Copper/silver ionizers

Mietzner, S. Schwille, R. C. Farley, A. et al. (1997). Efficiency of Thermal Treatment and Copper Silver Ionization for Control of Legionnella pneumophila in High Volume Hot Water Plumbing Systems in Hospitals. American Journal of Infection Control 25 452 57. 

Silver and copper ions act synergistically in the killing of Legionella bacteria, which are known to multiply in biofilms in hot water distribution systems. Copper-silver ionization has been used successfully to control Legionella spp. in many US hospital hot water systems after 5 to 11 years of operation however, high pH values and elevated chloride concentrations have negative effects on the biocidal efficacy of copper and silver, respectively, in water systems (Lin et al., 2002). 

National Spa and Pool Institute. 1997. Copper/Silver Ionizers Information Bulletin, NSPI, Alexandria, VA. 

D.V. Davis, V.D. Mistry, C.A. Quarles, Inner shell ionization of copper, silver and gold by electron bombardment, Phys. Lett. 38A (1972) 169. 

Like copper, silver and gold have a single s electron outside the completed d shell, but in spite of the similarity in electronic structures and ionization potential, the chemistries of Ag, Au, and Cu differ more than might be expected. There are no simple explanations for many of the differences although some of the differences between Ag and Au may be traced to relativistic effects on the 6s electrons of the latter. The covalent radii of the triad follow the trend Cu < Ag Au, i.e., gold has about the same or a slightly smaller covalent radius than silver in comparable compounds, a phenomenon frequently referred to as relativistic contraction (c/. lanthanide contraction). 

Ionizers, Ionizers generate small concentrations of copper and silver ions (by electrochemical dissolution of a copper—silver electrode) that function as algicide and bactericide, respectively (10). Although the concentration of copper (. 3 ppm) is adequate, the concentration of silver, a poor disinfectant, is very low (<50 ppb). Consequendy chlorine sanitizers are necessary not only for effective disinfection but also for oxidation of swimming pool contaminants. Another disadvantage is that copper and silver ions form colored insoluble precipitates, which can cause staining. 

Experiment demonstrating the displacement of silver from solution by copper. A copper coil is placed in a solution of silver nitrate (colorless). After some time, the solution turns blue, and dendritic crystals form on the coil. The copper from the coil displaces silver ions in solution. The copper becomes ionized as copper(ll), seen as a characteristic blue color, and the silver is deposited as a metal crystal. (Courtesy of Jerry Mason/Science Photo Library)... 

Like copper, silver and gold have a single s electron outside a completed d shell, but in spite of the similarity in electronic structures and ionization potentials there are few resemblances between Ag, Au and Cu, and there are no simple explanations for many of the differences. 

The derivation of the Debye-Hiickel equations is not included here, but only the end results. A complete discussion is given by Bull (1964), Chapter 3. There are, however, several basic phenomena that we need to examine. There are three mechanisms which produce ions in water solutions. These are (1) solution of an ionic crystal, (2) oxidation of a metal or reduction of a nonmetal, and (3) ionization of a neutral molecule. Most metals when they ionize give up electrons to an electronegative element so that both acquire the electronic structure of a rare gas. Exceptions of interest in electrode work are iron, copper, silver, mercury, and zinc. In the ionized state, these metals do not acquire the completed outer shell structure of a rare gas and do have residual valences. They are then somewhat unstable and complex with various molecules more easily than do the stable ionized metals with completed shells. This accounts for the poisoning of silver-silver chloride electrodes and p02-measuring electrodes when used in high-protein environments such as blood. 

Silver-copper (Ag-Cu) ionization systems, environmental limits on, 22 652 Silver-copper system, properties of, 22 644 Silver cyanide, 22 670-671, 674-675 in electroplating, 22 685-686 Silver cyclohexanebutyrate, 22 671 Silver development, corrosion model of, 19 245... 

Dialysis units provided highly efficient means for increasing selectivity in a dynamic system by placement in front of a lithium-selective electrode constructed by incorporating 14-crown-4 ether 3-dodecyl-3 -methyl-1,5,8,12-tetraoxacyclotetradecane into a PVC membrane that was in turn positioned in a microconduit circuit by deposition on platinum, silver or copper wires. The circuit was used to analyse undiluted blood serum samples by flow injection analysis with the aid of an on-line coupled dialysis membrane. For this purpose, a volume of 200 pL of sample was injected into a de-ionized water carrier (donor) stream and a 7 mM tetraborate buffer of pH 9.2 was... 

Hydrofluoric acid like water is an associated liquid, and even the gas, as we shall soon see, is associated. It has the power of uniting with fluorides. It also seems to be an ionizing solvent for a soln. of potassium fluoride in liquid hydrogen fluoride is an excellent conductor it also possesses marked solvent powers. According to E. C. Franklin,7 the liquid readily dissolves potassium fluoride, ehloride, and sulphate sodium fluoride, bromide, nitrate, chlorate, and bromate acetamide and urea. The solvent action is not so marked with barium fluoride, cupric chloride, and silver cyanide while calcium and lead fluorides copper sulphate and nitrate ferric chloride, mercuric oxide, and magnesium metal, are virtually insoluble in this menstruum. Glass also is not affected by the liquid if moisture be absent. The liquid scarcely acts on most of the metals or non-metals at ordinary temp., though it does act on the alkali metals at ordinary temp., much the same as does water, with the simultaneous production of flame. 

These points are well illustrated by comparing Cu, Ag and Au with respect to the relative stabilities of their oxidation states. Although few compounds formed by these elements can properly be described as ionic, the model can quite successfully rationalise the basic facts. The copper Group 1 Id is perhaps the untidiest in the Periodic Table. For Cu, II is the most common oxidation state Cu(I) compounds are quite numerous but have some tendency towards oxidation or disproportionation, and Cu(III) compounds are rare, being easily reduced. With silver, I is the dominant oxidation state the II oxidation state tends to disproportionate to I and III. For gold, III is the dominant state I tends to disproportionate and II is very rare. No clear trend can be discerned. The relevant quantities are the ionization energies Iu l2 and A the atomisation enthalpies of the metallic substances and the relative sizes of the atoms and their cations. These are collected below / and the atomisation enthalpies AH%tom are in kJ mol-1 and r, the metallic radii, are in pm. 

Fig. 5.23. Ratio of K-shell ionization cross sections for electrons and positrons scattering from silver and copper at various impact energies -----, Born approximation calculation including a Coulomb correction (see text) -, Born...

One type that is a bit more complex but that shows up a fair amount is the addition of a metal to a strong oxoacid solution (usually nitric or sulfuric). The reason these are selected as often as they are is that they violate the typical rules for the replacement of hydrogen in solution. This is because the acids act as strong oxidizing agents that will ionize the metal. Copper or silver typically appear on the test because they won t react with other acids but they will with the oxoacids. Both metals are oxidized by these acids. 

---