Electrons can be transferred from microorganisms to multivalent metal ions that are associated with minerals and vice versa. As the microbial cell envelope is neither physically permeable to minerals nor electrically conductive, microorganisms have evolved strategies to exchange electrons with extracellular minerals. In this Review, we discuss the molecular mechanisms that underlie the ability of microorganisms to exchange electrons, such as c-type cytochromes and microbial nanowires, with extracellular minerals and with microorganisms of the same or different species. Microorganisms that have extracellular electron transfer capability can be used for biotechnological applications, including bioremediation, biomining and the production of biofuels and nanomaterials.

Extracellular electron transfer mechanisms between microorganisms and minerals

https://www.eng.uwo.ca/grc/pdfs/groundwater_remediation/Nanoscale.pdf

Nanoscale zero valent iron and bimetallic particles for contaminated site remediation

The limitations of applying zero-valent iron technology in contaminants sequestration and the corresponding countermeasures: the development in zero-valent iron technology in the last two decades (1994-2014).

A combination of new and previously reported data on the kinetics of dehalogenation by zero-valent iron (Fe0) has been subjected to an analysis of factors effecting contaminant degradation rates. First-order rate constants (kobs) from both batch and column studies vary widely and without meaningful correlation. However, normalization of these data to iron surface area concentration yields a specific rate constant (kSA) that varies by only 1 order of magnitude for individual halocarbons. Correlation analysis using kSA reveals that dechlorination is generally more rapid at saturated carbon centers than unsaturated carbons and that high degrees of halogenation favor rapid reduction. However, new data and additional analysis will be necessary to obtain reliable quantitative structure−activity relationships. Further generalization of our kinetic model has been obtained by accounting for the concentration and saturation of reactive surface sites, but kSA is still the most appropriate starting point for design c...

Kinetics of Halogenated Organic Compound Degradation by Iron Metal

The kinetics of nitrate, nitrite, and Cr(VI) reduction by three types of iron metal (Fe0) were studied in batch reactors for a range of Fe0 surface area concentrations and solution pH values (5.5−9.0). At pH 7.0, there was only a modest difference (2−4×) in first-order rate coefficients (kobs) for each contaminant among the three Fe0 types investigated (Fisher, Peerless, and Connelly). The kobs values at pH 7.0 for both nitrite and Cr(VI) reduction were first-order with respect to Fe0 surface area concentration, and average surface area normalized rate coefficients (kSA) of 9.0 × 10-3 and 2.2 × 10-1 L m-2 h-1 were determined for nitrite and Cr(VI), respectively. Unlike nitrite and Cr(VI), Fe0 surface area concentration had little effect on rates of nitrate reduction (with the exception of Connelly Fe0, which reduced nitrate at slower rates at higher Fe0 surface areas). The rates of nitrate, nitrite, and Cr(VI) reduction by Fisher Fe0 decreased with increasing pH with apparent reaction orders of 0.49 ± 0.0...

Kinetics of nitrate, nitrite, and Cr(VI) reduction by iron metal.

This study investigated the kinetics and reaction mechanisms associated with advanced oxidation of 2,4‐dinitroanisole (DNAN) with light emitting diodes (LEDs) in the UV/H2O2 process. The pseudo first‐order reaction rate constants for DNAN oxidation depended on the H2O2/DNAN molar ratio and were between 0.017 and 0.026 min−1. Hydroxyl radical scavenging was strongly implicated by the experimental results. High mass spectrophotometric chromatograms showed the presence of several by‐products, including three with ecotoxicity that is greater than that of DNAN. Transformation pathways were analysed using Density Functional Theory (DFT), which helped to predict the presence of experimentally detected DNAN by‐products by considering Mulliken charges. This study is the first to elucidate DNAN transformation mechanisms using both experimental studies and computational chemistry.

Abinash Agrawal

Papers

2,4‐dinitroanisole transformation during advanced oxidation with ultraviolet light emitting diodes and hydrogen peroxide