Self-diffusion in the noble metals

Elastic measurements made using polycrystalline copper, gold, silver and palladium wires show that the Young's modulus in these metals does not vary in a linear manner with temperature. Measurements using a Cu single crystal wire show that this is also true of C₁₁ and C₄₄. Simple elastic theory indicates qualitatively that this behavior will lead to a positive curvature in the Arrhenius plots for self-diffusion at high temperatures.     

Extracting noble metals from industrial solutions and waste waters with biosorbents

The chemical composition of various industrial solutions of the Shchelkovo Plant of Secondary Noble Metals is evaluated. It is established that the excess content of heavy metals with respect to gold and silver is larger by a factor of more than 1000. The microbial biomasses of various systematic groups are approved for extracting Au and Ag from solutions with a high salt background. The appropriateness of selectively extracting heavy metals from such complex solutions is shown. The behavior of heavy metals is investigated for sorption on biosorbents from individual solutions within the pH limits of 1.0–6.0 for the medium. The decisive significance of the pH of the solution (within the limits 1.0–3.0) on selectively extracting Ag from industrial solutions is determined. The notion that silver and heavy metals are attributed to different groups of metals by varying the degree of sorption with microorganisms, depending on the pH medium, is confirmed. The specific behavior of the biomass cells in the acidic medium also promotes the separation of these elements. Testing the biosorbed extraction of silver from the industrial solution on a granulated lincomycin biomass is approved under industrial conditions. The average degree of extraction was Cu ≤ 8.1, Ni 4.2, Zn 4.0, Fe 15.5%. The losses of biosorbent are about 70 g/m³ of the solution.     

Extraction of noble metals from the recycle slag of refining production

Results of investigations of concentration of metallurgical slag using electrical separators, jugs and flotation machines, sluices, concentration table, and Itomack centrifugal separator are presented. As a result, two production flowsheets are suggested, wet and dry, which provide recovery of ～95% silver and ～89% gold mixed with a ～15.5% metal content.     

Thermodynamics of interaction between sulfite-thiosulfate solutions and noble metals

The thermodynamic probability of dissolution of noble metals in aqueous solutions of sodium thiosulfate, sodium sulfite, and their mixture under standard conditions (without heating of the solution) is considered. The influence of impurities and catalysts (divalent copper, elemental sulfur, oxygen access into the solution, and ammonia) is evaluated. Theoretical calculations of reaction rates are performed. As a result of theoretical investigations, a conclusion about the usefulness of applying sulfite-thiosulfate solvents of noble metals from ores and concentrates is made.     

The diffusivity of hydrogen in the noble metals at low temperature

An electrolytic method has been used to measure the diffusivity of hydrogen in the noble metals Pt, Au, and Ag in the low-temperature range 280–330 K. The data obtained have been considered in conjunction with those for other noble metals (Pd and Cu) in order to draw conclusions concerning the interactions between dissolved H-atoms and lattice vacancies. It has been concluded that, at least in Pd, Cu, and Au, the H-vacancy interaction energy is too low to render diffusion anomalies observable at high temperatures. This is in accord with theoretical calculations based on the effective medium technique.     

Rare earth oxides and their supported noble metals in application of environmental catalysis

Volatile organic compounds(VOCs),methane,carbon monoxide,soot,automotive exhaust,and nitrogen oxides are harmful to the atmosphere and human health.It is urgent to strictly control their emissions.Heterogeneous catalysis is an effective pathway for the removal of these pollutants,and the critical issue is the development of novel and high-performance catalysts.In this review,we briefly summarize the preparation methods,physicochemical properties,catalytic activities,and related reaction mechanis...