Modelling PCC flocculation by bridging mechanism using population balances: Effect of polymer characteristics on flocculation

Abstract

A population balance model for flocculation of PCC particles with polyelectrolytes of very high molecular weight, medium charge density and different degree of branching is presented. The model considers simultaneously aggregation, breakage and flocs restructuring to describe the PCC flocculation by bridging mechanism. The maximum collision efficiency factor, a parameter related with the fragmentation rate and a time constant for flocs restructuring have been taken as fitting parameters. These fitting parameters are optimized to get the best fit between experimental data obtained by LDS in a previous study and the modelled results. The optimized parameters were correlated with flocculant concentration, flocs structure and polymer branching. The correlations obtained show well the effects of flocculant concentration, flocs structure and polymer structure on the flocculation kinetics and flocs restructuring which are translated in the model parameters. Moreover, the flocs break up due to polymer degradation was introduced in the model by decreasing, with time, the maximum collision efficiency factor. It was shown that this effect can be neglected since the improvement in the results is too small relatively to the high increase of the computational time required to perform the simulation.

Switch Effect, Water‐Like State, and New Interaction Mechanism of an H‐Bonded Polycation–Polyacrylamide System to Realize Instant Decolorization of Dyeing Wastewater

“…[22][23][24] For the flocculation According to the current understanding, charge neutralization and bridging are regarded as the most basic two interaction mechanisms of flocculants.…”

“…[22][23][24] Because of the abovementioned newly discovered essential characteristics of the WLPS, the WLPS realized an instantaneous and highly adaptable decolorization of dyeing wastewater. When our designed WLPS decolorant interacted with the anionic dyes in water for only 10 s, large flocs with the bridging structures were directly formed; indeed, the rate-controlling step of the formation of small precipitates was so fast that it was almost omitted, thus, the colored dyes could be separated from the water phase almost instantaneously.…”

“…[12][13][14][15][16][17][18] Of these, flocculation is still more advantageous than the other technologies in the engineering applications of large-scale water treatment due to its simplicity, high efficiency, and cost-effectiveness. [22][23][24] Small precipitations are first formed by the electrostatic interactions (i.e., charge neutralization) between the polycationic flocculants and the anionic dye (it takes a relatively long time as a rate-controlling step). [13,[19][20][21] According to the current understanding, the flocculation decolorization of dyeing wastewater primarily depends on the two basic processes of charge neutralization and bridging.…”

Modeling Vertical Transport of Cohesive Fine Sediment

“…Considering the hydrodynamic and electrostatic forces between particles, Winterwerp [1998] proposed a simple model for turbulence model of cohesive fine sediment. Antunes et al [2010] adopted population balance method and discussed the impact of polymer characteristics on flocculation.…”

Time-Varying Hydraulic Gradient Model of Paste-Like Tailings in Long-Distance Pipeline Transportation

“…Consequently, the thick hydration shells get thinner. The long molecular chains from CPAM will release linearly structured reactive groups after the process of hydrolysis and polycondensation; they then experience mutual attraction by the formation of multiple colloidal bonds, capturing and gathering through bridging, and finally developing into FS [15]. FS, which are unstable, can not only be stretched or damaged by mechanical mixing, but also lapped or recombined by bridging ( Figure 3) [16].…”