Innovative strategy for dechlorination of halogenated organic Pollutants: Microbial-Derived formate production and Immobilized-PdNP biosynthesis

Abstract

Halogenated organic pollutants (HOPs) are accumulating in the environment, posing significant ecological risks. Microbial-driven palladium nanoparticles (PdNPs) facilitate efficient reductive hydrodehalogenation, offering a promising approach for HOPs remediation. To address the limitations associated with hydrogen donor addition and catalyst detachment, this study proposed a proof-of-concept strategy for developing a novel two-stage dehalogenation reactor. We initially constructed genetically engineered Shewanella oneidensis MR-1 to enhance the production and accumulation of formate as the hydrogen donor. Subsequently, encapsulated PdNPs was biosynthesized within alginate beads for efficient immobilization. Finally, a two-stage reactor was constructed for dechlorination of 2,4,6-trichlorophenol (2,4,6-TCP). In the first-stage reactor, the immobilized engineered strain accumulated 2.04 mM formate, providing sufficient hydrogen donors. In the second-stage reactor, 40 μM 2,4,6-TCP was completely dechlorinated within 10 h. Reactor performance was optimized through pH, lactate concentration, and initial pollutant load. Degradation product analysis revealed that dechlorination of 2,4,6-TCP was occurred via a one-electron transfer reaction, with the chlorinated intermediates being progressively hydrodechlorinated until the final product phenol. Furthermore, this constructed reactor exhibited high dechlorination efficiency for 2,4,6-TCP in real water samples and showed remediation potential for other HOPs. This study provides a promising strategy for the effective management of halogenated wastewater pollution.