Zinc bearings

Zinc bacitracin Zinc bearings Zinc blende... 

In this process EAF dust, other zinc-bearing wastes, recycled materials, coke or coal, lime, and silica are mixed and fed to a rotary furnace. The zinc and other volatile nonferrous metals in the feed are entrained in the furnace off-gas and are carried from the furnace to an external dust collection system. The resulting oxide (zinc calcine) is a crude zinc-bearing product that is further refined at zinc smelters. A byproduct of the process is a nonhazardous, iron-rich slag that can be used in road construction. Solidification technologies change the physical form of the waste to produce a solid structure in which the contaminant is mechanically trapped. 

For the most part, the zinc materials recovered from secondary materials such as slab zinc, alloys, dusts, and compounds are comparable in quality to primary products. Zinc in brass is the principal form of secondary recovery, although secondary slab zinc has risen substantially over the last few years because it has been the principal zinc product of electric arc furnace (EAF) dust recycling. Impure zinc oxide products and zinc-bearing slags are sometimes used as trace element additives in fertilizers and animal feeds. About 10% of the domestic requirement for zinc is satisfied by old scrap. 

Cadmium, as cadmium oxide, is obtained mainly as a by-product during the processing of zinc-bearing ores and also from the refining of lead and copper from sulfide ores (USPHS 1993). In 1989, the United States produced 1.4 million kg of cadmium (usually 0.6 to 1.8 million kg) and imported an additional 2.7 million kg (usually 1.8 to 3.2 million kg). Cadmium is used mainly for the production of nickel-cadmium batteries (35%), in metal plating (30%), and for the manufacture of pigments (15%), plastics and synthetics (10%), and alloys and miscellaneous uses (10%) (USPHS 1993). 

A great many of the less common cations occur in the octahedral sheet of the trioctahedral smectites. Zn, Cr, Ni, Cu, Ti, Mn, and V have all been reported as occurring in significant amounts. The first five can occur as predominant ions. The zinc-bearing smectite, sauconite, is more common and occurs as a purer clay than any of these others. A number of these clays have been described by Ross (1946) and Faust (1951). Analyses of sauconite are reported by Ross (1946) some of these data are reproduced in Table XL along with two other analyses of impure samples. 

After ore is mined at Polaris, metallurgists must separate the valuable lead- and zinc-bearing compounds from the waste or "slag." First the ore is crushed and ground with water to produce flour-like particles. Next a process called flotation is used to separate the minerals from the slag. 

A class of mixed zinc reagents, e.g., (trimethylsilylmethyl)(2-pyrrolyl or 2-indolyl)zincs, bearing one transferable functional group (2-pyrrolyl or 2-indolyl) and one nontransferable group (the trimethylsilylmethyl group), add efficiently to Michael acceptors, for example, as in Scheme 141 <1998T1471>. 

The fractionated methyl esters can be converted into fatty alcohols by the high-pressure hydrogenation process in the presence of a catalyst. Usually, copper chromite catalyst is used. Copper chromite catalyst also converts any unsamrated carbon double bonds so that only saturated fatty alcohols are formed. If unsamrated fatty alcohols are desired, a special zinc-bearing catalyst is employed. 

We have tried here to incorporate the ferrocene moiety into amino alcohol catalysts and have synthesized the following four kinds of compounds (a) chiral ferrocenyl zincs bearing an aminoethanol auxiliary [12] (b) iV-(l-ferrocenylalkyl)-iV-alkylnorephedrines [13] (c) chiral polymers bearing iV-ferrocenylmethylephe-drine [14] and (d) chiral 1,2-disubstituted ferrocenyl amino alcohols (Fig. 3-2) [15-17]. 

M.R. Khan and D.J. Barber, Composition-related microstructures in zinc-bearing carbonate assemblages from Broken Hill, New South Wales. Mineralogy and Petrology 41, pp, 229-245 (1990). 

The jarosite process separates icon(III) from zinc in acid solution by precipitation of MFe2(0H)g(S0 2 where M is an alkali metal (usuaUy sodium) or ammonium (see Fig. 2) (40,41). Other monovalent and hydronium ions also form jarosites which are found in the precipitate to some degree. Properly seeded, the relatively coarse jarosite can be separated from the zinc-bearing solution efficiently. The reaction is usuaUy carried out at 95 0 by adding ammonia or sodium hydroxide after the pH has been adjusted with calcine and the iron oxidized. The neutral leach residue is leached in hot acid (spent + makeup) with final acidity >20 g/L and essentiaUy aU the zinc, including ferrite, is solubilized. Ammonium jarosite is then precipitated in the presence of the residue or after separating it. If the residue contains appreciable lead or silver, they are first separated to avoid loss to the jarosite waste solids. Minimum use of calcine in jarosite neutralization is required for TnaxiTniiTn recovery of lead and silver as weU as zinc and other metals. 

Several successful applications of the ELM in the removal of heavy metals from industrial wastewaters have been reported in the literature. These include the Zn removal from wastewater at the viscous fiber plant located in Lenzing, AG, Austria [89]. This process can treat up to 75 m. h of zinc bearing wastewater with the zinc concentration ranging from 0.3 to 200 mg dm Zn can be removed with up to 99.5% efficiency [89]. Other two industrial applications are also aimed at Zn removal, and the respective plants are located in Glanzstoff, AG, Austria (with the reported capacity of 700 m .li j, at the CFK Schwarza plant, Germany and the AKZO Ede plant ill the Netherlands (both with the reported capacity of 200 m h [67]). 

Based upon the total zinc content of this preparation of enzyme, 3.5 gram atoms per mole, the lines drawn through the linear portions of the experimental data intersect at 64 mole % of zinc. The point of intersection would be expected to be 50 mole % of zinc if OP were to form a 1 1 complex with each zinc atom of LADH. However, if only 2 of the 3.5 zinc atoms of the enzyme react with OP under these conditions, maximal formation of the 1 1 Zn OP complex occurs when the molar ratio of OP to total zinc bears the relationship 2/3.5—t.e., at the point of 3.5/(3.5 + 2.0) corresponding to 64 mole % of zinc, as here observed. Hence, it appears that the method of continuous variations is capable of signaling the presence of "nonreacting zinc atoms, in accord with the titration data shown previously (20). 

Over the period 1955-1961, the electrolytic plant processed only calcined zinc oxide having a composition of 60% Zn, 3-4% Pb and 0.03% Cd. The zinc oxide was produced by calcination of the fumes from the Waelz process at temperatures from 1420 to 1470 K. Zinc carbonate ores, Zn-Fe residues and other zinc-bearing materials were used as raw materials in the Waelz process. After enhancement of the electrolytic zinc plant in 1962, the importance of roasted sulphide concentrates was continuously growing in the feed. Currently, only the calcine from fluid-bed roasters is processed. Table I shows the analysis of the raw materials processed over the period 1998-1999. 

At the same time, changes were introduced in the feed residues from the electrolytic zinc plant are processed with some addition of zinc-bearing materials from the waste water treatment plant, and other secondaries like EAF dusts coming from steel mills (electric arc... 

Zinc-bearing base or filler metals or metals coated with zinc-bearing materials ... 

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