Experimental study on treatment of Fe²⁺ and Mn²⁺ in AMD with lignite combined with Pseudomonas aeruginosa immobilized SRB particles

Sulfate-Reducing Bacteria (SRB) are easily inhibited by high concentrations of heavy metals, low pH as well as the need to add carbon source materials, the microbial immobilization technology was adopted, with SRB, Pseudomonas aeruginosa and lignite as the main immobilization substrates, to prepare lignite and Pseudomonas aeruginosa immobilized SRB particles (L-P-SRB) and the removal effect of L-P-SRB on Fe²⁺, Mn²⁺ and SO₄ ²⁻ in acid mine wastewater (AMD) was investigated. Based on the reduction kinetics and adsorption kinetics, the mechanism of AMD treatment by L-P-SRB was revealed by means of scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR), and the mechanism of L-P-SRB treating AMD was revealed. At the same time, the repair effect of low temperature treatment of L-P-SRB on AMD is explored, which provides a certain basis for the treatment of AMD in mining areas under the condition of low temperature. The results show that the removal rates of Fe²⁺ and Mn²⁺ by L-P-SRB are 91% and 79% respectively, and the process of adsorption of Fe²⁺ and Mn²⁺ conforms to the pseudo-first-order kinetics; the removal rate of SO₄ ²⁻ reaches 91.28% and 81.94% respectively, and the process of reducing SO₄ ²⁻ is in accordance with the first-order kinetics. Compared with Fe²⁺, Mn²⁺ has a certain inhibitory effect on the activity of L-P-SRB. L-P-SRB can remove Fe²⁺, Mn²⁺ and SO₄ ²⁻ in wastewater at one time, which well solves the problem that lignite can only adsorb heavy metal ions and SRB needs to add carbon source. Low temperature cold storage treatment will not inhibit the activity of L-P-SRB, which provides a basis for one-time preparation and multiple use. According to the detection of SEM and FT-IR, pseudomonas aeruginosa plays a priority role in the treatment of wastewater by L-P-SRB, destroying the structure of lignite, destroying some functional groups, breaking the C—C bond, C=O bond and side chain of cycloalkanes, alkanes and olefins in lignite, producing a large number of small molecule organic substances, increasing the specific surface area of particles, and improving the adsorption capacity of particles. At the same time, lignite provides a carrier and a large number of carbon sources for the reduction of SO₄ ²⁻ by SRB, which promotes the growth of SRB and improves the treatment effect of AMD.