Study on direct leaching of rare earth elements from phosphogypsum with sulfuric acid
In order to comprehend the leaching rule of phosphogypsum(PG)with low rare earth element(REE)content and the improvement of phosphogypsum quality after leaching,the process kinetics of direct leaching of REE from PG with sul-furic acid and the changes of PG phase were studied.The results showed that the leaching rate of REE was initially de-creased and then increased with the elevating of leaching temperature,enhanced along with liquid-solid ratio,and firstly in-creased and then decreased with the rising of acid concentration.The total leaching rate could be achieved up to 25%at 25℃,with the leaching rate of La as the highest and that of Pr as the lowest.The REE leaching rate was increased rapidly in 0～20 min and then leveled off.The kinetics of the whole leaching process was controlled by ash layer diffusion.The surface of gypsum was dissolved during the leaching,and then recrystallized into acicular CaSO4 particles of dehydrated phase after the solution was saturated.However,the overall morphology of gypsum bulk phase changed little,resulting in a low REE leaching rate.Moreover,the fraction of the PG with a particle size less than 10 µm was 14.90%,increased by 5.16%com-pared with the original sample.The particle size of PG after acid leaching was smaller and the impurities were reduced.The results could provide reference for comprehensive utilization of phosphogypsum.
NETL
NSTL
万方数据
维普
