Enhanced decolorization of methyl orange by Bacillus sp. strain with magnetic humic acid nanoparticles under high salt conditions

In this study, magnetic humic acid (MHA) nanoparticle was prepared and confirmed the enhancement on reduction of azo dyes under high salt concentration. The anaerobic growth of the strain Bacillus sp. on quinones makes the biogenic hydroquinone feasible, and the latter was proven to reduce the azo dyes stoichiometrically. This in-situ reversibly oxidation and reduction of MHA acts as electron shuttle to catalyze the biotic reduction of the azo dyes. The biodegradation efficiencies in batch experiments and sequencing batch reactor with MHA were increased by 1.5–2.5 times as compared to that of control without the catalyzer. Moreover, the negligible leaching of HA under various environmental conditions suggests the robustness of the coating of HA on Fe/O surface. These results indicated that the as-prepared MHA could be used as redox mediator to accelerate the extracellular electron transfer, which is of great environmental significance for the removal of hazardous compounds.