环境因子对两种纳米金属氧化物在水体中稳定性的影响

以纳米二氧化铈(Nano-Ce O2)及纳米二氧化钛(Nano-Ti O2)为主要实验材料,研究腐植酸(HA)、离子强度(IS)与p H对其在水体中稳定性的影响。结果表明:HA浓度升高(0~5 mg·L-1),两种纳米颗粒在水体中的稳定性均增强,其原因是吸附在纳米颗粒表面的HA使颗粒间产生巨大的空间位阻斥力与静电斥力,从而减弱了颗粒的凝聚;IS增加(1~50 mmol·L-1Na Cl),两种纳米材料稳定性均降低,颗粒凝聚后粒径变大,且HA的存在(5 mg·L-1)能显著减弱IS对其稳定性的影响,其原因是吸附在纳米颗粒表面的HA使颗粒间产生空间位阻斥力及静电斥力且这两种斥力占主导作用。实验p H范围内(6.01~10.02),随着p H的增加,纳米颗粒的稳定性增强,但当本体溶液中存在HA(5 mg·L-1),p H变化对纳米颗粒稳定性几乎不产生影响。此外,计算并运用XDLVO(extended Derjaguin-Landau-Verwey-Overbeek)理论进行预测分析的结果表明,XDLVO理论的预测与实验结果非常吻合。该研究结果有助于深入了解Nano-Ce O2及Nano-Ti O2在水体中的环境行为,并为进一步预测两者的生态环境风险提供理论依据。

Effects of Environmental Factors on Stability of Two Metal Oxide Nanoparticles in Aqueous Medium

The ecological and environmental effects of nanoparticles in the aqueous medium are dependent on their stability. However, the stability is greatly influenced by environmental factors. This work examined the effects of humic acid(HA) concentration, ionic strength(IS)and pH on the stability of Nano-CeO₂ and Nano-TiO₂ in aqueous suspension. The presence of HA significantly promoted the stability of nanoparticles(NPs) in the suspension(0~5 mg·L^-1), due to increased steric effect and electrostatic repulsion between NPs by HA coated on the NPs. Although increasing IS(1~50 mmol·L^-1 NaCl) could decrease NP stability in the suspension, HA(5 mg·L^-1) could weaken this effect by introducing greater steric repulsion. Similarly, the presence of 5 mg·L^-1 HA decreased the effects of pH increasing from 6.01 to 10.02 on NP stability. In addition, all the experimental data matched well with the predictions based on extended Derjaguin-Landau-Verwey-Overbeek(XDLVO) theory. Our findings could gain insights into the behavior of Nano-CeO₂ and Nano-TiO₂ in aqueous medium, and provide theoretical basis for environmental risk assessment of Nano-CeO₂ and Nano-TiO₂.