Evaluation of structural effects on the flocculation performance of a co-graft starch-based flocculant

The molecular structure of a material substantially determines its final application performance. In this work, a series of starch-based flocculants with different charge densities and average graft chain lengths were prepared by the co-graft polymerization of acrylamide and [(2-methacryloyloxyethyl) trimethyl ammonium chloride] (St-g-PAM-co-PDMC). The flocculation performance of St-g-PAM-co-PDMC was studied systematically at neutral pH using kaolin suspension and sodium humate (NaHA) aqueous solution as synthetic wastewaters. The effects of the two structural factors on the flocculation efficiency of the starch-based flocculants have been investigated. The experimental results showed that the charge density and average graft chain length contributed distinctly to flocculation performance during the removal of both kaolin particles and NaHA under insufficient and excessive flocculant dose conditions. The flocculation mechanisms of this starch-based flocculant were discussed in detail on the basis of the structure-activity relationship, which are significant to optimize the flocculation conditions and guide the development of novel high-performance flocculants. [Display omitted] •A series of starch-based flocculants with different molecular structure was prepared.•Kaolin particles and sodium humate were used as synthetic contaminants.•Flocculation performance of those starch-based flocculants was studied in detail.•Charge density and average graft chain length contributed distinctly to flocculation.•The flocculation mechanism was discussed from its structure–activity relationship.