Determination of lanthanides (La, Ce, Nd, Sm) and other elements in metallic gallium by instrumental neutron activation analysis

Abstract

This paper reports the analytical results of lanthanides and other elements in pure elemental gallium. The analyses were performed by instrumental neutron activation analysis (INAA) at the nuclear reactor IEA-R1, IPEN, São Paulo. INAA has the advantage of being a multi-elemental and non-destructive analytical method. After irradiation, the samples were set aside for some days before running high resolution gamma spectrometry with a hyper-pure Ge detector. Gallium was recovered from the Bayer process alkaline leach solution, named by local aluminum industry as ‘weak soda’, (spent liquor) with a concentration of about 150 mg l −1. As a first step, gallium was recovered from the ‘weak soda’ and enriched using a complexing ion-exchanger of the polyamidoxime type specially synthesized in the country for this purpose. After washing the column with water and then with pure sodium hydroxide to remove the interstitial ‘spent liquor’, gallium was eluted from the resin. The eluted gallium solution was made to 4 mol l −1 in NaOH and subject to electrolysis. The metal was then collected from the electrodes and given a final purification step by dilute inorganic acid stripping. The most representative lanthanide elements found and analyzed in the metallic gallium were La, Ce, Nd and Sm. One of the most recent samples exhibited the following results: (μg g −1) La (16.1), Ce (15.5), Nd (11.8) and Sm (3.6). Besides the lanthanides, the following elements were also analyzed: U, Cr, Fe, Co, Zn, Mo, Se, Sb and Ba. The results showed that the metal obtained is highly pure. The purity can be enhanced by stripping the metallic gallium with a dilute mineral acid.