Zinc extraction from contaminated

Aqueous parenteral preparations can contain trace amounts of heavy metal ions in concentrations sufficient to catalyze oxidative reactions. Aqueous parenterals are produced with the use of Water for injection, which complies with the limit test for heavy metals (European Pharmacopoeia, 2002). This is, however, no guarantee for exclusion of metal ions. Heavy metal contamination brought into the formulation by excipients is also a problem, especially for sugars, phosphate, and citrate (Nema et al., 2002). Heavy metals may also be extracted from the container by the preparation (European Pharmacopoeia, 2002 see Section 14.3). Moreover, trace elements like zinc, copper, manganese, and chromium constitute important components in several parenteral nutrition formulas (Trissel, 2001). 

Parkes process A metallurgical process for the removal of silver from lead using zinc in liquid-liquid extraction. Zinc is immiscible with lead and Its addition to lead containing silver as a contaminant results in silver dissolving in the zinc. The zinc-silver solution is then separated and the zinc removed from the silver by distillation. The process was patented in 1850 by British metallurgist Alexander Parkes (1813-90). 

In addition to the analyses of the zinc concentrations in both the aqueous feed and strip solutions, the solutions were also analyzed for the other metals, that is, cobalt, nickel, aluminum, manganese, and cadmium. There were no significant changes in the concentrations of aluminum, manganese, and cadmium in both the aqueous feed and strip solutions before and after the pilot plant run. However, about 35% of the cobalt and 25% of the nickel extracted from the feed solution were transferred to the aqueous strip solution. The cobalt and nickel were about 0.1 and 0.04 wt% of the zinc concentration in the aqueous strip solution recovered, respectively. Thus, there were no significant contaminants in the concentrated strip solution recovered, that is, the strip solution product had high quality. This also demonstrated the selective removal and recovery of zinc from the feed solution containing the contaminant metals. This also reinforced the reuse opportunity of the strip solution recovered. 

Solutions in contact with polyvinyl chloride can become contaminated with trace amounts of lead, titanium, tin, zinc, iron, magnesium or cadmium from additives used in the manufacture and moulding of PVC. V-Phenyl-2-naphthylamine is a contaminant of solvents and biological materials that have been in contact with black rubber or neoprene (in which it is used as an antioxidant). Although it was only an artefact of the separation procedure it has been isolated as an apparent component of vitamin K preparations, extracts of plant lipids, algae, livers, butter, eye tissue and kidney tissue [Brown Chem Br 3 524 1967]. 

The process flow sheet was first tested for direct leaching of steel mill flue dust and production of zinc metal by electrowinning. The tests were performed in a continuously operating pilot plant, producing 10-20 kg/day zinc metal. The same pilot plant was then used for treating copper/zinc-rich brass mill flue dust in a closed loop operation, recycling all the zinc solvent extraction raffinate to the copper circuit leach section. In the zinc circuit leach section, only the amount of zinc rich dust necessary for neutralization of the copper solvent extraction raffinate was used. The results obtained from the pilot plant tests indicated contamination problems within the solvent extraction loops. The estimation of economic data showed a weak return on the assets compared with the alkali route, and sensitivity toward the raw material price. 

The normally moderate to high zinc contents in foodstuffs coupled with excellent AAS detectivity for this element, indicate FAAS to be the technique of choice for virtually all food analyses. Should in the odd instance, greater detectivity be required, resort can be made to chelation-extraction with APDC—MIBK as outlined in Section IV.B.ll(ii), or EAAS [227], The ubiquitous nature of zinc can lead to problems with contamination from reagents, glassware, plastic ware and other apparatus when low levels are determined. 

In the analysis of metals in petroleum and petroleum products one of the most common sample preparation procedures is the dilution of the sample with an organic solvent such as xylene, methyl isobutyl ketone (MIBK) or white spirit. It is of great importance that the solvent system chosen is as free as possible from metallic contamination. Elements such as sodium and zinc are commonly found in many organic solvents. Similarly, other reagents such as mineral acids must be investigated for metal content before use. Where ultra-trace level determinations are to be attempted the reagents used may need to be purified. For solvents, the use of redistillation or extraction with mineral acid may improve the blank levels. 

The acid-extracted metals are usually analyzed by conventional flame AAS. However, the Chelex-lOO can also be analyzed directly for cadmium, cobalt, manganese, and zinc by NAA if the resin is first rinsed with deionized water after sample passage to reduce salt content and then dried. The carefully purified ammonium form of Chelex-lOO after NAA was essentially free from trace metal contamination. 

Even at pH levels in the range 7 to 9, water can extract iron, copper and lead from piping and zinc from galvanised steel. This can result in contamination of the water as well as corrosion of the distribution system. 

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