The treatment of aniline in aqueous solutions by gamma irradiation

Abstract A laboratory investigation of the radiation-induced degradation of aniline by gamma irradiation is the subject of this paper. During the inquiry, several aqueous samples with aniline concentrations of 25, 50, 75, 100 and 200 mg/L were irradiated for 5, 10, 15, 20, 25 and 30 h, respectively, by a 60Co source with an absorbed dose rate of 0.78 kGy/h at the core channel. After the testing, the project authors scrutinized the aqueous samples to determine the effects of their irradiation by analyzing the pH, the hydroxyl radical and the H2O2 of the individual initial concentrations. The findings showed that gamma irradiation is effective in removing aniline from aqueous solutions and, in the process, tends to remove the chemical oxygen demand (COD). Among other findings, the tests revealed that at a 25 mg/L aniline concentration, up to 100 % removal is possible after only 5 h of exposure. The authors explained that kinetic studies have shown that the degradation of aniline follows a pseudo first-order reaction. They have also shown that pH plays a significant role in aniline-removal efficiency. The tests in this study revealed that with a dose of 7.8 kGy, the removal efficiency of COD in an alkaline environment is higher than that of an acidic environment. With the absorbed dose increases, the authors learned that an acidic environment is helpful for the removal efficiency of COD. They also found that by adding 50 g/L of sodium bicarbonate as the hydroxyl radical scavenger, there was an 8 % decrease in the removal efficiency of COD at the absorbed dose of 23.4 kGy. This indicates the importance of using a hydroxyl radical in the gamma irradiation process. Also, a 1 g/L H2O2 addition increases the COD removal rate from 31 % to 55 %. This percentage-point jump shows a synergistic effect in the use of gamma irradiation. The authors also identified several major decomposition products by GC/MS which are useful in the radiation-induced degradation of aniline by gamma irradiation process. Finally, they present proposals of possible pathways for successful aniline decomposition.