Sustainable Nickel Extraction from Low-Grade Ores via <i>Trametes versicolor</i>: A Bioleaching Case Study on Olivine and Serpentine

Nickel's versatile properties and growing demand, particularly in stainless steel and electric vehicle industries, highlight the need for environmentally sustainable recovery methods amid depleting high-grade reserves. This study explores the bioleaching potential of Trametes versicolor OG2 for nickel extraction from chromite tailings, olivine, and serpentine under varying pH (4.5-6.3) and retention times (3 and 7 days). Optimal recovery from olivine (41.82%) and serpentine (30.97%) was achieved at pH 5 after 7 days, underscoring the influence of extended processing. The fungus demonstrated high tolerance to heavy metals, including nickel and chromium. Organic acids, particularly oxalic and citric acids, produced by the fungus, were identified as key leaching agents, enhancing the extraction of nickel and iron. However, high chromite levels in serpentine reduced metal dissolution due to toxic hexavalent chromium. These findings position T. versicolor as a sustainable and effective agent for nickel recovery, offering a promising pathway toward environmentally friendly mining and heavy metal remediation.