Amphiphilic polyelectrolytes: Characterization and application in coagulation/flocculation

Abstract

Macromolecules that possess charges as well as hydrophobes along with or pendent to the polymer backbone are one of the most important classes of polyelectrolytes, which are often termed as ‘amphiphilic polyelectrolytes’ or ‘hydrophobically modified polyelectrolytes’. Recently, amphiphilic polyelectrolytes are potentially used in variety of commercial applications, such as associative thickeners, rheology modifiers, polymer-based surfactants and flocculants, emulsifiers and solubilizers. In aqueous solution, amphiphilic polyelectrolytes exhibit self-assembling phenomena, analogous to conventional surfactant micelles, driven by the balance between electrostatic repulsion and hydrophobic interactions. Novel hydrophobically modified polyelectrolytes based on quaternary ammonium salt and sulfur dioxide have been synthesized. Characterization of this novel class of amphiphilic polyelectrolytes has been performed by (1) static (SLS) and quasielastic (QELS) light-scattering experiment, (2) Rheological properties measurement, (3) Fluorescent spectroscopy, and (4) surface tension measurement. These techniques emphasize the hydrophobic association (intermolecular) phenomena, flow properties, formation of hydrophobic microdomain and surface activity of this novel polymer. Currently, iron-based coagulants or polymer-based flocculants are preferred in water treatment over the conventional aluminum-based coagulants, which have been recently linked to Alzheimer's disease. In water treatment, polymer-based coagulants such as cationic polyelectrolytes are used in two distinct ways, as coagulant aids and as primary coagulants. This study evaluates the use of the synthesized amphiphilic polyelectrolyte as a primary coagulant in groundwater/wastewater treatment. It is interesting observed that appreciably low polyelectrolyte dose (0.3 ppm) is required for NOM removal from contaminated water.