Mussel-inspired cationic chitosan-based flocculants with floc enlarging capacity for efficient removal of anionic dye

Abstract

Biomass-based flocculants have been widely studied and applied to wastewater treatment due to their environmental friendliness. However, these flocculants tend to generate flocs with small size and lead to difficult solid-liquid separation after the flocculation. The key to solving the floc size problem is enhancing intermolecular or intramolecular interaction forces by changing the molecular structure and functional groups of flocculants. Herein, we developed a mussel-inspired cationic biomass flocculant by functionalizing chitosan (CS) with cation component acryloyloxyethyltrimethyl ammonium chloride (DAC) and mussel-inspired monomer N-2-(3, 4-dihydroxyphenethyl) acrylamide (DAA) through free radical polymerization. The prepared flocculant could provide multiple interaction forces such as electrostatic interaction, cation-π interaction, π −π stacking, and hydrogen bonding to pollutants. As a result, the spent CS-g-p (DAC-co-DAA) flocculant generate dye-containing flocs with dramatically increased size when compared with its counterpart CS-g-pDAC without catechol groups and are capable to realize more than 95% removal efficiency towards organic dyes such as MB and CR over a broad pH range from 3 to 9. This study provides some insights in how to apply this mussel-inspired strategy to develop environmentally friendly biomass-derived flocculants with floc enlarging capacity to treat organic wastewaters in wide pH range.