by murine macrophages induced by LPS E. coli were suppressed by essential oil in a dose dependent fashion, suggesting anti-inflammatory activities. Curatively, increased doses of the essential oil resulted in increased its anti-inflammatory functions. Five micro liter of the essential oil was preventively the most concentration as anti inflammation."