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Substitution route has been traditionally proposed for the synthesis of new Tc complexes. In particular, Tc(III) coordination compounds can be successfully prepared by substitution on [Tc(tu) 6 ] 3+ (tu = thiourea). In this substitution reaction, Tc0 2 is a side product that should be minimized. The success of these synthetic procedures is based on controlling the reaction conditions in order that pure substitution could be faster enough compared to decomposition. In this work, the substitution of [Tc(tu) 6 ] 3+ by polycarboxylic acids (ethylenediaminetetraacetate (edta), diethylenetriaminepentaacetate (dtpa), iV-tris(2-aminoethyl)amin N', N', N", N" N"\ W'-hcxaacetate (ttaha) and 3-bromo-2,4,6-trimethylacetanilideiminodiacetate (mebrofenin)) is kinetically studied in order to obtain the best conditions for preparing Tc(III) complexes. As a general conclusion, substitution constants are strongly dependent on the pH. k" bs values fall in the range 0.1 -13 X 10" 2 M"'s"', depending on the pH value and the temperature. No strong differences are found with different incoming ligands. For the four ligands (L), a straight line is obtained when plotting log Ä obK /([L'"~]) vs. pH. This is consistent with a rate constant -{+ X| 11 ] '/Κ,.} [ I], where η represents the charge of the incoming ligand and m is the maximum value of n.

This paper aimed at studying the effect of magnesium concentration in molten aluminum produced from beverage cans on the process of aluminothermic reduction of Mn2O3 particles obtained from the cathodes of discharged alkaline batteries. The experimental results were analyzed by using thermodynamic fundamentals and kinetic modeling, while the characterization of the reaction products obtained allowed the mechanism of the process to be described. It was found that the addition of magnesium improves the wettability of solid particles by molten aluminum, thus increasing the reaction and its subsequent incorporation into the molten aluminum solution of Mn released from the reduction reaction. This work was carried out using several initial magnesium concentrations; 1.0, 2.0, 3.0, and 4.0 wt %, under a constant temperature of 1073 K, a constant treatment time of 240 min, and a constant agitation speed of 200 rpm. The results show that the higher the initial magnesium concentration in the molten alloy, the higher the speed of the chemical reduction reaction of the Mn2O3 particles.

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The Merrill-Crowe or Cementation process is used for concentration and purification of gold and silver from cyanide solutions. Among other available options for recovery of precious metals from cyanide solutions, Electrocoagulation (EC) is a very promising electrochemical technique for the recovery of this precious metals. In this work first, an introduction to the fundamentals of the Merrill Crowe and EC process are given, then Kinetic aspects conditions and results of the both process, for the removal of gold and silver from cyanide solutions are presented, and finally the characterization of the solid products formed during the EC process with X-ray Diffraction and SEM are shown. Results suggests that The cementation of both gold and silver by suspended zinc particles conforms to well-behaved fist order kinetics and for the EC process the results show that is an excellent option to remove Au and Ag from cyanide solution by using iron electrodes. Finally, 99.5% of gold and silver were removed in the experimental EC reactor, and it was achieved in 5 minutes or less.