improved method for leaching of thorium in monazite using sodium hydroxide

The leaching of monazite with sodium hydroxide has been attempted. Factors such as time of leaching, concentration of sodium hydroxide sclution and temperature were tested with the hope to optimize the leaching efficiency. XRF technique was used in the determination of concentration. In this work Egyptian monastic leached by alkaline treatment in reflux instead of the pyrometallurgical process using mechanochemical treatment where grinding is carried out in the presence of sodium hydroxide and followed by pressure leaching in autoclave that gives an incongruent result. It has been found that the monazite was effectively decomposed in 2hr at - 130°C using 600g/1 sodium hydroxide in the reflux. The recovery of thorium by this method and under these conditions is about 98.1%. A mathematical formula is also deduced which enables the calculation of thorium concentration in ppm obtained from the leaching in reflux system under different conditions with a good agreement with the experimental values and that obtained from the XRF technique

Selective spectrophotometric determination of thorium, uranium and lanthanum using arsenazo I

Several techniques are used for the determination of Th, U and La in different media. But these techniques are limited considering the performance, including UV/VIS Spectrophotometer, X-ray fluorescence spectrometry, atomic absorption and emission spectrometry [1,2]. The atomic absorption spectrometry isn't applicable for the determination of Th and U because of the non-availability of the hollow cathode lamps[3]. Strong claims are made for the specificity and sensitivity of NAA, ICP-AES and ICP-MS, inspite of the fact that interference is a problem using these techniques. Hence the application of organic reagents for the spectrophotometric determination of these elements is well-known and continues to be applied[4]. Several organic and inorganic reagent have been reported for the spectrophotometric determination of Th, U, and La[5,6]. Arsenazo I is considered to be suitable for the spectrophotometric determination for many elements because it is commercially available and is water-soluble. The reagent has ability to form stable complexes in strong acidic and basic media. Th, U and La often coexist in ores like monazite and other minerals and their selective determination is a problem in analytical chemistry[4] therefore the aim of the present investigation is to establish a procedure for the selective determination of Th, U, and La depending on pH adjustment