Experimental Study Of Melting Temperature Of REO-SiO₂-Al₂O₃Based Slag

In our country, there are a mass of rare-earth permanent magnetic material and Nickelmetal hydride battery electrode material, which are wide used. Rare is an importantstrategic resource of high-tech materials’ development, but the amount of producedrare-earth waste materials is also considerable. These waste materials not only give rise toenvironmental pollution but also waste resources. Rare-earth waste materials have a highcontent of rare earth elements, Ni, and Co, which is a high value secondary resource,therefore, the recycle used of NdFeB waste materials has important economic value andsocial value.“Combined pyro-and hydrometallurgical recycling process” is a kind of resourcescomprehensive utilization technology, pyrometallurgy takes the selective oxidationreduction and melting separation method to deal with rare-earth slag, get high purity ironcobalt alloy, hydrometallurgy takes decompose-leach-precipitate method to recyclerare-earth slag, and pure rare earth oxides were achieved. The process including H2selective reduction of rare earth waste slag, H2processed materials gold melting points andrare-earth slag wet processing three parts.For the after H2selective oxidation–reduction’s melting separation process,La2O3–SiO2–Al2O3was selected as the basic slag system. In order to find the Ratio of slagseries in specified areas and to establish compositional areas where high rare earth contentsand low melting temperatures can be obtained. Paper in La2O3mass fraction is45%~65%range studied La2O3-SiO2-Al2O3slag melting temperature. A hemispherical method wasused to measure the melting temperature for different La2O3mass contents (45%,50%, and55%) in the La2O3–SiO2–Al2O3slag, the slag sample melting temperature was the lowestwhen the SiO2/Al2O3mass fraction was approximately2. A small amount of the minorcomponent, FeO, B2O3, and MnO could lower the La2O3–SiO2–Al2O3based slag meltingtemperature. The effect of B2O3was particularly significant. The addition of a smallamount of FeO and B2O3has an additive effect on slag melting temperature reduction. Determined a series of melting temperatures of slags with the content of high rare earth(La2O3, PrNdxOy). In which, the highest content of La2O3is65%, its Ratio of slag seriesand low melting temperatures are:65%La2O3–16%SiO2–8%Al2O3–7%FeO–4%B2O3and65%La2O3–19.3%SiO2–9.7%Al2O3–2%FeO–4%B2O3slage, melting temperatures is1319°C and1386°C. The highest content of PrNdxOyis68%, its Ratio of slag series andlow melting temperature is:68%PrNdxOy-14%SiO2-7%Al2O3-7%FeO-4%B2O3slage,melting temperature is1227℃. For melting separation method of Nickel metal hydridebattery electrode material’s recycle used process, determined melting temperatures ofLa2O3-CeO2-SiO2-Al2O3-MnO slags with the content of high rare earth(45%~65%), thehighest content of REO, ratio of slag series and low melting temperature is:43.3%La2O3-21.7%CeO2-18.7%SiO2-9.3%Al2O3-7%MnO slage, melting temperature is1334℃.The paper based on the study in melting temperature of slag, making sure that theLa2O3content is high enough to determine the best ratio of melting temperature of slagseries. This research provides a theoretical basis and experimental support forindustrialization and scale in Rare-earth waste materials recycling.