Lead, solvent extraction

Spinbath concentration can be adjusted to obtain the desired microstmcture. Low spinbath concentration promotes rapid solvent extraction but this also produces a thick skin on each filament which ultimately reduces the rate of solvent extraction and may lead to the formation of macrovoids. High spinbath concentrations give a denser microstmcture, but solvent extraction is slow and filament fusion can occur. Other spinbath conditions that affect coagulation and microstmcture are dope soHds, spinbath temperature, jet stretch, and immersion time. 

The electrowinning process developed by Ginatta (34) has been purchased by M.A. Industries (Atlanta, Georgia), and the process is available for licensing (qv). MA Industries have also developed a process to upgrade the polypropylene chips from the battery breaking operation to pellets for use by the plastics industry. Additionally, East Penn (Lyons Station, Pennsylvania), has developed a solvent-extraction process to purify the spent acid from lead—acid batteries and use the purified acid in battery production (35). 

Direct attack by hot 70—80 wt % hydrofluoric acid, sometimes with nitric acid (qv), is effective for processiag columbites and tantalo-columbites. Yields are >90 wt%. This method, used in the first commercial separation of tantalum and niobium, is used commercially as a lead-in to solvent extraction procedures. The method is not suited to direct processiag of pyrochlores because of the large alkaU and alkaline-earth oxide content therein, ie, ca 30 wt %, and the corresponding high consumption of acid. 

Many antioxidants ia these classes are volatile to some extent at elevated temperatures and almost all antioxidants are readily extracted from their vulcanizates by the proper solvent. These disadvantages have become more pronounced as performance requirements for mbber products have been iacreased. Higher operating temperatures and the need for improved oxidation resistance under conditions of repeated extraction have accelerated the search for new techniques for polymer stabilization. Carpet backiag, seals, gaskets, and hose are some examples where high temperatures and/or solvent extraction can combine to deplete a mbber product of its antioxidant and thus lead to its oxidative deterioration faster (38,40). 

V. H. Aprahamian and D. G. Demopoulos, The Solution Chemistry and Solvent Extraction Behaviour of copper, iron, nickel, zinc, lead, tin, Ag, arsenic, antimony, bismuth, selenium and tellurium in Acid Chloride Solutions Reviewed from the Standpoint of PGM Refining, Mineral Processing and Extractive Metallurgy Review, Vol. 14, p. 143,1995. 

Shah, D.B. and Phadke, A.V., Lead removal of foundry waste by solvent extraction, Journal of Air and Waste Management, 45, 150-155, 1995. 

Garcia, M. A. Mejias, A. Martin, D. Diaz, G. Upcoming zinc mine projects the key for success is ZINCEX solvent extraction. Lead-Zinc 2000, Proceedings of the Lead-Zinc 2000 Symposium, Pittsburgh, PA, United States, Oct. 22-25, 2000, 751-761. 

Regnouf-de-Vains, J. B. Dalbavie, J. O. Lamartine, R. Fenet, B. Quantitative solvent extraction from neutral aqueous nitrate media of silver(I) against lead(II) with a new calix-4-arene-based bipyridine podand. Tetrahedron Lett. 2001, 42, 2681-2684. 

A comparison was carried out on the results obtained using ICP-AES and AAS for eight elements in coastal Pacific Ocean water. The results for cadmium, lead, copper, iron, zinc, and nickel are in good agreement. For iron, the data obtained by the solvent extraction ICP method are also in good agreement with those determined directly by ICP-AES. In most of the results the relative standard deviations were 4% for all elements except cadmium and lead, which had relative standard deviations of about 20% owing to the low concentrations determined. 

Jagner et al. [802] used this technique to determine zinc, cadmium, lead, and copper in seawater. Their method includes computer control of the potentiometric stripping technique. They compared their results with those obtained by solvent extraction-AAS and showed that the computer-controlled potentiometric stripping technique is more sensitive, and has advantages over ASV. Computer control makes deoxygenation of the sample unnecessary. 

Kingston et al. [32] preconcentrated the eight transition elements cadmium, cobalt, copper, iron, manganese, nickel, lead, and zinc from estuarine and seawater using solvent extraction/chelation and determined them at sub ng/1 levels by GFA-AS. 

Eluex An early process for extracting uranium from its ores, using both ion-exchange and solvent extraction. Developed by the National Lead Company, United States. 

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