Studies on effective decomposition of monazite minerals by variety of phosphate fluxes for simple and direct determination of uranium by LED fluorimeter

Chemistry Laboratory, Atomic Minerals Directorate for Exploration and Research, Begumpet, Hyderabad-500 016, India E-mail : chakrapanigotur@yahoo.com Fax : 91-40-27762940 A simple, rapid, effective sample decomposition method is developed for the determination of uranium (U) in monazite minerals by fluorimetric (Light Emitting Diodes (LED) based) technique. The salts of sodium di hydrogen phosphate (NaH2PO4), di sodium hydrogen phosphate (Na2HPO4) and tetra sodium pyrophosphate (Na4P2O7) were used to conduct studies on effective decomposition and dissolution of monazite minerals. The flux shortlisted for sample decomposition has several advantages. The fusion is very simple (involve minimal skills), time saving and eco-friendly (no acids were used for sample dissolution), where as in the reported conventional sample decomposition methods involving fusion with sodium peroxide, mixture of KHF2 and NaF, mineral acids are being used for sample decomposition to get clear solution. Further this solution cannot be used directly for uranium determination by LED fluorimetry; hence separation is required, resulting in low sample throughput. In the present method no such separation is required as the flux itself acts as a fluorescence enhancing reagent and buffer (maintaining the optimum pH of 7.1 ± 0.1). The fused melt of the flux mixture when dissolved in water, gives clear and stable solution. The accuracy and precision of the method was evaluated by analyzing Certified Reference Material, IGS-36 (Institute of Geological Sciences, UK) and monazite samples received from BSOI, Trivandrum. The accuracy of the data was further evaluated by comparing with conventional standard decomposition methods. The results are well within experimental error. RSD of the method is ±2% at 0.30% U3O8 in monazite minerals.