title: Cyclodextrin polymers as highly effective adsorbents for removal and recovery of polychlorobiphenyl (PCB) contaminants in insulating oil.
abstract: A total of 179 countries (parties) ratified the Stockholm Convention on persistent organic pollutants (POPs) and agreed to destroy polychlorobiphenyls (PCBs) and develop a sound management plan by 2028. Currently, still 3 million tons of PCB-contaminated oil and equipment need to be managed under the Stockholm Convention. Thus, the development of a facile and environmentally benign method to treat large amounts of oil stockpiles contaminated with PCBs is a crucial subject. Herein, we report that cyclodextrin (CD) polymers, which are easily prepared by cross-linking the renewable cyclic oligosaccharide γ-cyclodextrin (γ-CD) with dibasic acid dichlorides, are a new selective and powerful adsorbent to remove PCB contaminants in oil. When PCB (100 ppm)-contaminated oil was passed through a column packed with the terephthaloyl-cross-linked γ-CD polymer (TP-γ-CD polymer) at 80-110 °C, the PCB contaminants were completely removed from the oil. Additionally, methyl esterification of the free carboxylic groups of the TP-γ-CD polymer enabled the complete recovery of the PCBs adsorbed on the polymer (with >99.9% recovery efficiency) by simply washing with acetone. The methyl-esterified TP-γ-CD polymer could be recycled at least 10 times for PCB adsorption without any loss in the adsorption capability. These results revealed that the γ-CD polymers can function as highly effective and powerful adsorbents for the removal and recovery of PCBs from PCB-contaminated oil and, thus, significantly contribute to the protection of the global environment.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University , 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Shintaro
authors.initials: S
authors.lastname: Kawano
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kida
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Miyawaki
authors.forename: Yuki
authors.initials: Y
authors.lastname: Noguchi
authors.forename: Eiichi
authors.initials: E
authors.lastname: Kato
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakano
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Akashi
mesh_terms: D000327:Adsorption; D002482:Cellulose / Q000138:chemical synthesis / Q000737:chemistry*; D003505:Cyclodextrins / Q000138:chemical synthesis / Q000737:chemistry*; D004785:Environmental Pollutants / Q000302:isolation & purification*; D009821:Oils / Q000737:chemistry*; D011078:Polychlorinated Biphenyls / Q000737:chemistry / Q000302:isolation & purification*; D013696:Temperature; D047408:gamma-Cyclodextrins / Q000737:chemistry
chemical_list: D003505:Cyclodextrins; D004785:Environmental Pollutants; D009821:Oils; C041953:cyclodextrin polymer; D047408:gamma-Cyclodextrins; D002482:Cellulose; D011078:Polychlorinated Biphenyls; C023792:gamma-cyclodextrin