Factors affecting the Faradaic efficiency of Fe(0) electrocoagulation

C.M. van Genuchten, K.N. Dalby, M. Ceccato, S.L.S. Stipp, K. Dideriksen

Publikation: Bidrag til tidsskriftArtikelForskningpeer review

27 Citationer (Scopus)

Abstrakt

Electrocoagulation (EC) using Fe(0) electrodes is a low cost water treatment technology that relies on efficient production of Fe(II) from the electrolytic dissolution of Fe(0) electrodes (i.e. a high Faradaic efficiency). However, the (electro)chemical factors that favor Fe(0) oxidation rather than O2 evolution during Fe(0) EC have not been identified. In this study, we combined electrochemical methods, electron microscopy and Fe measurements to systematically examine the interdependent effects of current density (i), anodic interface potential (EA) and solution chemistry on the Faradaic efficiency. We found that Fe(0) oxidation was favored (Faradaic efficiency >0.85) in chloride and bromide solutions at all i, whereas carbonate, phosphate, citrate, and nitrate solutions lead to Faradaic efficiencies <0.1. The anodic reaction (i.e. Fe(0) oxidation or O2 evolution) only depended on i in the sulfate and formate solutions. Experiments in binary-anion solutions revealed that molar ratios of [HCO3-]/[Cl-] near 100 and [NO3-]/[Cl-] near 20 separated the electrochemical domains of Fe(0) oxidation and O2 evolution in the EC system. These molar ratios were supported by experiments in synthetic groundwater solutions. We also found that the EA vs i curves for solutions with poor Faradaic efficiency overlapped but were situated 2-4 V vs Ag/AgCl higher than those of solutions with high Faradaic efficiency. Therefore, the position of the EA vs i curve, rather than the EA alone, can be used to determine unambiguously the reaction occurring on the Fe(0) anode during EC treatment.Graphical abstract

OriginalsprogEngelsk
Sider (fra-til)4958-4968
Antal sider11
TidsskriftJournal of Environmental Chemical Engineering
Vol/bind5
Udgave nummer5
DOI
StatusUdgivet - okt. 2017
Udgivet eksterntJa

Programområde

  • Programområde 2: Vandressourcer

Fingeraftryk

Dyk ned i forskningsemnerne om 'Factors affecting the Faradaic efficiency of Fe(0) electrocoagulation'. Sammen danner de et unikt fingeraftryk.

Citationsformater