| Abstract: | Effects of nitrogen-containing biodegradation enhancers(methyl diethanolamine oleate(MDEAO) and oleic diethanolamide(ODEA)) on the adsorption of n-hexadecane in soil were studied by laboratory batch experiments. The partition coefficients(K_d values) of n-hexadecane sorption in soil-water system and those partition coefficients normalized to organic matter(K_(oc) values) were both determined. The adsorption isotherm curve of n-hexadecane in soil-water system was plotted. The measured results demonstrated that K_(oc) values changed in the soil-water system with different enhancers but are relatively invariant for the soil at the same site. The K_d values rose with the increase of the organic matter content in different soil. The average values of K_(oc) in the soil-water system with MDEAO, ODEA,and blank soil were 0.412, 0.252,and 0.309, respectively. The critical micelle concentration of ODEA and MDEAO was 0.7 mg/L and 1.9 mg/L, respectively,denoting that the solubilization capacity of ODEA was much stronger than MDEAO in the soil-water system. Consequently,the adsorption of MDEAO onto the solid surface increased the organic matter content in soil,which could make it more effective in enhancing the n-hexadecane adsorption. On the contrary, ODEA could inhibit the adsorption of n-hexadecane because of its less adsorption rate onto the soil particle surface and higher concentration in the soil-water system. According to the correlation coefficients, it was found that both the Henry linear and the Freundlich nonlinear isotherm sorption models were fitted to the data very well, however the Freundlich model was better than the Henry model. |
