No abstract

Photosynthesis is considered to be one of the promising areas of cheap and environmentally friendly energy. Photosynthesis involves the process of water oxidation with the formation of molecular oxygen and hydrogen as byproducts. The aim of the present article is to review the energy (light) phase of photosynthesis based on the published X-ray studies of photosystems I and II (PS-I and PS-II). Using modern ideas about semiconductors and biological semiconductor structures, the mechanisms of H+, O2↑, e− generation from water are described. At the initial stage, PS II produces hydrogen peroxide from water as a result of the photoenzymatic reaction, which is oxidized in the active center of PS-II on the Mn4CaO5 cluster to form O2↑, H+, e−. Mn4+ is reduced to Mn2+ and then oxidized to Mn4+ with the transfer of reducing the equivalents of PS-I. The electrons formed are transported to PS-I (P 700), where the electrochemical reaction of water decomposition takes place in a two-electrode electrolysis system with the formation of gaseous oxygen and hydrogen. The proposed functioning mechanisms of PS-I and PS-II can be used in the development of environmentally friendly technologies for the production of molecular hydrogen.

No abstract

The processes of extraction of cerium and neodymium from Kazakhstan phosphogypsum, a large-tonnage waste of mineral fertilizer production of "Kazphosphate" LLP, have been studied. The influence of the nature of the leaching agent, temperature and duration of the process on the efficiency of cerium, neodymium leaching using the methods of X-ray fluorescence, X-ray phase and energy dispersive elemental analysis was studied. It has been found that the use of hydrogen peroxide as an oxidizer in the leaching of rare earth metals intensifies the process of recovery from phosphogypsum by 20% for cerium and by 28% for neodymium. Optimal parameters of cerium and neodymium leaching under atmospheric and autoclave conditions have been found. In atmospheric conditions, recovery of cerium and neodymium were 70.3% and 92.0%, in autoclave conditions 72.9% and 87.5%, respectively. The obtained results allow us to hope for the processing possibility of these wastes with the aim of rare-earth metals and other valuable products recovery.

No abstract