title: Evaluation of a novel chitosan-based flocculant with high flocculation performance, low toxicity and good floc properties.
abstract: In this work, a novel chitosan-based flocculant, carboxymethyl chitosan-graft-poly[(2-methacryloyloxyethyl) trimethyl ammonium chloride] (CMC-g-PDMC), was designed and prepared successfully. Flocculation performance of CMC-g-PDMC was systematically evaluated using kaolin suspension, humic acid (HA) solution and kaolin-HA mixed suspension as synthetic wastewater under acidic, neutral and alkaline conditions, respectively. The experimental results demonstrated that CMC-g-PDMC exhibited lower optimal dosage, higher contaminant removal efficiency, wider applicable pH range, lower effluent toxicity and better floc properties for handling and disposal, in comparison with polyaluminum chloride. The high flocculation performance of CMC-g-PDMC was ascribed to two structural advantages of improved both positive charges and molecular weight. In addition, flocs characteristics including flocs formation, breakage, regrowth and fractal structure, were studied by an in-situ light scattering system during the flocculation process. Detailed analysis clearly illuminated the differences and relationship among floc size, fractal dimension and floc strength. Based on analysis of floc properties in combination with zeta potential measurements, flocculation mechanisms in different synthetic wastewater at various pHs were deeply discussed: charge neutralization or patching played the key role under different conditions, and the relationship between flocculation mechanisms and floc properties has been built. The effective and environment-friendly flocculant bear significant application potentials in water treatment fields.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, School of Chemistry & Chemical Engineering, Nanjing University, No. 22 Hankou Road, Nanjing 210093, PR China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, School of Chemistry & Chemical Engineering, Nanjing University, No. 22 Hankou Road, Nanjing 210093, PR China.
authors.forename: Haijiang
authors.initials: H
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, School of Chemistry & Chemical Engineering, Nanjing University, No. 22 Hankou Road, Nanjing 210093, PR China.
authors.forename: Han
authors.initials: H
authors.lastname: Yan
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, School of Chemistry & Chemical Engineering, Nanjing University, No. 22 Hankou Road, Nanjing 210093, PR China.
authors.forename: Hu
authors.initials: H
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, School of Chemistry & Chemical Engineering, Nanjing University, No. 22 Hankou Road, Nanjing 210093, PR China. Electronic address: yanghu@nju.edu.cn.
authors.forename: Hu
authors.initials: H
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, School of Chemistry & Chemical Engineering, Nanjing University, No. 22 Hankou Road, Nanjing 210093, PR China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, School of Chemistry & Chemical Engineering, Nanjing University, No. 22 Hankou Road, Nanjing 210093, PR China.
authors.forename: Haibo
authors.initials: H
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, School of Chemistry & Chemical Engineering, Nanjing University, No. 22 Hankou Road, Nanjing 210093, PR China.
authors.forename: Aimin
authors.initials: A
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, School of Chemistry & Chemical Engineering, Nanjing University, No. 22 Hankou Road, Nanjing 210093, PR China.
authors.forename: Rongshi
authors.initials: R
authors.lastname: Cheng
mesh_terms: D048271:Chitosan / Q000737:chemistry* / Q000633:toxicity; D005427:Flocculation; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D048271:Chitosan
keywords: Chitosan-based flocculant; Floc properties; Floc strength; Flocculation mechanism; Fractal dimension