Promotion of Para-Chlorophenol Reduction and Extracellular Electron Transfer in an Anaerobic System at the Presence of Iron-Oxides

Abstract

Anaerobic dechlorination of chlorophenols often subjects to their toxicity and recalcitrance, presenting low loading rate and poor degradation efficiency. In this study, in order to accelerate p-chlorophenol (p-CP) reduction and extracellular electron transfer in an anaerobic system, three iron-oxide nanoparticles, namely hematite, magnetite and ferrihydrite, were coupled into an anaerobic system, with the performance and underlying role of iron-oxide nanoparticles elucidated. The reductive dechlorination of p-CP was notably improved in the anaerobic systems coupled by hematite and magnetite, although ferrihydrite did not plays a positive role. Enhanced dechlorination of p-CP in hematite or magnetite coupled anaerobic system was linked to the obvious accumulation of acetate, lower oxidation–reduction potential and pH, which were beneficial for reductive dechlorination. Electron transfer could be enhanced by Fe2+/Fe3+ redox couple on the iron oxides surface formed through dissimilatory iron-reduction. This study demonstrated that the coupling of iron-oxide nanoparticles such as hematite and magnetite could be a promising alternative to the conventional anaerobic reduction process for the removal of CPs from wastewater.

Perspectives on Potential Applications of Nanometal Derivatives in Gaseous Bioenergy Pathways: Mechanisms, Life Cycle, and Toxicity

“…Metal oxides in anaerobic media can be subjected to dissolution via abiotic and biotic reactions. In addition to the impacts on the enzymatic activity, the dissolution of metal oxide to metal ions decreases the redox potential of the system, creating a favorable environment for the anaerobic consortia. , The abiotic dissolution of metal oxides depends mainly on the relative electrochemical stability of the solid metal phase and soluble ions . As displayed in Figure , a stable state of Fe 2 O 3 presents at alkaline condition, whereas the solubility of Fe 3+ increases under an acidic condition (eq ).…”

A designed plasmid‐transition strategy enables rapid construction of robust and versatile synthetic exoelectrogens for environmental applications

“…Exoelectrogens thrive and are distributed ubiquitously in aquatic, sediment, wetland and wastewater habitats (Lovley & Holmes, 2022). They have evolved unique extracellular electron transfer (EET) mechanisms that couple carbon source metabolism with extracellular respiration of a variety of terminal electron acceptors (Shi et al, 2016), including Fe(III) and Mn(IV) oxides (Myers & Nealson, 1988), electrodes (Yang et al, 2015b) and various types of pollutants, such as antibiotics (Yan et al, 2016), chloronitrobenzenes (Jiang et al, 2018), azo dye (Zhao et al, 2019) and toxic heavy metals (e.g., Cr 6+ , Pu 4+ , U 6+ ) (Anderson et al, 2003; Methe et al, 2003; Xie et al, 2017). Such features render exoelectrogenic species important in wastewater treatment and simultaneous energy harvesting (Su et al, 2022), valuable chemical green production (Cheng & Logan, 2007) and environmental remediation (Yamamura et al, 2018).…”

Synthesis of intracellular polyhydroxyalkanoates (PHA) from mixed phenolic substrates in an acclimated consortium and the mechanisms of toxicity

“…One representative of such toxic organics is the phenolic compounds often generated in oil and gas, paint and resin, paper and pulp, and pharmaceutical industries. They are usually of considerable cytotoxicity, some of which are mildly inhibitory while others are directly bactericidal [13]. Their toxic and inhibitory effects can significantly hinder a range of bioactivities including the conversion to cellular storage compounds, thereby impairing their applicability as PHA raw materials.…”