不同极性有机污染物在腐殖质-蒙脱石复合物上的吸附特性

Adsorption mechanism of the organic contaminants with dissimilar polarity on humussmectite complexes

研究了3种具有不同结构和极性的芳香类疏水有机污染物(非极性的菲和1,2,4,5-四氯苯、极性的1,2-二氯苯)在蒙脱石及富里酸/胡敏酸-蒙脱石复合物上的界面行为。由于疏水性分配作用,与富里酸和胡敏酸复合后的蒙脱石对非极性的菲和1,2,4,5-四氯苯的吸附量增加。元素分析结果表明,胡敏酸的(N+O)/C值低于富里酸,因此其疏水性强于富里酸,这使得菲和1,2,4,5-四氯苯在胡敏酸-蒙脱石复合物上的吸附量均高于富里酸-蒙脱石复合物。极性的1,2-二氯苯在水中的溶解度最高(131 mg/L),其在蒙脱石上的吸附量远高于非极性的菲和1,2,4,5-四氯苯。1,2-二氯苯主要通过与蒙脱石表面形成偶极作用吸附在蒙脱石上,且富里酸和胡敏酸对蒙脱石吸附1,2-二氯苯的影响较小。1,2-二氯苯的Freundlich吸附曲线的n大于1,表明1,2-二氯苯之间能形成偶极-偶极作用,进一步加大其在蒙脱石上的吸附量。富里酸和胡敏酸降低了菲在蒙脱石上的解吸率,且菲在疏水性最强的胡敏酸-蒙脱石复合物上的解吸率最低,表明菲与胡敏酸-蒙脱石复合物的作用力最强。

The given paper is intended to introduce its research results on the adsorption mechanism of the organic contaminants with dissimilar polarity on humus-smectite complexes. As is known,the organic matters and clay minerals are two important components in controlling the adsorption of organic contaminants in the soil,which may account for our choice for the topic. To achieve its purpose,we have investigated the adsorption of the three organic contaminants with different structures and polarities including the nonpolar phenanthrene,1,2,4,5-tetrachlorobenzene,and the polar 1,2-dichlorobenzene onto the original smectite and fulvic acid（ FA） /humic acid（ HA）-smectite complexes. At the same time,we have also made a simulation research of the equilibrium data with the Freundlich models. The FA / HA-smectite complex has been found revealing a stronger affinity for phenanthrene and 1,2,4,5-tetrachlorobenzene than the original smectite due to the FA / HA-facilitated hydrophobic partition. What is more,the elemental analysis we have done is also useful for us to know that HA has a lower（ N＋ O） / C ratio than FA,which implies that HA is more hydrophobic than FA. Moreover,since the water solubility of 1,2-dichlorobenzene（ 131 mg / L） is the highest,the adsorbed amount of the polar 1,2-dichlorobenzene on smectite should be much greater than that of the non-polar phenanthrene and 1,2,4,5-tetrachlorobenzene. Besides,since 1,2-dichlorobenzene adsorption on smectite is mainly due to the dipole-dipole interactions, FA / HA wouldn＇t be able to affect the adsorption of the polar 1,2-dichlorobenzene on smectite significantly. What is more,since the nonlinearity parameter value of n for the Freundlich adsorption isotherms of 1,2-dichlorobenzene is greater than 1,it implies the formation of dipole-dipole interactions between 1,2-dichlorobenzene molecules,which may further facilitate the adsorption of 1,2-dichlorobenzene on smectite. And,in turn,FA and HA can reduce the desorption rate of phenanthrene on smectite,which on the most hydrophobic HA-smectite complex tends to be the lowest,whereas the interactive force between the phenanthrene and HA-smectite complex can be the strongest. Thus,it can be seen that the results of our study can help us to improve understanding of the roles of the characteristics of FA / HA on the adsorption of organic pollutants to the clay minerals.