Decomposition of ferronickel slag through alkali fusion in the roasting process

Abstract

Ferronickel slag is a by-product of the nickel smelting process. Recycling of ferronickel slag is required since it contains valuable elements besides its potency to pollute the environment. In order to take advantage of the valuable materials and reducing the potential hazard, beneficiation of ferronickel slag is essential. Alkali fusion of ferronickel slag using Na2CO3 in the roasting process was carried out. This study aims to determine the decomposition of the mixture of ferronickel slag-Na2CO3 in the roasting process. Roasting temperature and time were 800–1,000 °C and 60‒240 minutes, respectively. Characterizations of the ferronickel slag were conducted by XRF, ICP-OES, XRD and SEM-EDS. Meanwhile, roasted products were characterized using ICP-OES, XRD and SEM-EDS. Characterization of the ferronickel slag indicates that Mg and Si are the main elements followed by Fe, Al and Cr. Moreover, olivine is detected as the main phase. The roasting process caused percent weight loss of the roasted products, which indicates decomposition occurred and affected the elements content, phases and morphology. The roasting process at about 900 °C for 60 minutes is a preferable decomposition base on the process conditions applied and the change of elements content. Aluminum (Al) and chromium (Cr) content in the roasted products upgraded significantly compared to iron (Fe) and magnesium (Mg) content. Olivine phase transforms to some phases, which were bounded with the sodium compound such as Na2MgSiO4, Na4SiO4 and Na2CrO4. The rough layer is observed on the surface of the roasted product as a result of the decomposition process. It indicates that liquid-solid mass transfer is initiated from the surface

Initial extraction of sodium silicate from sidoarjo mud by alkaline fusion and water leaching

“…The data shows the same pattern as this research. The results of the XRD analysis of the Sidoarjo mud are in accordance with several previous researchers [ 27 , 37 ]. The XRD analysis of the alkaline fusion process product is shown in Fig.…”

“…Alkaline fusion is carried out by mixing a 100-mesh warp with sodium carbonate (Na 2 CO 3 ). Size reduction aims to increase the porosity of the warp and facilitate the fusion process of bound alkali silicate into sodium silicate (Na 2 SiO 3 ) [ 37 ]. Mixing based on the mass ratio was varied as 1:1, 1:2, and 1:3.…”

Effect of Mixing Methods Prior the Decomposition Process on the Decomposed Ferronickel Slag

“…Previous studies were conducted to utilize ferronickel slag as materials for cement [4] - [7], concrete [8]- [11], polymer [12], mortar [7], [8], magnesium [13] - [15], magnesium metal and ferro alloy [16] as well as for refractory [17]. The ferronickel slag contains SiO2 41 -46%, MgO 30 -41%, Fe2O3 10 -14%, Al2O3 2 -5%, Cr2O3 1,4 -1,9% and other compounds including rare earth elements (REE) in the amount of less than 1% [15], [18]. It allows ferronickel slag to be used as secondary raw materials for Si, Mg and REE as well through pyrometallurgy, hydrometallurgy, and combination of both processes.…”

“…Decomposition process can be performed to reduce high energy that is required for the process. Some processes such as alkali roasting [18], reduction process [16], [19] - [21], leaching [12], [22] - [23], and combination of these processes [14] - [15], [24] - [26] were studied. Na2CO3 addition could reduce the melting point of the mixture to about 850 ̊ C [18], [27].…”

“…Some processes such as alkali roasting [18], reduction process [16], [19] - [21], leaching [12], [22] - [23], and combination of these processes [14] - [15], [24] - [26] were studied. Na2CO3 addition could reduce the melting point of the mixture to about 850 ̊ C [18], [27]. Utilization of lower melting point chemicals such as Na2O2 [26], NaOH, and Na2SiO3 [12] allow decomposition process conducted at lower temperature.…”