Studies on the Fate of Nonionic Surfactant in the Soil Environment

我们研究了烷基聚氧乙烯醚等非离子表面活性剂在土壤环境中的去向。鉴于表面活性剂的命运是由吸附和生物降解造成的，本研究考察了AE(C_&lt；12&gt；POE_n；n=5，C_&lt；12&gt；E_5，n=8，C_&lt；12&gt；E_8)在高岭土、白云母和可生物降解性AE等粘土矿物上的吸附等温线。E_8在粘土矿物上的吸附在临界胶束浓度(CMC)以下可分为两个阶段或两个以上阶段，此时吸附量接近恒定值。吸附等温线在较低浓度范围内表现为朗缪尔型，C&lt；12&gt；E_5、C_&lt；12&gt；E_8在高岭土和白陶土上的饱和吸附量分别为相同的值。当粘土矿物在CMC上与-AE的初始溶液接触时，吸附等温线的第二阶段开始于接近浓度的饱和吸附。在第二阶段等温线中，饱和吸附量是第一阶段的两倍。这些结果表明，Ae的吸附可能是在CMC以下的粘土表面形成单分子层，但当粘土与Cmc以上的较高浓度接触时，则是多分子层的形成。考察了阴离子-非离子表面活性剂溶液中非离子表面活性剂和/或阴离子表面活性剂在粘土上的吸附行为。阴离子表面活性剂在混合体系中的吸附量远高于单一体系。通过河床消亡试验考察了AE在单独溶液和AE-阴离子表面活性剂溶液中的生物降解行为。与阴离子表面活性剂LAS相比，AE更容易降解到最终生物降解的程度。随着EO单元数目的增加，AE的生物降解性呈下降趋势。

We have studied on the fate of nonionic surfactants such as alkyl ethoxylates(alkylpoly(oxyethylene)ethers : AE)in the soil environment. Since it was already clarified that the fate of surfactants was caused by the adsorption on soil and biodegradation, adsorptivities of AE(C_<12>POE_n ; n=5, C_<12>E_5, n=8, C_<12>E_8)on such clay minerals as kaolin, cericite, and biodegradabilites of AE were examined in this study.Adsorption isotherms of C_<12>E_5 and C_<12>E_8on clay minerals could be divided into two stages or more below cmc (critical micelle concentration), at which adsorption amount attained nearly constant values. isotherms showed a Langmuir-type in a lower concentration range, and saturated adosorption amounts on both clays, kaolin and cericite, were the same values for C_<12>E_5, C_<12>E_8, respectively.The second stage of the isotherms started at a near concentration to saturated adsorption in the first stage, in the case where clay minerals came to contact with the initial solutions of, -AE at cmc. In the second stage of isotherms the saturated adsorption amount was twice as much as in the first stage. These results suggest that the adsorption of AE is probably the formation of a monomolecular layer over the clay surface below cmc, but is the formation of multimolecular layer in the case where the clay come to contact with a higher conceutration above cmc.Adsorption behaviors of nonionic surfactant and/or anionic surfactant onto clays in anionic-nonionic surfactant solutions were examined. Adsorption of anionic surfactant in mixed system was much higher than that in alone system. Biodegradation behaviors of AE in alone and AE-anionic surfactant solutions were tested by river die-away test. AE was easier decomposed to the extent of ultimate biodegradation than LAS (anionic surfactant). Biodegradability of AE was showing a tendency to decrease with increasing the number of EO-unit.