Cai Li, Peng Shengnan, Wu Dan, Tong Meiping
The Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, PR China; Currently at Natural History Research Center, Shanghai Natural History Museum, Shanghai Science and Technology Museum, Shanghai, 200127, PR China.
School of Environment and Energy, Shenzhen, Shenzhen Graduate School of Peking University, Shenzhen, 518055, PR China.
Environ Pollut. 2016 Jan;208(Pt B):637-44. doi: 10.1016/j.envpol.2015.10.040. Epub 2015 Nov 10.
Colloids (non-biological and biological) with different sizes are ubiquitous in natural environment. The investigations regarding the influence of different-sized colloids on the transport and deposition behaviors of engineered-nanoparticles in porous media yet are still largely lacking. This study investigated the effects of different-sized non-biological and biological colloids on the transport of titanium dioxide nanoparticles (nTiO2) in quartz sand under both electrostatically favorable and unfavorable conditions. Fluorescent carboxylate-modified polystyrene latex microspheres (CML) with sizes of 0.2-2 μm were utilized as model non-biological colloids, while Gram-negative Escherichia coli (∼ 1 μm) and Gram-positive Bacillus subtilis (∼ 2 μm) were employed as model biological colloids. Under the examined solution conditions, both breakthrough curves and retained profiles of nTiO2 with different-sized CML particles/bacteria were similar as those without colloids under favorable conditions, indicating that the copresence of model colloids in suspensions had negligible effects on the transport and deposition of nTiO2 under favorable conditions. In contrast, higher breakthrough curves and lower retained profiles of nTiO2 with CML particles/bacteria relative to those without copresent colloids were observed under unfavorable conditions. Clearly, the copresence of model colloids increased the transport and decreased the deposition of nTiO2 in quartz sand under unfavorable conditions (solution conditions examined in present study). Both competition of deposition sites on quartz sand surfaces and the enhanced stability/dispersion of nTiO2 induced by copresent colloids were found to be responsible for the increased nTiO2 transport with colloids under unfavorable conditions. Moreover, the smallest colloids had the highest coverage on sand surface and most significant dispersion effect on nTiO2, resulting in the greatest nTiO2 transport.
不同尺寸的胶体（非生物和生物胶体）在自然环境中普遍存在。然而，关于不同尺寸胶体对工程纳米颗粒在多孔介质中传输和沉积行为影响的研究仍十分匮乏。本研究考察了在静电有利和不利条件下，不同尺寸的非生物和生物胶体对石英砂中二氧化钛纳米颗粒（nTiO₂）传输的影响。将尺寸为0.2 - 2μm的荧光羧酸盐改性聚苯乙烯乳胶微球（CML）用作模型非生物胶体，而革兰氏阴性大肠杆菌（约1μm）和革兰氏阳性枯草芽孢杆菌（约2μm）用作模型生物胶体。在所考察的溶液条件下，在有利条件下，含有不同尺寸CML颗粒/细菌的nTiO₂的穿透曲线和保留曲线与不含胶体时的相似，这表明在有利条件下，悬浮液中模型胶体的共存对nTiO₂的传输和沉积影响可忽略不计。相比之下，在不利条件下，观察到含有CML颗粒/细菌的nTiO₂的穿透曲线高于且保留曲线低于不含共存胶体时的情况。显然，在不利条件下（本研究考察的溶液条件），模型胶体的共存增加了nTiO₂在石英砂中的传输并减少了其沉积。发现石英砂表面沉积位点的竞争以及共存胶体诱导的nTiO₂稳定性/分散性增强是导致不利条件下nTiO₂随胶体传输增加的原因。此外，最小的胶体在砂表面的覆盖率最高，对nTiO₂的分散作用最显著，导致nTiO₂的传输量最大。
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