Effect of pH Variation on Nickel Recovery and Iron Dissolution during Microwave-Assisted Sulfuric Acid Leaching of Limonite Ore

Abstrak

This study examined the effect of pH variation on nickel recovery from limonite ore following microwave-assisted sulfuric acid leaching. The limonite samples were characterized by X-ray fluorescence (XRF) to determine their elemental composition. Leaching was conducted using 4 M H₂SO₄ under microwave irradiation at 270 W for 10 min. The resulting leachate was then subjected to sequential pH adjustment from 4 to 7 by adding NaOH solution. At each pH, aliquots of the leachate were analyzed by atomic absorption spectroscopy (AAS) to determine the concentrations of dissolved nickel (Ni) and iron (Fe). Metal recoveries were calculated by mass balance using the initial metal contents determined by XRF and the dissolved metal concentrations measured by AAS. The dissolved nickel mass increased from 0.00616 g at pH 4 to 0.01635 g at pH 7, corresponding to an increase in nickel recovery from 9.40% to 24.97%. In contrast, iron recovery remained low, decreasing from 1.30% at pH 4 to 0.98% at pH 6 before increasing slightly to 1.09% at pH 7. The results indicate that increasing the pH during post-leaching neutralization was associated with higher nickel recovery and limited iron dissolution. These findings highlight the role of pH adjustment in controlling dissolved metal distribution and provide insight into optimizing nickel recovery from limonite ore after microwave-assisted leaching.

Kata kunci

• imonite ore
• microwave-assisted leaching
• nickel recovery
• pH variation
• sulfuric acid leaching