不同类型表面活性剂在土壤上的吸附特征比较研究

应用平衡振荡法，研究了阴、阳和非离子表面活性剂在土壤上的吸附．结果表明，阳离子表面活性剂十六烷基三甲基溴化铵能强列吸附在6种不同性质的土壤上，吸附等温线为L型，分配常数Kd，为3．0×10^2～48×10^2L·kg^-1；阴离子表面活性剂十二烷基苯磺酸钠、非离子表面活性剂OP及Tween-20的吸附等温线随土壤类型不同而不同，有L、S等型，吸附强度远弱于阳离子表面活性剂，Kd分别大体处于5．3～39、0．13～0．44(Tween-20)和4．4～22．4L·kg^-1(OP)．阳离子表面活性剂的土壤最大吸附量与土壤阳离子交换容量呈线性相关．低浓度范围内，阴离子表面活性剂的土壤分配常数与土壤粘粒含量呈正相关．同时土壤颗粒表面的电荷特性也影响吸附．非离子表面活性剂的Kd与土壤粘粒、砂粒、粉沙含量及表面积存在经验函数关系．

Adsorption characteristics of three types of surfactants in soils

Surfactants after entering soil may interact with other xenobiotics of sufactant and alter their behaviors. These interactions are very complex, and depend heavily on a range of parameters including surfactant concentration in soil-water, its CMC and adsorption characteristics of sufactant and pollutant etc. In this paper, batch sorption experiment was employed to study the adsorption characteristics of three types of surfactants, viz. an anionic, a cationic, and two nonionic surfactants, in 6 soils. The results showed that the adsorption isotherms of cetyltrimethylammonium bromide (CTMAB) were L-shape, with distribution coefficients (Kd) varied between 300 to 4800 L x kg(-1) in lower concentration range. The adsorption isotherms of sodium dodecyl benzene sulfonate C12 LABS, OP and Tween-20 were L- or S-shape, depending on surface-active molecular and soil properties. The affinity of anionic and nonionic surfactants to soil was weaker than that of cationic surfactant. The Kd for C12 LABS, Tween-20 and OP was within 5.3-39, 0.13-0.44 and 4.4-22.4 L x kg(-1), respectively. For sodium dodecyl benzene sulfonate, Kd was positively correlated with soil clay fraction, and the charge property of soil was also influential in its sorption. For OP and Tween-20, the empirical relations of Kd to soil properties, clay, silt, sand contents, and surface area, were established by using regression analysis. Cationic exchange capacity showed a strong positive correlation with the maximum adsorption capacity of soils, which might indicate that the ionic exchange mechanism played an important role in adsorption of CTMAB.