Metal oxide minerals

Flotation is certainly the major separation method based on the surface chemistry of mineral particles. It is, however, not the only method. Selective flocculation and agglomeration may be mentioned as other methods used commercially to a limited extent. The former is for hematite, while the latter is for coal and finely divided metallic oxide minerals. Both processes use the same principles as described for flotation to obtain selectivity. In selective flocculation, polymeric flocculants are used. The flocculants selectively adsorb on the hematite, and the hematite floes form and settle readily. Thereby separation from the sili-... 

In this paper, a review of the mechanistic information that has been obtained in chemical relaxation studies of reactions of ions with metal oxide minerals in aqueous suspensions is discussed. The... 

Vaughan, D. J. Tossell, J. A. (1978) Major transition metal oxide minerals Their electronic structures and interpretations of mineralogical properties. Canad. Mineral., 16, 159-68. 

Molecular oxygen, if bonded to certain transition metal ions in solution or at oxide surfaces, can be more reactive than dissolved free oxygen. This property may contribute to the catalytic activity of metal oxide minerals in oxidation reactions. 

Mineral systems Sultide minerals Transitional metal oxide minerals Oxide or salt-type minerals... 

Examples of bulk-sensitive NEXAFS spectroscopy studies include investigations of the coordination environments of oxygen in metal oxide minerals (Brown et al. 1986), Al... 

Vibratory disk mills These are designed for rapid, efficient, and lossless fine-grinding of medium-hard, hard-brittle, as well as tough materials in dry and wet conditions. They are specifically suitable for use with such substances as soil samples, ores, coal, coke, corundum, metal oxides, minerals, dry plant samples, slag, silicates, cement, cement clinker. Figure 3C shows that the sample material is ground down by... 

Schindler and Stnmm (1987) snmmarized the intrinsic acidity constants of various metal oxides/ minerals under solution chemistry. In this system, H+ and OH" are potential determining ions and the surface charge and surface potential are defined by the pH of the solution. There is a particular pH at which the surface charge becomes zero, that is, the point of zero charge (pzc) or the isoelectric point (iep). is correlated to the pzc, which is as follows (Bin et al., 2011) ... 

The conventional way of expressing the composition of mixed metal oxide minerals is in terms of the metal oxide content. Thus, Fe304 can be formulated as Fe0 Fe203 which reveals that it is a mixed iron(II)/iron(III) oxide. 

Chapter 7 is devoted to Electrometallurgy of Production of Metals. This topic includes principles electrochemical which are essential in recovering metals and precious metals (gold, silver, platinum) for metal oxides (minerals) in acid solutions. 

As one might expeet, the rates of reductive dissolution of a mineral depend upon the concentrations of reduced metals at the surface. These concentrations, in turn, depend on the concentrations of eleetron-donating ligands at the surface and the rates of electron transfer. This subjeet is immensely eomplicated because the rates of electron transfer ean depend on many variables, including the stoichiometry of the adsorbate, the electronic stracture of the metal oxide mineral, and whether light is involved. Many adsorbates that are important in natiue are chromophores, and the electron transfer is facilitated by adsorption of light at the appropriate wavelength. 

Surface heterogeneity may be inferred from emission studies such as those studies by de Schrijver and co-workers on P and on R adsorbed on clay minerals [197,198]. In the case of adsorbed pyrene and its derivatives, there is considerable evidence for surface mobility (on clays, metal oxides, sulfides), as from the work of Thomas [199], de Mayo and co-workers [200], Singer [201] and Stahlberg et al. [202]. There has also been evidence for ground-state bimolecular association of adsorbed pyrene [66,203]. The sensitivity of pyrene to the polarity of its environment allows its use as a probe of surface polarity [204,205]. Pyrene or ofter emitters may be used as probes to study the structure of an adsorbate film, as in the case of Triton X-100 on silica [206], sodium dodecyl sulfate at the alumina surface [207] and hexadecyltrimethylammonium chloride adsorbed onto silver electrodes from water and dimethylformamide [208]. In all cases progressive structural changes were concluded to occur with increasing surfactant adsorption. 

Mixed oxides of Fe(IV) can be prepared by heating iron(III) oxide with a metal oxide or hydroxide in oxygen at elevated temperatures. These black compounds have general formulas M FeO, M monovalent, or M2Fe04, M divalent, but do not contain discrete [FeOJ" ions. They are readily decomposed by mineral acids to iron(III) and oxygen. 

Pyrolusite is a black, opaque mineral with a metallic luster and is frequendy soft enough to soil the fingers. Most varieties contain several percent water. Pyrolusite is usually a secondary mineral formed by the oxidation of other manganese minerals. Romanechite, a newer name for what was once known as psilomelane [12322-95-1] (now a group name) (7), is an oxide of variable composition, usually containing several percent water. It is a hard, black amorphous material with a dull luster and commonly found ia the massive form. When free of other oxide minerals, romanechite can be identified readily by its superior hardness and lack of crystallinity. 

The transformations are aided by or may requke the presence of impurities or added mineralizers such as alkaH metal oxides. Indeed, it has been suggested that tridymite cannot be formed at all in the absence of impurities, and some texts assert that pure Si02 occurs in only two forms quartz and cristobaHte... 

Bromine is used as an analytical reagent to determine the amount of unsaturation in organic compounds because carbon—carbon double bonds add bromine quantitatively, and for phenols which add bromine in the ortho and para positions. Standard bromine is added in excess and the amount unreacted is deterrnined by an indirect iodine titration. Bromine is also used to oxidize several elements, such as T1(I) to T1(III). Excess bromine is removed by adding phenol. Bromine plus an acid, such as nitric and/or hydrochloric, provides an oxidizing acid mixture usefiil in dissolving metal or mineral samples prior to analysis for sulfur. 

Zinc occurs most abundantly in tire mineral. Sphalerite, ZnS, which is roasted to produce the oxide before the metal production stage. The products of the roast are then reduced by carbon to yield zinc oxide and CO(g). In the older process, tire Belgian retort process, the metal oxide and carbon are mixed together in a reactor which allows the indirect heating of the charge to produce the gaseous products followed by tire condensation of zinc at a lower temperature in a zone of the reactor which is outside the heating chamber. The carbon monoxide is allowed to escape from the vessel and is immediately burnt in... 

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