Lead extraction from contaminated

A. Smaniotto, A. Antunes, I. Do Nascimento Filho, L. Dornelles Venquiaruto, D. De Oliveira, A. Mossi, M. Di Luccio, H. Treichel and R. Dallago, Optimisation of the methodology for lead extraction from waste contaminated with heavy metals, Environ. TechnoL, 2010, 31(4), 365-371. 

Another point is related to the high acidity level of the final solution, which leads to certain limitations in the subsequent technological steps. Specifically, the high acidity of the initial solution eliminates any possibility for selective extraction, i.e. sequential separation of tantalum and then of niobium. Due to the high concentration of acids, only collective extraction (of tantalum and niobium together) can be performed, at least at the first step. In addition, extraction from a highly acidic solution might cause additional contamination of the final products with antimony and other related impurities. In order to reduce the level of contaminants in the initial solution, some special additives are applied prior to the liquid-liquid extraction. For instance, some mineral acids and base metals are added to the solution at certain temperatures to cause the precipitation of antimony [455 - 457]. 

TBP is less soluble and less dangerous but is more problematic due to its relatively high density. This can lead to poor stratification, especially during the stripping process. Hence, insufficient separation of the strip solution from the extractant can lead to additional contamination, by phosphorous, of the final products [458,462]. 

Because complete containment is physically impracticable in many cases, local exhaust ventilation is often applied to remove contaminants. The objective is to extract pollutant as near as practicable to its source and before it enters, or passes through, a worker s breathing zone. Vents should lead away from personnel, with scrubbing/filtering as appropriate. Common examples are ... 

By the nature of the process by which olive oil is extracted from the olive, the oil is susceptible to contamination. The high price associated with olive oil of the highest purity— extra virgin olive oil — also leads to falsification by unscrupulous vendors who blend with less costly oils such as com, peanut, and soybean oil. Various analytical techniques have been devised to authenticate the purity of olive oil by detecting certain oil components. 

Lead was extracted from nine replicates of NIST standard reference material 2709 (a contaminated soil) using various methods. The efficiencies of the various extraction methods were compared. 

Similarly, concern about minute amounts of contaminants co-purified with human growth hormone extracted from brain tissues, which could lead to the development of Jacob-Kreutzfeld syndrome, inevitably resulted in the development of recombinant human growth hormone. Inactivated hepatitis B particles isolated from hepatitis B-positive patients were originally used to prevent hepatitis B virus infection, but a small fraction of individuals became infected through vaccination. When the hepatitis B surface antigen was... 

In brief, the isolation scheme is as follows. First, the lipids are all extracted from the animal tissue, generally by using chloroform-methanol or chloroform-methanol-water. An increase in the polarity of the extracting system makes it possible to extract more fully the polar glycosphingolipids, especially polysialoglycolipids, but may, however, lead to contamination... 

Chen and Hong [126] found that 5-carboxy methyl-L-cysteine was especially effective for the chelating extraction of lead from contaminated soils. The chelator could be recovered and reused over consecutive runs with no loss in performance. 

Dust Extraction. Adequate dust extraction is necessary to maintain high-speed operation for extended periods of time. The entire compression area should be shrouded to minimize dust infiltration into other press areas. Effective dust extraction minimizes dust and oil contamination on the surface of the tablets, which could produce black specs. Insufficient dust extraction results in excessive material build-up on the lower and upper punches leading to tight punches. However, the proper balance of dust extraction without high levels of material loss must be determined. If the dust extraction level is too high material could be extracted from the die cavities and the recirculation channel. Furthermore, the dust extraction systems preferentially removes the fine particles. Therefore, if the granulation is a direct-compression blend where the active constituent is of fine particle size, minimum dust extraction levels combined with minimal recirculation may be necessary to prevent a loss of active constituents (resulting in possible low assay). 

Rutile is extracted from river, coastal and dune sands yielding concentrates with 90 to 98% Ti02, which may be contaminated with Fe, Zr, V, Cr, Al, Si, Mg etc. Australia is the leading producing country supplying 216 10 t in 1994. 

Figure 2. Lead ccxicentradon in solutitHi following extractitni of lead from contaminated soil using various extractive a nts.

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