Hasil Pencarian  ::  Simpan CSV :: Kembali

Abstrak :
This paper presents an investigation on the method for synthesizing hematite nanoparticle using ultrasonic sonochemistry. The effect of various bases with different basicity strengths, i.e. NaOH, NH4OH, and butylamine, as well as sintering treatment on the purity and crystallinity of hematite nanoparticles was studied. In this work, the as-synthesized hematite nanoparticles were characterized using FTIR, XRD, and HR-TEM analyses. The results showed that the formation of hematite crystal can undergo two possible reaction pathways depending on the basicity of the solution. When strong bases like NaOH and butylamine were used, iron(III) ion could react with water to form iron complexes, which further grow into rod-like magnetite nanocrystals as the major product. However, direct reaction of iron(III) ion with hydroxide ion to form hematite was observed when a weak base like NH4OH was used. Furthermore, it was also found that most of the polymorphous iron oxide precursors can be transformed into hematite crystals via high-temperature sintering.

Abstrak :


ABSTRAK
Kegiatan eksploitasi bijih besi secara besar-besaran untuk memenuhi permintaan pasar dunia yang terus meningkat telah menyebabkan penipisan cadangan bijih besi dengan kualitas tinggi secara signifikan. Hal tersebut mengakibatkan pada naiknya cadangan bijih besi dengan kualitas rendah, yang memerlukan teknologi benefisiasi tingkat tinggi untuk meningkatkan kandungan besi dan menurunkan kandungan silika. Bijih besi dengan kualitas rendah tersebut pada umumnya mempunyai komposisi mineral yang kompleks dan kandungan mineral yang tidak berharga atau disebut gangue. Flotasi adalah solusi yang ekonomis, efektif dan umum digunakan untuk menaikkan kadar konsentrat bijih besi yang berkualitas rendah, terkhusus pada partikel besi yang halus dan sangat halus. Performa flotasi tersebut, yang dilambangkan dengan kadar besi dan silika pada konsentrat bijih besi, dipengaruhi oleh ukuran partikel besi, jenis dan dosis bahan pereaksi kimia yang digunakan. Studi ini akan mengidentifikasi pengaruh dari ukuran partikel besi, dosis kolektor dan depresan terhadap performa flotasi, yang akan dilambangkan dengan rasio massa besi terhadap silika. Eksperimen dilakukan pada sel flotasi dengan kapasitas 140 ml dengan menggunakan desain eksperimen central composite rotatable design CCRD . Melalui analisa statistik, ditemukan bahwa hanya dosis kolektor dan depresan yang berpengaruh secara signifikan terhadap rasio massa besi terhadap silika pada konsentrat bijih besi.

---

ABSTRAK
High grade iron ore reserves are being significantly depleted due to massive exploitation, as the global iron demand is continuously increasing over time. This issue has led to significant gain of lower grade iron reserves that require advanced beneficiation technologies to increase the iron content and decrease silica content. Lower grade iron ores commonly have complex mineral composition and high content of gangue minerals. Flotation is an economical, effective and extensively used beneficiation solution to concentrate lower grade iron ores, especially for fine and ultrafine particles. The performance of flotation, i.e. iron grade and silica content in the concentrate, is influenced by particle size, reagent type and dosage. This project investigated the effects of particle size, collector and depressant dosages on the flotation separation performance represented by an integrated parameter, the mass ratio of iron to silica. The project was conducted in a 140 ml flotation cell via central composite rotatable experimental design CCRD . By using statistical analysis, it was found that only collector and depressant dosage would significantly affect the iron silica ratio.

Abstrak :
Ceramic magnets with the chemical composition of barium hexaferrite (BaFe12O19) were obtained through the synthesis of magnetite powder from iron sand taken from the Southern Coast of Yogyakarta in Indonesia. The iron sand was dissolved and then synthesized to produce magnetite powder. Subsequently, the magnetite powder was oxidized at temperatures of 700, 900, and 1100°C for five hours to produce hematite. The un-oxidized magnetite and the magnetite which was oxidized at the different temperatures were each mixed with barium carbonate, respectively. The mixtures were then calcined at 1100°C for two hours. The calcined products were compacted and then sintered at 1100°C for one hour to produce sintered ceramic magnets. X-ray diffraction (XRD), a vibrating sample magnetometer (VSM), a scanning electron microscope (SEM) with an energy dispersive X-ray spectroscope (EDS), and thermogravimetry analysis (TGA) were used to characterize the ceramic magnets. The results showed the magnetite that was directly calcined, compacted, and sintered had a BaFe12O19 phase and also had the presence of a Fe2O3 phase with a BH(max) of 0.26 MGOe, Hc of 1.27 kOe, and Ms of 31.421 emu/g. The sintered ceramic magnet which was initially oxidized at a temperature of 900°C had a BaFe12O19 phase with a BH(max) of 0.78 MGOe, Hc of 1.95 kOe, and Ms of 46.970 emu/g. These results indicate satisfactory results as a permanent magnet. Thus, the iron sand from the Southern Coast of Yogyakarta in Indonesia has potential for the production of ceramic permanent magnets.

Abstrak :
Mineral oksida besi merupakan salah satu komponen utama impurities pada bauksit dan limbah bauksit. Menghilangkan kandungan besi oksida dari bauksit dan limbah bauksit dapat menghasilkan produk yang bisa diproses kembali dengan Proses Bayer. Dilakukan pengujian beberapa parameter leaching, antara lain pH awal larutan asam, temperatur leaching, konsentrasi asam oksalat, serta penggunaan ion fero (Fe2+) sebagai katalis. Hasil penelitian menunjukkan bahwa hematit dapat dilarutkan dari residu limbah bauksit dengan efektif, namun selektivitas terhadap pelarutan aluminium masih rendah. Kandungan besi yang terdapat di dalam larutan asam dapat kembali diambil dengan menggunakan metode presipitasi goetit yang menunjukkan hasil recovery tinggi. ......Iron oxides, namely hematite, is one of the main impurities in both low grade bauxite ores and red mud. Studies found that hematite can be leached effectively using oxalic acid and the removal of iron oxides from low grade bauxite or red mud will increase the feasibility of processing by means of Bayer Process. Several leaching parameters were tested, namely initial solution pH, leaching temperature, oxalate concentration, all with the use of catalyst. The tests concluded that hematite can be leached effectively from bauxite waste residue by using oxalic acid, however selectivity is still an issue as the amount aluminium leached is still high. The leached iron could then be recovered as goethite through the goethite precipitation method that yielded high recovery value.