Potassium Jarosite Research Articles

Characterization and alkaline decomposition/cyanidation of beudantite–jarosite materials from Rio Tinto gossan ores

Jarosite-type minerals are the major silver carriers in the gossan ores from Rio Tinto (Spain). Two types of minerals were found: one corresponding to beudantite variable enriched in sulfate; the other is potassium jarosite containing various amounts of arsenate and lead. They are isostructural with cell parameters intermediate between those reported for end members. Silver is present in both jarosites as dilute solid solution (230 ppm Ag in average). The cyanidation of potassium jarosite in saturated Ca(OH) 2 at 70–100°C consists of two step in series: a slow step of alkaline decomposition followed by a fast step of Ag complexation from the decomposition solids. The alkaline decomposition is characterized by the simultaneous removal of sulfate and K ions and the formation of an amorphous hydroxy-arsenate of Fe, Pb and Ca. The kinetics are chemically controlled, with an activation energy of 86.5 kJ mol −1. The nature of the alkaline decomposition of beudantite was similar but extremely slow at ≤100°C.

The behavior of thallium during jarosite precipitation

Jarosite precipitation provides an effective means of eliminating thallium from zinc processing circuits, and a systematic study of the extent and mechanism of thallium removal during the precipitation of ammonium, sodium, and potassium jarosites was carried out. Thallium (as Tl+) substitutes for the “alkali” ion in the jarosite structure. Nearly ideal jarosite solid solutions are formed with potassium, but thallium is preferentially precipitated relative to either ammonium or sodium. Approximately 80 pct of the dissolved thallium precipitates during the formation of ammonium jarosite; the extent of thallium removal is virtually independent of thallium concentrations in the 0 to 3000 mg/L Tl range and of the presence of 75 g/L of dissolved Zn. Although the deportment of thallium is nearly independent of (NH4)2SO4 or Na2SO4 concentrations >0.1 M, the precipitates made from more dilute media are relatively enriched in thallium. Likewise, the precipitates made from dilute ferric ion media are also Tl-rich. Low solution pH values or low temperatures both significantly reduce the amount of jarosite formed, but the precipitates made under these conditions are enriched in thallium. Furthermore, because thallium jarosite is more stable than the ammonium or sodium analogues, the initially formed precipitates are consistently Tl rich. The presence of jarosite seed accelerates the precipitation reaction, but dilutes the thallium content of the product. The results suggest that most of the thallium in a hydrometallurgical zinc circuit could be selectively precipitated in a small amount of jarosite, by carrying out the precipitation reaction for a short time in the absence of seed and from solutions having low alkali concentrations.

The behaviour of thiocyanate and cyanate during jarosite precipitation

The behaviour of thiocyanate and cyanate during the precipitation of potassium jarosite was investigated. Thiocyanate strongly complexes dissolved ferric ion and thereby reduces the amount of jarosite precipitated. The composition of the jarosite, however, is virtually independent of the thiocyanate concentration, and < 0.1 wt% SCN is incorporated in the jarosite structure. Some hydrolysis of the SCN occurs at the 98°C precipitation temperature, and the reaction yields minor amounts of elemental sulphur. The presence of cyanate has little effect on either the amount of jarosite formed or its composition; the jarosite consistently contains < 0.1 wt% CNO. Variations in the pH of the solution at constant concentrations of either thiocyanate or cyanate have little effect on the composition of the jarosite, and negligible amounts of thiocyanate or cyanate are incorporated in the jarosite structure regardless of the pH. Of course, the amount of precipitate decreases as the pH decreases. X-ray diffraction analysis showed all the precipitates to be potassium jarosite, and SEM studies indicated that all the products were composed of ∼ 30 μm cauliflower-like aggregates of tiny jarosite crystals.

Nutrient Effect on the Biological Leaching of a Black-Schist Ore

The purpose of the study was to examine the influence of inorganic N (NH(4), NO(3)) and phosphate on the biological oxidation of a sulfidic black-schist ore which contained pyrrhotite as the main iron sulfide. Iron was initially solubilized as Fe from the ore and subsequently oxidized to Fe in shake flask experiments. Under these experimental conditions, iron dissolution from pyrrhotite was mainly a chemical reaction, with some enhancement by bacteria, whereas the subsequent Fe oxidation was bacterially mediated, with negligible contribution from chemical oxidation. Phosphate amendment did not enhance Fe oxidation. Chemical analysis of leach solutions with no exogenous phosphate revealed that phosphate was solubilized from the black-schist ore. Ammonium amendment (6 mM) enhanced Fe oxidation, whereas the addition of nitrate (6 and 12 mM) had a negative effect. An increase in the temperature from 30 to 35 degrees C slightly enhanced Fe oxidation, but the effect was statistically not significant. The precipitation of potassium jarosite was indicative of Fe oxidation and was absent in nitrate-inhibited cultures because of the lack of Fe oxidation. The black-schist ore also contained phlogopite, which was altered to vermiculite in iron-oxidizing cultures.

Catalytic effects of silver in the microbiological leaching of finely ground chalcopyrite-containing ore materials in shake flasks

The microbiological leaching of copper ores was evaluated with samples that contained chalcopyrite (CuFeS 2), pyrite (FeS 2), pyrrhotite (Fe 1− x S), and sphalerite (ZnS) in varying proportions as the main sulfide minerals. The solubilization of copper from chalcopyrite was slow in contrast to the rapid solubilization of zinc. The addition of up to 30 mg/l silver, either as a sulfate or nitrate salt, enhanced the bacterial leaching of copper from chalcopyrite. The positive catalytic effect was related to the concentration of the silver added. The enhancement of the copper leaching due to the silver addition was negligible in the absence of bacteria. Only trace concentrations of silver were detected in leach solution samples. The leaching of iron and zinc was inhibited by silver addition and a transient period of depressed Eh was typically associated with this phase. The addition of silver also enhanced the bacterial leaching of a purified chalcopyrite sample. Increased solubilization of copper and iron was obtained concurrently with the formation of sulfate. Mass balance studies and stoichiometric calculations indicated elemental sulfur formation and the precipitation of iron and sulfate during the leaching. Potassium jarosite [KFe 3(SO 4) 2(OH) 6] was identified by X-ray diffraction in Fe(III)-containing precipitates.

Sulphate control in chloride leaching processes

The deportment of sulphate during the ferric chloride leaching of a pyritic ZnPbCuAg bulk concentrate has been elucidated, and several sulphate control options have been investigated. Sulphate accumulates in the pregnant leach solution even in the presence of high concentrations of dissolved lead. The addition of > 0.6 M CaCl 2 to the leaching medium precipitates anhydrous CaSO 4, and gives final sulphate concentrations of 1–3 gl −1SO 4. Calcium sulphate contamination of the intermediate PbCl 2 product is a concern, but this problem can be minimized by rapid crystallization of the PbCl 2. Although sulphate can be limited by the precipitation of potassium jarosite, the final SO 4 concentration of the leach liquor is high and all the free acidity must be neutralized prior to jarosite precipitation. Significant contamination of the PbCl 2 product by KPb 2Cl 3 also occurs. Sodium jarosite and ammonium jarosite are not precipitated under the conditions examined. Barium chloride additions effectively control sulphate, and the BaSO 4 precipitation reaction is nearly stoichiometric. Excess BaCl 2, however, results in the precipitation of BaCl 2-H 2O which impedes residue filtration and contaminates the PbCl 2 intermediate product.

Characterization of Jarosite Formed upon Bacterial Oxidation of Ferrous Sulfate in a Packed-Bed Reactor

A packed-bed bioreactor with activated-carbon particles as a carrier matrix material inoculated with Thiobacillus ferrooxidans was operated at a pH of 1.35 to 1.5 to convert ferrous sulfate to ferric sulfate. Despite the low operating pH, trace amounts of precipitates were produced in both the reactor and the oxidized effluent. X-ray diffraction and chemical analyses indicated that the precipitates were well-ordered potassium jarosite. The chemical analyses also revealed a relative deficiency of Fe and an excess of S in the reactor sample compared with the theoretical composition of potassium jarosite.

Utilizing Iron Residues from Zinc Production in the U.S.S.R.

When zinc calcine leach residues are subjected to conventional hydro-metallurgical treatment, iron is removed from the production circuit in the form of jarosite or goethite. A combined hydrometallurgical treatment of zinc calcine and zinc oxide fume leach residues applied at a zinc plant in the U.S.S.R. produces potassium jarosite containing undesirable impurities of 1.5–2.0 wt.% Zn, 0.2–0.3 wt.% Cu, 0.2–0.6 wt.% Pb, 0.005–0.01 wt. % Cd and 27–29 wt. % Fe. After some study, it was found that low-contaminant jarosite can be used in iron-oxide pigments and in cement clinker production. Methods for manufacturing such products have been developed and tested on a pilot-plant scale, and commercial tests are in progress. The investigations carried out for low-contaminantjarosite utilization resulted not only in the development of a wasteless and environmentally acceptable technology for zinc calcine treatment, but made it possible to recover one more valuable component—iron—from zinc raw materials.

The Behaviour of Arsenic During Jarosite Precipitation: Reactions at 150°C and the Mechanism of Arsenic Precipitation

The behaviour of arsenate (As5+) during jarosite precipitation at 150°C has been elucidated as a function of the solution composition and the initial solution pH. Arsenate is preferentially precipitated during jarosite formation, and nearly complete arsenic precipitation occurs from solutions containing > 5 g/l As5+. Arsenic precipitation is retarded at initial solution pHs < 1.0, but is nearly independent of the concentration of a given alkali sulphate, copper sulphate or zinc sulphate. Low ferric sulphate concentrations result in the selective formation of scorodite (FeAsO4·2H2O), but the mass of precipitate is small. The chemical and X-ray diffraction results suggest a low level of AsO4 substitution in jarositetype compounds: ≍ 1.5 wt % AsO4 is structurally incorporated in sodium jarosite or lead jarosite, and up to 4 wt % AsO4 substitution occurs in potassium jarosite. Large amounts of arsenate are present as a separate well crystallized scorodite phase. It is thought that AsO43− substitutes for SO42− in the jarosite structure, with charge neutrality maintained by the conversion of appropriate amounts of OH− to H2O. Substitution of the larger AsO4 anion does not noticeably affect the jarosite cell parameters. Lastly, it is demonstrated that not only do many jarosite-family minerals contain arsenate, but the amounts are consistent with the results obtained in the synthesis experiments.

The Behaviour of Arsenic During Jarosite Precipitation: Reactions at 150°C and the Mechanism of Arsenic Precipitation

The behaviour of arsenate (As5+) during jarosite precipitation at 150°C has been elucidated as a function of the solution composition and the initial solution pH. Arsenate is preferentially precipitated during jarosite formation, and nearly complete arsenic precipitation occurs from solutions containing > 5 g/l As5+. Arsenic precipitation is retarded at initial solution pHs < 1.0, but is nearly independent of the concentration of a given alkali sulphate, copper sulphate or zinc sulphate. Low ferric sulphate concentrations result in the selective formation of scorodite (FeAsO4·2H2O), but the mass of precipitate is small. The chemical and X-ray diffraction results suggest a low level of AsO4 substitution in jarositetype compounds: ≍ 1.5 wt % AsO4 is structurally incorporated in sodium jarosite or lead jarosite, and up to 4 wt % AsO4 substitution occurs in potassium jarosite. Large amounts of arsenate are present as a separate well crystallized scorodite phase. It is thought that AsO43− substitutes for SO42− in the jarosite structure, with charge neutrality maintained by the conversion of appropriate amounts of OH− to H2O. Substitution of the larger AsO4 anion does not noticeably affect the jarosite cell parameters. Lastly, it is demonstrated that not only do many jarosite-family minerals contain arsenate, but the amounts are consistent with the results obtained in the synthesis experiments.

Behaviour of cesium and lithium during the precipitation of jarosite-type compounds

End-member cesium jarosite [CsFe 3(SO 4) 2(OH) 6] and end-member lithium jarosite [LiFe 3(SO 4) 2(OH) 6] do not exist. Cesium-bearing potassium, sodium and rubidium jarosites were synthesized, however, with cesium contents > 2 wt% being noted in potassium jarosite. The cesium content of the jarosites increases with increasing cesium concentration in solution, and the order of cesiumincorporation is potassium jarosite > sodium jarosite > rubidium jarosite. Only trace amounts of lithium are incorporated in jarosite; the maximum obtained was ∼ 0.2 wt% lithium in potassium jarosite. The lithium content increases with increasing lithium concentration in the synthesis solution, but is nearly independent of the potassium concentration or the solution pH. Although some of the lithium may be structurally incorporated in the jarosite, most seems to be physically entrained.

A Mineralogical Study of the Jarosite Phase Formed During the Autoclave Leaching of Zinc Concentrate

The jarosite residues formed during the commercial-scale autoclave leaching of zinc concentrates at Cominco Ltd, Trail, B.C. have been examined chemically and mineralogically. The residues consist predominantly of lead jarosite (< 20μm) together with lesser amounts of elemental sulphur, lead sulphate, silicate minerals and traces of residual sulphides. The lead jarosite contains minor amounts of potassium substituting for lead and zinc replacing trivalent iron as well as traces of silver which also substitutes for Pb. The results suggest that galena is rapidly oxidized to PbSO4 which then reacts with ferric sulphate to form lead jarosite incorporating potassium, zinc and silver. There was no indication of separate hydronium jarosite or potassium jarosite phases. Electron microprobe study of the coarser lead jarosite grains found them to contain silver in small but variable amounts. The average silver concentration and the relative amounts of the jarosite phase formed suggest that the lead jarosite is the dominant Ag carrier; no other silverbearing phases were detected. X-ray diffraction studies on cleaned and cyclosized fractions showed only single lead jarosite phases whose cell parameters are consistent with published values. Chemical synthesis of lead jarosite in the presence of dissolved silver or potassium has confirmed the selective incorporation of these elements into the jarosite phase. Lead jarosite formed in the presence of low concentrations of silver (<1000 ppm Ag) collects nearly all of the precious metal. Résumé On a fait l'analyse chimique et minéralogique des résidus de jarosite formés lors de la lixiviation dans un autoclave à l'échelle commerciale des concentrés de zinc à la Cominco Ltd, à Trail en Colombie Britannique. Les résidus sont composés principalement de jarosite de plomb (<20μm) et de soufre élémentaire en moins grande quantité, de sulfate de plomb, et minéraux de silicate et de traces de sulfures résiduels. La jarosite de plomb contient du potassium en faible quantité qui remplace le plomb et le zinc qui, à son tour, remplace le fer trivalent de même que les traces d'argent, qui lui aussi remplace le plomb. Les résultats mènent à croire que la galène s'oxyde en PbSO4 qui, à son tour, réagit avec les sulfates ferriques pour former de la jarosite de plomb comprenant du potassium, du zinc et de l'argent. Il n'y avait pas d'indice de la présence de jarosite d'hydronium séparé ou de phases de jarosite de potassium. On a effectué, à l'aide d'une microsonde électronique, une étude des grains les plus grossiers de jarosite de plomb qui a révélé la présence d'argent en petite quantité variable. La concentration moyenne d'argent et la quantité relative de phases de jarosite formées suggerent que lajarosite de plomb est le principal composé porteur de Ag; on a relevé aucune autre phase où l'argent était présent. Les études par diffraction de rayons-X portant sur des fractions nettoyées et passées au cyclone n'ont indiqué qu'une seule phase de jarosite de plomb dont les paramètres des cellules sont en conformité aux valeurs publiées. La synthèse chimique de la jarosite de plomb effectuée en présence d'argent ou de potassium dissous a confirmé l'incorporation sélective de ces éléments dans la phase de jarosite. La jarosite de plomb formée en présence d'argent en faible concentration (<1000 ppm Ag) a recueilli presque tout le métal précieux.

Factors affecting alkali jarosite precipitation

Several factors affecting the precipitation of the alkali jarosites (sodium jarosite, potassium jarosite, rubidium jarosite, and ammonium jarosite) have been studied systematically using sodium jarosite as the model. The pH of the reacting solution exercises a major influence on the amount of jarosite formed, but has little effect on the composition of the washed product. Higher temperatures significantly increase the yield and slightly raise the alkali content of the jarosites. The yield and alkali content both increase greatly with the alkali concentration to about twice the stoichiometric requirement but, thereafter, remain nearly constant. At 97 °C, the amount of product increases with longer retention times to about 15 hours, but more prolonged reaction times are without significant effect on the amount or composition of the jarosite. Factors such as the presence of seed or ionic strength have little effect on the yield or jarosite composition. The amount of precipitate augments directly as the iron concentration of the solution increases, but the product composition is nearly independent of this variable. A significant degree of agitation is necessary to suspend the product and to prevent the jarosite from coating the apparatus with correspondingly small yields. Once the product is adequately suspended, however, further agitation is without significant effect. The partitioning of alkali ions during jarosite precipitation was ascertained for K:Na, Na:NH4, K:NH4, and K:Rb. Potassium jarosite is the most stable of the alkali jarosites and the stability falls systematically for lighter or heavier congeners; ammonium jarosite is slightly more stable than the sodium analogue. Complete solid solubility among the various alkali jarosite-type compounds was established.

高マグネシア酸化ニッケル鉱の還元アンモニア浸出に及ぼすジャロサイト添加の影響

In order to investigate the reducibility of Ouinne ore (from New Caleuonia) known as nickel oxide ore containing a significant amount of magnesia, reduction roasting and ammonia leaching have been conducted for the ore. Moreover, trials of improving the reducibility have been done by means of adding jarosite to the ore. Some of results obtained are as follows.1) Leaching rates of Ni and Co in ammonia leaching were improved by heating reduction (simultaneous reduction with heating) as compared with preheat reduction (reduction after preparatory heating). When the ore was roasted by heating reduction in H2 (50%)-H2O mixed gas atmosphere at 973 K, leaching rates of Ni and Co were about 65% and 55% respectively.2) When the ore was roasted with a small amount of ferric sulfate or potassium jarosite in the reducing atmosphere, thel eaching rate of Ni improved remarkably in the ammonia leaching. These additives seem to act as sulfidation agent on amorphous oxide temporarily and to prevent crystallization to forsterite of difficult reducibility.3) When the ore was roasted with about 1O% potassium jarosite in H2 (99.9%) atmosphere by heating reduction at temperature between 873 and 973 K for 40-50 minutes, leaching rates of Ni and Co were 85% and 65% or more respectively. These results are also interesting from the point of utilization of jarosite.

Jarosite法における鉄の沈殿反応速度

Measurements of elimination rate of iron have been carried out by addition of K2 SO4, Na2SO4, or (NH4) 2SO4 to the leaching solution of zinc ferrite residue producted in hydrometallurgical zinc process.A small amount of precipitation was producted in the leaching solution without any addition of alkali sulfate only by the treatment of pH conditioning and heating. This precipitation was found to be amorphous S-Fe0.OH, and filtration property was poor.The elimination of iron was improved with formation of jarosite by addition of alkali sulfate. The elimination rate of iron increased with elevating temperature. Potassium jarosite have the best effect upon the elimination of iron among the three kinds of jarosite. Good crystallinity of each jarosite was observed with scanning electron microscope. Good filtration property of jarosite seems to be due to the good crystallinity.The precipitation reaction of iron in jarosite method was indicated to follow the following rate equation of 2 order reaction._??_k2; rate constant, t; time, a; Fe2 (SO4) 3 concentration, b; M2 SO4 concentration, x; formation amount of jarosite. Activation energy of the reaction for each jarosite was calculated as follows, Potassium jarosite; 5.43 kcal/mol 22.73 kJ/mop Sodium jarosite; 8.394 kcal/mol 34.96 kJ/mop Ammonium jarosite; 16.675 kcal/mol (69.81 kJ/mol)From the aspect of the kinetics, addition of K2SO4 is favorable to the elimination reaction of iron.

Selenate analogues of jarosite-type compounds

Selenate analogues of sodium jarosite and potassium jarosite have been produced by precipitation from aqueous solution; it is concluded that selenate analogues probably exist for the nine known jarosite-type compounds. The selenium compounds possess the ( R 3 ̄ m ) structure of their jarosite analogues, although the unit cell dimensions are somewhat larger. During jarosite formation, sulphate and selenate are precipitated in approximately the same ratio as they are present in solution; also, the unit cell parameters of the mixed sulphate—selenate compounds increase linearly with increasing selenium concentration. The thermal decomposition behaviour of the selenate analogues is generally similar to that of sodium or potassium jarosite. Initially, water is evolved and subsequently selenium oxides are emitted. The selenium oxides are, however, evolved at a lower temperature (400–450°C) than for their sulphur counterparts, and the two weight-loss reactions tend to overlap slightly for the selenate analogues.

Potassium Jarosite for fertilizer

Abstract Japan has scarcely any potassic resource in her country. Therefore, the shortage was severe in the second world war. In this time I had investigated the fertilizer utilization of many potassic minerals, such as liparite, alunite, glauconite and vermiculite in this country. The potassium jarosite was discovered for the first time at Gumma limonite mine by Katayama and Saito in 1947n. Since then, the many deposites were found out at such places as Suwa Mine in Nagano prefecture, Mitsui-Aso Mine in Kumamoto prefecture and several mines in the Hokkaido district.