Study On The Joint Determination Of Thorium And Rare Earth Eements In Sichuan Hydro-smelting Bastnasite

Thorium is a toxic and harmful element to human for radioactivity .It is associated in rare earth ore yet. With the hydro-smelting rare earth ore, Thorium was migrated and enriched inevitably. Thorium is the contaminants of hudrometallurgy and the main impurity targets of rare earth productions. Thus, the joint determination is needed not only in technology manipulation of the rare earth produce processing and examination of production impurity .but also in supervision of the quantity on Thorium in environment. No articals today, however have soon the joint determination of the rare earth elements and ThoriumImmobilizing waxberry is a novel adsorbents which is made of oxhide and cortex of waxberry. Immobilizing waxberry tannin onto collagen fibre matrices. It is demonstrated by experiments that thorium is adsorbed by the immobilizing waxberry selectively and the maximum adsorption capacity is 108.75 mgTh4+/g, 21.92mgLa3+/g and 21.92Ce3+/g, respectively. The selective adsorption of immobilizing waxberry for Thorium resulted from the pyrogallol structure of tannin. Thorium and the rare earth are separated by the selective adsorption. The advantage of this method is as follows.(1) The method using solvent extracting Thorium in aqueous solution and the method using extraction-elution resins eluting Thorium from aqueous solution both need a large quantity of organic solvents. The organic solvents are toxic and cost highly. The waste solvent and extraction-elution resins are treated very difficult. However immobilizing waxberry is derived from natural material of collagen fibres and larch tannin which can be decomposed by microorganism. So immobilizing waxberry is a kind of inexpensive, environmental benign and natural adsorbents.(2) The manipulation of immobilizing waxberry is easier than its solvent extraction or extraction-elution resins. It is the matter that Solventsis easy to lose from solvent extraction or extraction-elution resins. So, the living period is few for extraction-elution resins. When Thorium is adsorbed by immobilizing waxberry adsorption column, pH of the Th4+ solution is adjusted to 3.5with 0.1mol/LHNO3 and 0.lmol/L NaOH, and the effluent velocity of solution is controlled at 0.5mL/min.Sequencely the solution of HNO3(pH=4.5~5.5) elute rare earth elements and 0.lmol /LHNO3 elute Thorium from the adsorption column. The column is regenerated by 0.1mol/LHNO3 and 0.lmol/L NaOH.Low pressure ion chromatography continuously determine the content of ions(La3+ Ce3+ Pr3+ Nd3+) which mainly have more than 98% in the light rare earth.. Their detection limits of La3+, Ce3+, Pr3+, Nd3+ are 0.25mg/L, 0.20mg/L. 0.16mg/L, 0.15mg/L, respectively. Separated Thorium from rare earth by immobilizing waxberry, determined the quantity of the light rare earth by low pressure ion chromatography and determined the quantity of Thorium by chromatography (detective range 0 ~ 30 g/25mL). It is demonstrate by the experiments that joint application of immobilizing waxberry, low pressure ion chromatography and chromatography can determine the component of the light rare earth and Thorium in the rare earth concentrate, products(RECl3,CeO2), slag and wastewater. The recovery of Th4+ is 95.2-107.2%, RSD is 0.31-1.79%. Under the determined conditions of research, the other elements in rare earth ore make no effects on determination of the rare earth and Thorium.