SYNTHESIS OF FEPO4 FROM NICKEL LATERITE HPAL PLANT TAILINGS BY ATMOSPHERIC LEACHING AND PRECIPITATION METHODS

• Main Author: Reynaldo Kanekaputra, Mikhael
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/77149
• Institution: Institut Teknologi Bandung

The issue of global warming encourages development of electrification of vehicles and alternative energy sources. Batteries are an important component in energy storage systems. Li-ion batteries with nickel and iron-based cathodes are a type of battery that has been widely developed. As the world's demand for nickel increases, the extraction of nickel from low-grade limonitic type ore increases, which is generally produced through High Pressure Acid Leaching (HPAL) technology. One of the main problems with the HPAL process is the production of very large volumes of tailings. Meanwhile, HPAL tailings contain high concentrations of iron. The high iron content in HPAL tailings has the potential as a source of raw material in the manufacture of FePO4, which is the cathode precursor of LiFePO4 batteries that are widely used in society. The precipitation method is the most widely used method in the synthesis of FePO4 because it is relatively cheap and easy. In the precipitation process, the iron needs to be dissolved first. Therefore, in this research, the FePO4 synthesis process was carried out from HPAL tailings of lateritic nickel ore through atmospheric leaching followed by precipitation. A series of experiments were carried out to obtain the best conditions for synthesizing FePO4 from the tailings of the lateritic nickel HPAL plant. The experiment began with the characterization and preparation of the tailings. The tailings sample that has been prepared is then used in the leaching stage. The leaching experiments were carried out at varying concentrations of sulfuric acid 3 – 6 M, S/L ratios of 0.2 – 0.5 g/ml, and temperatures of 35 – 95 °C for 4 hours to obtain the best leaching conditions for dissolving iron. Apart from iron, impurities in tailings such as Al, Cr, Ni, and Ca were also studied for their dissolution and precipitation behavior during the FePO4 synthesis process. Elemental concentration in experiment samples were measured using Atomic Absorption Spectroscopy (AAS). The leaching solution at the best conditions was used as an iron-rich solution in the precipitation process, while the leaching residue was analyzed by X-Ray Diffraction (XRD). Precipitation was carried out using (NH4)2HPO4 as a source of phosphate and NH4OH as a pH regulator. The best precipitation conditions were studied by varying the pH of 1 to 2.5, temperature of 30 to 90 °C, P/Fe mole ratio of 0.8 to 1.4, and the seed addition of 0 to 6%. The metal precipitation behavior and the characteristics of the precipitate obtained were studied by analysis using AAS, XRD, Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS), Particle Size Analyzer (PSA), and Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS). The results of the leaching experiments at atmospheric pressure showed that increasing the acid concentration and temperature increased the percent extraction of iron, aluminum, chromium, and nickel. Meanwhile, an increase in the S/L ratio tends to decrease the percent extraction of these metals. Calcium tends to be difficult to dissolve in sulfuric acid solution during leaching. The best leaching conditions at atmospheric pressure occurred at a concentration of 5 M sulfuric acid, S/L ratio of 0.25 g/ml, and temperature of 95 °C with a percent iron extraction of 98.02%. The results of precipitation experiments showed that increasing the pH from 1 to 2.5 increased the percent precipitation of iron, aluminum, chromium, and nickel. Meanwhile, the percentage of calcium precipitation increased to a pH of 1.5 and then decreased by increasing pH to 2.5. The percentage of iron and chromium precipitation increased with increasing temperature, while the precipitation percentage of aluminum and nickel tend to decrease with increasing temperature. Calcium decreased in precipitation at a temperature change of 30 °C to 50 °C and increased with increasing temperature thereafter. Increasing the P/Fe mole ratio increases the percentage of metal precipitation. The addition of seed tends not to have a significant effect on the percentage of metal precipitation. The best precipitation conditions were obtained at a pH of 2.5, a temperature of 90 °C, a P/Fe mole ratio of 1.2, and without the addition of seeds with an iron precipitation percentage of more than 99%. The FePO4 precipitate obtained under the best conditions had a bulky aggregation morphology with a Fe/P mole ratio of 0.7631 and an average particle size of 1.1 ?m.