Materials Science and Engineering, Sharif University of Technology
Thermodynamics and kinetics of vaporization of lead sulfide from typical copper-smelting mattes of commercial interest are investigated in the temperature range 1388 K to 1573 K by vapor transport technique and plasma arc spectroscopy. The total mass of the dominant vaporizing species PbS that leaves the matte is described by the Newman's numerical solution to the second Fick's law combined with the experimental boundary conditions of the system. This solution is obtained through the application of the Laplace transform series expansion method stated by Crank. The three steps that are used to describe the rate of vaporization of PbS are: the diffusive transport of PbS through the liquid phase, the equilibrium at the gas-matte interface and the diffusion through the stagnant layer of gas above the surface of the melt. With the particular experimental set-up and the condenser weight gain, it is shown that the activity coefficient of PbS is simply a function of the temperature and the composition of the bearing phase. The enthalpy and the entropy of dissolution of PbS in hot liquid mattes are estimated to berespectively-41 KJ/mol and 20 to 40 J/mol.K depending on the temperature and the composition of the liquid mattes of this investigation.