Copper transport phases

Figure 12. Copper transport phases in the upper Mississippi River,...

Caeruloplasmin (Cp) is an acute phase glycoprotein with a copper transport function. At least 90% of total plasma copper is bound to Cp with the remaining 10% associated with albumin, histidine and small peptides. Lipid peroxidation requires the presence of trace amounts of transition metals and the copper-containing active site of Cp endows it with antioxidant capacity... 

Wilson disease is an autosomal recessive disorder of copper transport (Figure 1). It results in the toxic accumulation of copper in various tissues, but mainly in the liver, kidney, and brain. Wilson disease occurs worldwide with an average prevalence of about 1 in 30 000 in most populations. The age of onset for Wilson disease is variable and can extend from 3-4 years into the mid-50s. There are three phases in the progression of the disease. In the first phase, copper accumulates in the cytoplasm of hepatocytes. As more copper is absorbed, in the second phase the increased concentration of... 

The high-affinity pathway involves oxidation of Fe to Fe by the ferroxidase FET3 and subsequent transport of Fe " " across the plasma membrane by the permease FTRl. FET3p is a member of the family of multicopper oxidases, which include ascorbate oxidase, laccase, and ceruloplasmin (see Chapter 14), and does not become functional until it is loaded with copper intracellularly through the activities of the copper chaperone ATX Ip and the copper transporter CCC2p. It appears that Fe " " produced by FET3 is transferred directly to FTRl, and does not equilibrate with the bulk phase, as is illustrated in Fig. 7.13. This is almost certainly achieved by the classic metabolite-channeling mechanism, a common feature of multifunctional enzymes. 

Total copper and cadmium concentrations increased from Sites 1-4, ranging from 1.2 to 6.8 /xg/L for copper, and 0.2 to 1.0 /xg/L for cadmium. Copper transported in the dissolved phase ranged from 56% at Site 4 to 68% at Sites 1 and 3, and 80% at Site 2. Dissolved cadmium accounted for more than 50% of the total concentrations at all sites. Thus, copper and cadmium transport in the Mississippi River was dominated by apparent solution-phase transport. Total mean lead concentrations ranged from 2.3 to 5.7 /xg/L at Sites 1-4, with dissolved metal accounting for 16 to 38% of the total. The unexpectedly large contribution of dissolved lead indicates the potential role played by organic matter in maintaining lead in solution. 

Metal transport phases for iron, manganese, copper, cadmium, and lead are shown in Figures 10-14, with individual elemental data given in Tables VIll and IX. The fractionation scheme was applied to composite samples for Sites 1 and 2, and all fractionations were performed in duplicate. 

The transport of copper and lead in the vapour phase under such volcanic conditions is well documented. While the Cu3Clj trimer might be important for the former, abundant evidence for CuCl(g) has accrued. It has been observed spectrographically in volcanic flames at Kilaue,158 and in high-temperature volcanic gases by other workers.159,160 The sublimation of CuCl from lavas leading to the crystallization of primary atacamite, Cu3(OH)3Cl, upon condensation has also been reported.161 Zinc may also be transported as the volatile chloride under the same conditions and has been noted in fumarolic emissions from the Showashinzan volcano, Japan.162... 

Recovery of metals such as copper, the operation of batteries (cells) in portable electronic equipment, the reprocessing of fission products in the nuclear power industry and a very wide range of gas-phase processes catalysed by condensed phase materials are applied chemical processes, other than PTC, in which chemical reactions are coupled to mass transport within phases, or across phase boundaries. Their mechanistic investigation requires special techniques, instrumentation and skills covered here in Chapter 5, but not usually encountered in undergraduate chemistry degrees. Electrochemistry generally involves reactions at phase boundaries, so there are connections here between Chapter 5 (Reaction kinetics in multiphase systems) and Chapter 6 (Electrochemical methods of investigating reaction mechanisms). 

The systems described above all result in the transport of metal cations across a metal-recovery circuit. In many cases this leads to very good materials balances in metal-recovery, especially when the circuit uses acid-leaching of the ore followed by solvent extraction using an organic acid (LH). The extraction then releases protons back into the aqueous phase, regenerating the acid needed for leaching. This underpins the very successful copper recovery operations outlined in Figure 7 in which copper oxide in the crude ore is essentially split into its component elements with the consumption of only electrical power. 

When CO alone is used as reducing agent, e.g. for reduction of Cu(hfac)(l,5-cod) (10c), the copper films are contaminated mostly with significant amounts of carbon impurities, while the use of CO/H2 mixtures results in the formation of high-purity metallic copper films. Under the CVD conditions applied, it is proposed that the copper(I) species is transported as Cu(hfac)(CO) in the gas phase . 

Type 2 facilitation is also known as carrier facilitated transport, since a carrier compound, that is, an extractant or complexing agent, solubilized in the organic phase is used to assist transfer across the membrane. In this simation, the solute of interest reacts with the carrier to form a complex that is only soluble in the membrane phase. The solute is de-complexed by a stripping solution contained in the internal phase. An example of such a process is the removal of a metal ion such as copper or zinc from wastewater by the extractant DEHPA (di-2-ethyUiexyl phosphoric acid, represented as HE) as shown in Figure 25.2. In this case, the carrier also enhances the selectivity as most extractants are specifically designed to extract particular metal ions... 

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