Efficient removal of dissolved tri-n-butyl phosphate from aqueous solution by immobilized bacterial microspheres

Tri-n-butyl phosphate (TBP), a widely used organophosphorus flame retardants, is bioaccumulative, persistent, and toxic. In the real world, heavy metals co-occurrence with TBP often inhibit biodegradation of this pollutant. Immobilized microbial technology offers a promising way for mitigating TBP contamination. In this study, immobilized bacterial microspheres were prepared with sodium alginate (SA) and polyvinyl alcohol (PVA) as carrier materials and Sphingobium xenophagum as the functional microorganism to enhance TBP removal. Magnetic nanoparticles Fe 3 O 4 (sizes of 20 nm, 100 nm, and 200 nm) were introduced to enhance the mechanical strength and microbial activity of the microspheres. The results showed that the optimal environmental conditions for TBP removal were 35 °C and pH 8.0. The Fe 3 O 4 (200 nm)-PVA-SA bacterial microspheres exhibited the best performance, with larger specific surface area and abundant active groups (O-H, -OH, and -COOH). The removal rate exhibited 81.72 % at 5 mg/L within 4 d, which was higher than that of free microorganisms (62.23 %). For Cu 2+ , Zn 2+ , Ni 2+ , and Cd 2+ , the toxicity of Cd 2+ to free microorganisms was greater, while the bacterial microspheres were tolerant to heavy metal stress, especially the Fe 3 O 4 (200 nm)-PVA-SA bacterial microspheres; the TBP removal rate remained at approximately 80.00 % even under multiple heavy metals contamination. Additionally, the Fe 3 O 4 (200 nm)-PVA-SA microspheres maintained high stability and TBP removal rate in 5 consecutive cycles of TBP removal tests and 50 days of storage at 4 °C. The magnetic recyclability, stability, and reusability of the bacterial microspheres offer the potential for efficient and environmentally friendly wastewater treatment. The results provide a theoretical foundation for the development of high-performance immobilized microbial materials and technical support for the effective treatment of organic pollutants in harsh environments.