几种土壤粘粒对铅的吸附特性研究

Research on Adsorption Characteristics of Soil Clays on Lead(Ⅱ)

研究了4种土壤粘粒的基本性质及其对铅的吸附特性。结果表明,红砂土的有机质含量、阳离子交换量(CEC)和比表面积(SSA)都明显低于棕色石灰土,而等电点(IEP)高于棕色石灰土;红壤和黄棕壤的这些基本性质介于红砂土和棕色石灰土之间。吸附体系的p H为3~5时,土样对铅的吸附量随pH升高而缓慢增加;p H为5~7时,吸附量随pH升高而急剧增加。准1级动力学吸附模型对4种土样的吸附数据拟合度都较低(R^2=0.798~0.863),准2级模型的拟合结果较好(R^2=0.987~0.994)。红砂土、红壤、黄棕壤和棕色石灰土对铅的最大吸附量(qmax)分别为27.44,29.87,34.63和41.72 mg/g;Langmuir吸附模型可较好地拟合土样对铅的等温吸附数据(R^2=0.984~0.993),而Freundlich模型的拟合度较低(R^2=0.834~0.862)。土壤粘粒对铅的吸附主要属于单层吸附模式,化学吸附是其重要作用机制,不同粘粒的吸附量有较大差异。

The basic properties of four soil clays and their adsorption characteristics on Lead（ II） have been studied. Results show that the content of organic matter,cation exchange capacity,and specific surface area of red sand soil were obviously lower than those of brown calcareous soil,while the isoelectric point higher than that of brown calcareous soil. These basic properties of red soil and yellow- brown soil are between the red sand soil and brown calcareous soil. When absorbent＇s p H is 3 ~ 5,the adsorption capacities（ qe） of the samples on lead（ II） increases slowly with the growth of p H,when p H = 5 ~ 7,the adsorption capacities grows significantly. According to pseudo- first- order model of（ R^2= 0. 798 ~ 0. 863） of kinetics model of adsorption,the fitting degree of the four soil samples adsorption kinetic data are lower,while the better fitting results can be obtained by using the pseudo- second- order（ R^2= 0. 987 ~ 0. 994）. The isotherm adsorption capacity（ qmax）of RSS,RS,YBS and BCS was 27. 44,29. 87,34. 63 and 41. 72 mg / g,respectively. Langmuir model was suitable to describe the isotherm adsorption（ R^2= 0. 984 ~ 0. 993）,and the R^2 values of Freundlich model were low（ R^2= 0. 834 ~ 0. 862）. This indicated that the mono- layer adsorption with a chemisorption mechanism was important in adsorbing lead（ II） onto the clays.