Application of biogenic iron precipitation by strain H117 for tetracycline removal: mechanism of adsorption and activation

To date, biogenic metals have opened up a window for new applications in adsorption of contaminants. But there is still little attention to be paid in the removal of tetracycline (TC) by biogenic iron precipitation (BIP). In this paper, the BIP, from iron-based mixotrophic denitrification batch reactor, was estimated for its adsorption property of TC under various parameters to simulate the behavior in aquatic environment. The maximum adsorption capacity for TC was 195.336 mg g^-1. Analyses of spectrum verified the existence of Fe₃O₄ and FeOOH in BIP, which was the main reason for the removal of TC. The adsorption kinetic and isotherm of TC were well fitted to Elovich and Langmuir isotherm models, respectively, indicating that the adsorption process was mainly controlled by chemical adsorption. Furthermore, we proposed a potential mechanism of adsorption: a combination of cation-π, hydrogen bonding (H-bonding), and electrostatic interaction. Additionally, the activation experiment showed that BIP could enhance the degradation of TC (more than 98.00% removal within 1.0 h) by advanced oxidation process (AOP), due to the existence of FeOOH and Fe₃O₄. Considering its effectiveness in both adsorption and activation performance, BIP is highlighted as an economical and eco-friendly material for TC removal and offers a promising method to resolve sludge disposal in biological treatment of iron-rich groundwater.