nTiO2在水中的分散沉降行为研究

nTiO2进入水环境后,其存在形态及环境行为主要受水环境因素影响.以P25 nTiO2为研究对象,通过改变nTiO2悬浊液的pH值、电解质和表面活性剂种类,分析了nTiO2的分散、团聚及沉降行为.结果表明,pH通过改变nTiO2颗粒的Zeta电位影响nTiO2在水中的稳定性,等电点附近nTiO2发生显著聚沉.nTiO2颗粒选择性吸附AlCl3、CaCl2、NaCl及Na2SO4电离产生的荷电离子,阳离子的吸附中和了TiO2颗粒表面的负电荷,导致颗粒急速聚沉;阴离子的吸附使颗粒间静电斥力增强,颗粒稳定存在于水中.不同类型的表面活性剂通过改变nTiO2颗粒表面性质,增强nTiO2颗粒在水中的稳定性.运用DLVO理论建立了nTiO2的势能方程,势能曲线拟合结果表明,水环境条件通过影响颗粒间势能大小影响nTiO2在水中的分散沉降行为.

Studies on the Dispersion and Deposition Behavior of Nano-TiO2 in Aquatic System

The existing form and environmental behavior of nTiO₂ in aquatic system are mainly affected by environmental factors. The dispension and deposition behavior of nTiO₂ was investigated by changing pH values of the suspension liquid and adding electrolytes and surfactants using P25 nano-TiO₂ as the research object. The results indicated that the pH value obviously affected the stability of nTiO₂ by changing the charge distribution on the nTiO₂ particles. TiO₂ nanoparticles were highly aggregated to deposit when the pH value was close to the isoelectric point. The characteristic adsorption ion of AlCl₃, CaCl₂, NaCl and Na₂SO₄ after ionization on the surface of nTiO₂ particles varied from each other. The adsorption of cations neutralized the negative charge on the surface of nTiO₂ particles which led to the quick aggregation and deposition of nTiO₂ particles. The adsorption of anions improved the stability of nTiO₂ particles in water by increasing electrostatic repulsion between TiO₂ particles. Surfactants would adsorb onto the surface of nTiO₂ particles and enhance the stability of nTiO₂ by changing the surface properties of the nanoparticles. The potential energy of nTiO₂ particles were simulated by the DLVO theory. The simulative potential energy curve confirmed that the change of relevant water environment conditions led to the change of potential energy of nTiO₂ particles, which determined the dispension and deposition behavior of nTiO₂ particles.