The hydration mechanism between the leaching agent and ore surface during the leaching process of ionic rare earth ore is complicated, and the inter-particle bridge cementation is prone to fracture due to the existence of multiple forces and dispersion during ion adsorption and exchange, resulting in migration and rearrangement of microfine particles, and precipitation at the pore throat, producing blockage phenomenon and affecting the leaching efficiency of ionic rare earths. In order to reveal the migration law of microfine particles during in situ leaching of ionic rare earth ores and to find suitable regulation methods, this paper investigates the effects of leaching agent mass concentration, viscosity, flow rate, hydraulic gradient, ore body height, and ore body water content on the migration of microfine particles. We compared ionic rare earth ores as raw ores and rare earth ores with particle sizes ranging from 0.075 to 0.09 mm using the laboratory column leaching method. The results showed that the migration of microfine particles during ionic rare earth ore leaching was an important factor affecting leaching efficiency. Under the action of external forces, the microfine particles tended to migrate with the leaching agent during the leaching process.
The yttrium (Y) element in the calciothermic
reduction
YF3 smelting slag (YSS) has a recovery value, and the conventional
direct
alkali transformation-acid leaching method of recovering rare earth
elements (REEs) from solid waste, which contains rare earth fluoride,
has encountered problems of high energy and alkali consumption and
low leaching rate. In this study, a green process for the transformation
of YF3 to Y(OH)3 at room temperature was achieved
by employing a mechanochemical method. The process is environment-friendly,
with zero emission, less acid/alkali consumption, and water recyclability.
It was found that YF3 will be “passivated”
by a newly formed Y(OH)3 product layer under the alkaline
condition, resulting in the unsustainable transformation of YF3 to Y(OH)3. However, the mechanical force could
destroy the coating of Y(OH)3 and promoted the transformation
of YF3 to Y(OH)3 completely; as such, the transformation
efficiency of YF3 reached 98.2%. On this basis, the process
of extracting Y from YSS was further studied, and the results showed
that YF3 in YSS was successfully transformed into Y(OH)3 and the leaching rate of Y reached 96.2%. Therefore, it is
expected to be a new technology to recover REEs from waste slag or
minerals that contain rare earth fluoride and has good industrial
application prospect.
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