Extraction of Thorium(IV) with N-Methyl-N,N,N-trioctylammonium Chloride from Monazite Acidic Leach Liquor and Its Use for Spectrophotometric Determination

N-Methyl-N,N,N-trioctylammonium chloride was applied for selective extraction and separation of thorium. The Th extraction and stripping conditions were experimentally optimized. 0.75 M N-methyl-N,N,N-trioctylammonium chloride was found to be suitable for the Th separation. The extraction of Th(IV) form monazite is an exothermic process. The optimum parameters were applied to the spectrophotometric determination of Th using Thoron I at lambda(max) = 540 nm with accurate results. From the stripped liquor (1 M HNO3), Th was precipitated as thorium oxalate for technological application. Thus, marketable pure thorium product was prepared in addition to uranium and rare earth concentrates.