Electrochemical Generation of Green Rust using Electrocoagulation

Abstract

Green rusts are unstable compounds containing a mixture of ferrous and ferric hydroxides that belong to a family of minerals known as layered double hydroxides (LDH). They can be represented with the general formula [FeII(6-x) FeIIIx (OH)12] x+[Ax/n-*yH2O] x-, where A is an n-valent anion mainly Cl-, CO3-2 and SO4-2, and in which either the bivalent or the trivalent iron can be replaced for other trivalent or bivalent metal ions. Green rust was first identified and studied as a corrosion product later it was identified in soils and related to interactions between microbes and metals in soils. Green rusts have been shown to be highly reactive compounds that are useful in the reduction of organic compounds such as methachlor, of inorganic elements such as Chromium, Selenium and Uranium; Arsenic removal, and in the treatment of Acid mine drainage (AMD). Green rust has been synthesized combining Fe(II) and Fe(III), by air oxidation of FeCl2 and other methods. In this paper, the electrochemical generation of green rust, its characterization by X-ray Diffraction (XRD), and implications to electrocoagulation will be discussed

Electrochemical Reactions for Electrocoagulation Using Iron Electrodes

“…It has also been employed in removing anions such as CN -, PO 4 3-, SO 4 2-, NO 3 -, F -, and Cl -, nonmetals such as P, organic compounds such as total petroleum hydrocarbons (TPH), toluene, benzene and xylenes (TBX), methyl tert-butyl ether (MTBE), chemical oxygen demand (COD), biological oxygen demand (BOD), suspended solids, clay minerals, organic dyes, oil, and greases from a variety of industrial effluents. 1,2,[5][6][7][8][9] Comments about the EC Mechanisms. EC can be considered as an accelerated corrosion process.…”

Removal of Soluble Phosphorus from Surface Water Using Iron (Fe–Fe) and Aluminum (Al–Al) Electrodes

“…When Faraday’s constant (9.64870 × 10 4 C mol –1 ) is taken into account, a molar flow of electrons per ampere applied can be estimated. Thus, a constant current ensured that the rate of metal dissolution did not fluctuate, as demonstrated by half-cell reactions (reactions and ). ,, The setup was therefore analogous to a metering pump dosing coagulant at a constant flow.…”

“…Thus, a constant current ensured that the rate of metal dissolution did not fluctuate, as demonstrated by half-cell reactions (reactions i and ii). 20,25,26 The setup was therefore analogous to a metering pump dosing coagulant at a constant flow.…”

Systematic study on sulfate removal from mining waters by electrocoagulation

“…In case of iron electrodes, better removal at higher currents is likely because of the more intensive release of iron ions from the anode surface, resulting in the formation of greater amount of insoluble iron precipitates. Among the possible precipitates with the presence of sulfate in electrolyte are Fe3O4, αFeO(OH), γFeO(OH), FeSO4(OH) and positively charged iron hydroxides [31,40,41]. Thus, higher removal may occur due to the more efficient enmeshment of sulfate in iron oxide and hydroxide and possible charge neutralisation by the excess amount of positively charged iron ions.…”