Enhanced remediation of phenanthrene in water and soil by novel biochar-immobilized bacterial microspheres

Bioaugmentation is often considered a promising technology for the removal of polycyclic aromatic hydrocarbons; however, available high-efficiency microbial agents remain very limited. In this study, the green solvent polyethylene glycol 200 and Fe (NO3)3·9H2O were introduced to prepare iron-modified biochar materials by one-step pyrolysis. This material had a specific surface area of 407 m2⋅g−1 and high microbial immobilization efficiency. The addition of polyethylene glycol 200 promoted hydrolysis of iron ions, improved the surface structure and roughness of the biochar material, and promoted attachment of microorganisms on its surface. Using a polyvinyl alcohol–sodium alginate–iron-modified biochar composite, Pseudomonas aeruginosa bacteria were fixed by boric acid–CaCl2 cross-linking to remove phenanthrene from aqueous solution and soil. The results showed that the iron-modified biochar microorganism spheres could completely degrade 20 mg·L−1 of phenanthrene in solution within 12 h; degradation efficiency of 80 mg·L−1 phenanthrene was 50%. In the soil system, the modified biochar spheres had higher degradation performance compared with P. aeruginosa alone, reaching a removal efficiency of 30% in 6 d. This study provides a strategy for the effective treatment of organic pollutants in harsh environments by coupling the efficient adsorption of green materials with the biodegradability of microorganisms.