Coagulation of Colloidal Particles

研究了纳米级胶粒的凝聚过程，考察了其稳定性是否符合所谓的DLVO理论，并用修正的Smoluchowski理论对凝聚速率进行了估算。二氧化硅粒子、聚苯乙烯乳胶粒子和氧化锆粒子的直径为5 nm~200 nm。用停流法将胶体溶液和电解质溶液(或聚合物溶液)混合，用小角度光散射仪测量凝血速率的变化。考察了电解液、颗粒和聚合物对混凝速率的影响。得到了以下结果：1)直径小于100 nm的胶体颗粒的快速凝聚速率常数随着粒径的减小而减小。2)直径小于100 nm的胶体颗粒的快速凝聚速率常数随着阳离子的水化热的增大和阴离子的水化热的减小而减小。3)过高的电解液浓度下的快速凝聚速率随浓度的增加而降低。4)超细颗粒形成的絮体很难在外力的作用下解聚。5)这些结果表明，直径小于100 nm的胶体颗粒的稳定性不符合DLVO理论和DLVO理论凝聚速率不能用Smoluchowski理论来预测。6)吸附在表面的聚合物颗粒的絮凝速率随着以颗粒直径归一化的聚合物尺寸的增加而增加。

The coagulation of colloidal particles of nm order in size was investigated; it was examined whether the stability is consistent with the so-called DLVO theory and the rate can be evaluated by the modified Smoluchowski theory. Silica particles, poly-styrene latex particles and zirconia particles of 5 nm to 200 nm in diameter were employed. A colloidal solution and an electrolyte solution (or polymer solution) were mixed by a stopped flow method, and then the change of coagulation rate was measured by a low angle light scattering apparatus. The dependences of the coagulation rate on electrolytes, particles and polymers were investigated. Following results were obtained.1) The rapid coagulation rate constant for colloidal particles smaller than about 100 nm in diameter decreases with decreasing particle size.2) The rapid coagulation rate constant for colloidal particles smaller than about 100 nm in diameter decreases with increasing hydration enthalpy of cations and de-creasing enthalpy of anions.3) The rapid coagulation rate at the excessively high electrolyte concentration de-creases with the increasing concentration.4) Flocs formed with ultrafine particles were hardly deflocculated by external forces.5) These results imply that the stability of particles smaller than about 100 nm in diameter is not consistent with the DLVO theory and the coagulation rate can not be predicted by the Smoluchowski theory.6) The flocculation rate of particles with polymers adsorbed on the surface in-creases with the increase of the polymer size normalized by the particle diameter.