水中氧化石墨烯稳定性研究

Stability of graphene oxide in aquatic system

以氧化石墨烯(GO)分散水溶液为对象,采用动态光散射技术研究了pH、电解质、天然有机物以及不同尺寸等环境因素对其稳定性和凝聚特性的影响。结果表明:pH升高可提高水中GO的稳定性;投加电解质会产生压缩双电层作用,导致GO发生凝聚,反应后GO颗粒的静电斥能减小、粒径增大。相比于,一价电解质,二价电解质对GO纳米颗粒凝聚具有更强的促进作用。小尺寸的GO分散性更好,凝聚速度相对较慢,稳定性高。200nm粒径的GO颗粒在水中的凝聚过程与经典的胶体稳定性理论相符合,分为反应控制和扩散控制两个阶段;Na^+和Ca^(2+)的临界凝聚浓度分别为186.0和1.8mmol/L。当富里酸(FA)存在时,可通过空间位阻效应使GO颗粒间有效碰撞概率和凝聚反应速度降低,临界凝聚浓度提高,增强了其在水中的稳定性。GO在水中的凝聚和分散行为将受到pH、电解质和有机物等复杂因素的影响。

The influence of pH,electrolytes,organic matters and different size on the stability and aggregation kinetics of graphene oxide(GO)in aqueous solutions were investigated by dynamic light scattering.Results showed that GO nanoparticles were more stable in a higher pH condition.Adding electrolytes induced the aggregation of GO nanoparticles through compressing electric double layer,which made an increase in the particle size and sharply decrease in the surface zeta potential of GO,to promote the aggregation between particles.The GO with smaller size had the better dispersion and the slower condensation rate,which was more stable in water.The two-valent electrolyte had the stronger effect on the aggregation of GO nanoparticles than monovalent electrolyte.The aggregation process of GO with200nm was divided into two parts,reaction limited aggregation and diffusion limited aggregation,which was found to conform to the classic Derjaguin-Landau-Verwey-Overbeek(DLVO)theory of colloidal stability.The critical coagulation concentration(CCC)values of GO was equal to 186.0mmol/L Na+,1.8mmol/L Ca2+.The presence of fulvic acid(FA)decreased the attachment efficiency and aggregation rate of GO and increased CCCs due to steric repulsion.The aggregation and dispersion of GO in water was affected by the characteristics of pH,electrolyte species,organic matters and other complex factors.