On the Possibility of Urea Peroxide Formation in ɤ- Irradiated Urea Aqueous Solution : A Spectroscopic Study

Abstract

In order to investigate the possibility of urea peroxide formation in ɤ-irradiated urea aqueous solutions (UAS), energy-dispersive x-ray (EDS), mass (MS), 1H-NMR, and Raman spectral studies were conducted on UAS and its solid residues (SR) that remain after water evaporation. Spectroscopic data of SR for both irradiated and unirradiated samples were analyzed and compared. EDS data showed an increase in the oxygen content in SR of UAS upon radiolysis. Comparison of mass spectrum of RS of irradiated sample and that of urea shows a significant increase in m/z 16 peak intensity of O + as well as m/z 61of M+1in the former. The 1H-NMR spectrum of SR of an irradiated sample shows a signal down field shift of urea protons, as well as the appearance of new signals, which were assigned to H 2 O 2. The Raman spectral study of both RS and UAS evinces differences in all band positions and intensities for irradiated samples relative to their corresponding unirradiated samples. As a consequence of this study, it seems that the possibility of urea peroxide formation in ɤ-irradiated UAS cannot be ruled out.

Particle size effect of silica gel on the ɤ-radiation induced electrical conductivity of urea aqueous solutions

“…at solute concentrations below about 10 % per weight [18]. The author of the present work suggested in a previous publication the formation of urea peroxide (UP) when urea aqueous solution is -irradiated [14]. Herein, it should be mentioned that UP increases the electrical conductivity of the medium [12,13,15].…”

“…The data in the Tables (3 and 5) clearly shows the increase of RIC as the absorbed doses increase for each particle size of SG for 3 and 6M urea aqueous solutions. This observation can be related to the radiation-induced formation of UP and H 2 O 2 [14]. It is obvious that the magnitude of the measured RIC increases as the concentration of urea increases at the same absorbed dose and particle size.…”

“…This observation can be explained by the electron-hole (e /h+) pairs generated in SG (eq.1) via interactions with ionizing radiation [3,19]. It should be mentioned that UP formation in irradiated urea aqueous solutions was discussed before in a previous work [14]. The released e ─ from the irradiated SG (eq.3) will be hydrated by the silanol groups and residual water on the gel [17] (eq.3).…”

“…Moreover, it was reported that the RIC of urea aqueous solutions significantly increases upon radiolysis [12,13]. This phenomenon was attributed to the UP formation [14]. The aim of the present work is to investigate the effect of SG particle size on the radiation-induced electrical conductivity (RIC) of urea aqueous solutions.…”

“…Seino et al, noted that radiolytic yield of hydrogen depends on gamma radiation dose absorbed and metal oxide particle size [9,10]. Radiolysis of urea aqueous solutions was studied before in different workers [11][12][13][14][15][16]. Urea is relatively stable to ionizing radiation in aqueous solutions up to 20 kGy [11].…”