Studies on the Fate of Nonionic Surfactant in the Soil Environment

研究了烷基聚氧乙烯醚（AE）等非离子表面活性剂在土壤环境中的归趋。由于表面活性剂在土壤中的吸附和生物降解是表面活性剂最终归宿的主要原因，本文研究了AE（C_<12>POE_n ; n=5，C_<12>E_5，n=8，C_<12>E_8）在高岭土、铈矿和AE的生物降解性粘土矿物上的吸附性能，发现C_<12>E_5和C_<12>E_8在粘土矿物上的吸附等温线在临界胶束浓度（cmc）以下可分为两个或两个以上阶段，此时吸附量接近恒定值。在较低浓度范围内，吸附等温线呈Langmuir型，饱和吸附量在粘土（高岭土和铈石）上均相同<12><12>，吸附等温线的第二阶段开始于接近第一阶段饱和吸附的浓度，此时粘土矿物与初始溶液接触的临界胶束浓度为cmc。第二阶段的饱和吸附量是第一阶段的2倍。这些结果表明，在cmc以下，AE在粘土表面的吸附可能是单分子层的形成，而在cmc以上，当粘土与更高浓度的AE接触时，AE在粘土表面的吸附可能是多分子层的形成。阴离子表面活性剂在混合体系中的吸附量远高于单独体系。采用河流消亡试验研究了AE在单独和AE-阴离子表面活性剂溶液中的生物降解行为。AE比LAS（阴离子表面活性剂）更容易降解到最终生物降解的程度。AE的生物降解性随着EO单元数的增加而呈下降趋势。

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.