By-products, metals

Ultimately, as the stabilization reactions continue, the metallic salts or soaps are depleted and the by-product metal chlorides result. These metal chlorides are potential Lewis acid catalysts and can greatiy accelerate the undesired dehydrochlorination of PVC. Both zinc chloride and cadmium chloride are particularly strong Lewis acids compared to the weakly acidic organotin chlorides and lead chlorides. This significant complication is effectively dealt with in commercial practice by the co-addition of alkaline-earth soaps or salts, such as calcium stearate or barium stearate, ie, by the use of mixed metal stabilizers. 

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

Polyaromatic hydrocarbons Not applicable Combustion by-products, metal treatment, wood treatment (creosote) and others... 

Zhabrova etal. [151] identified the reactions of nickel, cobalt and copper oxalates ( , = 150, 159 and 129 kJ mol respectively) as redox processes in which there is an autocatalytic effect by product metal on the electron transfer step. The decomposition rate was determined by the area of the reactant and results were fitted by the Prout-Tompkins equation. In contrast, the reactions of magnesium, manganese and iron oxalates (f, = 200,167 and 184 kJ mol ) are not autocatalytic and the area... 

The high concentration of metals in the eastern oil shales has led to considerable speculation concerning the potential for by-product metals recovery (23-27). Much of this interest has centered on the recovery of such metals as Mo, V, Ni, Cu, U, Th, and Al. At present, the potential for the recovery of these metals appears to be sub-economic (l). 

Maximization of Aromatic Yields LPG as By Product Metal Modified ZSM-5 Incorporated with Non Nobel Metal... 

Electrochemical processes, primarily in the refining of copper, lead, and zinc, yield certain rare metals as by-products. The value of these by-product metals should be included within the electrochemical industry. In Table 7, the major metals derived as byproducts of electrorefining operations are listed. The total value of shipments for each of these metals was based on data contained in the Bureau of Mines Minerals Yearbook Since copper refining... 

This part of the text covers refining methods used for the removal of a range of impurity eiements from crude iead bullion produced by smelting operations. It also covers the recovery of valuable by-product metals such as silver. 

Silver normally reports to lead bullion during smelting but will also report to any matte formed. It is the most valuable by-product metal contained in primary lead bullion and efficient recovery is of key importance. 

Electrolytic refining involves electrochemically dissolving lead from an impure anode and depositing lead free of impurities onto a lead cathode. The impurities predominantly remain at the anode as a residue or anode slime, from which valuable by-product metals can be recovered. 

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