PELINDIAN ALUMINA DAN BESI OKSIDA BIJIH BAUKSIT KALIMANTAN BARAT DENGAN METODE PELINDIAN ASAM KLORIDA

Pada umumnya industri alumina menggunakan proses Bayer untuk mengekstraksi alumina bijih bauksit. Namun proses ini menghasilkan limbah red mud yang sangat besar jumlahnya, sehingga diperlukan teknologi alternatif untuk mengekstraksi bijih bauksit tersebut. Pelindian dengan asam dapat mengekstraksi berbagai jenis mineral bauksit dan tidak menghasilkan red mud. Serangkaian percobaan dan analisis dilakukan untuk mempelajari perilaku pelindian bijih bauksit Tayan, Kalimantan Barat menggunakan asam klorida tanpa melakukan proses pemanggangan atau roasting bauksit terlebih dahulu. Tujuan penelitian ini adalah mempelajari pengaruh variasi ukuran partikel bauksit, konsentrasi asam klorida, suhu pelindian dan persen padatan pada proses pelindian terhadap persen ekstraksi Al dan Fe. Persen ekstraksi Al dapat mencapai 90,26% dan Fe 98,95% pada kondisi suhu pelindian 100°C, konsentrasi asam klorida 15%, persen padatan 10% dan ukuran partikel -270 mesh

THE CURRENT STATUS OF IRON MINERALS IN INDONESIA

Indonesia has great iron mineral resources, comprising primary iron ore (17 %), iron sand (8 %) and lateritic iron ore (75 %). Nowadays, Indonesia’s primary iron (hematite, magnetite) has not been em- powered yet, due to the scattered area of the resources location. Meanwhile, national iron sand is commonly used for cement industries and its potency has not supported national steel industries yet because of low iron content (45-48 %). However there is an opportunity to be processed by using Ausmelt process technology. At present, lateritic iron ore is being used as coal liquefaction catalyst in the form of limonite, but hydrometallurgy would be a promising solution to beneficiate lateritic iron ore for steel industries

THE KINETICS OF INDONESIAN GALENA CONCENTRATE LEACHING IN FLUOROSILICIC ACID AND HYDROGEN PEROXIDE AS ITS OXIDANTS

Lead smelting is known as a lead extraction technique which has negative impact to environment because it produces emissions of dust, SO2 gas and lead. The leaching is conducted to reduce the smelting’s weaknesses by extracting the lead without damaging the environment. This technique, often called hydrometallurgical lead extraction, uses liquid media to extract the lead and separate it from the elemental sulphur (S0) by filtration. Particle size, slurry density (solid percentage) and acid concentration affect the dissolution of Indonesian galena concentrate with fluorosilicic acid and hydrogen peroxide as oxidants. By means of these reagents, it is expected that the Pb extraction process from galena concentrate resulted from flotation of sulfide ore can be carried out at low temperatures and lead recovery can be accomplished from the leach solution by electrowining. Studying galena leaching kinetics is required to perform galena leaching with high Pb extraction percentages. Two kinetics models are commonly used to study leaching kinetics, namely shrinking core model (SCM) and shrinking particle model (SPM). These models are used to determine the mechanism which controls leach reaction and reaction rate constant or diffusion constant of the reacting species. Total plotting of sulfide fraction dissolves with time adjusted to the existing mathematical model, and fitting the curve from the dummy model to the experimental data, are two techniques that are utilized to obtain the best kinetics model which important in controlling the leaching reaction rate. Applying the Arrhenius equation, the relation of the reaction rate constant or the diffusion constant and the temperature is determined to calculate the leaching activation energy. The result from kinetics analysis showed that the leaching of Indonesian galena concentrate in fluorosilicic acid with hydrogen peroxide as oxidants followed the shrinking core model with diffusion through porous solid product layer as the reaction controller with activation energy of 45.81 kJ/mol or 10.91 kcal/mol

PARAMETERS THAT AFFECT THE DISSOLUTION OF INDONESIAN GALENA CONCENTRATE IN FLUOROSILICIC ACID AND HYDROGEN PEROXIDE

Pyrometallurgical process still dominates the extraction of galena concentrates. The process used to extract the lead includes reduction smelting in a blast furnace, air flash smelting (Boliden process), oxygen flash smelting (Kivcet, Boliden Kaldo, Outokumpu), air-slag bath smelting (Isasmelt) and oxygen-slag bath smelting (QSL). However, those generate dust, SO2 gas and volatile Pb liquid. As a result, such processes are ineffective to treat the complex sulfides and low-grade flotation con concentrates. Referring to the lack of high-grade lead ore the lead pyrometallurgical is a problem in the future. In addition, the environmental regulation becomes very strict lately. Those pushes the metallurgist to seek the alternative process that are environmentally friendly and able to treat the low-grade concentrates. Lead extraction through hydrometallurgical process is considered to be safer as the process do not produce dust, SO2 gas and lead vapor.Researches for lead extraction through hydrometallurgical routes have been performed using various leaching agents such as acetic acid, ferric methanesulfonate, ferric chloride, ferric fluorosilicate and nitric acid with hydrogen peroxide and ferric ion as the oxidants. So far, no lead plant operates hydrometallurgically in an industrial scale. Fluorosilicic acid has a potential to be used as the leaching reagent for concentrating the lead because of high lead solubility in this solution and cheaper price of the reagent in compared to sulfamate and fluoroborate solutions. This research used galena concentrates from a mining area in Bogor, Indonesia, fluorosilicic acid and hydrogen peroxide as the oxidants. The highest Pb extraction percentage of 99.26% was achieved from the leaching experiment using 3.44 M of H2SiF6 and 9.79 M of H2O2, at 97oC and concentrate particle size distribution of -100+150 mesh after 135 minutes. The XRD analysis of the leaching residue with no oxidant showed the presence of galena, sphalerite and chalcopyrite, while the residue of the leaching with oxidant showed anglesite (PbSO4), galena, sphalerite, sulphur and pyrite. Lead extractions were increased by the increase of temperature and concentration of fluorosilicic acid. The best solid percentage that gave the highest lead extraction percentage was 12%. Variations of rotation speeds at the range of 300-700 rpm did not significantly influence lead extraction percentage. However, the particle size distribution that resulted in the best extraction percentage of lead is 100+150#, at which the finer particle size of the concentrate give a lower extraction percentage of the lead due to PbSO4precipitation.