title: Removal of dispersant-stabilized carbon nanotubes by regular coagulants.
abstract: Coagulation followed by sedimentation, as a conventional technique in the water treatment plant, can be the first line of defense against exposures of carbon nanotubes (CNTs) to aquatic organisms and human beings, which has been rarely documented. This study investigated the removal of dispersant-stabilized CNT suspensions by poly aluminum chloride (PACl) and KAl(SO4)2 x 12H2O (alum), with a focus on the effects of dispersant type, coagulant type and dosage. PACl performed better than alum in the removal of tannic acid-, humic acid-, and sodium dodecyl benzenesulfonate-stabilized CNTs, but worse for polyethylene glycol octylphenyl ether (TX100)-stabilized CNTs. Neither coagulant could effectively precipitate cetyltrimethyl ammonium bromide-stabilized CNTs. The removal by PACl first increased up to a plateau and then decreased with the continued increase of coagulant dosage. However, the removal rates leveled off but did not decrease after achieving their highest level with the continued addition of alum. The coagulation and flocculation of the CNT suspensions by PACl could be regulated mainly by the mechanism of adsorption charge neutralization, whereas the coagulation by alum mainly involved electrical double-layer compression.
authors.affiliation: Department of Environmental Science, Zhejiang University, Hangzhou 310058, China.
authors.forename: Ni
authors.initials: N
authors.lastname: Liu
authors.forename: Changli
authors.initials: C
authors.lastname: Liu
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Daohui
authors.initials: D
authors.lastname: Lin
mesh_terms: D000534:Alum Compounds / Q000737:chemistry; D000536:Aluminum Hydroxide / Q000737:chemistry; D037742:Nanotubes, Carbon; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification
chemical_list: D000534:Alum Compounds; D037742:Nanotubes, Carbon; D014874:Water Pollutants, Chemical; C016213:aluminum oxychloride; C041524:aluminum sulfate; D000536:Aluminum Hydroxide