Polymeric flocculants calculation

Four types of colloids were considered in the WIPP program intrinsic actinide colloids, mineral colloids, microbes, and humic acid colloids (US DOE, 1996). Intrinsic actinide colloids, consisting of polymerized hydrated actinide hydroxides, are not stable in the neutral to moderately basic pH conditions expected in the WIPP, and were assumed not to contribute to the total actinide concentrations in solution. Mineral colloids are destabilized and tend to flocculate in the high-ionic-strength WIPP brines (Kelly et al., 1999). In the performance assessment calculations for the WIPP, a highly conservative value of 2.6 X 10 mol actinide per liter, for each actinide, was assumed to be bound to mineral colloids and to contribute to the mobile fraction. Actinides sorbed onto microbes and humic acids were estimated to contribute significantly to the concentration of mobile actinides in WIPP brines as discussed above (Section 9.06.3.2.2). 

The attractive forces between suspension particles are considered to be exclusively London-van der Waals interactions (except where interparticle bridging by long polymeric chains occurs). The repulsive forces, as discussed in Chapter 8, comprise both electrostatic repulsion and entropic and enthalpic forces. In aqueous systems the hydrophobic dispersed phase is coated with hydrophilic surfactant or polymer. As adsorption of surfactant or polymer (or, of course, both) at the solid-liquid interface alters the negative charge on the suspension particles, the adsorbed layer may not necessarily confer a repulsive effect. Ionic surfactants may neutralize the charge of the particles and result in their flocculation. The addition of electrolyte such as aluminium chloride can further complicate interpretation of results electrolyte can alter the charge on the suspension particles by specific adsorption, and can affect the solution properties of the surfactants and polymers in the formulation. Some aspects of the application of DLVO theory to pharmaceutical suspensions and the use of computer programmes to calculate interaction curves are discussed by Schneider et al. [4]. 

Poehlein [40] summarized previous work and proposed a comprehensive particle nucleation mechanism involved in a persulfate initiated emulsion polymerization system, as shown schematically in Figure 3.5. Song and Poehlein [41, 42] developed a general kinetic model taking into account micellar nucleation, homogeneous nucleation, and monomer droplet nucleation in emulsion polymerization. The chain transfer and termination reactions occurring in the continuous aqueous phase, capture of oligomeric radicals by particle nuclei, and flocculation of particle nuclei were also incorporated into the model development. The resultant expressions for calculation of the rate of particle nucleation can be written as... 

---