1、附录 A Selective flotation of bastnaesite from monazite inrare earth concentrates using potassium alum asdepressant Jun Rena, Shaoxian Song b, Alejandro Lopez-Valdiviesob,Shouci Lu c aCenter of Research on Surfaces and Interfaces, Nanjing Uniersity, Nanjing 210093, China bInstituto de Metalurgia, Unie
2、rsidadAutonoma de San Luis Potosi, Sierra Leona 550, Lomas 2aSeccion, San Luis Potosi, C.P. 78210, S.L.P., Mexico cResources Engineering School, Uniersity of Science and Technology Beijing, 40 Xueyuan Road, Beijing100083,China. Abstract Flotation studies were carried out on single particles of bastn
3、aesiteandmonazite to develop a flotation scheme for selectively removing monazite in the rare earth bulkconcentrate from the Baiyunebo mine, in China 60.7% rare earth oxides or REO, 75% as bastnaesite and 25% as monazite . Low additions of potassium alum were found to efficientlydepress monazite at
4、pH 5 without affecting the flotability of bastnaesite with the collector benzoicacid. The bulk concentrate was treated through this scheme, and 85% of the bastnaesite wasrecovered in a concentrate that assayed 69.5% REO and contained 97% bastnaesite. Thedepressing effect of potassium alum appeared t
5、o be due to the preferential adsorption ofhydrolyzed aluminum species on monazite in comparison to bastnaesite. Keywords:bastnaesite flotation； monazite flotation； rare earth mineral separation； alum as depressant；hydrolyzed aluminum ions. 1. Introduction 1. Introduction Bastnaesite theoretica
6、lly contains about 75% combined rare earth oxides REO and only minor amounts of yttrium. Flotation concentrates of bastnaesite usually containing. 60% REO can be upgraded to 70% REO by acid leaching to remove calcite and to 85%by a combination of acid leaching and calcining, which removes carbon dio
7、xide fromthe carbonate. Monazite theoretically can contain 70% REO including about 2% yttriumoxide, but most concentrates contain about 5565% REO. Of the two minerals,bastnaesite is referred as the principal source of REO because it has high percentages ofthe light rare earth elements or the cerium
8、group, namely elements having atomicnumbers 57 through 63. monazite is recovered as a byproduct, needed to be stockpiled when produced inexcess . The commercial bastnaesite deposit in Mountain Pass, California, USA is processedby flotation using a mixture of tall oil and lignin sulfonate at elevated
9、 temperature to selectively float bastnaesite.The main deposit of rare earth minerals located in the Baiyunebo mine, in China represents 80% of the total REO world reserves Falconnet,1985 . Here, bastnaesite occurs together with monazite and they are both recovered inthe form of a bulk concentrate a
10、s a byproduct of iron ore mining. Currently, there is aneed for further treatment of the bulk concentrate since its hydrometallurgical processinginvolves high costs due to the high content of monazite. Numerous investigations havebeen carried out pursuing a flotation scheme for selectively separatin
11、g bastnaesite andmonazite. Gu and Zhu 1988 reported on the flotation separation of bastnaesite andmonazite using N-hydroxylphthalimade as collector. Phthalic acid in a weakly acidic.slurry was used by Zhang 1985 as a selective collector to produce a bastnaesiteconcentrate of 98% purity, but with onl
12、y 38% recovery. Other collectors have been alsorecommended, namely Hydroxy-naphthlylhydroxamic acid and N-hydroxyl ph-thalicimideRen, 1993； Ren et al., 1997 . Not only effective collectors, but also efficient depressants play an important role inthe flotation of rare earth minerals(Pradip and Fuerstenau, 1991 ). While searching forcollectors to selectively float bastnaesite over monazite, investigations were also per-formed in our laboratory to find a depressant that could be used to achieve the
