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The processes occurring in the DMSO-HBr aq system at different ratios of the components were studied by electronic and IR spectroscopy. The interaction of the components in the system results in the accumulation and consumption as oxidants of bromine containing (Me 2 S(OH)Br, Me 2 S•Br 2 ) and oxygen containing compounds (H 2 O 2 , HBrO). It was shown by the pH metric method that the equilibrium concentration of species that are accumulated in the system and oxidize the metal is achieved on the fifth day after mixing of the components. The dependence of the dissolution rate of platinum (Pt 0 ) on the ratio of components (DMSO : HBr) has three maxima, whose positions are determined by the nature of intermediate species formed in the system and the state of the metal surface containing the oxide film.Key words: donor acceptor electron transport system, dimethyl sulfoxide, hydrobromic acid, oxidative dissolution, noble metals, metal surface, oxide film, IR spectroscopy, pH metry.Studies of donor acceptor organic and aqueous organic systems that oxidize transition metals are still important for both an understanding of processes occurring in the liquid phase and on the metal surface and the solution of prac tical problems on extraction of precious metals from indus trial waste and various types of mineral raw materials. 1 Similarly to aqua regia, the aqueous organic donor ac ceptor electron transport DMSO-HBr aq system («cher nogolovskaya vodka») studied in this work dissolves tran sition metals, including noble metals (Au 0 , Ag 0 , Pd 0 , Pt 0 , Rh 0 , and others). 2 A distinctive feature of metal disso lution in the DMSO-HBr aq system is the presence of several maxima in the plot of the metal dissolution rate vs DMSO : HBr ratio. This possibly indicates the forma tion in the system (due to the interaction of the compo nents) of several reactive species that oxidize the metal. 3,4The DMSO-HBr aq system was studied by electronic and IR spectroscopy and the dynamics of the change in time of its state was examined by pH metry in order to reveal the processes occurring in the system upon a change in the ratio of the components in the liquid phase and to determine the nature of species oxidizing the metal.The dependence of the dissolution rate of platinum (Pt 0 ) on the DMSO : HBr ratio was studied and the posi tions of maxima in the curves of the dependence of the dissolution rate of metals (Pt 0 , Au 0 , Ag 0 , Pd 0 , Cu 0 ) on the ratio of the components of the system were examined in comparison.

The products of interaction of componen,'s m the donor-acceptor electron-transport (DAETI DMSO--HBr system and their complex formation with the metallic palladium surface ~,ere studied. H20 and Me~S tmain reaction products) and CO, CS 2. C2H+ ,, MeBr, H, and CH 4 (nlinor reaction products) were fiaund m the gas phase by mass spectrometq,' (MS). The samples of metallic palladium treated with lhe DAET system with a components ratio corresponding to the minimum and maximuna rates of metal dissolution were studied by the methods of thermoprogrammed desorption v.ith MS detection (TPD-MS) and XPS. According to the FPD-MS data. two forms of Me-S are presen{ on the metal surface, whereas the XPS metl'od detected two complexes ,.v~th lhe molecular compositions pdttBr4Si2,, and pdlIBQ.a6S~ 42-The addilion of an aqueou.,, solution or NaOH to the system results in the Pbrmation of HCOONa. which indicates that compounds (CH20. HCOOH) capable of reducing the palladium complexes are present in {be DAET system.Key words: donor-acceptor electron-tram, po~l system, dimethyl st, lfl)xide, hydrogen bromide, palladium, complex formation, surface, metal, mass spectroscopy, XPS.Dissolution of metals is an important stage in solvometallurgy and the synthetic chemistry of metal complexes, especially m the chemistry of noble metals. The systems that oxidize these metals can be classified depending on the role of the starting components of the liquid phase during metal dissolution as folk)ws. Mo&culor donor-acceptor (MDAJ .systems. The sys-tem contains a ligand-conaplex-forming agent (donor) and an oxidant (acceptor~ that form molecular complexes. The metal is oxidized by a complex-bound acceptor such as molecular ha ogen. ntolecular or peroxide oxygen, quinone, and others, lbr example,t.2 2 Au ~ + 4 GN = 1/2 02 + H20 ," ," 2 [AuI(CN)2] -+ 2 OH-.This class also contains systems with complex ions of metals or compounds of elements in high oxidation states as oxidantsa: Donor-acceptor electron-transport (DA ET) .gvstemsflUnlike the MDA systems, in the DAET systems molecular complexes undergo further transformation with complete electron transfer from a donor to an acceptor. New species capable of oxidizing the metal are generated in the systems.Inorganic DAETsystems. The system contains inorganic ligand-complex-forming agents (donor) and acceptor that do not directly react with the metal. Cornpounds capable of metal oxidizing are lormed due to the interaction of the components of the inorganic donoracceptor system. This type of systems is exemplified by aqua regia, whose oxidants are nitrosyl chloride and molecular chlorine (or its hydrate) formed by the interaction of concentrated nitric and hydrochloric acids5:Au 0 4 4 HCI 4-HNO3 -,----,'-H[AuCI4]'-+ NO + 2 H20.Organic DAET.systems. The system contains an organic ligand-comptex-forming agent (donor) and an organic or inorganic acceptor inert toward the metal. The DMSO--HBr system ("Chernogolovskaya Vodka") 4 studied in this work is an example of organic DAET systems. Systems of this type e...

Сopper dissolution in the aqueous systems DMSO-HХ solv (solv = H 2 O; X = Cl, Br) under the inert atmosphere and under aerobic conditions at different acid concentrations was studied by the resistometric method by measuring the resistance of a metal sample in the course of the reaction. The overall activity of the system decreases with a decrease in the concentration of the starting hydrohalic acid. The rate of copper dissolution in the extremum points also decreases. The process of the metallic copper dissolution in nonaqueous systems, such as DMSO-HCl solv (solv = MeCN, PhNO 2 ), was studied. In the latter systems, as opposed to aqueous systems, only one maximum in the plot of the copper dissolution rate versus the component ratio is observed. The change in the nature of the solvent in the donor acceptor electron transport system DMSO-HCl solv (solv = H 2 O, MeCN, PhNO 2 ) results in the change in the position of the maximum of the copper dissolution rate, as well as in the change in its value. The rate of copper dissolution in the above mentioned systems varies in the following series:Comprehensive studies of organic and aqueous organ ic donor acceptor electron transport systems (DAET sys tems) capable of oxidizing zero valent transition metals along with noble metals are important for the optimal use of these systems for both the direct synthesis of coordina tion compounds of metals and the solution of the practical problems in the metal extraction from industrial waste and from different types of mineral raw materials, which contain precious metals and concomitant elements. 1 The oxidative dissolution of metals in DAET systems, such as DMSO-HBr solv (solv = H 2 O, "Chernogolovskaya Vodka"), 2 occurs due to the formation of intermediate particles, which are the products of donor acceptor inter action of the liquid phase components between each other and with the surface of the solid phase (i.e., with the metal). The nature of the oxidants of aqua regia (HNO 3 + HCl) is well known and studied (NOCl, Cl 2 •H 2 O). The principle of the action of "Chernogolovskaya Vodka" is similar to that of aqua regia; the active particles are formed as a result of the reaction of the starting reagents (components of the liquid phase), which are inert toward the metal, between each other and with the surface of the solid phase (metal). As in the case of aqua regia one of the metal oxidizing particles is a solvated halogen molecule (Me 2 S•X 2 ). 2 Previously, 3-6 the resistometric method has been pro posed for the study of the metal dissolution kinetics in DAET systems. In this method, the metal dissolution rate (metal wire is used) is calculated from the change in its electric resistance in the course of the reaction. The study of the copper and gold dissolution in the system DMSO-HХ aq * (X = Br, Cl) by resistometric method showed that the dissolution rate depends on the DMSO to HX ratio, as well as on the concentration of the initial solution of hydrohalic acid (water content). The stronger the acid used in the experiment, t...

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