Judul: Sintesis Nanokristal Magnetit Menggunakan Urea sebagai Penjerap Cr(VI)
Abstrak: The study was to synthesize and characterize magnetite nanocrystal. Magnetite powder was synthesized using hydrothermal method from FeSO4 as precursor and sodium hydroxide and urea as the base sources. Characterization of the obtained powder was carried out using X-ray diffraction, scanning electron microscope, and energy dispersive X-ray analyzer. The crystallite size of magnetite by X-ray diffraction was obtained from 18,23 to 67,34 nm. The scanning electron microscope observations showed that magnetite particles underwent agglomeration. Magnetite powder was used as Cr(VI) adsorbent. The results showed that adsorption capacity for urea-based magnetite at pH 1-5 in 2 hours were 1.92; 1.91; 1.59; 1.20; and 1.21 mg/g, respectively. Adsorption capacity for sodium hydroxide-based magnetite (pH 1-5, 2 hours) were 1.74; 1.83; 0.64; 0.69; and 0.77 mg/g. The results indicated that urea-based magnetite is able to increase adsorption capacity.
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Judul: Keragaan Nitrogen-Amonium dalam Magnetit Sintetik (Fe3O4)
Abstrak: One form of nitrogen that can be used directly by plant is ammonium. Magnetite can be used as ammonium carrier. Magnetite has been synthesized by hydrothermal treatment of FeCl3, urea, and citrate. The synthesis time was varied for 3, 4, 6, and 12 hours. The synthesis products were characterized by X-ray diffraction and were analyzed for its ammonium contain. The aim of this study was to obtain magnetite with high ammonium content in short synthesis time. Based on X-ray diffraction pattern, cristallinity increased as the synthesis time increased. The highest ammonium content was 0,92% in magnetite synthesized in 3 hours. Release of ammonium in water for magnetite synthesized in 3 hours showed that maximum release time was 12 hours. Increasing synthesis time would decrease solubility of the magnetite in water. The results showed that the best magnetite for ammonium carrier was magnetite synthesized in 3 hours.
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Judul: Tingkah Laku Lumba-Lumba Hidung Botol Indo-Pasifik (Tursiops aduncus) di Umah Lumba, Teluk Banyuwedang, Bali
Abstrak: Lumba-lumba Hidung Botol Indo-Pasifik (Tursiops aduncus) merupakan mamalia laut yang umum ditemukan di perairan Indonesia dan telah dikategorikan sebagai hewan hampir terancam punah oleh IUCN, salah satunya akibat tingginya tingkat eksploitasi untuk atraksi mamalia laut. Penelitian ini bertujuan mendeskripsikan tingkah laku Tursiops aduncus di Umah Lumba, Teluk Banyuwedang, Bali. Observasi visual dilakukan pada 3 individu Tursiops aduncus, yaitu Rambo, Rocky, dan Jhony yang telah direhabilitasi sejak September 2019. Ketiga individu dapat diidentifikasi melalui ciri fisik di bagian kepala dan sirip dorsal. Beberapa lumba-lumba telah mengembangkan sifat liar dengan adanya 9 jenis tingkah laku yang mendukung kehidupan di alam, yaitu bernapas, istirahat, jelajah, reproduksi, sosial, berburu, spy hopping, tail clapping, dan sneezing. Sebanyak 3 jenis tingkah laku dikategorikan sebagai tingkah laku dominan karena ditemukan pada setiap sesi waktu penelitian, yaitu bernapas, istirahat, dan jelajah. Program rehabilitasi lumba-lumba sangat penting dilakukan untuk aklimatitasi, adaptasi, dan melatih lumba-lumba bertahan hidup sebelum dilepasliarkan.
Keyword: behavior, dolphin, rehabilitation, Tursiops aduncus, Umah Lumba