How Do You Know When a Copper Ion Converted to Copper Metal

Proceedings of the International Conference on Colloid and Surface Science

Yasushige Kuroda , ... Mahiko Nagao , in Studies in Surface Scientific discipline and Catalysis, 2001

ane INTRODUCTION

Copper ion-exchanged ZSM-5 zeolite (CuZSM-v) exhibits high and sustained activities for NOx decomposition [i,two] and specific N₂ adsorption [3,4]. A large number of studies have been made on the catalytic backdrop of this sample, intending to develop new applied catalysts, and have reached the conclusion that Cu⁺ is in the center of the agile sites in CuZSM-five. Nevertheless, little is known about the electronic and structural environment of the copper-ion exchanged and such information could also help to rationalize the catalytic behavior exhibited by the monovalent copper ion. Considering the outer beat orbitals, Ag⁺ takes the isoelectronic structure with Cu⁺. To examine the country of Ag⁺ is helpful for getting the information on the specificity of Cu⁺ in zeolite. In the present paper, a thorough report of ZSM-v, silica-alumina, and SiO_ii that were modified past copper or silver ions is presented to clarify the specificity of the electronic country of Cu⁺ in CuZSM-5. In particular, the IR technique in combination with microcalorimetry was used to picture the bonding nature of metal ion supported on the solid materials by utilizing CO equally a probe molecule.

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Nutrition of Minerals in Relation to Human Function

J.J.B. Anderson , in Reference Module in Biomedical Sciences, 2019

Copper (Cu): Roles in Enzymes

Copper ions serve as enzyme cofactors in a few cellular reactions. If zinc intakes are too great, specially from supplements, copper deficiency may result because the intestinal absorption mechanism for both these ions favors zinc. Copper is carried in blood by ceruloplasmin, a protein that acts as an enzyme in catalyzing the synthesis of hemoglobin in premature ruddy blood cells that exist in bone marrow. Copper exists in a multifariousness of foods, including nuts, poultry, and whole grains, and therefore deficiency is very rare. Toxicity from excessive intakes has not been reported.

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Inorganic/Bioinorganic Reaction Mechanisms

Ariela Burg , Dan Meyerstein , in Advances in Inorganic Chemistry, 2012

A Catalysis of Redox Reactions in Aqueous Solutions

Copper ions catalyze a variety of inorganic redox reactions. The kinetics and mechanisms of some of these reactions were analyzed in item. Thus, the reduction of V(IV) past Sn(II) and Ge(Two) is catalyzed by Cu ions in the presence of high concentrations of Cl ⁻. The mechanism involves the reduction of Cu(2) past Sn(2) or by Ge(II) followed by the reduction of 5(IV) past Cu(I) ( 134 ). These reactions go on via the inner-sphere mechanism ( 134 ). Also the copper-catalyzed reduction of peroxonitrite past sulfite ( 135 ), the copper-catalyzed reduction of a Ni(IV) circuitous past thiols ( 136 ), and the reduction of superoxide bound to binuclear cobalt(3) complexes by thiols ( 137 ) and by ascorbate ( 138 ) follow coordinating inner-sphere mechanisms. Copper ions also catalyze the reduction of peroxide-bound Cr(4) by ascorbate( 139 ).

A machinery involving the polarization of the ascorbate ligand by a Cu(II) central ion was proposed ( 138 ), though the involvement of Cu(I) cannot be ruled out ( 139 ). All these reactions proceed via the inner-sphere machinery; nonetheless, the copper-catalyzed reduction of superoxide bound to a binuclear cobalt(III) circuitous past 2-aminoethanethiol proceeds via the outer-sphere mechanism ( 140 ). This is attributed to the effect of 2-aminoethanethiol as a ligand on the rate abiding of the Cu(Ii/I) electron self-substitution reaction which is suggested to proceed via the "gated" machinery.

When copper ions are added to the Fenton reaction, the mechanism changes from

(76) $\text{Fe}{\left({\text{H}}_{\mathrm{two}}\text{O}\right)}_6{}^{\mathrm{ii}+}+{\text{H}}_{\mathrm{ii}}{\text{O}}_2\to \text{Fe}{\left({\text{H}}_{\mathrm{two}}\text{O}\right)}_{\mathrm{vi}}{}^{3+}+{}^{•}\text{O}\text{H}+{\text{OH}}^{-}$

(77) $\text{RH}+{}^{•}\text{O}\text{H}\to {\text{R}}^{•}+{\text{H}}_2\text{O}$

(78) $\mathrm{ii}{\text{R}}^{•}\to {\text{R}}_2/\left(\text{R–H}+\text{RH}\right)$

(79) ${\text{R}}^{•}+\text{Iron}{\left({\text{H}}_2\text{O}\right)}_6{}^{3+}\to {\text{R}}^{+}+\text{Fe}{\left({\text{H}}_2\text{O}\right)}_{\mathrm{six}}{}^{2+}$

to

(lxxx) ${\text{R}}^{•}+\text{Cu}{\left({\text{H}}_2\text{O}\right)}_{\mathrm{northward}}{}^{2+}\to {\text{Cu}}^{\text{III}}\text{–R}\left(\text{aq}\right)$

(81) ${\text{Cu}}^{\text{Three}}\text{–R}\left(\text{aq}\right)\to \text{Cu}\left(\text{I}\right)\left(\text{aq}\right)+\text{ROH}/{\text{R}}_{-\text{H}}$

(82) $\text{Cu}\left(\text{I}\right)\left(\text{aq}\right)+\text{Atomic number 26}{\left({\text{H}}_2\text{O}\right)}_6{}^{\mathrm{three}+}\to \text{Cu}{\left({\text{H}}_2\text{O}\right)}_{\mathrm{due\; north}}{}^{2+}+\text{Fe}{\left({\text{H}}_2\text{O}\right)}_6{}^{2+}$

This shift in machinery is due to the fact that reaction (79) is considerably slower than reaction (80) ( 115,141 ). These reactions have naturally to be considered besides in the Cu(I)-catalyzed Fenton-similar reactions where R^• radicals are formed. These processes are of special importance in biological systems in which copper complexes are known to induce oxidative stress ( 142–147 ). The Cu(I) species are formed in biological systems past reduction of Cu(Two) past ascorbate, thiols, etc.

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Control of Legionella in hospital drinkable h2o systems

J.50. Businesswoman , ... J.E. Stout , in Decontamination in Hospitals and Healthcare (Second Edition), 2020

iv.2.2 Copper-silver ionization

Copper and silver ions are released into the hot water organisation from metal electrodes. The system is typically installed on the hot water recirculation system. The mechanism of action involves positively charged copper and silver ions forming bonds with negatively charged ions on the bacterial prison cell wall. Lysis and bacterial cell death is the result. Copper and silver ion concentrations in the ranges of 0.3–0.eight mg/L copper and 0.01–0.08 mg/L silver are typically recommended for Legionella control [53–56] . Copper ion concentrations should be monitored weekly with a field examination kit. Silver concentrations can simply be tested past a certificated reference laboratory and should be tested bimonthly. Water samples for ion analysis should be articulate and free of sediment. Ions can demark to particulates and result in high readings. Monitoring ion concentrations and maintenance of equipment to reduce scale formation on the electrodes is necessary and this applied science tin can be used for both short-term and long-term disinfection.

The start installation of a copper‑argent ionization system in the United States was in 1990 [57]. A Pittsburgh, Pennsylvania hospital showed that Legionella colonization of distal outlets was reduced from 75% to 0% in 3 months. Copper and silver ion concentrations were in a higher place 0.4 and 0.04 mg/L, respectively [58]. When the ionization unit was deliberately inactivated, recolonization was delayed, and the water organization remained costless of Legionella for an additional 2–3 months. Accumulation of ions inside the biofilm was demonstrated to exist the basis for the prolonged bactericidal effect [58, 59]. Copper‑silver ionization has been used in hospitals, long-term care facilities [60], office buildings [58], and apartment buildings [61].

Copper‑silver ionization has been used to control Legionella in hospitals worldwide [53–56, 62–65]. Sixteen US hospitals were followed that had ionization systems in place for 5–11 years and showed success where other methods such as superheat and flush, ultraviolet light, and hyperchlorination had failed [25]. Fifty percent of the hospitals reported 0% positivity within 0–5 years after treatment with copper‑silver ions, and 43% all the same reported 0% positivity five years later. More importantly, no cases of hospital-acquired Legionnaires' disease had occurred in any of these hospitals afterwards installing ionization systems. 10 cases of Legionnaires' disease occurred at the University of Wisconsin hospital from 1985 to 1995, despite hyperchlorination. Following installation of copper‑silver ionization, Legionella was eliminated from the drinking water system and no cases were diagnosed [66].

A 1998 survey of U.s. National Nosocomial Infections Surveillance hospitals showed that copper‑silvery ionization was used in 32% (12/38) of hospitals that had instituted disinfection measures [67]. The kickoff three hospitals to apply hyperchlorination for Legionella disinfection (Wadsworth VA Medical Center, California; University of Vermont Medical Center, Vermont; University of Pittsburgh Medical Centre, Pennsylvania) ultimately switched to ionization because of failure to control Legionella and chlorine-induced corrosion. A review of x published studies also concluded that copper‑argent ionization is an constructive method to command Legionella as long as ion levels were properly monitored [64]. A metadata assay of 3 studies comparing copper‑silver ionization to no treatment indicated a 95% risk reduction of Legionella distal site positivity [68]. In the United kingdom of great britain and northern ireland, a new hospital compared reducing hot water temperatures (to 43°C, ranging 37–44°C) and utilizing copper‑silver ionization to control Legionella in their water system. No L. pneumophila was isolated from whatsoever of the samples nerveless after the ionization system was installed. However, it is not clear whether in that location was any Legionella colonization or recovery prior to the installation of the copper‑argent ionization system and edifice commissioning [69]. It should besides be noted that in the United Kingdom, the Health and Safety Executive (HSE) stipulate that "Hot water should be stored at least at 60 °C and distributed so that information technology reaches a temperature of 50 °C (55 °C in healthcare premises) within one infinitesimal at the outlets" [70].

Advantages of copper‑argent ionization include easy installation and maintenance. Oral consumption is limited since the ions are typically added but into the hot h2o recirculating lines. The demonstrated prolonged efficacy of ionization after an interruption provides added margin of safety. This is different hyperchlorination in which Legionella can speedily appear in the event of arrangement malfunction. The biocidal activity of copper‑silver ionization is not compromised by higher h2o temperature [71], which is the instance for chlorine and chlorine dioxide.

Elevated water pH [72] and depression ion concentrations [73] may compromise the efficacy of ionization then these have to exist addressed at the time of installation and monitored. High pH of the hospital water (>   8.5) interferes with the disinfecting activeness of both chlorine and the copper‑silver ions [74, 75]. Copper‑silvery ionization was demonstrated to be constructive in decision-making Legionella in an astute intendance facility, previously treated with chlorine dioxide, and long-term care facility nether alkali metal water atmospheric condition [76]. Low ion levels in ii German hospitals were responsible for copper‑argent ionization systems failure to control Legionella [73, 77]. In both hospitals, the concentrations of copper and silver ion concentrations were well beneath the recommended concentrations of copper and silver so as to comply with the German drinking water standard (maximal silver of 0.01 mg/L) [78]. One French hospital besides reported the failure of ionization [79]. In this example, phosphate added to the water organisation to control corrosion may have interfered with the efficacy of ionization [lxxx].

Resistance of Legionella pneumophila to copper‑silver ions has been documented in a few hospitals following installation of copper‑silver ionization systems [81]; nonetheless in that location is no indication that resistance is frequent or widespread. Hospitals that maintain control by monitoring ion concentrations and Legionella distal site positivity are less likely to experience this phenomenon. Rigorous maintenance plans with regular monitoring of both ion concentrations and culturing for Legionella positivity are necessary to ensure long-term success.

The Environmental Protection Agency (EPA) fix a maximum containment level (MCL) for copper in drinking water of 1.3 mg/Fifty, and 0.1 mg/L for silver (nonenforceable). EPA at present requires ionization systems to "annals" as a biocide for use in beverage h2o [72]. This registration falls nether the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) for devices claiming biocidal action. In the U.k., Spain, kingdom of the netherlands, and Poland carve up applications allow for these products to be used, though non authorized for the whole of the EU, whose members must use alternative methods for treatment [82].

Copper and silver ions take been demonstrated to exist bactericidal in vitro and in model plumbing systems confronting other waterborne pathogens including Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Acinetobacter baumannii [83, 84]. One study demonstrated the inefficiency of copper‑silver ionization against nontuberculous mycobacterium at levels sufficient to command Legionella in a hospital system [53].

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Characterization of Porous Solids VI

Giovanni Ferraris , ... Mariano Lo Jacono , in Studies in Surface Science and Catalysis, 2002

1 INTRODUCTION

Copper ions exchanged microporous molecular sieves, in particular Cu-ZSM-five, are agile catalysts for the selective catalytic reduction of NO and North₂O with hydrocarbons in the presence of O_two (HC-SCR). It has been reported that the catalytic activity may exist controlled by intra-crystalline diffusivity and by geometry-limited diffusion depending on the hydrocarbon molecular size and the zeolite pore size [one]. Therefore, it is of involvement to set up Cu-Al-MCM-41 mesoporous molecular sieves and to compare their activeness with that of Cu-ZSM-5.

The synthesis of Al-MCM-41 has been reported past several authors and the distribution between framework and actress-framework aluminum species has been found to depend strongly on the silica and aluminum sources, the nature of templating surfactant and synthesis atmospheric condition [Ref. 2 and references therein]. In this contribution we investigate a simple grooming method based on hexadecyltrimethylammonium cloride, tetraethyl orthosilicate, aluminum isopropoxide and an ammonia solution.

The Cu-Al-MCM-41 catalysts where prepared by standard ion substitution process and tested for the selective catalytic reduction (SCR) of NO with propane in the presence of O₂, under the same experimental atmospheric condition employed for Cu-ZSM-five catalysts with similar copper loading and Si/Al diminutive ratio.

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Integrated modeling of the cobalt removal process

Chunhua Yang , Bei Sun , in Modeling, Optimization, and Control of Zinc Hydrometallurgical Purification Process, 2021

6.2.1.v Concentration of zinc ions and copper ions

If the concentration of zinc ions in the feeding solution is too high, then the concentration of zinc ions surrounding zinc powder particles is besides high. The difficulty of zinc ions entering the solution is increased. Equally a result, zinc tin inappreciably lose electrons and be converted to zinc ions. In addition, it is difficult for cobalt ions to obtain electrons and deposit on the surface of zinc powder particles. Cobalt ions tin be chop-chop removed to a depression concentration if zinc ions are non nowadays in the solution.

An appropriate amount of copper ions in the feeding solution is beneficial for cobalt removal. Compared with cobalt removal activated by antimonic salt, in ACP, copper ions take a larger promoting effect on cobalt removal. Therefore, in exercise, the copper ions are not completely removed in the copper removal process. Part of the copper ions are reserved for the cobalt removal procedure. Yet, excessive copper ions volition increment zinc powder consumption. The promoting effect of copper ions on cobalt removal can be explained from two aspects:

(i)

Copper ions react with metaarsenous acid, producing copper arsenide. Copper arsenide volition form a microcell with zinc powder, which acts every bit a cathode to promote the precipitation of cobalt ions.

(ii)

Although the formation of zinc-cobalt alloy will reduce the potential difference between cobalt and zinc, thereby reducing the thermodynamic impetus of the replacement reaction, if the formation of the alloy is not between the replacement metal and the replaced metal, but two or more replaced metals, then the situation is totally different. In this case, the metal with the most positive deposition potential (such as copper) tin can move the degradation potential of some electronegative impurities towards a positive direction. As a result, the potential divergence of the original zinc-cobalt microcell is increased, i.e., the thermodynamic impetus of the replacement reaction is increased.

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Long-Acting Reversible Contraception in Adolescents

Megen Vo , in Reference Module in Biomedical Sciences, 2021

Copper IUD

The copper IUD (Cu-IUD, merchandise name Paragard) is the simply non-hormonal LARC available in the United states of america. It consists of a 380   mm copper wire wrapped around a T-shaped polyethylene frame. Information technology is FDA approved for 10   years but has been shown to provide up to 12   years of effective contraception in studies. Because it has no hormonal effects, information technology is an excellent choice for women who wish to avoid hormones for whatsoever reason or accept medical conditions which prevent them from using hormonal contraception (Curtis et al., 2016). Information technology is also the only LARC that may exist used for emergency contraception (Committee on Practice Bulletins Gynecology and Long Acting Reversible Contraception Work Group, 2017).

Mechanism of action

The copper IUD releases copper ions locally in the uterus afterwards placement. These copper ions are spermicidal, inhibiting fertilization, and inhibit implantation, which is the mechanism of activity when Cu-IUD is used for emergency contraception. The copper IUD does non affect ovulation, therefore patients continue to have menstrual bleeding.

Benefits

Cu-IUD is the longest-interim LARC, is constructive for emergency contraception, and contains no hormones, and therefore may exist the only LARC option for patients with conditions that forbid use of hormonal contraception. The efficacy of Cu-IUD is like to female person sterilization, with a failure charge per unit of 0.six–0.8% per year (Oritz and Croxatto, 2007). Like all IUDs, Cu-IUD also has the benefit of being a detached grade of contraception.

Risks

Because Cu-IUD contains no hormones, patients may experience changes in menstrual bleeding that include increased frequency or quantity of bleeding or increased cramping with menses. Studies accept shown that 70% of women experienced heavier bleeding afterwards Cu-IUD placement and sixty% reported increased cramping (Hubacher et al., 2009); some studies show that increased haemorrhage/cramping was more than likely in patients who had heavy periods prior to using the IUD. While these effects appear to decrease with time (Hubacher et al., 2009), it is very of import to counsel patients to expect increased haemorrhage/cramping, especially during the first 3   months of employ. These risks should exist explained in detail, as patients may cull to discontinue the Cu-IUD early due to dissatisfaction with the bleeding profile (Abraham et al., 2015). As with all IUDs, there is an increased adventure of uterine perforation, expulsion, and PID within the first thirty   days of placement. Patients may also experience pain in the starting time 2 weeks following placement (Sinning et al., 2018).

Translational implications

The impact of long-acting reversible contraception on the wellness of adolescents cannot be overstated. Long-acting reversible contraceptives are prophylactic, effective, and adequate for apply for pregnancy prevention in adolescents. Where LARC methods are made available and affordable to adolescents, rates of unintended pregnancy decrease, with notable, far-reaching public wellness implications. While use of LARC methods for contraception has increased among adolescents in recent years, increasing counseling regarding LARCs as contraceptive options, every bit well as ensuring adequate access, is critical. Access to LARCs includes coverage through private or public insurance or assistance programs for low income youth, as well as ensuring adequate admission to providers trained in placing LARCs.

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Leaching of Copper Sulphides

Tomáš Havlík , in Hydrometallurgy, 2008

12.ane.4 Leaching of chalcopyrite in sulphuric acid using ozone as the oxidation amanuensis [106–121]

For the transfer of copper ions into the solution in acrid leaching of chalcopyrite CuFeS ₂ in sulphuric acrid, the redox potential of the acrid medium must be theoretically higher than +   0.iv   V. These conditions may be ensured using ozone every bit an oxidation amanuensis. The principle of application of ozone as the oxidation agent in oxidation leaching of ores and concentrates of nonferrous metals is based on the loftier value of the oxidation potential of ozone, +2.07   V, which oxidises (with the exception of platinum, gilt and iridium) all metals and their compounds in the solution. This was used as a basis in the leaching experiments of chalcopyrite [107–120, 122] which confirmed the high efficiency of ozone equally the oxidation amanuensis.

Ozone was prepared in a commercial ozoniser of Fischer® Model 502 (Switzerland) whose operating principle is based on repose discharge by the issue of high-voltage with a loftier frequency in oxygen, using a Siemens ozoniser. The amount of ozone in the working atmosphere, produced by this equipment, is in the range 2060   g/m³ of O_three in one   m^three of the atmosphere and depends on the menstruation rate of oxygen through the ozoniser. The leaching medium was represented by the aqueous solutions of sulphuric acrid, concentration 0–1.0   M.

The leaching of chalcopyrite using ozone took place according to the reaction

(12.40) $3{\mathrm{CuFeS}}_{\mathrm{two}}+\mathrm{eight}{\mathrm{O}}_3\to 3{\mathrm{CuSO}}_4+3{\mathrm{FeSO}}_4$

Experiments with acrid oxidation leaching of chalcopyrite in sulphuric acid using ozone as the oxidation agent take been expanded by the examination of conversion of atomic number 26 in the solution. When using the ferric ion as the oxidation agent, either in the form of sulphate or chloride, this was not possible because of the minimum alter of the concentration of iron during the process in the leaching medium in comparing with the initial concentration, given by the composition of the medium.

Figure 12.8 shows the kinetic curves of the yield of copper, obtained past leaching a chalcopyrite concentrate in a 0.v   M solution of H_iiSo₄ in the temperature range 3.5–75   °C using ozone every bit the oxidation agent in the amount of approximately 2.5 volume % in the oxygen atmosphere with continuous bubbles through the working solution during the experiment. Similarly, Fig. 12.9 shows the kinetic curves of the yield of iron from chalcopyrite.

Fig. 12.8. Dependence of the yield of copper on the leaching time of chalcopyrite using ozone.

Fig. 12.9. Dependence of the yield of iron on the leaching fourth dimension of chalcopyrite using ozone.

The curves are exponential and since no continuous layer of elemental sulphur or whatsoever other reaction production forms during the process on the leached surface, they are described most efficiently by the shrinking core model without the germination of a solid reaction production.

The oxidation leaching of sulphides in the acid medium is characterised by the increase of the leaching rate with increasing temperature. However, Figs. 12.viii and 12.9, showing the kinetic curves of chalcopyrite leaching with ozone signal however, the complete contrary. This is given by a rapid decrease of the solubility of ozone nether the effect of temperature, equally shown past Fig. 12.10.

Fig. 12.ten. The temperature dependence of solubility of oxygen and ozone in h2o.

Although the data for the solubility of ozone have been obtained only for temperatures of upwards to l   °C, the experiments show that the consequence of ozone is besides potent at higher temperatures, for example at experiment temperatures of xc   °C the corporeality of dissolved copper was approximately 5 times greater when using ozone in comparing with the one when using oxygen. According to [122], the solubility of ozone at 60   °C is 0 and information technology therefore appears that the oxidation capacity of ozone is also strong at higher temperatures. Gazo et al. [10] described the existence of activated states of oxygen which have, like ozone, oxidation properties, but it is very difficult to estimate the contribution of the activated grade of oxygen and of ozone to the reaction.

Ii competing phenomena take place during the process: the increase of the dissolution charge per unit nether the effect of temperature, and a subtract of the rate under the result of the subtract of the amount of ozone in the solution. The curves at 3.5 and fifteen   °C should exist the manifestation of these tendencies. The class of these curves slightly differs from the other curves and the accented amount of dissolved copper or atomic number 26 in unit fourth dimension is lower than at 22   °C, but college than at other temperatures.

Since the highest yield of the metals has been obtained at room temperature, the effect of the corporeality of dissolved ozone in the leaching medium is evident. Therefore, investigations were also carried out into the effect of the contact time of gaseous ozone with the liquid and its chapters to dissolve in copper. Figure 12.11 shows the course copper leaching from chalcopyrite in different volumes of the solutions of sulphuric acrid. It may be seen that the corporeality of leached copper from chalcopyrite increases with increase of the volume of the leaching amanuensis, i.eastward. with increase of the acme of the level of the column of the leaching solution. The initial supposition according to which the leaching kinetics depends on the amount of ozone in the solution has been confirmed.

Fig. 12.11. Dependence of the leaching charge per unit on the amount of the leaching solution.

The dependence of the leaching rate on the corporeality of the solution, Fig. 12.xi, shows that the solution is not saturated even when using thousand   ml of the solution which is the maximum height from the design viewpoint of the equipment, because the leaching charge per unit increases in direct proportion. This means that to increase the efficiency of leaching it is necessary, in these weather condition, to keep increasing the height of the liquid column.

The amount of ozone in the working atmosphere has a stiff effect on the corporeality of metallic leached into the solution. Effigy 12.12 shows the kinetic curves of leaching of copper in relation to the amount of ozone in the working atmosphere.

Fig. 12.12. Kinetic curves of copper leached depending on the amount of ozone in the working atmosphere.

Effigy 12.13 is the dependence of the leaching rate of copper from chalcopyrite on the amount of ozone in the working atmosphere. In may be seen that the increase of the corporeality of ozone in the working atmosphere increases well-nigh proportionately to the leaching rate.

Fig. 12.thirteen. Dependence of the corporeality of leached copper on the amount of ozone in the working atmosphere.

These results show the controlling upshot of ozone on the leaching charge per unit of chalcopyrite. To decide the exact outcome of all the factors influencing leaching, it is necessary to know the exact corporeality of ozone in the solution in the given conditions. Nevertheless, information technology has not equally even so been possible to solve the problem satisfactorily because of technical reasons. Consequently, it has not been possible to determine the activation energy nor other kinetic characteristics. Despite these facts, it may exist seen that the leaching charge per unit is the highest at a temperature of 22   °C. Taking into account the temperature dependence of the solubility of ozone, shown in Fig. 12.10, it may be causeless that although the amount of the oxidation amanuensis in the solution at low temperatures is sufficiently large, a controlling role is played past the temperature and viscosity of the leaching medium.

The charge per unit-decision-making footstep could be the external diffusion of ozone to the leached surface and the removal of the reaction products through the layer of the viscous medium and/or slow reaction under the issue of depression temperature. At higher temperatures, the shortage of the oxidation agent in the leaching medium is already evident and the diffusion of the agent to the leached surface from the volume of the leaching solution manifestly limits the overall reaction rate. The amount of the leached metal increases with increase in the volume of the leaching solution, i.e., with increase of the meridian of the liquid column, and this results in an increment of the contact time of the gas bubble, containing ozone, with the pulp.

The highest yield was obtained at a leaching temperature of approximately 20   °C. This is a positive event – in practice, the toll of heating, holding at a temperature and cooling of the large volumes of the diluted solution would be profoundly reduced. In addition, this oxidation agent does not contaminate the solution with strange anions and ensures complete transfer of sulphur to the soluble form.

An of import advantage of the use of ozone every bit the oxidation agent in acrid oxidation leaching is also the availability of high operation commercial ozone generators (Fisher, Brown Boveri) used, for example, for ozonation of drinking water. Therefore, information technology appears that it may also exist used every bit an efficient and cheap oxidation agent in the hydrometallurgy of copper and may improve the economical parameters of this production procedure.

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The Employ of Silvery Salts for Photochromic Glasses

H.J. Hoffmann , in Photochromism, 2003

iv ORIGIN OF THE INDUCED ABSORPTION EFFECT

The glasses of the compositions given in Tabular array 1 are not photochromic if they are quenched from the melt. They are not photochromic even afterward their usual heat handling if either the silvery or halide ions are missing. Thus, one must dominion out that the absorptivity, which is induced past the UV–irradiation in these glasses is due to isolated silver, chlorine or bromine atoms or ions. This is supported by the following experimental results: Isolated silvery atoms or ions absorb mainly in the range of wavelength λ < 400 nm (refs. 33–35). The same is true for chlorine ions or Cl₂ molecules, as is well–known from chemistry. Br₂ molecules, notwithstanding, absorb electromagnetic radiation in the visible (refs. 36, 37). The absorbance of Br_ii molecules in an Ar–matrix, e.thousand., extends from nigh 370 to 540 nm with a top molar absorbance of 205 cm⁻¹/(mol/liter).

This value corresponds to a tiptop absorption cross section of near 7.8 • 10⁻¹⁹ cm², which is likewise small by more than one order of magnitude to account for the photochromic darkening as will be seen in the post-obit. Like arguments concord for the assimilation of BrCl molecules (ref. 36). In addition, the glasses in Table 1 get photochromic with silver and chlorine ions added to the melt and omitting bromine ions. Thus, one has to conclude that the absorptivity induced by UV–irradiation of the photochromic spectacles from Tabular array one are due to silver clusters.

The photolytic decomposition of silver halides and the concomitant formation of silver clusters are well–known phenomena in chemistry and physics. The absorption of silver colloids has been understood fairly well since the pioneering work of Mie (ref. 38). The assimilation is due to the surface plasmon resonance of the colloids. These resonances take been observed for silverish colloids both in spectacles and other matrices (refs. 35, 39–47). In oxide glasses it is betwixt 400 nm and 500 nm (refs. 39, 40).

The peak of the absorption maximum shifts slightly to shorter wavelengths and its halfwidth increases with decreasing diameter (refs. 41–45). Charlé, Frank, and Schulze (refs. 45, 46) ended from their experimental results that the position and halfwidth of the assimilation acme depends strongly on the surrounding matrix. The optical properties of the colloids change with decreasing bore due to quantum size effects. Much theoretical and experimental piece of work on these effects has been published in the literature.

However, the assimilation coefficient of spherical silver colloids as a part of the wavelength cannot account for the rather broad absorption band which is induced by the UV–irradiation in photochromic glasses (see Fig. 1). During the UV–irradiation the diameter of spherical argent colloids would increase from minor clusters of silver atoms to large silverish colloids with the cube–root of time. Consequently, the halfwidth would subtract considerably equally well as the energetic position of the induced absorption band would shift. This has non been observed upwardly to at present. Instead, the spectrum of the induced absorption constant remains very broad which corresponds to a big constructive damping of the plasma resonance during the irradiation. Thus, one can conclude that at least i dimension of the silver clusters, which are formed by photolytic decomposition in the photochromic glasses, does not change with time appreciably and remains rather pocket-sized in order to account for the very large halfwidth. In other words, the dimensionality of the photolytically deposited silver clusters must be lower than 3. The silver can be deposited, e.g., equally a chain (1–dimensional) or as a layer (ii–dimensional) or in an arrangement of fractal dimensionality. At present, the dimensionality of the silver clusters in photochromic spectacles is not known. However, there are several reasons to presume a 2–dimensional arrangement of the silver, e.g. a sparse silver layer may exist deposited on the surface of the silvery halide particles during the photolysis (refs. 48,49).

In the following we will focus on the absorption due to Cu ions in the photochromic drinking glass. Copper ions have been detected in oxidic glasses in their monovalent (Cu ⁺, cuprous ions) and their divalent (Cu²⁺, cupric ions) states (refs. 19, l–53). In these glasses, divalent copper ions show a wide absorption band in the cherry-red and almost–infrared spectral regions with a maximum assimilation cantankerous section in the range of some ten^−nineteen cmⁱⁱ. For alkali borate glasses it has been shown that the shape besides as the maximum molar absorbance depend on the concentration and type of the corresponding alkali–ions (ref. 54). Cu⁺ ions dispersed in an oxidic glass, on the other hand, exercise not blot in the visible spectral region. Consequently, oxidic glasses are not colored past dispersed Cu⁺ ions. In commercial photochromic glassses, copper is congenital in the matrix predominantly equally Cu⁺ ions as a effect of the high melting temperatures and the reducing melting weather.

In principle, photochromic spectacles tin be colored by copper ions due to the following processes:

1.

Because of the phase separation during the heat treatment procedure of alumo–boro–silicate glasses, the cuprous ions concentrate in the borate rich phase of the glass. This can result in a supersaturation of Cu⁺ ions in that phase and clusters of Cu₂O may be precipitated depending on the concentration of copper ions, on the temperature and on the appropriate partial pressure of oxygen (ref. 55). According to ref. 55 Cu₂O particles tin cause a red color. In social club to avoid this upshot, the amount of Cu ions to be added to the cook of photochromic spectacles is limited to the order of some 10⁻² mass% and the partial pressure level of oxygen has to be controlled very carefully. Co-ordinate to the results of other workers, copper may be precipitated every bit metal colloids which cause a reddish color (ref. xix).

2.

Both cupric and cuprous ions show strong charge–transfer assimilation bands in the UV. Cu⁺ ions tin can be photooxidized into Cu²⁺ ions by UV–irradiation (ref. 50). This issue, notwithstanding, is rather small in a photochromic drinking glass matrix, since with an absorption cross section in the range of some 10^−nineteen cm² and a full concentration of some 10¹⁸ cm⁻³ copper ions (encounter Table 1) one can only induce an absorption constant between 0.ane and 1 cm^−ane, instead of x cm⁻ⁱ which is necessary for adjustable sunglasses. In addition, Cu^two+ ions in oxidic glasses absorb in the red and nearly–infrared spectral region (whereas Cu⁺ does not absorb in the visible). Thus, the photochemical oxidation of Cu⁺ into Cu²⁺ contributes simply trivial to the induced absorbance of silver halide photochromic sunglasses, if it occurs in the glass matrix.

3.

Cu⁺ ions can be congenital into the silverish halide particles of the photochromic glasses. Results of the absorption abiding of AgCl doped with Cu²⁺ or Cu⁺ from ref. 56 are shown in Fig. 9. The absorption of small-scale concentrations of Cu⁺ can be neglected equally compared to that of AgCl. Still, Cu^two+ ions in AgCl can cause an appreciable assimilation constant in the visible spectral region. Marquardt and coworkers (refs. 49, 57, 58) investigated the different contributions to the UV–induced assimilation coefficient of photochromic glasses. They separated the induced absorption constant into different contributions due to photolytically deposited silver clusters, Cu²⁺ ions in the argent halide particles and other possible unspecified ions in the glass matrix. The optical transformation of Cu⁺ into Cu²⁺ was detected by electron spin resonance. Information technology turned out that there is a considerable contribution of the induced absorption coefficient due to Cu²⁺. According to ref. 58 that contribution can be equally large equally 50%. Thus, a major fraction of the copper ions take to be built into the silvery halide particles. The time calibration for the optical transformation of Cu⁺ into Cu^two+ was shorter than 20 ns upon irradiation.

Fig. 9. Optical absorption spectrum of crystalline AgCl in the visible spectral region at 23 °C; (a), (b), and (c) unirradiated samples, (a) pure AgCl, (b) AgCl doped with 10¹⁷ Cu⁺ ions per cm³, (c) AgCl doped with 10¹⁷ Cu²⁺ ions per cm³, (d) sample (b) after irradiation past a flux density of v.10¹⁵ photons per cm² and per s of 436 nm wavelength until the absorbance saturated. Thickness of the samples: 6.2 mm.

(Data from ref. 56)

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ATMOSPHERIC CORROSION

Zaki Ahmad , in Principles of Corrosion Engineering science and Corrosion Control, 2006

10.9.2 REQUIREMENTS FOR PATINA Germination

The germination of brochantite in patina requires four ingredients, copper ions, an aqueous layer on copper substrate, a source of sulfur and an oxidizer which is summarized beneath:

(1)

Copper ions (Cu⁺⁺): These are produced past oxidation of copper by SO_two in the atmosphere.

(2)

Aqueous layer: Several monolayers of water may be adsorbed on copper at moderate to high humidity even in the absence of atmospheric precipitation. Water monolayers ranging from 5 nm to 10 nm thickness may be formed on clean copper exposed to sixty–90% RH.

(iii)

Sulfur: Oxidized sulfur species are present in copper minerals.

(4)

Oxidizer: An atmospheric gas or a product of precipitates.

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