Rapid oxidative removal of Fe2+ and Mn2+ from acidic mining wastewater by a new-type biofilter system: application and mechanism

Aimed at the problem of excessive concentration of Fe2+ and Mn2+ in acidic mining wastewater during mining and utilization, a new rapid oxidative removal technology of Fe2+ and Mn2+ by a new-type biofilter system was designed and tested. The new-type biofilter system was constructed using a bioreactor filled with special mature bioceramic pellets after continuous biofilm cultivation as the filter layers. The results indicated that the biofilter system could efficiently treat five times its volume of wastewater per hour. The Fe2+ concentration of the influent wastewater was about 500 mg/L, and its Mn2+ concentration was about 20 mg/L. The average Fe2+ and Mn2+ removal rates could reach 99.7% and 90.8%, respectively. In addition, scanning electron microscopy and energy dispersive spectroscopy-energy dispersive spectroscopy and X-ray photoelectron spectroscopy were applied to analyze the migration distribution and valence change of Fe and Mn ions to clarify the removal mechanism of Fe2+ and Mn2+ using the biofilter system. The results showed that iron oxidation products were mainly coated at the surface of the mature bioceramic pellets and could be easily washed out from the filter layer with flowing water, while manganese oxidation products tended to accumulate between the pores of the mature bioceramic pellets. Furthermore, the final filtration products were multivalent complex oxides, indicating that the high-valent oxidation products could adsorb Fe and Mn ions, which were mainly removed by the oxidation effect.