Potassium jarosite

In this case study, the selected phases are pyrite, amorphous FeS, calcite (present in limestones in the roof strata Fig. 5), dolomite (possibly also present in the limestones), siderite (which occurs as nodules in roof-strata mudstones), ankerite (present on coal cleats in the Shilbottle Seam), melanterite and potassium-jarosite (representing the hydroxysulphate minerals see Table 3), amorphous ferric hydroxide (i.e., the ochre commonly observed in these workings, forming by precipitation from ferruginous mine waters), and gypsum (a mineral known to precipitate subaqueously from mine waters with SO4 contents in excess of about 2500 mg/L at ambient groundwater temperatures in this region, and with which most of the mine waters in the district are known to be in equilibrium). In addition, sorption reactions were included in some of the simulations, to contribute to the mole transfer balances for Ca, Na, and Fe. 

The residue from any hydrometallurgical process would be similar. Clearly, if iron was not a part of the starting material some would usually be added to remove the sulphate either as sodium or potassium jarosite and there would be less ferric hydroxide and a greater proportion of sulphur. 

The arsenic and iron in solution did not reflect the full extent to which the arsenopyrite had been oxidized. Acidiflcation of the culture medium in each flask with 1 ml of concentrated HCl at the end of the experiment increased the arsenic concentration in solution 1.6-fold and the iron concentration 4.4-fold in uninoculated flasks and 1.6- and 7.2-fold, respectively, in inoculated flasks. The increase in dissolved As and Fe on acidification suggests that a portion of the mobilized iron and arsenic was precipitated as iron arsenate and arsenite in inoculated as well as uninoculated flasks. The weight ratios of Fe/As were always higher over 21 days in uninoculated flasks than in inoculated flasks, and in both types of flasks dropped in the first few days of incubation and then increased again. Precipitation of ferric arsenate (scorodite) as well as potassium jarosite [KFcs (804)2(011)6] in bacterial arsenical pyrite oxidation was reported by Carlson et al.(35). 

Schwertmannite is metastable with respect to goethite, except at very low pH (ca. < 3) and in the presence of potassium when jarosite is stable. Schwertmannite, therefore, transforms spontaneously to goethite via solution at 25 °C... 

If substantial potassium and sulfate are present under strongly oxidizing and pH 2-3.5 conditions, As(V) may coprecipitate with jarosite (KFe3(S04)2(0H)6) (Savage et al., 2000, 1240). 

Abundant yellow or white salt crusts are present on waste rock and at the surface of the soil. The crusts comprise alum-like sulfate minerals containing variable amounts of sodium, potassium, iron and aluminium, such as the mineral jarosite. They are often very soluble in water, releasing acid and precipitating ferric hydroxides. 

Brown, J. B. A chemical study of some synthetic potassium-hydronium jarosites. Amer. Mineralog. 10, 696-703 (1970). 

The usual jarosites formed in these situations are hydronium, potassium or ammonium forms in which A is hydrogen, potassium or ammonium ion. In leaching situations, jarosite formation can strip out essential microbial nutrients such as potassium and ammonium ions (Duncan and Walden, 1972 L.A.V. Sulligoi, 1972, personal communication). 

Figure 1. Activity diagram of jarosite-alunite-potassium feldspar-gibbsite-goethite system at 1 bar and 298 K. Modified from Bladh (18). Tailings pore water from Grants Mineral Belt, New Mexico and Maybell, Colorado are denoted by O and, respectively. Median ground water composition (19) is represented by. ...

Development of the Jarosite process in the zinc industry in the 1960s led to an understanding that iron could be precipitated from nickel laterite atmospheric leach solutions, at moderate acid levels, by the addition of an alkali such as potassium, sodium, or ammonia, whilst maintaining a temperature in excess of 90°C [4]. 

In addition to the hematite precipitation - acid regeneration chemistry, sodium and potassium in seawater react with aluminum in solution to form alunite, resulting in low net extraction. Alunite precipitation also regenerates acid, helping to minimize acid consumption, analogous to jarosite precipitation in atmospheric leaching. Sodium alunite precipitation, as shown in equation 9, is an analogue of jarosite precipitation in equation 3. 

Aluminum to sulfiir ratios in residues point to iron co-precipitation, such that an alunite-jarosite compound is formed, typically about two-thirds alunite and one-third jarosite. The sodium plus potassium to sulfur ratios indicate that 10 to 20% of the alunite-jarosite is in the hydronium form. Kyle [27] gives a useful summary of these phenomena while Johnson and co-workers [15, 16] have carried out detailed studies into the effects of alkali addition and leach liquor salinity on PAL. Some typical assays are shown in Table 2 and Table 3. 

The potassium in jarosite may be replaced by sodium, producing natrojarosite (. v.) from which it is indistinguishable optically. Jarosite is also closely related in chemistry to hydronium-jarosite (q.v.), also known as carphosiderite, which has the chemical formula (H20)Fe3(S04)2 (0H5)H20 (Moss, 1957). The particle morphology of hydronium-jarosite and jarosite are so similar that they may be confused if optical mineralogy is used alone for identification. 

Fairen et ah, 2009 [124] conclude from data from the Mars Exploration Rover (Guseev Crater, impact occurred 2 Gyr BP) that minor amounts of shallow acidic liquid water have been present on the surface of Mars at local scales during the Amazonian Period. They investigated jarosite deposits. Jarosite is a basic hydrous sulfate of potassium and iron with a chemical formula of KFe3 (OH)6(804)2. 

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