Preliminary Assessment of Ferrate Treatment of Metals in Acid Mine Drainage

Abstract

We report a preliminary assessment of ferrate [Fe(VI)] for the treatment of acid mine drainage (AMD), focused on precipitation of metals (i.e., iron [Fe] and manganese [Mn]) and subsequent removal. Two dosing approaches were studied to simulate the two commercially viable forms of Fe(VI) production: Fe(VI) only, and Fe(VI) with sodium hydroxide (NaOH). Subsequent metal speciation was assessed via filter fractionation. When only Fe(VI) was added, the pH remained <3.6, and the precipitation of Mn and Fe was <30 and <70%, respectively, at the highest, stoichiometrically excessive Fe(VI) dose. When NaOH and Fe(VI) were added simultaneously, precipitation of Mn was much more complete, at doses near the predicted oxidation stoichiometric requirement. The optimal dosage of Fe(VI) for Mn treatment was 25 μM. The formation of Mn(VII) was noted at Fe(VI) dosages above the stoichiometric requirement, which would be problematic in full‐scale AMD treatment systems. Precipitation of Fe was >99% when only NaOH was added, indicating that oxidation by Fe(VI) did not play a significant role when added. The Fe(III) and Al(III) particles were relatively large, suggesting probable success in subsequent removal through sedimentation. Resultant Mn‐oxide particles were relatively small, indicating that additional particle destabilization may be required to meet Mn effluent goals. Ferrate seems viable for the treatment of AMD, especially when sourced through onsite generation due to the coexistence of NaOH in the product stream. More research on the use of Fe(VI) for AMD treatment is required to answer extant questions. Core Ideas Ferrate is likely a viable option for acid mine drainage treatment. Oxidation of manganese with ferrate and NaOH approached stoichiometric prediction. Resultant particles may challenge downstream clarification.

Reactive High-Valent Iron Intermediates in Enhancing Treatment of Water by Ferrate

“…These iron species are commonly called ferrates, and their potentials in energy materials, sustainable organic synthesis, and contaminant treatment processes have been shown. In the last two decades, many reviews regarding the synthesis and properties of Fe VI O 4 2– have been published. − Fe VI O 4 2– possesses multimodal properties to induce simultaneous coagulation, disinfection, and oxidation in water treatment. − ,− Fe VI O 4 2– can be reduced to iron­(III) oxides/hydroxides, which have been exploited as coagulants for the removal of phosphate, metals (e.g., copper and cadmium), metalloids (e.g., arsenic), and radionuclides (e.g., thallium). − The generated core–shell structures of γ-Fe 2 O 3 and γ-FeOOH from Fe VI O 4 2– , identified by the unique combination of in-field low-temperature Mössbauer spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), were shown to capture metals directly from water.…”

Effective Desalination of Acid Mine Drainage Using an Advanced Oxidation Process: Sodium Ferrate (VI) Salt

“…To the best of our knowledge, there has not been a direct examination of the effectiveness of FeO 4 2− ions for the treatment of AMD. Most prior and preliminary works have focused on ferrate applications in wastewater [18][19][20][21], drinking water [4,22,23], oxidation of mine tailing and preventing acid drainage from uranium mill tailings [24], preliminary studies of ferrate treatment of metals in AMD [25], and TOC removal of surface water using ferrate (VI) [26]. However, this study aimed at conducting a preliminary treatment of synthetic AMD, using ferrate (VI) salt prepared through a wet oxidation method, assessment of metal concentrations in real AMD samples and their removal using sodium ferrate (VI) (Na 2 FeO 4 ) without using energy in a single mixing and dosing unit.…”

Mine drainage: Remediation technology and resource recovery

“…A preliminary study was conducted using ferrate [Fe(VI)] for AMD treatment using two commercial forms of Fe(VI) only and Fe(VI) with NaOH, focusing on Fe and Mn precipitation and As removal (Goodwill, LaBar, Slovikosky, & Strosnider, 2019). The investigators found ferrate to be a viable option for AMD treatment and recommended additional studies to better develop this approach.…”