EDTA对饱和多孔介质中纳米银迁移机制的影响

通过混合批实验及三脉冲饱和砂柱实验,研究了1 mmol·L^-1及300 mmol·L^-1离子强度下 EDTA 与聚乙烯吡咯烷酮(PVP)修饰的纳米银颗粒的相互作用机制及其对纳米银颗粒在石英砂柱和铁氧化物涂层石英砂柱中迁移行为的影响。批实验结果表明:高、低离子强度下,EDTA均能置换纳米银颗粒表面的PVP聚合物,使稳定纳米银颗粒的机理由PVP产生的空间位阻作用转变为EDTA产生的双电层稳定效应。柱实验结果表明:高离子强度降低纳米银内核与石英砂之间的双电层排斥作用,进而降低其迁移性能;铁氧化物涂层减少了石英砂面上纳米银的点位从而降低其沉降速率;EDTA对砂柱的淋洗未能明显释放沉积态纳米银,但可通过络合并溶解铁氧化物石英砂表面的铁氧涂层促进纳米银沉降。

Influence of EDTA on Transport of Silver Nanoparticles in Saturated Porous Media

The potential environmental risks of silver nanoparticles(AgNP) have aroused many concerns. In this study, batch experiment and triple pulse column test were employed to investigate the interaction of EDTA and AgNP in granular-free quiescent water and the control of EDTA on AgNP transport in flowing water-porous system in different porous media(quartz sand and iron-oxide coated sand) at distinct ionic strengths(IS:1 mmol·L^-1 and 300 mmol·L^-1). Batch experiments suggested that EDTA could replace the PVP in the AgNP surface at both low and high ISs, resulting in a change of stabilizing mechanisms from the steric effect of PVP to the electrical double layer(EDL) effect of EDTA. Column tests showed that higher IS could suppress the EDL interaction between the AgNP core and the sand surface, thus increasing the deposition; while iron oxide coating on sand reduced sorption sites of the PVP polymer layer, resulting in a reduced deposition rate. EDTA could complex with and dissolve the iron oxide coating on the sand, thus enhancing the rate of the subsequent deposition. Moreover, elution by EDTA did not mobilize the deposited nanoparticles.