Fe/Mn-modified biochar immobilizing Pseudomonas hunanensis SK-4 enhanced simultaneous nitrogen and copper removal: Mechanism and application.

To address the challenges posed by the complex composition and high treatment difficulty of composite pollutants, especially copper and nitrogen compounds in water. This study investigated the application of Pseudomonas hunanensis SK-4, which exhibited exceptional resistance to high concentrations of Cu(Ⅱ). Under 100 mg/L Cu(Ⅱ) stress, SK-4 maintained high removal efficiencies of 98.59 % for NH4+-N and 83.07 % for NO3--N. A novel biochar-microbial composite (FMABC@SK-4) was prepared by immobilizing SK-4 onto self-synthesized iron-manganese modified biochar. In practical tests, FMABC@SK-4 exhibited excellent simultaneous removal of nitrogen and copper, achieving maximum efficiencies of 99.6 % for NH4+-N and 99.43 % for Cu(Ⅱ). The results indicated that FMABC@SK-4 removes Cu2+ mainly through physical adsorption and surface complexation, whereas nitrogen removal is driven by heterotrophic nitrification-aerobic denitrification and ammonia assimilation processes. These findings underscored the potential of FMABC@SK-4 for treating complex wastewater containing both heavy metals and nitrogen, providing an efficient and mechanism-based strategy for enhanced pollutant removal.