Effects of NH4+ salts on sorption of Cd²⁺ and Zn²⁺ in soils

The effects of different NH4+ salts on Cd2+ and Zn2+ sorption in meadow cinnamon soils (MCS) and red soils (RS) were evaluated by batch method. The results showed that Cd2+ and Zn2+ amounts adsorbed by soils increased with the initial concentrations of added Cd2+ and Zn2+. The maximum amount of Cd2+ and Zn2+ sorption on MCS and RS were: Zn2+ Cd2+. The maximum amount of heavy metal ions adsorbed on soils was greater in meadow cinnamon soil than in red soil. The sorption percentage of Cd2+ and Zn2+ by soils decreased in the presence of NH4HCO3. NH4+ salts, such as NH4Cl, NH4NO3, and (NH4)2SO4 restrained Cd2+ and Zn2+ sorption in RS and Cd2+ sorption in MCS. There was no significant effect of NH4Cl, NH4NO3, and (NH4)2SO4 on Zn2+ sorption in MCS. At the same concentration of NH4+ salts, Cd2+ sorption percentage in RS was decreased in the following order: NH4HCO3NH4ClNH4NO3≈(NH4)2SO4, and Zn2+ sorption percentage in RS in the following order: NH4HCO3NH4ClNH4NO3(NH4)2SO4.