中文摘要：

【目的】分析介质pH及离子强度对纳米SiO_2（nSiO_2）颗粒分散度的影响。【方法】采用分散试验分析了不同介质pH和NaNO_3浓度对10nm nSiO_2颗粒分散度的影响,并通过多组分表面电荷调控模型理论及泊松-玻尔兹曼方程对影响机制进行了初步探讨。【结果】nSiO_2颗粒分散度随着NaNO_3浓度的增加而降低,但随着介质pH的升高而增加,并在pH 7.39以后逐渐趋于稳定;随着介质pH的增大,nSiO_2颗粒的表面电荷密度（σ）增加,但增加介质的离子强度及nSiO_2颗粒的粒径会逐渐降低σ。nSiO_2颗粒粒径的变化会导致其表面H＋的分布发生改变,从而引起σ的变化。双电层结构的拟合结果表明,当双电层结构厚度与粒径比值（λD/Dp）〈0.2时,nSiO_2颗粒的σ主要受控于粒径大小,可忽略离子强度和pH的影响;当λD/Dp〉0.2时,nSiO_2颗粒的σ不仅受控于粒径大小,还与介质的离子强度和pH密切相关。【结论】nSiO_2颗粒的σ与粒径大小、介质的pH和离子强度密切相关。

英文摘要：

【Objective】This study aimed to investigate the effects of aqueous pH and ion strength on dispersity of nano-SiO_2 particles.【Method】The effects of aqueous pH and ion strength on dispersity of nano-SiO_2 with diameter of 10 nm were tested through batch experiments,and the mechanism was proved through multi-ion surface charge-regulation model and Poisson-boltzmann equation analysis.【Result】Dispersity of SiO_2 particles increased with the increase of pH and gradually reached balance after pH 7.39,while it decreased with the increase of NaNO_3 concentration and nSiO_2 particle size.The further electrical double layer analysis proved that the surface charge density of nano-SiO_2 particles increased with the increase of pH,while it decreased with increasing ionic strength and particle size.Variation of the surface charge with the particle size was attributed to the change in the surface concentration of H＋ions.Particle diameter normalized with the EDL thickness was used to combine the effects of pH and salt concentration.ForλD/Dp0.2,the effect of particle size on its surface charge density was the main factor,while the pH and salt concentration could be neglected.However,forλD/Dp〉0.2,the surface charge density of silica nanoparticle was not only determined by particle size but also affected by aqueous pH and ion strength.【Conclusion】The dispersity of SiO_2 nanoparticles was affected by surface charge density which was controlled by particle size as well as media pH and salt concentration.