Nickel is obtained from laterite ores by a metallurgical process to produces ferronickel. Nickel metal is present in a carrier mineral, a nickel magnesium silicate hydrate compound called garnierite. Garnierite is the common name of magnesium silicate hydrate minerals including chlorite, clay and serpentine. This study to investigate the phase formed when the nickel ore is roasted from a temperature of 600°C to a temperature of 1000°C under atmospheric enviromental. Microscopic analysis of roasted samples was analyzed by SEM-EDX and the dehydroxylation and recrystallization was studied using DTA-TGA. The endothermic peak was appear at 78.8°C, 293.7°C and 638.0°C, this corresponds to the release of free water and the release of crystalline water. While the exothermic peak occurs at 828.0°C. The exothermic temperatures associated with structural changes due to dihydroxylation of serpentine into a forsterite phase. Based on the XRD graph it is known that the sample of the roasting will produce the olivine and forsterite phases.
Reduction and the compounds formed when the reduced laterite nickel has been investigated. Nickel laterite with average grain size below 0.149 mm mixed with 13% (weight percent) of coal as reductant then reduced in muffle furnace with temperature from 700 °C to 1000 °C. Type of laterite is used which has high iron (saprolite) and low iron content (limonite). Reaction time varied 30, 60 and 90 minutes. The reduction of nickel during reduction is determined by an analysis of metallization values. Metallization analysis used bromine methanol method, while the compound analysis was formed using x-ray Diffractometer. Based on the metallization test, it is known that the laterite nickel ore containing high iron will produce a higher nickel reduction than the laterite nickel ore containing low iron. This corresponds to the oxide phases formed. The higher iron contain on the ore tend to produce the fayalite mixture and slightly forsterite, while at low iron content will form a forsterite. Forsterite tends to inhibit reduction of nickel.
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