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Updated: Oct 27, 2026

A Microfluidic Platform to Investigate Microbial Precipitation of Metal Oxides in Porous Media
Published on: June 12, 2026
Opposite dual functions of sulfate: regulated iron redox cycling and microbial succession in pyrophosphate-mediated
Linji Xu1, Xingzu Wang2, Xinzhu Wang3
1College of Environment and Ecology, Chongqing University, Chongqing, 400044, China.
Abstract:
Sulfur cycling couples Feammox ammonium oxidation and iron redox turnover, yet sulfate's multi-scale regulatory mechanism remains unclear. This work integrated batch experiments, mineral characterization, microbial analysis, molecular dynamics (MD) simulations and density functional theory (DFT) calculations to reveal sulfate's dual opposing effects on ferric pyrophosphate-based Feammox. Low-to-moderate sulfate loading (0.2 g L⁻¹) boosted ammonium removal and reduced nitrite/nitrate accumulation, while high sulfate concentration (0.6 g L⁻¹) severely suppressed Feammox and disrupted nitrogen transformation pathways. Sulfate enriched sulfate-reducing Desulfobacterota and Ruminiclostridium, yet stable Candidatus Kuenenia abundance confirmed microbial succession did not exert a dominant effect. Excess. Excess sulfate fueled sulfide production, forming passivating FeS and Fe₃(PO₄)₂ precipitates and breaking iron redox balance (RFe-turn<1). MD simulations proved moderate sulfate aggregated interfacial NH₄⁺ and lowered system energy to favor Feammox pre-reaction environments, whereas surplus sulfate inhibited reactions via competitive surface adsorption. DFT further verified the thermodynamic feasibility of transient Fe-sulfate intermediates driving coupled with Fe-S redox. This study establishes an integrated physicochemical-microbial mechanism of sulfate-modulated Feammox, offering theoretical support and operational guidance for sulfate-laden ammonium wastewater treatment with Feammox systems.
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