Alternative treatment for metal ions removal from acid mine drainage using an organic biomixture as a low cost adsorbent

Acid mine drainage, characterized by low pH and elevated heavy metal ion concentrations, causes severe harm to the environment. In this study, the feasibility of a new organic biomixture adsorbent for removing Fe3+, Zn2+, Cu2+ and Mn2+ metal ions from synthetic acid mine drainage was evaluated. This kinetic study showed fast metal ions adsorption within the first four to eight hours, and adsorption over 80% in the organic biomixture. The equilibrium adsorption isotherms resulted in a metal ion uptake greater than 84%, and the Freundlich model fitted well the data. The Freundlich affinity coefficient (Kf) ranged from 1.44 to 3.82 in the following order: Zn2+>Cu2+>Fe3+>Mn2+. Scanning electron microscope images revealed the heterogeneous structure of the biomixture, and energy-dispersive X-ray analysis after adsorption confirmed the ability of the biomixture to remove the metal ions. In the fixed-bed column, the Thomas model described (R-2>0.95) the adsorption process of metal ions contained in the treated acid mine drainage well. The adsorption capacity (q0) of this system resulted in 164.2 mg g(-1), 129.2 mg g(-1), 26.0 mg g(-1) and 15.3 mg g(-1) of Fe3+, Zn2+, Cu2+ and Mn2+, respectively. This study confirmed the efficiency of an organic biomixture to adsorb metal ions and provide new and valuable information for the future design of low-cost treatments to reduce acid mine drainage pollution. (C) 2021 Elsevier B.V. All rights reserved.