分散剂对Fe_3O_4表面化学特性的影响

Effect of Dispersants on Surface Chemical Properties of Magnetite

以Zeta电位和电荷面密度为定量指标,研究了不同分散剂如十二烷基硫酸钠、聚乙二醇及柠檬酸对Fe3O4表面化学特性的影响.研究结果表明:Fe3O4等电点的pH值为6.4～6.8,当pH<6.4时,其表面带正电,当pH>6.8时,其表面带负电;十二烷基硫酸钠和柠檬酸通过静电吸附作用使Fe3O4的表面电荷发生非常显著的变化,等电点明显向酸性方向移动,Fe3O4粒径减小,分散稳定性能越强;聚乙二醇与Fe3O4形成配位键,提供位阻斥力改变Zeta电位和电荷面密度,对Fe3O4的粒径和分散性能无明显影响.

Surface chemical properties of magnetite were investigated by measuring Zeta potential and surface charge density. The effects of different dispersants, such as sodium lauryl sulfate, polyethylene glycol and citric acid on surface charge of magnetite were discussed. The results show that the zero point of charges (ZPC) for magnetite in KNO3 solution is determined to be 6. 4-6.8, the surface acquires a positive charge at pH value below 6. 4 and a negative charge at pH value above 6.8. In the presence of sodium lauryl sulfate and citric acid, surface charge of magnetite powder changes significantly and ZPC shifts toward acidic environment probably due to electrostatic adsorption, and as a result, the diameter of Fe3O4 is decreased and dispersing property is improved. In a solution containing polyethylene glycol, the change of Zeta potential and surface charge is considered to be brought about by complex bond and position obstruction repulsion, which has no obvious effect on the diameter and dispersing property of Fe3O4.