Extraction of nickel from nickel limonite ore using dissolved gaseous SO2 – air

This paper reports a method of extracting nickel from nickel limonite by using dissolved SO2-air in ambient pressure. This method has been reported in the literature to have advantages of a high selectivity of nickel towards iron and can be conducted at ambient conditions. The purpose of this study is to determine the optimal conditions for nickel extraction from limonite ore by conducting pre-treatment and varying temperature and pH. The experiments were carried out in a five-neck reactor and comprised three steps: pre-treatment of the sample by pre-heating at 650 °C, leaching of the pre-treated sample, and analysis. The leaching solution was analyzed using the AAS (Atomic Absorption Spectrometer) method to determine the concentration of nickel and iron in the solution. The operating parameters included pH levels of 3, 4, or 5, and temperatures of 30, 55, and 80 °C. The leaching was carried out for up to 180 minutes. Mineralogical analysis of the ore was conducted using XRD (X-Ray Diffraction) analysis. It was found that optimal conditions were achieved at pH 3, temperature of 80 °C, and a leaching time of 180 minutes, yielding a nickel leaching efficiency of 21% from the original nickel content. The selectivity of nickel towards iron was found to be as high as 2743, indicating that nickel extraction can be effectively performed under mild conditions including low temperature, atmospheric pressure, and low pH.