INITIAL TL/OSL/EPR CONSIDERATIONS FOR COMMERCIAL DIATOMACEOUS EARTH IN RETROSPECTIVE DOSIMETRY AND DATING.

Diatomaceous earth is found in various locations around the planet. It is caused by the deposited exoskeleton material formed by the death of large concentrated populations of diatoms. The exoskeleton is effectively pure silicate and as such becomes a prospective material for retrospective dosimetry and dating. This work investigated the thermoluminescence (TL) and optically stimulated luminescence properties of commercially obtained diatomaceous earth. The material was not found to have useful dosimetric properties with conventional TL methodologies but did provide large dose estimates using the Single Aliquot Regeneration technique on some subset samples. These findings for organic silicate did suggest some mechanisms explaining the sensitization process in geological silicate materials utilized in dosimetry and dating. Electron paramagnetic resonance was identified as a potential future method for evaluating this material as it revealed unique signal components not found in igneous or commercially produced silicates.

Characterization and improved solar light activity of vanadium doped TiO2/diatomite hybrid catalysts.

V-doped TiO2/diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol-gel method. The diatomite was responsible for the well dispersion of TiO2 nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO2/diatomite hybrids showed red shift in TiO2 absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO2 bandgap due to V(4+) ions substituted to Ti(4+) sites. The 0.5% V-TiO2/diatomite photocatalyst displayed narrower bandgap (2.95 eV) compared to undoped sample (3.13 eV) and other doped samples (3.05 eV) with higher doping concentration. The photocatalytic activities of V doped TiO2/diatomite samples for the degradation of Rhodamine B under stimulated solar light illumination were significantly improved compared with the undoped sample. In our case, V(4+) ions incorporated in TiO2 lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO2 to produce superoxide radicals ˙O2(-), while V(5+) species presented on the surface of TiO2 particles in the form of V2O5 contributed to e(-)-h(+) separation. In addition, due to the combination of diatomite as support, this hybrid photocatalyst could be separated from solution quickly by natural settlement and exhibited good reusability.

Micro-nanopores fabricated by high-energy electron beam irradiation: suitable structure for controlling pesticide loss.

Pesticide sprayed onto crop leaves tends to be washed off by rainwater and discharge into the environment through leaching and runoff, resulting in severe pollution to both soil and water. Here, to control pesticide loss, we developed a loss-control pesticide (LCP) by adding modified natural nanoclay (diatomite) through high-energy electron beam (HEEB) to traditional pesticide. After HEEB treatment, the originally clogged pores in diatomite opened, resulting in plenty of micro-nanopores in diatomite, which are beneficial for the pesticide molecules to access and be adsorbed. This pesticide-diatomite complex tended to be retained by the rough surface of crop leaves, displaying a high adhesion performance onto the leaves, so that the pesticide loss reduced, sufficient pesticide for crops was supplied, and the pollution risk of the pesticide could be substantially lowered.