Judul: Sintesis Partikel Nanobesi dengan Bioreduktor Polifenol dari Ekstrak Kulit Delima Merah
Abstrak: Partikel nano besi (nZVI) digunakan dalam proses remediasi lingkungan dan pengolahan air baku. Reduktor NaBH4 yang digunakan dalam sintesis nano besi menghasilkan material yang mudah teroksidasi dan beraglomerasi. Penggunaan polifenol sebagai bioreduktor menghasilkan material yang lebih stabil. Penelitian ini bertujuan menyintesis nZVI dengan reduktor NaBH4 (C-nZVI), polifenol dari ampas teh dan kulit delima (G-nZVI), membandingkan kualitas pada masing-masing nZVI, serta menentukan efektivitas G-nZVI kulit delima mendegradasi bahan organik terlarut. Sintesis material nano besi menggunakan metode reduksi garam FeCl3 dalam pelarut air. Material C-nZVI yang dihasilkan berupa serbuk hitam sedangkan G-nZVI berupa serpihan hitam. Nilai band gap energi ketiga material memprediksi ukuran yang nano. Ketiga material memiliki semua gugus sebagai kesatuan utuh nZVI. Difraktogram difraksi sinar-X pada ketiga material belum memperlihatkan fase kristal secara jelas. Distribusi dan rerata ukuran partikel G-nZVI kulit delima lebih baik daripada G-nZVI ampas teh. Nilai potensial zeta membuktikan kedua material G-nZVI bersifat stabil dalam pelarut air. Degradasi optimum bahan organik terlarut, yakni 98% oleh G-nZVI kulit delima dicapai setelah dua jam inkubasi., Nano zero valent iron (nZVI) has been used in environment remediating and raw water processing. NaBH4 reductor, used in iron nanoparticle synthesis, produced easily oxidised and agglomerate material. Using polyphenol as a bioreductor produced a more stabilised material. This study aims to synthesise nZVI using NaBH4 (C-nZVI), polyphenol from spend tea and pomegranate peel (G-nZVI) reductors, compare the quality of each material, and determine the effectiveness of dissolved organic matter reduction by pomegranate peel G-nZVI. The iron nanoparticle was synthesised by the method of FeCl3 salt reduction in a water solvent. C-nZVI material was produced as a black powder while G-nZVI materials were black flakes. The band gap energy values of those three materials predict that materials had reached the nano size. All three materials had intact nZVI unitary groups. X-ray diffractogram did not clearly show the core phase crystals. Distribution and mean of material size of the pomegranate peel G-nZVI was better than spend tea G-nZVI. Both zeta potential G-nZVI attest that the materials were stable in the water medium. Optimum dissolved organic matter degradation, namely 98%, by G-nZVI pomegranate peel was reached after two hours of incubation.
Keyword: bahan organik terlarut, kulit delima, partikel nano besi, polifenol

Judul: Green Synthesis Nanopartikel Perak Menggunakan Limbah Jeruk Purut (Citrus hystrix dc) dengan Variasi Konsentrasi AgNO3
Abstrak: Jeruk purut (Citrus hystrix) merupakan tumbuhan perdu yang kaya manfaat. Kandungan dalam kulit jeruk purut berpotensi dijadikan bahan bioreduktor dalam sintesis nanopartikel. Nanopartikel dengan sifat fisis dan kimiawinya yang unik diharapkan mampu meningkatkan nilai jual serta efektivitas pemanfaatannya. Nanopartikel perak sebagai salah satu jenis nanopartikel logam secara alami memiliki kemampuan antibakteri yang baik serta proses sintesisnya sudah banyak dilakukan. Pada penelitian ini, kulit jeruk purut dipilih sebagai bioreduktor dengan meninjau kondisi optimal pengaruh variasi konsentrasi AgNO3 dan waktu penyimpanan terhadap green synthesis nanopartikel perak. Rancangan percobaan dibuat menggunakan Response Surface Methodology dengan bentuk Central Composite Design. Ukuran partikel yang dihasilkan berkisar pada 86-236 nm yang masih dalam ukuran toleransi nanopartikel. Nilai absorbansi maksimum 0,241-0,506 yang tercapai pada panjang gelombang 268-279 nm. Hasil penelitian ini menunjukkan bahwa nanopartikel perak berdiameter kurang dari 100 nm tercapai pada variasi konsentrasi 1 mM dengan waktu simpan 1 dan 29 jam., Kaffir lime (Citrus hystrix) is a herbaceous plant that is rich in benefits. The content in kaffir lime peel has the potential to be used as a bioreductant in the synthesis of nanoparticles. Nanoparticles with unique physical and chemical properties are expected to increase the selling value and effectiveness of their utilization. Silver nanoparticles as a type of metal nanoparticles naturally have good antibacterial abilities and many synthesis processes have been carried out. In this study, kaffir lime peel was chosen as a bioreductant by reviewing the optimal conditions for the effect of variations in AgNO3 concentration and storage time on the green synthesis of silver nanoparticles. The experimental design was made using the Response Surface Methodology in the form of a Central Composite Design. The resulting particle size ranges from 86-236 nm which is still within the tolerance of nanoparticles. The maximum absorbance value of 0.241-0.506 is achieved at a wavelength of 267-279 nm. The results of this study showed that silver nanoparticles with a diameter of less than 100 nm were achieved at a concentration variation of 1 mM with a shelf life of 1 and 29 hours.
Keyword: AgNO3, Kulit jeruk purut, Nanopartikel, RSM, Sintesis hijau

Judul: Characteristic of Overshooting Top (OT) Based on  Himawari  8  Satellite  as  a  Convective  Cloud  Feature  that  Generates  Extreme Weather in the Java Island Region
Abstrak: Overshooting Top (OT) is a feature at the top of a convective cloud that is associated with extreme weather. Research on OT in tropical Indonesia is still very limited. The existence of geostationary satellites with wide area coverage and fast frequency observations is useful for observing the fast dynamics of the OT life cycle. Therefore, this study intends to analyze the relationship between OT and extreme weather, updraft and thermodynamic conditions of OT when extreme weather occurs, the best objective method for detecting OT in the day time and night time, and the spatiotemporal distribution of OT in the tropical region of Java Island during the 2018-2021 period. Based on visual analysis using visible channel and Himawari 8 sandwich products, 87% of extreme weather events in Java were accompanied by the appearance of OT. It indicates that the presence of the OT pattern is a convection cloud pattern or feature that is closely related to extreme weather events for the Java Island region. The existence of a time lag between the appearance of OT and extreme weather events on Java Island indicates that the OT of convection cloud can be used as a precursor or nowcasting for the appearance of extreme weather. Most of the convective cloud OT features during extreme weather events on Java Island have altitude that were only able to exceed the altitude of the equilibrium level and few were able to exceed the tropopause level of 9 km – 16 km. The difference in atmospheric conditions during extreme weather events on Java Island, which is in the tropics and subtropics, is a strong and unstable convective energy condition characterized by a larger CAPE, as well as unstable KI, LI, SI and TTI values. It is offset by kinematic factors in the form of a weak vertical wind shear (bulk wind shear 0-6 km) and a higher freezing point height. The difference between extreme weather events in the Java Island region and other tropical regions compared to subtropical regions is the strong updraft speed of convection clouds. The IRW Texture COMB algorithm based on the IRW-Texture Gradient modification and the COMB algorithm shows a significant increase in quality for detecting OT and non-OT pixels in Java. Rainy days with rainfall > 50 mm/day are very common in areas with an altitude of > 500 m. On the other hand, the level of convection activity which is indicated by the presence of OT and lightning is significantly reduced in this area. OT of convective clouds appear more frequently during the DJF season and less frequently during the JJA season. OT often appears during the day time and rarely at night time. Most OTs appear in the central part, away from the south and north coasts of Java Island during the day, while OTs that appear near the south and north coasts of Java Island can appear in the morning or afternoon.
Keyword: convective clouds, extreme weather, Overshooting Tops, Himawari 8 Satellite