水中多壁碳纳米管的凝聚动力学

Aggregation kinetics of multi-walled carbon nanotubes in aquatic systems

利用动态光散射技术研究了环境因素对水中多壁碳纳米管(Multi-walled carbon nanotubes,MWNTs)颗粒凝聚过程的影响.结果表明,投加一价、二价电解质均可使水中MWNTs颗粒Zeta电位减小、水合动力学半径增大,促进颗粒间凝聚的发生;水中MWNTs颗粒的凝聚过程可分为反应控制和扩散控制两个不同阶段,符合经典的胶体稳定性(DLVO)理论.经计算,Na+、K+、Ca2+和Mg2+的临界凝聚浓度分别为221、251、8.0、8.4 mmol·L-1.腐殖酸存在可通过空间位阻效应显著增强水中MWNTs的分散性,表明MWNTs可稳定存在于典型的水环境中.

The aggregation kinetics of multi-walled carbon nanotubes （MWNTs） in water were examined through time-resolved dynamic light scattering measurements. The results showed that both monovalent （NaCl） and divalent （CaCl2 and MgCl2） electrolytes induced dramatic decrease in the hydrodynamic surface zeta potential and increase in the particle size of MWNTs, thus promoting the aggregation between particles. The aggregation process of MWNTs in water was divided into two phases, reaction limited aggregation and diffusion limited aggregation, which was found to be consistent with the classic Derjaguin-Landau-Verwey-Overbeek （DLVO） theory on colloidal stability. The critical coagulation concentration （CCC） of MWNTs was 221 mmol·L^-1 Na^＋, 251 mmol·L^-1 K＋, 8.0 mmol·L^-1 Ca^2＋ and 8.4 mmol·L^-1 Mg^2＋. The enhanced stability of MWNTs in the presence of humic acid was due to steric repulsion. MWNTs can be relatively stable in typical aquatic environments.