Herein,
a new clean extraction technology for the decomposition
of bastnasite concentrate by utilizing the microwave radiation is
proposed, which prevented Ce(III) from being oxidized to its tetravalent
form. The process includes microwave radiation roasting to nonoxidatively
decompose the bastnasite concentrate, mechanism analysis of Ce(III)
not being oxidized to Ce(IV), hydrochloric acid leaching of the nonoxidative
roasted ore, and kinetics analysis of the leaching process. The experiments
were carried out concentrating on the effect of roasting temperature
and holding time on the decomposition rate of the bastnasite concentrate
and the oxidation rate of cerium and the effect of acidity, liquid–solid
ratio, leaching temperature, and stirring rate on the leaching kinetics
of the nonoxidative roasting ore. When the roasting temperature is
1100 °C, the holding time is 20 min, and the
m
(C)/
m
(REFCO
3
) ratio is 0.2, the results
show that the leaching efficiency of rare earths can reach 85.45%
under the conditions 3 mol/L HCl, 90 °C, 60 min, 9 mL/g liquid–solid
ratio, and 300 rpm stirring rate. The X-ray diffraction and scanning
electron microscopy analyses of the samples before and after acid
leaching show that the rare earth oxides were completely leached and
Ce(III) was not oxidized to its tetravalent form. The apparent activation
energies of leaching rare earths were calculated as 14.326 kJ/mol,
and the HCl leaching process can be described by a new variant of
the shrinking-core model, in which both the interfacial transfer and
the diffusion through the product layer influenced the reaction rate.
Furthermore, a semiempirical rate equation was created to describe
the leaching process of the nonoxidative roasted ore.
Zhoushan cattle are an endangered cattle breed in the Zhoushan islands in China. Since Zhoushan cattle have been bred in isolation, they show unique characteristics, such as dark black coat colour. However, no studies have been conducted on the genome of Zhoushan cattle. Here, we performed whole-genome sequencing of seven individuals of Zhoushan cattle and nine cattle in Wenling, geographically close to the Zhoushan islands. By integrating our data and publicly-available data, we found that Zhoushan cattle are genetically highly similar to Bos indicus cattle in south-eastern China. Furthermore, by identifying the genomic regions shared between Zhoushan cattle and Angus cattle, a Bos taurus breed, we found that the p.F195L mutation in melanocyte-stimulating hormone receptor (MC1R) could be associated with their dark black coat colour. Taken together, our results provide a valuable resource for characterising the uniqueness of Zhoushan cattle.
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