Synthesis of chitosan-based grafting magnetic flocculants for flocculation of kaolin suspensions

摘要

A series of novel chitosan-based magnetic flocculants FS@CTS-P（AM-DMC） was prepared by molecular structure control.The characterization results showed that FS@CTS-P（AM-DMC）had a uniform size of about 21.46 nm,featuring a typical core-shell structure,and the average coating layer thickness of CTS-P（AM-DMC） was about 5.03 nm.FS@CTS-P（AM-DMC）exhibited excellent flocculation performance for kaolin suspension,achieved 92.54%turbidity removal efficiency under dosage of 150 mg/L,pH 7.0,even at high turbidity （2000 NTU）with a removal efficiency of 96.96%.The flocculation mechanism was revealed to be dominated by charge neutralization under acidic and neutral conditions,while adsorption and bridging effects play an important role in alkaline environments.The properties of magnetic aggregates during flocculation,breakage,and regeneration were studied at different pH levels and dosages.In the process of magnetophoretic,magnetic particles collide and adsorb with kaolin particles continuously due to magnetic and electrostatic attraction,transform into magnetic chain clusters,and then further form three-dimensional network magnetic aggregates that can capture free kaolin particles and other chain clusters.Particle image velocimetry confirmed the formation of eddy current of magnetic flocs and experienced three stages:acceleration,stabilization,and deceleration.