Guide to ReCENT LITERATURE FOCUSED ON

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present day formation of arseniated ferrihydrite or crystalline scorodite. Demopoulos .... longer than chemical synthesis. A mixed culture of thermoacidophillic.
CAMP Project Report-May, 2014

A Guide to Recent Literature Focused on Scorodite for Containment of Arsenic

Dr. L.G. Twidwell Professor Emeritus Metallurgy/Materials Engineering Department Montana Tech of The University of Montana [email protected] 406 560 2263 ResearchGate Linkedin

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A GUIDE TO RECENT LITERATURE FOCUSED ON Scorodite for the Containment of Arsenic INTENT OF REPORT The intent of this series of CAMP reports is to provide current state-of-art guides to recent literature publications that are focused on the removal of metals and oxyanions by precipitation/adsorption processes using iron oxides; and, on the environmental stability of the precipitated/adsorbed solid and sludge products. Hopefully, these “guides” will be useful for not only current state-of-the-art information but also as an introductory text for planning future research directions. For detailed information on specific topics you will likely want to refer to the referenced publications; to facilitate this, we have collected most of the referenced publications as PDFs; and, also, we have included PDFs for many of the publications listed in the Bibliography. The PDFs are included on a DVD or memory key supplied with the printed report. Most of the referenced literature publications presented in this text are hyperlinked to the respective PDF. Control Click on the text reference (dark blue for those linked). However, the linked publications can only be accessed for use by authorized personnel at the Montana Tech of the University of Montana and the Center for Advanced Mineral and Metallurgical Processing (CAMP). BACKGROUND The removal of arsenic from solutions has been investigated for decades and continues to be a topic of intense research studies. The progressing of arsenic removal technologies has been from lime neutralization forming calcium arsenate to the present day formation of arseniated ferrihydrite or crystalline scorodite. Demopoulos (2005) has noted that “scorodite is considered from the stand point of treatment of arsenic-rich and iron-deficient waste solution or solids rather the removal of small amounts of arsenic from acidic processing effluents. For the later, the best treatment typically involves lime neutralization and co-precipitation with excess of ferric iron, at a Fe(III)/As(V) molar ratio >3 or 4.” “Typical arsenicrich waste solutions or solids that can be treated for the production of crystalline scorodite are: acid plant effluents, CuER electrolyte bleed streams, As2O3 flue dusts and arsenic-contaminated soils” (Demopoulos 2005). The neutralization/co-precipitation technology has been selected by USEPA to represent the Best Demonstrated Available Technology (BDAT) for treating arsenic bearing non-solids. The sequestering of arsenic in scorodite is considered to be the best environmentally friendly possible wasteform for stable outdoor storage. There are several technologies that can be used to form scorodite (example of each approach is presented in the following report table):     

Autoclave hydrothermal precipitation of scorodite from acidic solutions (pH ~1, ~150oC) containing Fe(III) and As(V) (Gomez et al. 2011a, many others-see Table) Elevated temperature ambient pressure precipitation from acidic solutions (pH ~1, 90-95oC) containing Fe(III) and As(V) or As (III) (Demopoulos 2008, 2005, many others-see Table) Intermediate temperature ambient pressure precipitation by insitu oxidation of Fe(II) in the presence of As(V) from acidic solutions (pH ~1, ~70oC, 95oC) (Fujita et al. 2012, many others-see Table) Intermediate temperature ambient pressure precipitation by biogenic insitu oxidation of Fe(II) in the presence of As(V) from acidic solutions (pH ~1, ~70oC) (Okibe et al. 2013) Intermediate temperature ambient pressure precipitation by biogenic insitu oxidation of Fe(II) and As(III) from acidic solutions (pH ~1, ~70oC) (Okibe et al. 2014).

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Guide to Recent Literature Focused on Scorodite for Containment of Arsenic, L.G. Twidwell Fe/As Form of Fe Pressur Time Process mole To C pH Comments and As e hrs ratio References are in Descending Order by year

Reference

Method development for analysis of As(III), As(V), and total As using ICP-OES and resin column separation technique (Auto-Pret).

Acidianus brierleyi (DSMZ 1651) microorganisms were demonstrated to oxidize concurrently As(III) and Fe(II). The presence of Fe(II) was needed to facilitate the oxidation of As(III). Results showed complete As(III) oxidation in 6 days exposure. The purpose of the study was to develop an analytical method to provide a complete mass balance on arsenic in the presence of A brierleyi.

Higashidani et al. 2014

Concurrent oxidation of As(III) and Fe(II) resulted in the formation of biogenic scorodite (bioscorodite) in copper refinery solutions

14 days

Acidianus brierleyi microorganisms were evaluated for treating As(III), Fe(II) solutions. The optimal cell growth conditions are: ~70oC, pH 1.5-2.0 (see Okibe et al 2013) which is similar to the conditions to form scorodite under ambient pressure precipitation. The study demonstrated the conditions (microorganism content, yeast addition, and time) needed to immobilize ~1 g As/L as scorodite (~1 µm particle size). The presence of phosphate must be considered.

Okibe et al. 2014

14 days

This study provides the bases for the application of Acidianus brierleyi to the copper refinery solutions described above. The study demonstrated that scorodite can be formed at Fe(II) concentrations