The Radiolytic-chain Dechlorination of Polychlorinated Biphenyls in Alkaline 2-Propanol Solutions

Abstract

The radiolysis of solutions of polychlorinated biphenyls (PCB’s) and potassium hydroxide in simple aliphatic alcohols was studied. The major products in alkaline 2-propanol solutions were potassium chloride, acetone, lower chlorinated biphenyls, and biphenyl. Their yields increased and the concentration of the hydroxide ions decreased with the dose. Acetone and potassium chloride were formed in high yields, and their concentrations were almost equal to the diminution in the hydroxide ions. The dechlorination yield was determined as a function of the dose, the dose rate, and the concentrations of PCB’s, potassium hydroxide, and organic solutes. The chain-dechlorination reaction proceeded in the alkaline 2-propanol solution, but not in alkaline methanol, ethanol, 1-propanol, and butanols. The 2-propoxide radical anion, which is formed by the electron transfer from the hydroxide ion to the 2-propanol radical, is the chain carrier for the dechlorination reaction of PCB’s in alkaline 2-propanol solutions. The mechanism is discussed in detail.

Degradation pathways of PCB upon gamma irradiation.

“…Most of the congeners for which levels were enhanced upon irradiation were apparently produced through the loss of an ortho chlorine atom from their immediate precursor. This degradation pathway is similar to that observed for UV irradiation of PCB, a process that generates similar reaction intermediates, namely, PCB radicals (2,3).…”

Radiation dechlorination of some chlorinated hydrocarbons particularly of carbon tetrachloride in presence of HCO3−- or NO3−-ions

“…Even if many of modifiers or scavengers exhibited an evident effect in radiation dechlorination none of them led to the radiation yields approaching to high values indicating a chain dechlorination reaction. Such high values were found [22,39,40,46,52,56] in the alkaline 2-propanol solutions only. Therefore, further investigations of radiation dechlorination are needed for introducing them into the industrial exploitation.…”

“…dichlorobenzenes [15][16][17][18][19][20][21][22], chlorophenols [22][23][24][25][26][27][28][29][30], chloroanilines [31,32], chlorinated benzaldehydes [33], pesticides [34], or herbicides [35], dioxin contained soils [36,37] or incinerator offgas [38] and, last but not least, polychlorinated biphenyls (PCBs) [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56]) and aliphatic (e.g. halomethanes [21,[57][58][59][60][61][62], haloethanes …”

An Approach to Reuse of PCB-Contaminated Transformer Oil Using Gamma Radiolysis

“…The decomposition of PCB with gamma radiolysis has been studied by many groups. [7][8][9][10][11][12][13][14][15][16] An important purpose of their previous studies was to find effective ways to decompose the oil with high PCB concentration. For this reason, some scavenger substances or solvents were added to PCB oil to investigate how the additives affect the PCB decomposition.…”

“…A conclusion of the previous studies is that alkaline isopropanol (IPA) is one of the best solvents because alkaline IPA enhances PCB decomposition. 7,8) However, when PCB in alkaline IPA is treated by gamma radiolysis, some chlorine dissociated from PCB and alkaline dissolved in IPA react to generate powdered salt. It is not easy to remove the salt from the IPA or transformer oil.…”