Spectroscopic, kinetic and dosimetric features of the radical species produced after radiodegradation of solid triclosan

Formation of environmentally persistent free radicals from photodegradation of triclosan by metal oxides/silica suspensions and particles

Metal oxides play an essential role in the photocatalysis of contaminants and substantially increase in the environment by the engineering production. However, whether emerging contaminants will be produced during photocatalysis of contaminants remains unclear. Here, triclosan (TCS) photodegradation in metal oxides/silica suspensions and particles, simulated as the states of metal oxides in water and soil environments, were studied. The photodegradation results confirmed that metal oxides exhibited a double-effect. They promoted TCS photodegradation by generating reactive oxidizing species (ROS) in metal oxides/silica suspensions and inhibited the photodegradation by competing with TCS for irradiation in metal oxides/silica particles. In this study, the critical discovery was the formation of emerging contaminants, environmentally persistent free radicals (EPFRs), and EPFRs yields were promoted by metal oxides (Al₂O₃, ZnO, TiO₂). They were more stable in metal oxides than silica, and the half-lives ranged from 6.7 h to 90.9 d. Although CuO did not increase EPFRs yields compared to silica, the half-lives of EPFRs were also longer. In addition, this study found that EPFRs yields were dependent on the metal oxides concentrations. Our results provided a new insight into the negative environmental impacts of metal oxides and improved our understanding of the formation and fate of EPFRs by metal oxides in soil and aquatic environments.

Dosimetric and kinetic investigations of γ-irradiated sodium tartrate dihydrate

Effects of gamma radiation on solid sodium tartrate dihydrate (NaTA) were studied using electron spin resonance (ESR) spectroscopy. One main singlet located at g = 2.0034 and many weak lines located at low and high magnetic field sides were found in the irradiated samples. Dosimetric and kinetic features of the radical species responsible for the experimental ESR spectra were explored through the variations in the signal intensities with respect to applied microwave power, temperature and storage time. Activation energies of the involved radical species were also determined using data derived from annealing studies.

Effects of gamma radiation on solid trisodium citrate dihydrate: radical kinetics, radiosensitivity and dosimetry

In the present work, radiosensitivity and dosimetric potential of solid trisodium citrate dihydrate (SC) were explored through a detailed electron spin resonance (ESR) study performed at various temperatures. Irradiated SC was observed to exhibit an ESR spectrum consisting of many intense and weak resonance lines spread over a magnetic field range of 7 mT and centered at g = 2.0039. An evaluation technique based on the variations of the characteristic resonance line intensities and the spectrum area under different experimental conditions was adopted, to determine the spectroscopic, kinetic and dosimetric features of radical species responsible for the observed experimental ESR spectrum. Radicals exhibiting similar ESR characteristics to those reported in the literature for irradiated tricarboxilic acids and their organic compounds were shown to be also produced in gamma-irradiated SC.