The bioleaching of sulphide minerals with emphasis on copper sulphides — A review

Despite the ubiquity of ferrihydrite in natural sediments and its importance as an industrial sorbent, the nanocrystallinity of this iron oxyhydroxide has hampered accurate structure determination by traditional methods that rely on long-range order. We uncovered the atomic arrangement by real-space modeling of the pair distribution function (PDF) derived from direct Fourier transformation of the total x-ray scattering. The PDF for ferrihydrite synthesized with the use of different routes is consistent with a single phase (hexagonal space group P6(3)mc; a = approximately 5.95 angstroms, c = approximately 9.06 angstroms). In its ideal form, this structure contains 20% tetrahedrally and 80% octahedrally coordinated iron and has a basic structural motif closely related to the Baker-Figgis delta-Keggin cluster. Real-space fitting indicates structural relaxation with decreasing particle size and also suggests that second-order effects such as internal strain, stacking faults, and particle shape contribute to the PDFs.

https://science.sciencemag.org/content/sci/316/5832/1726.full.pdf

The Structure of Ferrihydrite, a Nanocrystalline Material

Mossbauer spectra measured by the Opportunity rover revealed four mineralogical components in Meridiani Planum at Eagle crater: jarosite- and hematite-rich outcrop, hematite-rich soil, olivine-bearing basaltic soil, and a pyroxene-bearing basaltic rock (Bounce rock). Spherules, interpreted to be concretions, are hematite-rich and dispersed throughout the outcrop. Hematitic soils both within and outside Eagle crater are dominated by spherules and their fragments. Olivine-bearing basaltic soil is present throughout the region. Bounce rock is probably an impact erratic. Because jarosite is a hydroxide sulfate mineral, its presence at Meridiani Planum is mineralogical evidence for aqueous processes on Mars, probably under acid-sulfate conditions.

https://science.sciencemag.org/content/sci/306/5702/1740.full.pdf

Jarosite and hematite at Meridiani Planum from Opportunity's Mössbauer spectrometer

The kinetics and electrochemical rate-determining step of aqueous pyrite oxidation

Acid sulfate waters are produced mostly by the oxidation of common sulfide minerals such as pyrite, chalcopyrite, pyrrhotite, and marcasite in rocks, soils, sediments, and industrial wastes. This spontaneous process of mineral weathering plays a fundamental role in the supergene alteration of ore deposits, the formation of acid sulfate soils, and the mobilization and release of acidity and metals to surface and ground waters. The purely natural process of “acid rock drainage” is often intensified by human activities related to mining, mineral processing, construction, soil drainage, and dredging. Geochemical reaction rates are accelerated because physical disturbance gives greater exposure of mineral surfaces to air and water, and to microbes that catalyze the reaction process. Large quantities of reactive sulfides are also concentrated and exposed to air as a result of mining and mineral processing. Acid sulfate waters produce a number of fairly insoluble hydroxysulfate and oxyhydroxide minerals that precipitate during oxidation, hydrolysis, and neutralization. The objective of this chapter is to describe the formation, properties, fate, and environmental implications of the nano- to microphase hydroxy-sulfates of Fe and Al that are precipitated from acid sulfate waters. These minerals are commonly of poor crystallinity and difficult to characterize. Much remains to be learned about their occurrence, formation, and properties.

### Mine drainage

The best known examples of acid sulfate waters are those released from mines where coal and metallic sulfide ores have been exploited (Ash et al. 1951, Barton 1978, Nordstrom 1982a, Rose and Cravotta 1998, Nordstrom and Alpers 1999). There may be as many as 500,000 inactive or abandoned mine sites in the United States alone (Lyon et al. 1993). Although most of these pose no immediate water-quality problem, Kleinmann (1989) estimated that about 19,300 km of streams and more than 72,000 ha of lakes and reservoirs have been …

Iron and Aluminum Hydroxysulfates from Acid Sulfate Waters

VII. Synthesis 2569 VIII. Adsorption and Solid Solution 2570 A. General Observations 2570 B. Adsorption of Specific Species 2571 1. Various Cations 2571 2. Various Anions 2572 3. Organic Species 2573 C. Environmental Implications 2573 IX. Transformation of Ferrihydrite 2574 A. Dry Thermal Transformation 2574 B. Aqueous Transformation 2575 C. Effects of Various Ions on the Aqueous Transformation of Ferrihydrite 2576

Occurrence and Constitution of Natural and Synthetic Ferrihydrite, a Widespread Iron Oxyhydroxide

The alunite supergroup consists of more than 40 minerals with the general formula DG 3( T O4)2(OH,H2O)6, wherein D represents cations with a coordination number greater or equal to 9, and G and T represent sites with octahedral and tetrahedral coordination, respectively (Smith et al. 1998). The supergroup is commonly subdivided into various groups, but the simplest primary subdivision is on the basis of the G cations. For all of the minerals in the supergroup, the dominant G cation is trivalent; most of the minerals have G represented by Fe3+ or Al3+, but exceptions are the rare minerals gallobeudantite, in which G is Ga3+, and springcreekite, in which G is V3+ (Table 1⇓). Thus, the primary grouping adopted here is on whether formula Fe3+ exceeds or is subordinate to Al3+. The hierarchical sequence in mineralogy seems to be variable, but here the decreasing sequence is given as supergroup, family, group, and subgroup. Minerals with Fe3+ > Al3+ are referred to as belonging to the jarosite family, and those with A13+ > Fe3+ are allocated to the alunite family.

View this table:

 Table 1. 
Minerals of the alunite supergroup.



Subdivision of the alunite and jarosite families has also been variable; Scott (1987), for example, used seven groups, Novak et al. (1994) used six, Gaines et al. (1997) used four, and Mandarino (1999) used three. The arbitrary decision here is to use three groups, which differ from those of Mandarino (1999) but which, in general, indicate whether sulfate, phosphate, or arsenate predominates in the T O4 tetrahedra. The three groups are the alunite group, in which T O4 is dominated by SO4, the crandallite group, in which (PO4) is …

Jarosites and Their Application in Hydrometallurgy

Synthesis and phase transformations involving scorodite, ferric arsenate and arsenical ferrihydrite: Implications for arsenic mobility

The literature on the ferric ion leaching of chalcopyrite has been surveyed to identify those leaching parameters which are well established and to outline areas requiring additional study New experimental work was undertaken to resolve points still in dispute It seems well established that chalcopyrite dissolution in either ferric chloride or ferric sulfate media is independent of stirring speeds above those necessary to suspend the particles and of acid concentrations above those required to keep iron in solution The rates are faster in the chloride system and the activation energy in that medium is about 42 kJ/mol; the activation energy is about 75 kJ/mol in ferric sulfate solutions It has been confirmed that the rate is directly proportional to the surface area of the chalcopyrite in both chloride and sulfate media Sulfate concentrations, especially FeSO4 concentrations, decrease the leaching rate substantially; furthermore, CuSO4 does not promote leaching in the sulfate system Chloride additions to sulfate solutions accelerate slightly the dissolution rates at elevated temperatures It has been confirmed that leaching in the ferric sulfate system is nearly independent of the concentration of Fe3+, ka[Fe3+]012 In ferric chloride solutions, the ferric concentration dependence is greater and appears to be independent of temperature over the interval 45 to 100 °C

John E. Dutrizac

Papers

Occurrence and Constitution of Natural and Synthetic Ferrihydrite, a Widespread Iron Oxyhydroxide

Jarosites and Their Application in Hydrometallurgy

Synthesis and phase transformations involving scorodite, ferric arsenate and arsenical ferrihydrite: Implications for arsenic mobility

Occurrence and Constitution of Natural and Synthetic Ferrihydrite, a Widespread Iron Oxyhydroxide

The dissolution of chalcopyrite in ferric sulfate and ferric chloride media