The Impact of Zeta Potential on the Physical Properties of Ferric−NOM Flocs

Abstract

The physical properties of natural organic matter (NOM) flocs, such as size, growth rate, and strength, were investigated using a laser diffraction particle sizing device. Conditions were set such that varying carbon coagulant ratio and zeta potential could both be investigated. Results demonstrated a link between zeta potential and coagulation and flocculation performance, with the production of strong flocs and low residual concentrations when the zeta potential was minimized. The overall strength of the connection points within the floc were determined by a combination of steric interactions, polymer bridging, van der Waals forces, and electrostatic forces. Hence, both dose ratio and zeta potential are important in understanding floc properties. Floc growth was dominated by dose ratio, whereas the response to elevated shear was strongly related to zeta potential. The steady-state floc size was a combination of both factors. This allowed the continued development of a qualitative model in order to engineer optimal floc properties when coagulating NOM.

Characterization of floc structure and strength: Role of changing shear rates under various coagulation mechanisms

“…However, they provide only limited information on flocculation process. The information of floc size distribution and structure would be much expected [2].…”

Survey of treatment process in water treatment plant and the characteristics of flocs formed by two new coagulants

“…The concentration of nano particles used in this study was 1000 mg/L. The relationship between the applied shear and broken floc size has been used by many researchers to evaluate the floc strength as described in former studies [19][20][21][22]:…”

Coagulation effect and floc properties of polyferric silicate sulphate and polyferric sulphate in the Yellow River water treatment

“…By contrast, PFS flocs had fine re-growth capability with a 46.6% R f exposed to a 5 min shear of 200 rpm. Some researchers found that floc strength and floc regrowth capability depend on the coagulation mechanisms [9][10][11][12][13]. When charge neutrality dominates the coagulation mechanism, the negative charges in the colloid surfaces are neutralized by the positive charged coagulants and the destabilized colloids aggregate to form flocs.…”

“…Recently, much research focused on the breakage and re-growth capability of flocs formed by traditional inorganic coagulants [13][14][15], and there have been reports on the floc properties of organic flocculants and polyaluminum chloride [10,12,16]. Wei et al studied the size distribution and fractal of flocs of polyferric chloride and different ployferric-cationic polymer dual-coagulant in humic acid solution [17].…”