Biosorption of Cu2+ and Zn2+ by Rhodotorula sp. Kt, a Yeast Isolated from Acid Mine Drainage

Acid mine drainages (AMDs) enriched with toxic metals pose a significant environmental risk. Microbial bioremediation offers a sustainable and cost-effective approach for metal removal from AMD. In this study, a wild yeast isolated from the Kavart abandoned mine, identified as Rhodotorula sp., was evaluated for its copper (Cu2+) and zinc (Zn2+) biosorption ability. Biosorption was strongly pH-dependent. Cu2+ and Zn2+ removal was most efficient (48.1% or 10.07 mg/g and 35.7% or 6.07 mg/g, respectively) at pH 6. Increasing the biomass to 3 g/L at the same pH enhanced Cu2+ removal to 71.5% (26 mg/g). Biosorption kinetic analysis showed an excellent fit to the pseudo-second-order model (R2 > 0.99), indicating that the mechanism is chemisorption-dominated. Equilibrium data followed the Langmuir isotherm (R2 = 0.93), consistent with monolayer adsorption on homogeneous binding sites. SEM-EDS analysis confirmed Cu2+ association with the yeast surface, supporting the ICP-OES results. The results demonstrate the isolate as a promising biosorbent, particularly for Cu2+, and highlight its potential application in the remediation of AMD-contaminated waters.