几种土壤在单一Zn及Cd Cu共存条件下对Zn的吸附

研究了Zn2+在单一及与Cd2+、Cu2+共存条件下在塿土、黄绵土、黑垆土、黄褐土、砂土5种土壤中的吸附特征,并探讨了其吸附机制。结果表明,在20℃、30℃下,Zn2+在各供试土样中吸附等温线总体上均呈I或III型等温线形式,总体上黑垆土、塿土对Zn2+吸附最强,而砂土的吸附总是最差;塿土、黄绵土和黄褐土中Zn2+吸附的温度效应呈现升温正效应特征,砂土中则总体上表现出随温度上升呈下降趋势,黑垆土中Zn2+吸附的温度效应则与重金属处理有关。Freundlich模型是描述Zn2+吸附等温线最佳模型。Cd2+、Cu2+的共存对Zn2+的吸附均具有显著的拮抗作用,但对Zn2+吸附规律的影响不同。机理分析表明,Zn2+在土壤中的吸附主要以化学吸附为主,Cu2+由于其与Zn2+相似的化学吸附特点而竞争Zn2+化学吸附点位,但Cd2+吸附主要竞争以电性引力形式吸附的Zn2+,因而Cu2+对Zn2+吸附的影响较大,而Cd2+影响较小。

Adsorption of Zn in Different Soils with Single Zn or Zn in Combination with Cd and Cu

The studies of Zn2+ adsorption under single Zn2+ application or Zn in combination with Cd2+ and Cu2+ in 5 kinds of soils,i.e.Lou Soil,Loessial Soil,Dark Loessial Soil,Yellow Cinnamon Soil and Sandy Soil,are carried out,and Zn2+ adsorption mechanisms are discussed too.The results show that Zn2+ adsorption isotherms display type I or III at 20 and 30 ℃.Both Dark Loessial Soil and Lou Soil have the highest Zn adsorption capacity as a whole,while the Sandy soil’s adsorption is the lowest.The temperature effect on Zn2+ adsorption depends on soils’ properties: the positive temperature effect appeared in Lou soil,Loessial Soil and Yellow Cinnamon Soil;while Zn2+ adsorption decreases with an increase of temperature on Sandy Soil,and the temperature effect on Zn2+ adsorption in Dark Loessial Soil varies with the heavy metals’ coexistence.The Freundlich equation can be used to describe Zn2+ adsorption isotherm.The Zn2+ adsorption capacity can be decreased by the coexistence of Cd2+ or Cu2+,which indicating that an antagonistic action come from competitive adsorption of Cd2+ and Cu2+.The above Zn adsorption results suggest that Zn2+ adsorption is mainly decided by chemical adsorption of organic materials in soil,and the Zn2+ adsorption by the coexistence of Cu2+ is caused by the competition of chemical adsorption sites due to their analogical chemical adsorption characteristics,and Zn2+ adsorption by the coexistence of Cd2+ is mainly from the competition of electrostatic attraction,therefore,the effect of Cu2+ on Zn2+ adsorption is stronger than that of Cd2+.