Decomposition of aqueous solutions of phenol using high energy electron beam irradiation - A large scale study

High-energy electron-beam irradiation was used to remove phenol from aqueous solution. The variables that affected phenol decomposition were solute concentration, absorbed dose and total alkalinity. Experiments were conducted at large scale (480 L min(-1)), at solute concentrations of 10.6, 106 and 531 mu mol L(-1) (1, 10 and 50 mg L(-1)) over the pH range 5-9, and in the presence and absence of solids (3% w/w kaolin clay). Absorbed doses ranged from 0-7 kGy (0-700 krad). At low absorbed doses, catechol, hydroquinone and resorcinol were identified as the major reaction byproducts. These compounds are consistent with hydroxyl radical (OH) addition to phenol. Subsequent ring cleavage of hydroxylated phenolic radicals and continued oxidative processes resulted in the formation of formaldehyde, acetaldehyde, glyoxal and formic acid. At high doses only trace amounts of the carbonyl derivatives were observed. Two recirculation experiments were conducted at higher phenol concentrations (approximate to 950 mu mol L(-1)) and it was shown that phenol was removed while the total organic carbon of the solution decreased only slightly. These results suggest that phenol was not mineralized but, rather, that irradiation resulted in the possible formation of higher molecular weight polymers.