Colloidal Properties and Stability of Graphene Oxide Nanomaterials in the Aquatic Environment
Colloidal Properties and Stability of Graphene Oxide Nanomaterials in the Aquatic Environment
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DOI：
10.1021/es400483k
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发表时间：
2013-06-18
影响因子：
11.4
通讯作者：
Bouchard, Dermont
中科院分区：
文献类型：
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作者：
Chowdhury, Indranil;Duch, Matthew C.;Bouchard, Dermont
虽然氧化石墨烯（GO）已被发现是毒性最大的石墨烯基纳米材料，但其环境命运仍未被探索。在这项研究中，GO的聚集动力学和稳定性进行了研究，使用时间分辨动态光散射在广泛的水生化学（pH值，盐类型（NaCl，MgCl 2，CaCl 2），离子强度）有关的自然和工程系统。尽管在pH 4至10范围内，pH对GO稳定性没有显着影响，但与其他胶体颗粒类似，由于双电层压缩，盐类型和离子强度对GO稳定性有显着影响。GO的临界凝固浓度（CCC）值被确定为44 mM NaCl、0.9 mM CaCl 2和1.3 mM MgCl 2。GO在水环境中的聚集和稳定性符合胶体理论（DLVO和Schulze-Hardy规则），即使GO的形状不是球形。GO的CCC值低于报道的富勒烯CCC值，高于报道的碳纳米管CCC值。由于Ca 2+离子与GO的羟基和羰基官能团的结合能力，CaCl 2比MgCl 2和NaCl更积极地使GO不稳定。天然有机物显著提高了GO在水中的稳定性，主要是由于空间排斥。长期稳定性研究表明，GO在天然和合成地表沃茨中高度稳定，尽管其在合成地下水中快速沉降。虽然GO在合成流入废水中保持稳定，但从处理厂收集的流出废水迅速使GO不稳定，表明GO将在废水处理过程中沉降并可能在生物固体和污泥中积累。总的来说，我们的研究结果表明，GO纳米材料在自然水生环境中是稳定的，并且GO的显著水运输是可能的。
While graphene oxide (GO) has been found to be the most toxic graphene-based nanomaterial, its environmental fate is still unexplored. In this study, the aggregation kinetics and stability of GO were investigated using time-resolved dynamic light scattering over a wide range of aquatic chemistries (pH, salt types (NaCl, MgCl2, CaCl2), ionic strength) relevant to natural and engineered systems. Although pH did not have a notable influence on GO stability from pH 4 to 10, salt type and ionic strength had significant effects on GO stability due to electrical double layer compression, similar to other colloidal particles. The critical coagulation concentration (CCC) values of GO were determined to be 44 mM NaCl, 0.9 mM CaCl2, and 1.3 mM MgCl2. Aggregation and stability of GO in the aquatic environment followed colloidal theory (DLVO and Schulze-Hardy rule), even though GO's shape is not spherical. CCC values of GO were lower than reported fullerene CCC values and higher than reported carbon nanotube CCC values. CaCl2 destabilized GO more aggressively than MgCl2 and NaCl due to the binding capacity of Ca2+ ions with hydroxyl and carbonyl functional groups of GO. Natural organic matter significantly improved the stability of GO in water primarily due to steric repulsion. Long-term stability studies demonstrated that GO was highly stable in both natural and synthetic surface waters, although it settled quickly in synthetic groundwater. While GO remained stable in synthetic influent wastewater, effluent wastewater collected from a treatment plant rapidly destabilized GO, indicating GO will settle out during the wastewater treatment process and likely accumulate in biosolids and sludge. Overall, our findings indicate that GO nanomaterials will be stable in the natural aquatic environment and that significant aqueous transport of GO is possible.