DEVELOPING A TECHNOLOGY FOR PRODUCING LEAD MOLYBDATE FROM MOLYBDENITE CONCENTRATES AND GROWING ITS CRYSTALS AT LOW TEMPERATURE
Keywords:
molybdenite concentrate, lead molybdate, ammonium molybdate, roasting, growing, silicagel, crystals, lead acetate, leachingAbstract
A process has been developed for obtaining high-purity lead molybdate from solutions of ammonium molybdate and lead acetate, which are obtained by processing molybdenite concentrates. This process ensures the stability of the stoichiometric composition of the compound and minimizes the content of its main impurities. It is worth noting that these impurities are the primary cause of instability of the colour of the final product. During the solid-phase synthesis of lead molybdate PbMoO4, it is possible to fom the compound Pb2MoO5 due to the evaporation of molybdenum trioxide and lead oxide.
It is found that obtaining lead molybdate by chemical precipitation from solutions is more preferable and provides up to 99% yield of the required product. It is revealed that the stoichiometric composition of lead molybdate is obtained with an excess of 1% lead acetate. As a result of experiments, it is found that changing the concentration of solutions of ammonium molybdate and lead acetate does not affect the stoichiometric content of lead molybdate.
The process of growing lead molybdate crystals at low temperatures in a silica gel medium at 27°C is indicated. The crystals are formed through diffusion of nutrient solutions containing ammonium molybdate and lead acetate. The method requires simple equipment, and the process of crystal formation is easy to follow. The structure of the silicagel has a significant impact on the growth process and formation rates of the PbMoO4 crystals. The quality of the grown crystals may decrease as the density of the silicagel increases. On the other hand, it has been noted that lead molybdate crystals tend to grow at a very slow pace in low density silica gel, which is also known to be unstable. While it is true that the duration of crystallisation may be considered a disadvantage of this method, it is worth noting that it is possible to obtain homogeneous and colourless crystals.
