Experimental study on the treatment of AMD by SRB immobilized particles containing "active iron" system

Abstract

The inhibition and toxicity of high acidity and heavy metals on sulfate-reducing bacteria in acid mine drainage (AMD) were targeted. Highly active SRB immobilized particles were prepared using SRB, warm sticker wastes (iron powders), corncobs, and Maifan stones as the main matrix materials, employing microbial immobilization technology. The repair ability and reusability of highly active immobilized particles for AMD were explored. The results indicate that the adaptability of immobilized particles to AMD varied under different initial conditions, such as pH, Mn2+, and SO42-. The adsorption process of immobilized particles on Mn2+ follows the quasi-second-order kinetic model, suggesting that it involves both physical and chemical adsorption. The maximum adsorption capacity of immobilized particles for Mn2+ is 3.878 mg/g at a concentration of 2.0 mg/L and pH 6. On the other hand, the reduction process of immobilized particles on SO42- adheres to the first-order reaction kinetics, indicating that the reduction of SO42- is primarily driven by the dissimilation reduction of SRB. The maximum reduction rate of SO42- by immobilized particles is 94.23% at a concentration of 800 mg/L and pH 6. A layered structure with a flocculent appearance formed on the surface of the immobilized particles. The structure's characteristics were found to be consistent with sulfate green rust (FeII4FeIII2(OH)12SO4·8H2O). The chemisorption, ion exchange, dissimilation reduction, and surface complexation occurring between the matrices in the immobilized particles can enhance the alkalinity of AMD and decrease the concentration of heavy metals and sulfates. These results are expected to offer novel insights and materials for the treatment of AMD using biological immobilization technology, as well as improve our understanding of the mechanisms behind biological and abiotic enhanced synergistic decontamination.