Thermodynamics of Pb(II) Complex Equilibrium in Pb(II)-NH₃-NH₄CI-H₂O System

Abstract

Thermodynamics of Pb(II) complex equilibrium in Pb(II)-NH3-NH4Cl-H2O system were studied using the double equilibrium method. Varying the concentration of ammonia and ammonium chloride, respectively, in range of 0~5mol/L, the equilibrium concentration of all the species in the system are calculated, and thermodynamic diagram are plotted. The dissolution laws of Pb(II) in the system are revealed and the high dissolution fields of Pb(II) are found. The solubility of lead increase with the ammonium chloride concentration increasing, and the highest solubility reaches 0.29mol/L, whereas the concentration of lead always remains 0 in pure ammonia solution. Add ammonium chloride to the solution and maintain its concentration constant, the concentration of lead decreases with ammonia concentration increasing.

Studies on Phase Equilibria of Ternary Systems KCl–PbCl2–H2O and MgCl2−PbCl2–H2O at 323 K

“…The solubilities of lead chloride in different concentrations of HCl and NaCl were studied by Tan et al, which provided basic solubility data for hydrometallurgy of lead chloride. The solubilities of lead chloride in CaCl 2 solution were also studied by Holdich et al To solve the problem of leaching behavior and equilibrium rules of impurity metal ions in leached low-grade zinc oxide ore, through the studies of thermodynamic properties of Pb­(II)-NH 3 -NH 4 Cl–H 2 O, it is found that Pb­(II) can form complex compounds with Cl – , OH – , and NH 3 , and the lower solubilities of Pb­(II) in NH 3 –NH 4 Cl–H 2 O system were revealed, which are adverse for zinc extraction. The solubility relationships of the ternary systems KCl–PbCl 2 –H 2 O and MgCl 2 –PbCl 2 –H 2 O at 298 K were studied by Kendall, and the phase diagrams at 373 K were studied by Zhang et al , The phase diagram of the MgCl 2 –PbCl 2 –H 2 O system at 298 K was also studied by Hagemann .…”

“…of lead chloride in CaCl 2 solution were also studied by Holdich et al19 To solve the problem of leaching behavior and equilibrium rules of impurity metal ions in leached lowgrade zinc oxide ore, through the studies of thermodynamic properties of Pb(II)-NH 3 -NH 4 Cl−H 2 O,20 it is found that Pb(II) can form complex compounds with Cl − , OH − , and NH 3 , and the lower solubilities of Pb(II) in NH 3 −NH 4 Cl− H 2 O system were revealed, which are adverse for zinc extraction. The solubility relationships of the ternary systems KCl−PbCl 2 −H 2 O and MgCl 2 −PbCl 2 −H 2 O at 298 K were studied by Kendall,…”