KINETICS OF TURBULENT COAGULATION STUDIED BY MEANS OF END-OVER-END ROTATION

We have investigated the kinetics of coagulation of monodisperse polym er latices in turbulent flow, with the purpose of characterizing the f low in terms of the frequency of flow-induced (orthokinetic) collision s. We chose a very simple and practically convenient way to generate t urbulent flow, namely by pouring dispersions from one small bottle int o another, which is equivalent to rotating such bottles end over end. This method allows us to do experiments for times as short as 1 s, thu s giving access to the initial stages where binary collisions of prima ry particles (''monomers'') are dominant. The total number concentrati on of aggregates, as well as the size distribution of clusters, was me asured as a function of the number of mixing steps by means of a singl e particle optical sizer (SPOS). The data were analyzed assuming addit ivity of the perikinetic and orthokinetic coagulation rates, taking in to account the effect of hydrodynamic interaction. The dependence of t he rate of coagulation on the size of primary particles was found to a gree fully with theoretical predictions, thus providing clear evidence that the proposed method works, i.e., the adopted simple procedure yi elds quantitatively reproducible and detailed kinetic data on collisio n frequencies. This is of importance for subsequent studies of other r apid aggregation processes such as, e.g., bridging flocculation by pol ymeric flocculants. (C) 1994 Academic Press, Inc.