Extraction of limonite ore using dissolved SO2–air is an alternative hydrometallurgical method for nickel recovery. This process is carried out at atmospheric pressure and is shown to have good selectivity of nickel over iron, but with a low recovery yield. The literature refers to the application of alkali roasting as pretreatment in laterite ore leaching to increase nickel recovery. Thus, this study aims to apply the combination method of alkali roasting and leaching to extract nickel from limonite ore (1.33% Ni, 46.61% Fe) from the Southeast Sulawesi region. Three alkali compounds were included in the study (NaOH, Na2CO3 and Na2SO4). The batch-leaching process was carried out at pH 1 and 3 and temperatures of 55 and 80 °C for 180 min. The leach liquors were sampled at 15, 60, 90 and 120 min, and concentrations of the extracted metals were measured by Atomic Absorption Spectrometry (AAS). A mineralogy characterization of the raw ore and its residue after leaching was undertaken by using X-Ray Diffraction (XRD), while the thermal decomposition behavior of the ore was characterized by Thermogravimetry Analyzer (TGA)/Differential Scanning Calorimetry (DSC). The addition of Na2CO3, Na2SO4 and NaOH in the ore pretreatment increases nickel recovery from 14.80% without alkali roasting to 23.99%, 28.15% and 39.22%, respectively. The optimum extraction condition for nickel recovery is at pH 1 and a temperature of 80 °C. However, the highest Ni/Fe selectivity of 24,947 is obtained at pH 3 and a temperature of 80 °C, preceded by roasting in the absence of alkali. Compared to other hydrometallurgical processes, the process studied in this work exhibits lower recovery, but provides an alternative to extract nickel from low-grade limonite ore.
Biogas is a methane-rich gas produced from microbial digestion of waste (agricultural, sewage, and landfill) which can be used for power production. The low rate of biogas production from an anaerobic digester becomes a problem in cow manure processing increasing. Biogas production is influenced by the biomass of methanogenic bacteria in the conversion of organic matter contained in a digester, so other methanogenic bacteria are needed to accelerate the rate of biogas production, namely methanogenic bacteria from the anaerobic digester of cow manure. Bacterial isolation was carried out by isolating samples of the anaerobic digester of cow manure in fluid thioglycolate media using the pour plate method in a vial tube. Those samples were incubated at 37 °C in an anaerobic chamber where after isolation, the bacteria were identified through several biochemical tests. Based on research conducted, a single colony of methanogenic bacteria is gram negative bacterium where the results of the isolates show that the bacteria of the Methanobacterium genus. The highest biogas production was obtained from the addition of 15%v/v of bacterial isolate. It can be seen from the volume of biogas produced with the volume 40 mL for 14 days of the fermentation process.
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