The effect of addition of sodium sulphate (Na2SO4) to nickel slag pyrometallurgical process with temperature and additives ratio as variables

Abstract

Nickel industry is one of the most strategic industries because its widely used. Nickel slag as a by-product of nickel processing presents the potential for improving process efficiency. In this study aim to determine the effect of the addition of sodium sulfate additives and also the temperature in the reduction process of nickel slag. The research was preceded by preparation of nickel slag samples with crushing and sieving up to 200 mesh. The nickel slag is then reduced at 800°C, 900°C and 1000°C temperature without adding sodium sulfate and by adding sodium sulfate with 1 hour holding time. Furthermore, the results of the reduction is done XRD and AAS testing to see changes in the content of elements and compounds in nickel slag that has been tested. The results of the study explain that the content of the dominant impurities which is in the form of SiO2 decreases as the temperature of the reduction and iron from Fe-rich Forsterite compounds will be liberated and will bind to sulfur derived from sodium sulfate to form troilite (FeS). This results in an increasing content of valuable minerals present in the nickel slag.

Magnesium extraction of ferronickel slag processed by alkali fusion and hydrochloric acid leaching

“…Thermal characterization of ferronickel slag with Na2CO3 addition confirmed the formation of sodium silicate at minimal temperature of 900 °C [12]. Sodium silicate formation was also obtained from reduction of ferronickel slag using NaOH [13] and Na2SO4 [14] as additives. However, utilization of NaOH to form sodium silicate needs high quantity [18,23] and leads to high base condition which can affect the further treatments.…”

“…Prior research studies to increase the value of the ferronickel slag have been carried out using pyrometallurgy process [12][13][14] hydrometallurgy process [15,16] as well as combination of both processes [17][18][19]. Generally, flotation process is a commercially pre-tratment that carried out prior pyrometallurgy or hydrometallurgy process to separate or upgrade the specific element.…”

Decomposition of ferronickel slag through alkali fusion in the roasting process

“…The reduction process using coal as a reducing agent against ferronickel slag with the addition of Na 2 SO 4 resulted in phase transformation, Fe liberated from silicates and reacted with Na 2 SO 4 to form FeS [18]. Meanwhile, FeO resulted from the reduction of ferronickel slag with NaOH addition [19].…”

Reverse leaching of magnesium from ferronickel slag using alkali solvent NaOH

“…Research that has been done to process ferronickel slag waste has been carried out by several researchers, both with pyrometallurgical, hydrometallurgical processes and a mixture of both pyro-hydrometallurgy. Several studies with pyrometallurgical processes are by roasting or reducing ferronickel slag with a mixture of additives NaOH [13], Na 2 CO 3 [18] and Na 2 SO 4 [12]. The roasting process is carried out by adding an additive of Na 2 CO 3 for the decomposition of forsterite and enstatite into magnesium oxide and sodium silicate so that it will facilitate the process of separating precious metals, especially magnesium [4].…”

“…The ferronickel slag still contains some valuable minerals such as silica, magnesium, nickel, iron, cobalt and some rare-earth elements [4,[10][11][12][13][14]. The major element content in the ferronickel slag is Si about 30 %, others are 20 % of Mg, 12 % of Fe, 1-2 % of Al, and other elements [15].…”