金属氧化物纳米颗粒在水环境中的团聚与沉降

Aggregation and Sedimentation of Metal Oxides Nanoparticles in Aquatic Environment

采用吸光度动态分析、动态光散射(DLS)及电泳淌度等技术,对比了100 mg/L CuO、ZnO、SiO_2纳米颗粒(NPs)在:(1)无机盐(离子强度IS=18 mmol/L)模拟溶液;(2)天然有机质(NOM,TOC=8.96 mg/L)模拟溶液;(3)无机盐(IS=18 mmol/L)-NOM(TOC=8.96mg/L)模拟溶液;(4)太湖水(IS=4.5 mmol/L,TOC=2.42 mg/L)等介质中的48 h沉降动力学、水力学直径分布及Zeta电位。结果表明,NPs在水环境中的团聚与沉降不但取决于水化学因素,同时取决于NPs自身的化学性质。CuO NPs在太湖水与NOM模拟溶液中呈现类似的团聚与沉降现象,主要受NOM与表面Cu_(2+)的螯合作用主导。ZnO NPs的团聚与沉降主要受IS控制,因而在太湖水与IS模拟溶液中展现相似的行为。Si O2NPs具有对NOM较低的吸附能力和较小的Hamaker常数等内在特性,其在太湖水与模拟溶液中具有独特的团聚与沉降行为,并不取决于NOM或IS等水环境条件。在水环境中,这3种NPs都将通过团聚与沉降快速迁移至底泥,对水生生态造成潜在风险。

Via time-resolved optical absorbency,dynamic light scattering（DLS）,as well as electrophoretic mobility analysis,the 48-h sedimentation kinetics,the distributions of hydrodynamic diameters,and the Zeta potentials of respective100 mg/L CuO,ZnO and SiO2nanoparticles（NPs）in simulative waters containing inorganic salts with ionic strength（IS）as18 mmol/L,natural organic matter（NOM,TOC=8.96 mg/L）,or mixed IS（18 mmol/L） and NOM（8.96 mg/L TOC）,were determined and compared with those in Lake Taihu water（IS=4.5 mmol/L,TOC=2.42 mg/L）. The results indicate that aggregation and sedimentation of NPs depended not only on the water chemistry but also on their chemical properties of the NPs. The similar observations in Lake Taihu and NOM-containing simulative waters suggested that NOM controlled the aggregation and sedimentation of CuO NPs,probably through chelation of NOM with surface Cu-（2＋）. ZnO NPs were aggregated and sedimented with the presence of IS,hence similar performances in Lake Taihu water and simulative waters with IS were exhibited. The peculiar behaviors of SiO2 NPs in Lake Taihu and simulative waters manifested the predominance of its intrinsic properties over the aquatic factors（eg.,NOM and IS）in controlling the aggregation and sedimentation of SiO2 NPs.This may be attributable to low NOM adsorption capacity by the NPs and their small Hamaker constant. The three NPs will be largely transferred to the sediment compartment of water bodies via aggregation and sedimentation,and pose potential risks to aquatic ecosystem.