Environmental considerations in the selection of metallurgical processes for the extraction of molybdenum from low grade molybdenite concentrate

Environmental considerations are necessitating the development of new extractive processes for the production ofvarious non-ferrous metals from their sulphide ores. The current industrial practice, which involves roasting
of the sulphide ores, releases SO, and particulates to the atmosphere.These pollutants require expensive emission control and off-gas cleaning to environmentally acceptable limits before for their discharge to the atmosphere.
Of late, a need has been felt to develop new processes which not only can control the air pollution but also avoid the subsequent offgastreatment measures. The present paper deals with the development of two alternate processes, soda ash roasting and lime enhanced carbothermic
reduction, for processing the Rakha molybdenite concentrate. The effect of various experimental parameters on the recovery as well as purity of MoO3 and Mo has been discussed. These processes convert the sulphide content of molybdenite to sulphates, thereby avoiding the release of pollutants to the atmosphere.