SO 4 2- and Zn 2+ or Cd 2+ were added to three variable charge soils in different sequences. In one sequence sulfate was added first, and in the other, Zn 2+ or Cd 2+ ...SO 4 2- and Zn 2+ or Cd 2+ were added to three variable charge soils in different sequences. In one sequence sulfate was added first, and in the other, Zn 2+ or Cd 2+ first. The addition of sulfate to the system invariably caused an increase in adsorption of the heavy metal added, with the effect more remarkable when the soil reacted with the sulfate prior to the metal. The shift in pH 50 for both Zn and Cd adsorption was also comparatively larger in the first sequence of reactions. It was suggested that the increase in negative charge density and the resultant negative potential of the soil were the primary cause of the pronounced effect of sulfate on adsorption of Zn or Cd, and the formation of the ternary surface complex S SO 4 M might also play a role in the effect.展开更多
文摘SO 4 2- and Zn 2+ or Cd 2+ were added to three variable charge soils in different sequences. In one sequence sulfate was added first, and in the other, Zn 2+ or Cd 2+ first. The addition of sulfate to the system invariably caused an increase in adsorption of the heavy metal added, with the effect more remarkable when the soil reacted with the sulfate prior to the metal. The shift in pH 50 for both Zn and Cd adsorption was also comparatively larger in the first sequence of reactions. It was suggested that the increase in negative charge density and the resultant negative potential of the soil were the primary cause of the pronounced effect of sulfate on adsorption of Zn or Cd, and the formation of the ternary surface complex S SO 4 M might also play a role in the effect.
