Abstract
Abstract The viscosity and break temperature of La2O3–SiO2-FeO slag was investigated to develop low-Al2O3 or Al2O3-free slag for the effective recovery of rare-earth metals. When La2O3 content is fixed (45, 50 and 55 mass%), the viscosity and break temperature of La2O3–SiO2-FeO slag decrease with an increase in FeO content and a decrease in SiO2 content. A higher La2O3 content in the La2O3-SiO2-FeO ternary slag yields a lower slag viscosity but a higher break temperature. Individual minor components of Al2O3, MnO and B2O3 does not affect, or decreases slightly the viscosity of La2O3–SiO2-FeO slag, whereas the slag break temperature is reduced so that the reduction ability order is ranked as B2O3 > Al2O3 > MnO. A small amount of two components Al2O3 + MnO and Al2O3 + B2O3 has little effect on the viscosity of the slag but it has an additive effect on the slag break-temperature reduction.
Highlights
Rare-earth hydrogen-storage alloys and NdFeB magnets are used in various applications
The variation behavior of the viscosity and break temperature for the La2O3-SiO2-FeO slag and the CaO-SiO2-FeO slag is similar with an increase in FeO content
For La2O3-SiO2-FeO6 mass% Al2O3-3 mass% B2O3 slag, the reduction level is 134 and 142 K compared with La2O3-SiO2-FeO-6 mass% Al2O3 and La2O3-SiO2-FeO-3 mass% B2O3 slags, respectively
Summary
Rare-earth hydrogen-storage alloys and NdFeB magnets are used in various applications. The authors [11] used gas-selective reduction-oxidation to produce highadded-value alloy from the Ni-metal-hydride battery electrode waste and subsequently accomplished excellent slag-metal separation by SiO2-Al2O3 flux addition. This method yielded a ~50 mass% RexOy-containing slag, which contributed to a saving in hydrochloric-acid consumption in the acid-leaching process. In addition to the high rare-earth-oxides content and appropriate slag-metal separation characteristics for the formed slag, the selection of flux should be considered to ensure that other slag components do not enter the leaching solution or are separated and purified even if they enter the leaching solution The latter extraction separation of different rare-earth elements cannot be affected by additive slag components. The viscosity and break temperature of the La2O3-SiO2-FeO slag system, which are key parameters for effective separation of rare earth oxide-rich slag and valuable metal, were evaluated
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