Synthesis of Hydrophobic Cationic Chitosan Flocculant and Its Sludge Dewatering Property

The hydrophobic cationic chitosan (HTCC) flocculant was synthesized by reacting chitosan with epoxy propyl trimethyl ammonium chloride (EPTAC) and (2,3-epoxy propyl) dodecyl dimethyl ammonium chloride (EDC), to improve its waste sludge dewaterability. By FTIR and ¹H NMR analysis, EPTAC and EDC were confirmed to be grafted onto the molecular chains of chitosan (CTS) successfully. With the increase of EDC content, G′ of HTCC aqueous solution with 1:1.5:1.5 mole ratio of CTS:EPTAC:EDC consistently showed higher values than G″ over the entire frequency range explored, indicating the formation of a physically cross-linked network. The crystallization ability of HTCC decreased compared with pristine CTS. The long alkyl chains on the EDC molecules enhanced the hydrophobicity of HTCC, and better dewaterability of the waste sludge was achieved through the promoted bridging action of HTCC.