Superb green cycling strategies for microbe-Fe0 neural network-type interaction: Harnessing eight key genes encoding enzymes and mineral transformations to efficiently treat PFOA

Abstract

To address time-consuming and efficiency-limited challenges in conventional zero-valent iron (ZVI, Fe⁰) reduction or biotransformation for perfluorooctanoic acid (PFOA) treatment, two calcium alginate-embedded amendments (biochar-immobilized PFOA-degrading bacteria (CB) and ZVI (CZ)) were developed to construct microbe-Fe⁰ high-rate interaction systems. Interaction mechanisms and key metabolic pathways were systematically explored using metagenomics and a multi-process coupling model for PFOA under microbe-Fe⁰ interaction. Compared to Fe⁰ (0.0076 day^-1) or microbe (0.0172 day^-1) systems, the PFOA removal rate (0.0426 day^-1) increased by 1.5 to 4.6 folds in the batch microbe-Fe⁰ interaction system. Moreover, Pseudomonas accelerated the transformation of Fe⁰ into Fe³⁺, which profoundly impacted PFOA transport and fate. Model results demonstrated microbe-Fe⁰ interaction improved retardation effect for PFOA in columns, with decreased dispersivity a (0.48 to 0.20 cm), increased reaction rate λ (0.15 to 0.22 h^-1), distribution coefficient K_d (0.22 to 0.46 cm³∙g^-1), and fraction f´(52 % to 60 %) of first-order kinetic sorption of PFOA in microbe-Fe⁰ interaction column system. Moreover, intermediates analysis showed that microbe-Fe⁰ interaction diversified PFOA reaction pathways. Three key metabolic pathways (ko00362, ko00626, ko00361), eight functional genes, and corresponding enzymes for PFOA degradation were identified. These findings provide insights into microbe-Fe⁰ "neural network-type" interaction by unveiling biotransformation and mineral transformation mechanisms for efficient PFOA treatment.

Keywords: Functional gene; Metabolic pathway; Microbe-Fe(0); PFOA; Remediation.