Effect of oxidant addition on the elimination of 2-naphthalenesulfonate in aqueous solutions by electron beam irradiation

Aromatic sulfonated compounds and naphthalene derivatives are major chemical compounds used in the industry. Electron beam irradiation of aqueous solutions of 2-naphthalenesulfonate (90 µM) was investigated under various experimental conditions. The results obtained demonstrate that the 2-NS concentration decreased dramatically on increasing the absorbed dose in the range 0–1000 Gy. The effectiveness of the radiolytic system was demonstrably enhanced by the addition of oxidants (S 2 O 8 2− or H 2 O 2 ). 2-NS removal was higher with S 2 O 8 2− than with H 2 O 2 . For the EB, EB/H 2 O 2 , and EB/S 2 O 8 2− systems, the absorbed doses for 90% elimination of 2-NS (D 90 ) were 700, 480, and 274 Gy, respectively. 2-NS is poorly mineralized by EB but more than 35% mineralization was reached for 15 kGy when oxidants (820 µM S 2 O 8 2− or 935 µM H 2 O 2 ) were added. In all systems, the mineralization yield was markedly higher when air (i.e. dissolved oxygen increase) was introduced between successive doses. For 50% 2-NS removal, seven sulfonated transformation products were identified using LC/MS analyses. For the highest absorbed doses the sulfonate group in 2-NS was converted to sulfate ions in the radiolytic systems.