title: Separation and Sequential Recovery of Tetracycline and Cu(II) from Water Using Reusable Thermoresponsive Chitosan-Based Flocculant.
abstract: Coexistence of antibiotics and heavy metals is typically detected in water containing both organic and inorganic contaminants. In this work, a flocculation method using a reusable thermoresponsive chitosan-based flocculant (CS-g-PNNPAM) was applied for separation and sequential recovery of tetracycline (TC) and Cu(II) from water. High synergistic removal rates of both TC and Cu(II) from water (>90%) were reached. Interactive effects among targeted water temperature (T1), stock solution temperature (T2), and flocculant dosage on flocculation performance were assessed using response surface methodology. To optimize flocculation, operation strategies of adjusting T2and dosage according to T1based on the interactive effects were given through mathematical analyses. The flocculation mechanism as well as interfacial interactions among CS-g-PNNPAM, TC, and Cu(II) were studied through experimental investigations (floc size monitoring, X-ray photoelectron spectroscopy, and UV spectra) and theoretical calculations (density functional theory and molecular dynamics simulations). Coordination of Cu(II) with TC and the flocculant promoted flocculation; switchable interactions (H bonds and hydrophobic association) of the TC-flocculant at different temperatures were key factors affecting operation strategies. When these interactions were weakened step by step, TC and Cu(II) were sequentially recovered from flocs using certain solutions. Meanwhile, the flocculant in flocs was regenerated and found reusable with high flocculation efficiency.
authors.affiliation: School of Chemistry and Materials Science, Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing Normal University , Nanjing 210023, P. R. China.
authors.forename: Kexin
authors.initials: K
authors.lastname: Ren
authors.affiliation: School of Chemistry and Materials Science, Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing Normal University , Nanjing 210023, P. R. China.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Du
authors.affiliation: School of Chemistry and Materials Science, Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing Normal University , Nanjing 210023, P. R. China.
authors.forename: Zhen
authors.identifier: http://orcid.org/0000-0002-6032-3018
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Department of Chemistry, University of California , Riverside, California 92521, United States.
authors.forename: Ziqi
authors.initials: Z
authors.lastname: Tian
authors.affiliation: School of Chemistry and Materials Science, Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing Normal University , Nanjing 210023, P. R. China.
authors.forename: Xuntong
authors.initials: X
authors.lastname: Zhang
authors.affiliation: School of Chemistry and Materials Science, Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing Normal University , Nanjing 210023, P. R. China.
authors.forename: Weiben
authors.initials: W
authors.lastname: Yang
authors.affiliation: College of Biology and the Environment, Nanjing Forestry University , Nanjing 210037, P. R. China.
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Chen
keywords: antibiotics; heavy metals; reusable thermoresponsive flocculant; sequential recovery; theoretical calculation