Copper precipitation

Primary consumers for ferrous scrap are the iron and steel mills and foundries. Minor consumers iaclude ferroalloy producers, copper producers for use ia copper precipitation (see Recycling, nonferrous metals), and the chemical iadustry. The steel iadustry consumes about three-fourths of the total. Scrap consumption for ferroalloy production, copper precipitation, and the chemical iadustry total less than one million t. The United States is the leading exporter of ferrous scrap, exporting almost nine million t ia 1994, valued at about 1.3 biUioa. Total value of domestic scrap purchases and exports ia 1994 was 8 biUioa (2). 

The addition of thiosulfate to aqueous solutions of silver, lead, and copper precipitates the corresponding thiosulfates, which, on heating, decompose to the sulfides. In this manner, thiosulfate can be used as a reagent for most metals having insoluble sulfides. Details of the reactions of other metals with thiosulfate are available (21). 

Cementation. Cementation is the precipitation of copper from copper leach solutions by replacement with iron. It was formerly the most commonly used method of recovering copper from leach solutions but has been replaced by solvent extraction—electro winning. The type of iron used ia cementation is important, and the most widely used material is detinned, light-gauge, shredded scrap iron. This operation can be performed by the scrap iron cone (Keimecott Precipitation Cone) or a vibrating cementation mill that combines high copper precipitation efficiency and reduced iron consumption (41). 

On the other hand, CU-CUSO4 should not be used as built-in electrodes for potential test probes (see Section 3.3.3.2) because there is a danger of copper precipitating on the steel electrode. Calomel electrodes with saturated KCl solution are preferred in this case and present no problems. 

Kupfer-nickel, m. copper-nickel (niccolite). -niederschlag, m. copper precipitate or deposit. -ocher, -ocker, m. = Kupferbraun. 

The copper precipitate can be dried unchanged but is then difficult to decompose with hydrogen sulfide. 

As the zinc dissolves, more positive charge [i.e., Zn (aq)] is introduced into this side of the cell. As the copper precipitates, the concentration of positive charge declines on its side of the cell. To maintain electroneutrality throughout the cell, sulfate ions diffuse across a salt bridge from the copper to the zinc side of the cell. 

Few studies have evaluated the potential for use of microorganisms in the remediation of sea water however, the problems encountered are similar to those of other aquatic systems. Stupakova et al. (1988) proposed the use of the marine bacteria Deleya venustus and Moraxella sp. for copper uptake from sea water. Additionally, Corpe (1975) performed metal-binding studies with copper using exopolymer from film-producing marine bacteria and found that insoluble copper precipitates formed, effectively decreasing copper toxicity. 

The presence of copper(II) salts, in the optimum ratio Cu Rh=l or 2, considerably increases the rate and the selectivity of the reaction. Rhodium perchlorate alone acts as a catalyst, but cooxidizes the solvent alcohol to a carbonyl compound. With Cu Rh= 1, 85% of the copper precipitates from the reaction mixture as CuCl. 

Determination of the Copper.—i gram of the substance is dissolved in hydrochloric acid and the solution treated with excess of ammonium carbonate and filtered, the insoluble portion being well washed the filtrate is boiled and the copper precipitated by means of sodium hydroxide, the precipitate being filtered off, washed, calcined and weighed as copper oxide. 

The copper crossover from the anode to the cathode and copper precipitation inside the membrane and at the cathode were observed with a number of tested commercial membranes. It was found that the AHT membrane of Asahi Glass Inc. exhibited the highest tolerance to the copper crossover. 

VI. Twenty-one parts of chlorate of potassium, 23 of copper precipitated with chlorate of jw)tassium, 12 of sulphate of copper, 12 of calomel, 4 of milk sugar, and 3 of stearine. 

The use of particulate iron precipitant such as sponge iron gives a relatively faster copper precipitation rate than scrap iron of varying sizes. Back (Bl, B2) reported the development of an inverted cone type pre-... 

The morphology of nuclei can be characterized in terms of deposit size and density. Figure 6.14 shows copper precipitate size distribution ofn- and/ -Si materials in 0.5% HF solution." ° The density is higher on n- than on p-type silicon whereas the size is larger on p-Si than on n-Si indicating that the rate of nucleation is higher on... 

The sCf>aration must Be carried out in the same way, when mixtures of both sorts of gum with dextrin arc under Investigation. The copper precipitate, containing the acid gum products, is washed with distilled water, dissolved in hydrochloric add, and this solution... 

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