Fabrication and characterization of poly(ferric chloride)-polyamine flocculant and its application to the decolorization of reactive dyes

By combining polyferric chloride (PFC) and poly(epichlorohydrin-dimethylamine) [P(ECH-DAM)], the development, characterization, and application of PFC-P(ECH-DAM) was conducted in this paper. The novel reagents were characterized by means of several typical properties and morphological analysis. The flocculation performance and subsequent mechanism were also examined for the coagulation treatment of reactive dye suspensions. Experimental results showed that the composite PFC-P(ECH-DAM) exhibited promoted characteristics, such as increased efficient polymeric speciation concentration, improved zeta potential, and enhanced flocculation performance. The morphological analysis verified the amorphous molecular structure of PFC-P(ECH-DAM) with a relatively dense branch network and sheet-like structure adhesion to each other. Increase of cationic P(ECH-DAM) proportion resulted in gradual reduction of Fe-a/Fe-b content, increase of Fe-c concentration, and improvement of zeta potential in PFC-P(ECH-DAM). The positive charge in P(ECH-DAM) and PFC-P(ECH-DAM) exhibited a decreasing tendency with increase of amine group content in cross-linker molecule. The increase of P(ECH-DAM)/Fe mass ratio and amine group of cross-linker in PFC-P(ECH-DAM) favored the destabilization of dye molecules due to their disturbance on zeta potential, Fe polymerization degree, molecular weight, and flocculation mechanism of the composite reagent.