Widi Astuti

Ferromanganese production from the mixture of medium-grade and low-grade Indonesian manganese ore

Abstract In this present work, the ferromanganese was produced by mixing two different grades of Indonesian manganese ore. The possibility of mixing medium-grade manganese ore (27.77 Mn–4.44 Fe–14.7 Si) and low-grade manganese ore (16.39 Mn–19.22 Fe–20.23 Si) to produce ferromanganese was investigated clearly. The 30 Kg of manganese ore mixture was smelting by using sub-merged arc furnace (SAF). The composition of manganese ore mixture in percent weight to produce ferromanganese was 100–0, 75–25, 50–50, 25–75, and 0–100 for medium-grade and low-grade manganese ore, respectively. These ores were smelted together with stoichiometry cokes. Limestone was added in this smelting process to obtain 0.75 of basicity in this smelting process. The chemical composition of ferromanganese was analyzed with X-Ray Fluorescence (XRF). From the smelting process, the ferromanganese with 31.13 Mn–59.84 Fe–7.84 Si and 75.19 Mn–20.17 Fe–3.27 Si were resulted from 100% of low-grade and medium-grade manganese ore, respectively. The Mn-content in ferromanganese and the yield of ferromanganese production were decreased with the increasing of low-grade manganese ore in the mixture of low-grade and medium-grade manganese ore smelting process.

Effects of Individual Use, Mixed Culture and Sulfur Addition on the Effectiveness of Nickel Laterite Ore Bioelaching with Penicillium verruculosum and Galactomyces geotrichum

The type of fungi used in fungal bioleaching influence the effectiveness of metals extraction due to the dissimilarity of each microorganism survival in environments with certain metals content. Several metals have prominent toxicities to certain type of fungi, which result in low metals extraction and leaching rate. In the present work, the influences of individual use of Penicillium verruculosum and Galactomyces geotrichum on the nickel extraction from Indonesian laterite ore are compared with the fungis mixed culture. The effect of sulfur addition in the mixed culture of Penicillium verruculosum and Galactomyces geotrichum on the sulfate ion formation was also investigated. Shake flask bioleaching assays have been performed in a medium growth of Indonesian food production waste over the course of 28 days. It was observed that mixed culture of Penicillium verruculosum and Galactomyces geotrichum has a higher effect in nickel extraction compared with the use of individual fungi for both saprolite and limonite ores. For saprolite ore, the fungi species of Galactomyces geotrichum demonstrated a greater nickel extraction than Penicillium verruculosum. In contrast, the extraction of nickel from limonite ore by Penicillium verruculosum was slightly more effective than Galactomyces geotrichum. The addition of elemental sulfur in the mixed culture was found to generate sulfate anion, having a significant increase in its concentration with time and decreasing solution pH within 28-day of incubation. The proportion of sulfur addition must be optimized in order to avoid ore surface passivation with the excess of sulfur. XRD analysis detected the presence of un-oxidized sulfur on surface of the leaching residues along with the biomass.