| Along with the increasing progress of science and technology, rare and precious metals with excellent performance, such as rubidium?niobium and tantalum,are widely used in pharmaceutical?chemical?aerospace?steel?nuclear industry many other industries.They have significant commercial value and scientific sdudying significance.The western Qinling is a important metal mineralization area, and rubidium associated niobium and tantalum is one of the main mineral.In order to comprehensive utilization of rubidium, niobium, tantalum resources of western Qinling,we must establish an efficient and accurate analysis method of Rb, Nb and Ta.At present, the common analysis of Rb is atomic absorption spectrometry(AAS) and emission spectrometry, but these methods are complicated becouse of adding another deionization agent.And even so, the results for some samples of rock and soil are higher than actual data. Inductively coupled plasma atomic emission spectrometry(ICP-OES) and inductively coupled plasma mass spectrometry(ICP-MS) are the main analysis methods in the determination of Nb and Ta.There are still several problems to be solved,for example, incomplete dissolution of samples?the hydrolysis of elements?serious interference and complex process. According to the characteristics of crude mineral and metallurgical samples in western Qinling, this paper improves the existing analysis method of ICP-OES and establishs a simple, rapid and simultaneous analysis method of Rb, Nb and Ta. This method adopts a capped acid-solution with HNO3-HF-H2SO4, in addition, it selects n-butanol as a sensitizer and tartaric acid as a extraction reagent. The main results are as follows:1. Study on the selection and mechanism of sensitizers. N-butanol had remarkable sensitizing effect in the determination of Rb, Nb and Ta by ICP-OES. When the concentration of n-butanol was 2%(v/v),the sensitivities of Nb(292.781 nm),Ta(240.063 nm) and Rb(780.023 nm) increased of 246.6%, 265.2% and 149.5%,respectively. The sensitizing mechanism of n-butanol includes two aspects. The improvement of atomization and transmission efficiency was just one part of the reason, on the other hand, ionization behavior of elements changes in the plasma because of C+ atom charge transfer, which resulted in obvious sensitizing effect for elements with high ionization energy.2. The optimization of parameters of pretreatment and ICP-OES.The parameters of pretreatment were optimized by orthoganal experiment: the volume of HNO3, HF and H2SO4(1:1) are 4.0 m L, 6.0 m L, and 1.0 m L, respectively, and the concentration of tartaric acid is 2.0%(v/v). Moreover,the parameters of ICP-OES were optimized by single factor experiment:RF power 1350 W, viewing distance 14 mm(axial), nebulizer gas flow 0.6 L·min-1, auxiliary gas flow 1.0 L·min-1, pump flow rate is 1.0 m L·min-1, cooling gas flow for 14.0 L·min-1.3. Evaluation of the method. Though selecting suitable integration interval and correction interference by IEC,the correlation were more than 0.9999 when the concentration of three analyzed elements were between 0.1~100mg·m L-1. Meanwhile, the relative error was-3.86~+3.69% and RSD was less than 3.2%. After adding 2% n-alcohol, their recovery was increased from 96~106% to 98~104%, moreover, the detection limits of Rb2 O, Nb2O5 and Ta2O5 were reduced from 0.0315 to 0.0144 mg·m L-1,0.0243 to 0.0105 mg·m L-1 and 0.0426 to 0.0207 mg·m L-1, respectively. For the samples which to be determined were above the concentration range, the diluted data obtained with the theoretical value showed a good linear relationship and the reliability was high.4. The analysis of actual samples. For the crude ores and metallurgical samples from western Qinling, this method is very suitable.It not only can determine different grade ores from verious sampling points simultaneously, but also suitable for determing concentrates,middlings, tailings of metallurgical samples and leaching liquid, extraction liquid and stripping liquid of extraction samples from the same batch. The results show that, Rb2O grade was 0.11~0.19% in main mineral deposit which associated with 0.0098% Nb2O5 and 0.0032% Ta2O5. The utilization rate of this process which combined classification gravity concentration- weak magnetic separation- flotation- strong magnetic separation utilization rate reached 91%, which, the mica concentrate Rb2O grade reached 0.6014%, columbite-tantalite concentrate(Nb+Ta)2O5 grade reached 16.45%. The total recovery of Rb is 92.87% in the extraction progress of Rb by chloridizing roasting from mica concentrates, which of leaching rate 94.48%, extraction rate 98.52%, stripping rate of 99.78%, respectively.The method applicable for simultaneous determination of low and high contents of Rb, Nb and Ta, especially for the same batch of mineral process and hydrometallurgy process samples. It overcomes the bad agreement of recovery among AAS, ICP-OES and ICP-MS. |
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