Manganese hydroxides, solubility

If the Mn/(Mn+Co) ratio is not too high in the cobalt bleed from the main Cu hydrometallurgical circuit, it is possible to have a fairly good selective cobalt precipitation as hydroxide or basic sulphate after acid neutralisation, iron and copper removal [16]. This is due to the difference of solubility products of cobalt and manganese hydroxides with pS values for Co, and Mn hydroxides of respectively 15.4, and 12.7 (pS = -log [solubility product]). The cobalt precipitation will be done at a pH around 8.2, with close to 98% cobalt precipitation and 5-20% manganese co-precipitation. An even better selectivity can be reached by doing the precipitation in two steps counter-currently. This is probably, in most cases, the easiest and cheapest way to remove Mn from Co solutions. 

The reduced mobility of radium in comparison with uranium is explained by the solubility difference between the two elements, which occur in nature as sulphates and carbonates at 18°C radium sulphate = 1.410" g/1 uranyl sulphate = 205 g/1 radium carbonate is insoluble and uranyl carbonate = 60g/l. With the acidity and alkalinity of water, however, radium solubility changes. The radium content of water also depends on the salt concentration of certain elements—mainly alkaline chloride (radium replaces sodium). Radium precipitates with complexes of barium (S04Ba) and with calcium carbonates (travertine). Radium is also fixed by clay, organic matter, iron and manganese hydroxides. 

Kovalenko, P.N. (1956) The utilisation of a polarographic cell for the determination of the pH at the conunencement of the precipitation of manganese hydroxide and its solubility product. Russ. J. Inorg. Chem., 1, 22-27 (English translation). 

Rubidium metal alloys with the other alkaU metals, the alkaline-earth metals, antimony, bismuth, gold, and mercury. Rubidium forms double haUde salts with antimony, bismuth, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, thorium, and 2iac. These complexes are generally water iasoluble and not hygroscopic. The soluble mbidium compounds are acetate, bromide, carbonate, chloride, chromate, fluoride, formate, hydroxide, iodide. 

In addition to effects on the concentration of anions, the redox potential can affect the oxidation state and solubility of the metal ion directly. The most important examples of this are the dissolution of iron and manganese under reducing conditions. The oxidized forms of these elements (Fe(III) and Mn(IV)) form very insoluble oxides and hydroxides, while the reduced forms (Fe(II) and Mn(II)) are orders of magnitude more soluble (in the absence of S( — II)). The oxidation or reduction of the metals, which can occur fairly rapidly at oxic-anoxic interfaces, has an important "domino" effect on the distribution of many other metals in the system due to the importance of iron and manganese oxides in adsorption reactions. In an interesting example of this, it has been suggested that arsenate accumulates in the upper, oxidized layers of some sediments by diffusion of As(III), Fe(II), and Mn(II) from the deeper, reduced zones. In the aerobic zone, the cations are oxidized by oxygen, and precipitate. The solids can then oxidize, as As(III) to As(V), which is subsequently immobilized by sorption onto other Fe or Mn oxyhydroxide particles (Takamatsu et al, 1985). 

C04-0024. Determine whether the following salts are soluble or insoluble (a) sodium acetate (b) AgN03 (c) barium hydroxide (d) CaO (e) lead(II) sulfate (f) ZnCl2 and (g) manganese(II) sulfide. 

The reductase in Geobacter sulfurreducens is located in the outer membrane and a soluble Fe(III) reductase has been characterized from cells grown anaerobically with acetate as electron donor and Fe(III) citrate or fumarate as electron acceptor (Kaufmann and Lovley 2001). The enzyme contained Fe, acid-labile S, and FAD. An extracellular c-type cytochrome is distributed in the membranes, the periplasm, and the medium, and functions as a reductase for electron transfer to insoluble iron hydroxides, sulfur, or manganese dioxide (Seeliger et al. 1998). 

Manganese in soil has many characteristics that are similar to iron for instance, it exists in multiple oxidation states Mn2+, Mn3+, and Mn4+. Although manganese can exist in the laboratory in other oxidations states, from -3 to +7, the +2 to +4 species are the ones commonly found in soil. Manganese forms various oxide and hydroxide species and chelates with many soil components. Its low oxidation state (i.e., Mn2+) is more soluble and more available than its high oxidation state (i.e., Mn4+). 

MANDELONITRILE LYASE MANDELONITRILE LYASE Manganese(ll) carbonate (MnCOj), SOLUBILITY RRODUCT Manganese(ll) hydroxide (Mn(OH)2), SOLUBILITY RRODUCT Manganese ion,... 

The Mn3+/Mn2+ couple is ostensibly pH independent, but we must bear in mind that manganese(III), in particular, will hydrolyze unless the acidity is very high, and both Mn(OH)3 and Mn(OH)2 will come out of solution in alkaline media. Small degrees of hydrolysis in solution have little impact on E°, but precipitation of hydroxides (and all metal hydroxides except those of the alkali metals and Ca, Sr, Ba, and Ra are poorly soluble in water) affects E° profoundly. Thus, in alkaline media, the electrode potentials (often called Eh by geologists, wherever [H+] is not the standard value) of Mn2+ and Mn3+ are controlled by the solubility products (Ksp) of Mn(OH)2 and Mn(OH)3, respectively. In practice, Mn(OH)3 tends to dehydrate to MnO(OH), so we consider the Mn2+(aq)/Mn(s) couple ... 

The more finely divided the manganese dioxide the more rapid will be the reaction, so that the precipitated reagent is better than finely powdered pyrolusite. It is still better to prepare the precipitated hydroxide Mn(OH)4, by reducing the necessary quantity of potassium permanganate in neutral solution with alcohol and washing the precipitate from soluble potassium salts by decantation. 

The Dithionates or Hyposulphates.—These salts, like the nitrates, are all soluble in water only normal salts are known.4 They may be obtained by neutralising dithionic acid solution with the hydroxide of the base, and also by double decomposition between barium dithionate solution and the sulphate of the base, or between manganese dithionate solution and the hydroxide of the base 5 also by methods on pp. 206-8. 

T. Curtius and J. Rissom showed that the evaporation of a soln. of manganese carbonate in hydrazoic acid gives a pulverulent, non-crystalline manganese hydroxyazide, Mn(OH)(N3)2, which cannot be purified by re-crystallization. The product is sparingly soluble in water it does not explode by percussion, but does so on a hot plate. L. Wohler and F. Martin gave 203° for the explosion temp, of manganese azide. T. Curtius and J. Rissom obtained a colourless soln. of ferrous azide by the action of sodium azide on a soln. of ferrous ammonium sulphate when boiled, the salt decomposes and when shaken in air, a blood-red soln. of ferric azide is formed. The same salt can also be obtained directly from ferric salts. When the soln. of ferric azide is boiled, ferric hydroxide is precipitated and, added T. Curtius and A. Darapsky, if allowed to stand in... 

Gallionella sp. Aerobic bacteria with filamentous stalk. Organisms are found in water containing soluble iron, oxidizing ferrous hydroxide to ferric hydroxide and depositing it in their stalks. Also oxidizes manganese. 

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