Cationic-modified microporous zeolites/anionic polymer system for simultaneous removal of dissolved and colloidal substances from wastewater

Abstract

The simultaneous removal of both soluble and colloidal contaminants in wastewater has been a challenge. An innovative flocculation/sorption system has been developed in this work, which consisted of a cationic-modified microporous zeolite HY and an anionic polyacylamide-based polymer. The water-soluble anionic polymers act as flocculants for colloidal particles whereas the cationic-modified zeolite functions not only as an absorbent (towards the soluble or dissolved substances) but also a co-factor for the dual-component flocculation system. Such a system has been applied to clarify the wastewater containing the dissolved and colloidal substances (DCS) encountered in the pulp and paper industry. The quaternized zeolite HY was prepared using glycidyltrimethyl-ammonium chloride (GTMA-Cl) as a cationic reagent via a post-grafting approach to create the covalent bonds between GTMA-Cl and silanos (Si-OH) groups on the surface of zeolite HY. The pore structure and surface characteristics of the modified zeolite HY were determined based on XRD, N 2 adsorption and zeta-potential measurements. The sorption of modified zeolite HY towards benzoic acid and dissolved substances in DCS was determined using an UV spectrometer. The dynamic flocculation of DCS induced by the dual-component systems was monitored using a photometric dispersion analyzer (PDA). The results indicated that the simultaneous removal of DCS has been improved substantially due to the synergy between the cationic zeolites and anionic polymers in the dual-component system. The mechanisms involved in flocculation/sorption were also discussed.