Copper activity

This group is stable to acid and alkali. It has been used as a copper-activated leaving group for triphosphate protection. " ... 

As a part of their efforts to model dinuclear copper active sites, Reed and co-workers reported, using alkoxo-based dinucleating ligands, a few very interesting systems from the viewpoint of magnetostructural correlations (379) (TBP Cu-Cu 3.325A 2.1 278cm ), (380) (TBP ... 

Catalytic reduction of oxygen directly to water, while not as yet possible with traditional catalyst technology at neutral pH, is achieved with some biocatalysts, particularly by enzymes with multi-copper active sites such as the laccases, ceruloplasmins, ascorbate oxidase and bilirubin oxidases. The first report on the use of a biocatalyst... 

Figure 4.4. Schematic representation of laccase trinuclear copper active center.

Copper-activated zinc and cadmium sulphides exhibit a rather long afterglow when their irradiation has ceased, which is favourable for application in radar screens and self-luminous phosphors. 

More than 60 years after its simultaneous discovery by Rochow and Muller, the direct reaction of copper-activated silicon with alkyl chlorides is arguably still the most important industrial process for the preparation of basic organosilanes. An inspiring historic account highlighting the significance of this seminal work has been given by Seyferth.12 A comprehensive review on the subject has been written by Jung and Yoo.13 The most recent work associated with the direct process is concerned with the role of metallic promoters, such as Zn and Cd, as well as mechanistic aspects.14... 

The effect of DMPS on the flotation recovery of pyrrhotite and marmatite in the presence and absence of CUSO4 with butyl xanthate is shown in Fig. 5.16. It follows that the flotation of pyrrhotite and marmatite is greatly affected by DMPS addition. In the absence of cupric ion the recovery of pyrrhotite hardly exceeded 40%. At pH = 2, the recovery of marmatite is more than 90%, but the recovery sharply decreases to below 20% with pH increasing. These results show that pyrrhotite and marmatite can not be separated in the absence of cupric ion with DMPS as depressant and xanthate as a collector. In the presence of cupric ions, marmatite flotation improves under wide pH condition. The flotation of pyrrhotite is activated only aroimd pH = 2. The results demonstrate that flotation separation of copper-activated marmatite from pyrrhotite is possible in the presence of butyl xanthate and DMPS. 

Abstract Two systems are discussed in this chapter, which are copper activating zinc-iron system with and without depressants. Firstly, the system in the absence of depressants is discussed. And it is obtained that at a specific pH the activation for each mineral occurs in a certain range. Through the electrochemical methods and surface analysis the entity contributing to the activation can be identified which are usually copper sulphides and vary for different minerals. Secondly, the system with depressants is researched. And also the effects of pulp potential on the activation are discussed. The same conclusion can be obtained as the one from the former system. Furthermore, zeta potential are involved in the discussion of activation and die mechanism can be explained firom the changes of zeta potential. Similarly, the activation mechanism of this system is also studied through solution chemistry, bonding of activator with mineral surfaces and surface analysis. 

Electrochemical Mechanism of Copper Activating Zinc-Iron Sulphide Minerals... 

Figure 6.4 to Fig. 6.6 show the effect of pulp potential on the copper activation flotation of marmatite, arsenop5nrite and pyrrhotite in the presence of lO " mol/L Cu with 10" mol/L butyl xanthate as a collector. It is obvious that marmatite, arsenopyrite and pyrrhotite appear to have better flotation response at certain potential range at different pH conditions. 

Electrochemical mechanism of copper activating marmatite is investigated by using voltammetric method. The voltammogram of the marmatite electrode in the presence of 10 mol/L Cu is presented in Fig. 6.7. It can be seen that in the presence of cupric ion marmatite surface exhibits the electrochemical character of activation products. In the light of E h-pH diagram of the CU-S-H2O system... 

Surface Analysis of Mechanism of Copper Activating Marmatite... 

Yu Runlan, Qiu Guanzhou, Hu Yuehua, Qin Wenqing, 2004d. Electrochemistry of copper activation of marmatite. Metal Mine, (2) (in Chinese)... 

Zhao Jing et al., 1988. Research on the mechanism of chalcopyrite depressed by sodium mercaptoacetic. Nonferrous Metals (part of mineral processing), (3) 42 - 45 Zhuo Chen and Yoon, R. H., 2000. Electrochemistry of copper activation of sphalerite. Inter. J. Miner. Process, 58 57 - 66... 

A coupled binuclear copper active site is found in a variety of different metalloprotelns Involved in dloxygen reactions. These Include hemocyanln (reversible O- binding), tyrosinase (O2 activation and... 

SOLOMON Coupled Binuclear Copper Active Sites... 

Table 1. Proteins Containing Coupled Binuclear Copper Active Sites and Their Functions...

Our earlier research on the coupled binuclear copper proteins generated a series of protein derivatives in which the active site was systematically varied and subjected to a variety of spectroscopic probes. These studies developed a Spectroscopically Effective Model for the oxyhemocyanin active slte.(l) The coupled binuclear copper active site in tyrosinase was farther shown to be extremely similar to that of the hemocyanlns with differences in reactivity correlating to active site accessibility, and to the monophenol coordinating directly to the copper(II) of the oxytyroslnase site.(2) These studies have been presented in a number of reviews.(3) In the first part of this chapter, we summarize some of our more recent results related to the unique spectral features of oxyhemocyanin, and use... 

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