The photo is sourced from rscf.ru
Hydroxyapatite is a natural mineral with a porous structure, which makes it suitable for use in catalysts for oil purification. However, due to its inertness (i.e., inability to participate in chemical transformations), this material is never used to absorb pollutants. This drawback can be corrected through the use of so-called molybdate ions – molybdic acid residues that actively exchange electrons with other substances. This is why scientists are looking for the best possible way to obtain hydroxyapatite containing molybdate ions.
One such way, which is based on hydrothermal treatment, has been proposed by the researchers from the Baikov Institute of Metallurgy and Materials Science RAS. Upon obtaining synthetic hydroxyapatite from precursor salts, the authors put it into a hot solution, the temperature of which was maintained in the range from 140 to 180 degrees Celsius, and began to add various amounts of molybdenum salts to it. This was meant to demonstrate how the concentration of molybdate ions affects the properties of the material.
The optimal temperature for hydroxyapatite treatment turned out to be 140 degrees Celsius, with the concentration of molybdate ions at 1.5% of the total amount of the substance. This made it possible to produce a material with a homogeneous structure and a maximum number of nano-sized pores (hundreds of thousands of times less than a millimetre in size). If the number of molybdate ions was higher and the temperature reached 180 degrees Celsius, the material was split into two components, one of which consisted of nano-sized hydroxyapatite and the other of calcium molybdate. The latter formed larger crystals and intercrystalline pores, as a result of which the porosity of the material was reduced threefold and its properties as a catalyst and absorber of pollutants deteriorated dramatically.
“Our research has shown how the structure of hydroxyapatites containing molybdate ions can be controlled. The proposed approach will help streamline the production of such materials, which show promise in terms of oil purification and are used as catalysts in other processes, such as the breakdown of soil and water pollutants. In the future, we plan to study the catalytic activity of such materials for various green chemistry processes, including for the oxidation of benzyl alcohol and glycerol under mild conditions,” Margarita Goldberg, one of the authors of the study and candidate of chemical sciences, is quoted as saying by the Russian Science Foundation.
