Research On Deep Reduction Technology Of Gold Sulfite Based On Potential Control

This paper studies the Au-H2 O system, Au-Cl--H2 O system and H2SO3-H2 O system electrochemical reaction and the expression formula of ? and p H based on the possible electrochemical reaction by finding out the thermo-dynamic data of the reaction components with the thermodynamics manual in Au-Cl--SO32--H2 O system. The Au-H2 O system, Au-Cl--H2 O system and H2SO3-H2 O system ?-p H figure are charted by a number of thermo-dynamic calculation in the 298 K. At the same time the overlaped ?-p H figure with H2SO3 system and AuCl--H2 O system are also charted. Graphics shows that under the conditions of different p H and potential the thermo-dynamic stability region of various substances and the possibility of a chemical reaction. The results show that by dealing with the chloride the potential of gold decreased obviously and the potential value of H2SO3 system is significantly lower than the value of Au-Cl--H2 O system. And using H2SO3 for reducing gold liquid and controlling the p H value of 1.75 are to the best advantage.By determining the concentration of the reducing agent of sodium sulfite solution in the reduction process, analyzing the factors that impact the reduction process of liquid gold, and we finally select the concentration of the reducing agent of sodium sulfite is 60g/L. Theoretically, determining the optimum temperature of the reduction process is 30?, and the optimum acidity of the reduction process is 1mol/L. When the potential is about 505 m V, the reduction reaction ends; when the potential drops below to 585 m V, the rate of the reduction of gold could reach 99%.Studying the reduction series of gold sulfite solution by using the initial rate method, the results show that the reaction rate of H + is at-0.74 level, and that of Au3+ is at 0.14 level, the overall reaction order is at-0.6 level. This paper also studies the effect of temperature on reaction rate coefficients, deducing the activation energy Ea is-56KJ?mol-1, which also shows that as the temperature increases the reduction reaction rate becomes smaller which is not conducive to the reaction.Thus, by controlling the potential to restore the golden liquid of can effectively reduce the consumption of sodium sulfite, it is also can reduce the costs and improve the quality of the gold powder.