Green wastewater treatment flocculants and fixatives prepared from cellulose using high-consistency processing and deep eutectic solvents

Abstract

Cellulose offers a large renewable raw material base and can be chemically modified in a variety of ways to introduce new functionalities such as cationic charge, that are required in effective waste water treatment for any polymers. Cationic cellulose derivatives were synthesized using both conventional and novel methods from several commercially available cellulose pulps. The cationic derivatives were used as biobased flocculants to treat real-life wastewater samples in a head-to-head comparison with cationic polyacrylamides. A novel high-consistency, high shear mixing heterogeneous mixing method enables the preparation of cellulose derivatives without the use of solvent or high cost solubilization methods. When higher cationic charge is required, deep eutectic solvents can be used to modify cellulose. Both the molecular weight and charge of the cationic cellulose derivatives have a drastic influence on performance in water treatment applications. Flocculation experiments with real-life waste water samples revealed that cationic cellulose derivatives are able to effectively function as flocculants and fixatives, and even outperform commercial polyacrylamides. The highest achieved level of turbidity removal was 93.2%. Cationic cellulose derivatives provided good efficacy in sludge dewatering, Focused Beam Reflectance Measurement flocculation tests and anionic trash fixing, which are crucial properties for the pulp and paper industry.