Power Plants’ Coal Ash Treatment in Processes related to Bacterial Leaching of Rare Earth Metals

Abstract

The flotation process of power plants’ ash-slag materials treatment is considered in the article. The original method related to preparing of ash-slag waste before their further bioleaching processing is proposed. The positive results of rare earth metals extraction efficiency increase by bioleaching are obtained. The essence of proposed approach is as follows. Coal combustion’s ash-slag waste is mixed with water to obtain a fine suspension, in which the carbonaceous reagent is injected. Flotation treatment of ash suspension is carried out in mechanical flotation machine with flotation time equal to 15-18 min and air flow rate equal to about 0.7-0.8 m3/(m2·min). The chamber product as treated ash suspension is going to the separation in open hydrocyclone. In such a case the concentration product in the form of ash product is derived to special site, and hydrocyclone overflow is directed to the clearing in pressure flotation machine for extraction of metal ions from the liquid. A positive effect of rare earth metals’ extraction rising related in particular to scandium about 26.6-30.3%, yttrium — 28-34.7%, lanthanum — 50.5-21.5%, as well as precious metals such as gold — 18.7-21.6%, silver — 11.4-21.4% is obtained.