Leaching of silicon from ferronickel (FeNi) smelting slag with sodium hydroxide solution at atmospheric pressure

Reverse leaching of magnesium from ferronickel slag using alkali solvent NaOH

“…Other elements contained in ferronickel slag are magnesium, iron, and aluminum with the content of 29.32 %, 16.5 %, and 4.8 % respectively. These XRF analysis results are consistent with the previous study that carried out the analysis even though it has a different use of sources in the analyzed samples [21]. The compounds identified in the ferronickel slags are associated with different mineral phases that were characterized using X-Ray diffraction instruments shown in Fig.…”

“…5 shows that the percent extraction of magnesium increased from 9 M concentration of sodium hydroxide to 10 M concentration of sodium hydroxide and then decreased at 11 M concentration of sodium hydroxide. A similar trend occurred in previous studies which stated that the dissolution of silicon from the ferronickel slag increased significantly with increasing NaOH concentration until it got a certain concentration, then decreased significantly as well [11,21]. They conclude that the higher the concentration used in the solutions, the aluminosilicate precipitate formation will occur which can inhibit the silica dissolution at its higher NaOH concentrations.…”

“…Most of the silica can be dissolved effectively and just left 4.28 % low silica content in the residue [20]. Dissolving silica using NaOH solution at a lower temperature, 25-110 °C, can decrease energy consumption, however, it resulted in lower dissolved silica at about 31.48 % for 4 hours leaching process [21]. Increasing dissolution temperature can increase the solubility of silica from raw materials, thus it affects silica recovery.…”

“…The silica dissolved in the NaOH leaching agent reduces silica content in the residue so that it will increase the magnesium content. According to previous research, the reason for a leaching process using strong base solutions is to reduce the deposition of the metal elements that must be carried out if it is using acid solvents because valuable metals are found in the filtrate [21]. Moreover, the use of base solvents can reduce the damage of the leaching tank caused by acid solvents due to corrosion.…”

“…This is appropriate with the previous research which states that the longer the leaching time, the more silica dissolves in sodium hydroxide as there is more opportunity to contact reactions between the sodium hydroxide samples. Silica that is dissolved in the solutions increases and causes an increment of magnesium content in the residue from the leaching results [21].…”