纳米SiO_2表面吸附聚丙烯酰胺及其液相分散稳定性

POLYACRYLAMIDE ADSORPTION BEHAVIOR ON NANO-SIZED SILICA PARTICLES AND ITS STABILITY IN AQUEOUS DISPERSIONS

通过溶胶凝胶法制备纳米SiO2,讨论聚丙烯酰胺(polyacrylamide,PAM)在其水悬浮体系中的吸附行为。红外光谱分析和吸附实验结果表明:纳米SiO2通过氢键吸附PAM,吸附行为与PAM浓度、PAM分子量和pH值等因素相关。PAM吸附量随着浓度的增加而增大直至达饱和吸附量,并且饱和吸附量随着pH值的减小而增大。相同条件下,PAM分子量越大,表面吸附层的厚度越大,吸附量也越大。吸附PAM后纳米SiO2的表面电荷密度、扩散层电荷密度以及ζ电位发生变化。纳米SiO2吸附PAM后,增加了颗粒间的空间位阻作用,有效阻止纳米SiO2的团聚。若PAM加入量达到过饱和反而会引起纳米SiO2的团聚。

Nano-sized SiO2 particles were synthesized by sol-gel technology. Adsorption behavior of polyacrylamide (PAM) onto particle surfaces in aqueous suspensions was investigated. Infrared analysis and adsorption experimental results indicate that PAM is absorbed on SiO2 particles through hydrogen bonding, and the adsorption behavior is related to PAM concentration, pH values and molecular weight. Adsorption quantity of PAM on the particles increases with the increase of PAM concentration until saturation amount, which increases with the decrease of pH values etc. If other conditions are the same, the higher of PAM in mass, which induces to increase the thickness of adsorbed layer, the higher the amount of PAM adsorption. Surface charge density, diffuse charge density and measured zeta potential of SiO2 particles vary distinctly after PAM adsorption. The adsorption of PAM onto surface of nanoparticles can provide a high degree of stabilization and remarkably improve the stability of as-formed suspension against flocculation in water. However, the stability of SiO2 suspension will be destroyed when the added amount of PAM exceed the saturation adsorption.