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.
Peat can be used as a natural adsorbent due to its humic acid content having various active functional groups such as carboxylates and hydroxyl groups. Peat soil samples obtained from Pelalawan district, Riau province of Indonesia were selected and their adsorption capacities were investigated using Mn(II) solution as a model solution. The raw peat samples were first prepared by drying at 110°C for 12 h. The adsorption experiment was conducted in batch test using Mn(II) solutions for 360 mins at pH of 5.2 as optimum conditions. The peat samples were analyzed using the Fourier Transform Infrared Spectroscopy, Surface Area Analysis and Scanning Electron Microscopy- Energy Dispersive Spectroscopy. The obtained adsorption data were fitted using Langmuir, Freundlich and BET isotherm models. It was found that the adsorption data followed the Langmuir isotherm model with correlation coefficients (R2) ranging between 0.9866-0.9997 and the adsorption capacities were between 11.99-22.94 mg/g.
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