| Rare earth elements(REEs) are praised as "industrial monosodium glutamate", which are important strategic resources of non-renewable and increasingly widely required for many different applications in field of new energy, new materials, etc.. Because of the limit of technical level and the condition of production, recycling technical index of rare earth element was lower. There was many rare earth ore not being recovered. These tailings caused both a waste of resources and the hidden danger of polluting environment of mines in Dechang. With increasing depleted resources and the ongoing large-scale production in Dechang, the secondary utilization of tailings of rare earth element can generate very substantial economy grows and social benefits.In this paper, based on the process mineralogy property of Dechang tailings, the condition grinding and the condition floatation was made; a novel kind of hydroxamic acid collector was synthesised.The result of mineral sieving showed that 47.6% of the samples is greater than 100 mesh, 78.02% of the samples is greater than 200 mesh. The result of components analysis with XRD diffraction showed: The main rare earth mineral in the sample is bastnaesite. Gangue minerals are quartz, feldspar, calcite, fluorite, gypsum, celestite, illite and a few barites, galena and other minerals.4, 4-dihydroxy-3, 3-biphenyl dicarboxylic acid was prepared by 4,4-dihydroxy biphenyl, dry ice and trichlorobenzene, with 55.07% yield. 4, 4- dihydroxy biphenyl-3, 3- dihydroxamic acid was prepared by 4, 4-dihydroxy biphenyl-3, 3-dimethyl dicarboxylate, hydroxylamine hydrochloride and Sodium hydroxide, with 49.66% yield. The target product was characterized and confirmed by NMR, FTIR spectrum, Mass spectrum and elemental analyzer. 3-hydroxy-2-naphthoic hydroxamic acid was prepared by 3-hydroxy-2-naphthoic methyl formate, hydroxylamine hydrochloride and Sodium hydroxide, with 74% yield.In the grinding experiments, grinding time, pulp density, type and dosage of grinding aids were studied. The contents of-200 mesh in the grinding products were increased to 73.5%, 77.75%, 76.25%, 76%, with adding 1.25 kg/t hexametaphosphate, 1.05 kg/t sodium tripolyphosphate, 0.75 kg/t sodium citrate, 0.75 kg/t sodium silicate’s, successively. When the dosage of hexametaphosphate was 1.25 kg/t, it showed the best grinding efficiency. The influence of grinding aids on flotation of rare earth tailings was investigated. When the dosage of Sodium silicate was 0.75 kg/t, the CeO2 grade improved 0.82%.The usage of depressant and activators has been investigated.The results showed that: When the dosage of sodium silicate was 1000 g/t, the recovery rate was 54.90%, while the CeO2 grade was 8.52%. Meanwhile, when the dosage of sodium carbonate was 500 g/t, the recovery rate was 80.11%, while the CeO2 grade was 5.25%. At the same condition, when the dosage of ammonium chloride was 500 g/t, the recovery rate was 91.97%, while the CeO2 grade was 5.09%. When the dosage of sodium fluoride was 300 g/t, the recovery rate was 85.54%, while the CeO2 grade was 5.62%.The collecting ability of three kinds of hydroxamates has been investigated. The collecting ability of three kind of hydroxamic acid to rare earth ore was in the following order: 3-hydroxy-2-naphthalene hydroxamic acid > 4, 4-dihydroxy diphenyl-3,3-dimethyl hydroxamic acid > salicyl hydroxamic acid. The select ability was in the following order: salicyl hydroxamic acid > 4, 4-dihydroxy diphenyl-3, 3-dimethyl hydroxamic acid > 3-hydroxy-2-naphthalene hydroxamic acid.Study on beneficiation process showed good flotation indexes could be obtained under the condition of sodium silicate as depressant, salicyl hydroxamic acid as collector. The CeO2 grade of tailing could be concentrated 31.47% in open circuit test, and the recovery was 73.43%. |
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