Flocculation of kaolin from aqueous suspension using low dosages of acrylamide‐based cationic flocculants

Abstract

Flocculation of kaolin from aqueous streams has become very important in view of its wide range of applications. In this work, cationic flocculants based on copolymers of acrylamide (AM) and 3‐acrylamidopropyltrimethylammonium chloride (APTMAC) were synthesized with two different mole ratios of monomers, 80 mol % of AM (CP‐8020) and 40 mol % of AM (CP‐4060). The chemical structures of copolymers were confirmed by 1H and carbon‐13 nuclear magnetic resonance (13C NMR) spectroscopy. The molecular weight (MW) and zeta potential of the copolymers were determined. High MW was obtained for copolymer with high content of AM (CP‐8020) and high zeta potential was observed for copolymer with high content of APTMAC (CP‐4060). Flocculation of kaolin suspension was performed using both CP‐8020 and CP‐4060 and the flocculation was correlated to the zeta potential and MW of the copolymers. The optimum dosages of flocculants were determined. The mechanism of flocculation was discussed in terms of charge neutralization and bridging. The flocs of kaolin were characterized in terms of moisture content and size. To the best of our knowledge, this copolymer system was used for the first time for kaolin flocculation and found out to be efficient. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47286.

Extracellular Polymeric Substances (EPS) as Microalgal Bioproducts: A Review of Factors Affecting EPS Synthesis and Application in Flocculation Processes

“…The process consists in association of small particles in the colloid solution to form larger aggregates with high molecular weight, allowing the particles to settle [88]. The flocculation process is applied in algal harvesting [89], wastewater treatment [84], paper manufacture, clarification of sugarcane juice in the sugar industry [90,91], metal binding [92], and removal of color from textile wastewaters [93].…”

“…Substances used as flocculants must have specific properties, e.g., molecular weight, type, and ionic strength. Large amounts and small sizes of colloidal particles as well as their low distribution increase flocculation efficiency [91]. Synthetic polymers (polyacrylamide) cause contamination of harvested biomass with metals, metal hydroxides, and non-biodegradable polymers.…”

“…In turn, since they are non-toxic, biodegradable, and inexpensive, natural polymers are the most environmentally friendly group of this type of compound [91]. Natural polymers used in the flocculation process comprise EPS, chitosan, cellulose, starch, and natural gums with their derivatives.…”

“…They are characterized by high molecular weight, fixed molecular constitution, and mostly long chains. One of the prerequisites for flocculation of microalgal biomass to occur is the positive charge of the polymer (since the surface charge of algal cells is negative); however, it is not common in the environment [91,95]. Inorganic salts (ferric chloride, aluminium sulphate) are coagulants and may induce polymer flocculation [95].…”

Synthesis of the Hydrophobic Cationic Polyacrylamide (PADD) Initiated by Ultrasonic and its Flocculation and Treatment of Coal Mine Wastewater

“…This is mainly because the excessive cationic flocculant will encapsulate colloidal particles, and the vacant adsorption sites will be greatly reduced, which is not conducive to the role of bridging. In addition, it can also reverse the electrical properties of colloidal particles and enhance the electric repulsion between them, resulting in poor flocculation effect of coal mine wastewater [34,35]. At the same time, among all flocculants, PADD has the best flocculation performance in flocculants.…”