不同金属离子及三氯乙烯(TCE)初始浓度对有机-矿质复合体的吸附影响研究

The Influence of Different Metallic Cations and TCE Initial Concentration on the Sorption Behavior of Organo-mineral Complexes

有机-矿质复合体对有机污染物的吸附,是直接影响有机污染物在地质环境中迁移、转化及归宿的重要因素,多价金属离子在有机质与粘土矿物相互作用形成复合体的过程中起到重要作用。为研究不同离子对有机质与粘土矿物的结合及其对有机污染物吸附行为的影响,以蒙脱土和腐植酸模拟地质吸附剂中的粘土矿物和有机质,分别加入Ca2+、Fe3+和Al3+金属离子,制备成有机质含量一定的不同离子有机-矿质复合体,进行对TCE的吸附批实验。结果表明,模拟土样Ca2+离子复合体直接拟合曲线在叠加计算曲线之上,而Fe3+和Al3+离子复合体直接拟合曲线均在叠加计算曲线之下,说明Ca2+离子的加入增强了有机-矿质复合体整体对TCE的吸附能力,Fe3+和Al3+离子有机-矿质复合体吸附性能则减弱;Ca2+、Fe3+和Al3+金属离子的加入均降低了复合体中有机质对TCE的亲合力,但Ca-M-HA复合体中有机质对TCE的亲合力强于Fe(Al)-M-HA复合体;TCE初始浓度对不同离子有机-矿质复合体的影响存在差异,在TCE低浓度段,复合体Kom值随着TCE浓度的增高而增大,且Ca-M-HA复合体较Al-M-HA和Fe-M-HA复合体增加幅度更大,在TCE高浓度段,TCE初始浓度对Al-M-HA和Fe-M-HA复合体Kom值的影响随着浓度的增加而减小后趋于稳定,而此时TCE初始浓度对Ca-M-HA复合体吸附行为影响仍然不能忽略。

Organo-mineral complexes are commonly distributed in natural environments.They play very important roles in regulating the transport and retention of hydrophobic organic contaminants in soils and sediments.Among the studies of organo-mineral complexes properties to their sorption characteristics,the significant of polyvalent metallic cations in banding organic matters（OM） to mineral surfaces should be taken into account.In order to examined the formation of organo-mineral complexes with different metallic cations and determined its sorption characteristics,montmorillonite（MMT） and humic acid（HA） were used to represent clay mineral and OM of geo-sorbents respectively,while different polyvalent metallic cations（Ca2＋,Fe3＋ and Al3＋） were added into samples to simulate cation complexes.A hypothetical model was made to distinguish whether there were interactions between HA and MMT in our experiments.The results showed that the sorption capabilities of organo-mineral complexes were enhanced greatly,when Ca2＋ was added in the complexes.But the opposite phenomenon was observed when Fe3＋ and Al3＋ act were added.Kom calculation results showed that all the 3 kinds of cations decreased the humic acid affinity to the TCE.But the affinity to the TCE of humic acid in Ca-M-HA was stronger than in Fe（Al）-M-HA.The TCE initial concentration could also affect the sorption of organo-mineral complexes with different cations.At low initial concentrations,with C0=500 μg·L-1 as the boundary,the Kom of organo-mineral complexes increased with the increasing concentrations,and the increased degree of Ca-M-HA complexes were larger than the Al-M-HA complexes and Fe-M-HA complexes;while at the high initial concentrations,the Kom of organo-mineral complexes first decreased with the increasing initial concentrations and then tended to stability.However,the effect of TCE initial concentration to the sorption of Ca-M-HA complexes should not be neglected.