title: Flocculation of copper(II) and tetracycline from water using a novel pH- and temperature-responsive flocculants.
abstract: Insufficient research is available on flocculation of combined pollutants of heavy metals and antibiotics, which widely exist in livestock wastewaters. Aiming at solving difficulties in flocculation of this sort of combined pollution, a novel pH- and temperature-responsive biomass-based flocculant, carboxymethyl chitosan-graft-poly(N-isoproyl acrylamide-co-diallyl dimethyl ammonium chloride) (denoted as CND) with two responsive switches [lower critical solution temperature (LCST) and isoelectric point (IEP)], was designed and synthesized. Its flocculation performance at different temperatures and pHs was evaluated using copper(II) and tetracycline (TC) as model contaminants. CND exhibited high efficiency for coremoval of both contaminants, whereas two commercial flocculants (polyaluminum chloride and polyacrylamide) did not. Especially, flocculation performance of the dual-responsive flocculant under conditions of temperature>LCST and IEP(contaminants)<pH<IEP(CND) was much better than that under other conditions. Further investigation on flocculation mechanism via pH monitoring, zeta potential measurements, floc properties analyses and spectral characterization indicated that, pairwise interactions among CND, copper(II) and TC were present in bridging flocculation, including charge attraction, coordination and hydrophobic effect. Based on these pairwise interactions, copper(II) and TC exerted "aid" roles to each other's removal with the existence of CND, and preferable flocculation performance was thus achieved.
authors.affiliation: School of Chemistry and Materials Science, Jiangsu Provincial Key Laboratory of Carbon and Nitrogen Cycle Processes and Pollution Control, Nanjing Normal University, Nanjing 210046, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yang
authors.affiliation: School of Chemistry and Materials Science, Jiangsu Provincial Key Laboratory of Carbon and Nitrogen Cycle Processes and Pollution Control, Nanjing Normal University, Nanjing 210046, China.
authors.forename: Shuying
authors.initials: S
authors.lastname: Jia
authors.affiliation: School of Chemistry and Materials Science, Jiangsu Provincial Key Laboratory of Carbon and Nitrogen Cycle Processes and Pollution Control, Nanjing Normal University, Nanjing 210046, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Zhuo
authors.affiliation: School of Chemistry and Materials Science, Jiangsu Provincial Key Laboratory of Carbon and Nitrogen Cycle Processes and Pollution Control, Nanjing Normal University, Nanjing 210046, China. Electronic address: yangwb007@njnu.edu.cn.
authors.forename: Weiben
authors.initials: W
authors.lastname: Yang
authors.affiliation: School of Chemistry and Materials Science, Jiangsu Provincial Key Laboratory of Carbon and Nitrogen Cycle Processes and Pollution Control, Nanjing Normal University, Nanjing 210046, China.
authors.forename: Yuping
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000178:Acrylamides / Q000138:chemical synthesis / Q000737:chemistry*; D048271:Chitosan / Q000138:chemical synthesis / Q000737:chemistry*; D003300:Copper / Q000032:analysis*; D005427:Flocculation; D006863:Hydrogen-Ion Concentration; D011108:Polymers / Q000737:chemistry*; D013696:Temperature; D013752:Tetracycline / Q000032:analysis*; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*
chemical_list: D000178:Acrylamides; D048271:Chitosan; D003300:Copper; D011108:Polymers; D013752:Tetracycline; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Combined pollution; Copper(II); Flocculation; Temperature-responsive; Tetracycline; pH-responsive