PCB Formation from Pigment Manufacturing Process

Abstract

Summar y Unintentional formation of polychlorinated biphenyl (PCB) from chemical manufacturing process of organic pigment such as phthalocyanine pigment have been known since 1976. Regarding to unintentional formed congeners in disazo pigment, in the case of 3,3＇-dichloro benzidine, PCB-11(3,3＇-), PCB-35(3,3＇,4-), PCB-77(3,3＇,4,4＇-) were dominant congeners as a result of sandmeyer reaction via its diazonium salt. On the other hand, in the case of 2, 2＇, 5, 5＇-tetrachloro benzidine, PCB-52(2,2＇,5,5＇-) , PCB-101(2,2＇,4,5,5＇-) , PCB-153(2,2＇,4,4＇,5,5＇-) were dominant congeners as a result of sandmeyer reaction via its diazonium salt. This is common in HCBz and PCB-209 existing as dominant PCB congeners in pentachloro nitrobenzene (PCNB). PCB-209 in copper phthalocyanine green and PCNB could be forming in the similar process from HCBz by radical coupling. Regarding to dioxazine violet pigment such as PV23, this pigment is synthesized by ring-closing reaction of 3-amino-N-ethylcarbazole and chloranil in o-dichlorobenzene solvent.Thermal PCB product of o-dichlorobenzene with/without Chloranil, 3-amino-N-ethyl-carbazole, radical initiator have been determined congener specifically. The dominant congeners were PCB-5(2,3-), PCB-12(3,4-), PCB-40(2,2＇,3,3＇-), PCB-56(2,3,3＇,4-), PCB-77(3,3＇,4,4＇). The formation process of these congeners were estimated via 2 types of o-dichlorobenzene radicals. We investigated experimentally unintentional formation from o-dichlorobenzene to confirm their formation process. Controlling unintentional PCB formation should be required by utilizing Best Available Technologies (BAT) and Best Environmental Practice (BEP) for environment in the case of manufacture of an organic pigment, and managing the process of chemical synthesis properly to reduce human and environmental risk.