Transfer, capture, and conversion of low concentration CO2 in algae microbial fuel cells by algae bacteria symbiosis and cation intervention

Abstract

Algae microbial fuel cells (AMFCs) can be served as the distributed devices for CO₂ sequestration. In this study, effects of saline cations and algae-bacteria synergy on CO₂ transfer, capture, and conversion in AMFCs were quantified. Molecular dynamics (MD) simulations were used to compute diffusion coefficients and probe CO₂/HCO₃^- interactions with algal cell membranes. Experiments based on bench-scale AMFCs focused on CO₂ removal efficiency, dissolved inorganic carbon (DIC), biomass, electrochemical performance, and microbial community tests. MD simulations show that replacing Na⁺ with K⁺ increased diffusion coefficients of CO₂ and ${HCO}_3^{-}$ by 74 % and 70 %, respectively. SEM images confirmed MD results that K⁺ induced more folds and pits on algal plasma membranes, prolonging local CO₂/${HCO}_3^{-}$ residence. DIC and biomass experiments demonstrated that algae-bacteria synergy achieved higher CO₂ capture and conversion capacity by tuning dissolved O₂ and pH. 16S rRNA analysis indicated that algae and bioelectricity reshaped bacterial flora by selecting and enriching suitable species. Moreover, bacteria acted as CO₂ enrichment agents for algae by consuming the needless dissolve organic carbon. In brief, K⁺ improved mass transfer and absorption of CO₂/${HCO}_3^{-}$. Algae-bacteria symbiosis and bioelectronic stimulation boosted CO₂ capture and conversion.