Studies on the Fate of Nonionic Surfactant in the Soil Environment

为了弄清烷基聚氧乙烯醚、烷基酚聚氧乙烯醚等非离子表面活性剂在土壤环境中的去向，采用土壤灌注法进行了生物降解试验。在生物降解试验中，用总有机碳(TOC)对灌流液中残留的表面活性剂进行了分析。结果表明，灌流开始后，由于吸附在土壤上，TOC急剧下降，40d左右就发生了生物降解。结果表明，非离子表面活性剂在土壤上的吸附对土壤环境中的消失现象起着重要作用。然后，对非离子表面活性剂在土壤中的吸附行为进行了研究。结果表明，非离子表面活性剂在土壤中的吸附对土壤环境中的消解现象起着重要作用结果表明，NPE在高岭土、白陶土和钙基膨润土等粘土矿物上的吸附等温线在临界胶束浓度(CMC)以下可分为两个不同的阶段，在临界胶束浓度(CMC)以下，吸附量接近恒定值。结果表明，在较低浓度范围内，NPE分子在粘土表面呈平行排列，而在较高浓度范围内，则通过疏水作用在粘土表面形成二维或三维的胶束聚集体。NPE在土壤粘土上的吸附行为与粘土矿物的吸附行为相似。在较高浓度范围内，NPE在粘土表面的吸附行为与粘土矿物上的吸附行为相似腐殖质土壤在低于CmC浓度下的吸附等温线符合Freundrich方程。本实验旨在阐明非离子表面活性剂在腐殖质上的吸附特性。

In order to clarify the fate of such nonionic surfactants as alkyl ethoxylates,alkylphenol ethoxylates in the soil environment,the biodegradation test with soil perfusion method was carried out.In the biodegradation test, residual surfactants in the perfused fluid were analysed by total organic carban (TOC).It was observed that TOC decreased sharply immediately after the initiation of perfusion because of the adsorption onto soil,and biodegradation occured after lag time about 40 days.These results show that the adsorption of nonionic surfactants on the soil plays an inportant role in the disappearance phenomena in the soil environment.Then,the adsorption behavior of nonylphenol ethoxylate(NPE,n=10,15,18,20)on soil and soil clays in aqueous solution was examined.Adsorption isotherms of NPE on such clay minerals as Kaolin,Cericite and Ca-bentonite could be divided into two distinct stages below CMC (critical micelle concentration),at which adsorption amount attained nearly constant values. Isotherms showed a Langmuir-type in a lower concentration range,and then adsorption amount increased with an increase in concentration.The adsorption amounts decreased with increasing number of ethylene oxides,n, attached to nonylphenol.These results suggest that in a lower concentration range molecules of NPE arrange themselves on the clay surface in such a way that the hydrophilic constituents,ethylene oxides,are parrallel to the surface,while in a higher concentration range aggregates of two or three dimentional micelles are formed on the surface by the hydrophobic interaction.The adsorption behavior of NPE on soil clay was similer to that on clay minerals.On the other hand,adsorption isotherms on humic soil obeyed the Freundrich equation at concentration lower than CMC.This experiment is continued to clarify the adsorption properties of nonionic surfactants on humic substances.