Department of Chemical & Environmental Engineering, University of California, Riverside, CA 92521, USA.
J Colloid Interface Sci. 2011 Aug 15;360(2):548-55. doi: 10.1016/j.jcis.2011.04.111. Epub 2011 May 9.
The role of solution chemistry, nanoparticle concentration and hydrodynamic effects in the transport and deposition of TiO(2) nanoparticles through porous media has been systematically investigated. Two solution chemistry variables, pH and ionic strength (IS), showed a significant influence on the transport due to their involvement in the aggregation of the nanoparticles and interaction with quartz sand. An electrostatically unfavorable condition for deposition existed at pH 7, at which the greatest retention occurred in the column, likely due to aggregation (>1000 nm) and straining effects. Under electrostatically favorable conditions (pH 5) significant elution from the column was observed and attributed to smaller aggregate size (~300 nm) and blocking effects. Nanoparticle concentration was found to contribute to the increased breakthrough of nanoparticles at pH 5 due to blocking and subsequent particle-particle repulsion. Increased flowrate resulted in greater elution of nanoparticles due to hydrodynamic forces acting on aggregates and subsequently contributed to blocking. Overall, a combination of mechanisms including straining, blocking, and DLVO-type forces were involved over the range of solution chemistry and nanoparticle concentrations tested. Consideration of these mechanisms is necessary for improved removal of TiO(2) nanoparticles via filtration and reliable prediction of transport of these potentially problematic nanoparticles through the subsurface.
系统研究了溶液化学、纳米颗粒浓度和水动力效应对 TiO(2)纳米颗粒在多孔介质中传输和沉积的作用。两种溶液化学变量，pH 值和离子强度（IS），由于它们参与纳米颗粒的聚集和与石英砂的相互作用，对传输有显著影响。在 pH 值为 7 时，存在不利于沉积的静电条件，此时颗粒在柱中保留最大，可能是由于聚集（>1000nm）和过滤效应。在静电有利条件（pH 值为 5）下，观察到柱中明显的洗脱，这归因于较小的聚集尺寸（~300nm）和堵塞效应。由于堵塞和随后的颗粒间排斥作用，纳米颗粒浓度被发现导致在 pH 值为 5 时纳米颗粒的穿透增加。流速增加导致更多的纳米颗粒洗脱，这是由于作用在聚集体上的水动力引起的，并随后导致堵塞。总体而言，在测试的溶液化学和纳米颗粒浓度范围内，涉及到包括过滤、堵塞和 DLVO 型力在内的多种机制。考虑这些机制对于通过过滤去除 TiO(2)纳米颗粒以及可靠预测这些潜在问题纳米颗粒在地下的传输是必要的。
