Pengendapan Torium (Th) dari Monasit Bangka Setelah Proses Solvent Impregnated Resin (SIR)

ABSTRAKPengolahan monasit Bangka secara basa dilakukan melalui tahapan dekomposisi; pelarutan parsial pH 3,7; pengendapan parsial pH 6,3; dan pengendapan total pH 9,8. Proses tersebut menghasilkan natrium fosfat, Rare Earth (RE) hidroksida, uranium (U), dan torium (Th). Pada proses dekomposisi, 99 % natrium fosfat telah terambil dan RE hidroksida telah terpisah dari U dan Th dengan recovery 85 %. Sementara itu, U dan Th yang dihasilkan masih bercampur sehingga perlu dipisahkan. Pemurnian Th dari U pada monasit telah dilakukan dengan metode Solvent Impregnated Resin (SIR) dan dilanjutkan dengan proses elusi setelah SIR. Hasilnya, Th masih berada pada fase cairan berupa larutan torium nitrat [Th(NO3)2] sehingga perlu diendapkan sebagai torium hidroksida [Th(OH)2] untuk memudahkan proses berikutnya. Pengendapan Th setelah proses SIR dilakukan dengan tujuan memperoleh kondisi optimum pengendapan. Resin penyokong yang digunakan adalah amberlite XAD-16 menggunakan ekstraktan yang diimpregnasikan dengan tributyl phosphate (TBP), reagen elusi asam nitrat (HNO3) encer dan reagen pengendapan amoniak (NH4OH). Parameter yang diteliti adalah pengaruh pH dan waktu pengendapan terhadap recovery Th. Hasil penelitian menunjukkan kondisi optimum pengendapan Th dari monasit setelah proses SIR pada pH 1,2 dan waktu 60 menit dengan recovery 84,74 % Th; 3,26 % U; 34,74 % RE; dan 8,52 % PO4.ABSTRACTAlkaline processing of Bangka monazite is carried out through stages like decomposition; partial dissolution pH 3.7; partial precipitation pH 6.3; and total precipitation pH 9.8. These procesess produce sodium phosphate, Rare Earth (RE) Hydroxide, uranium (U), and thorium (Th). On decomposition procsess, 99 % of sodium phosphate had been recovered and RE Hydroxide was separated from U and Th with 85% recovery. Meanwhile, the U and Th products were still mixed so that needs to separate. Purification of Th from U in monazite had been carried out by using Solvent Impregnated Resin (SIR) method and continued by elution after SIR. The result is that Th is still in the liquid phase as thorium nitrate [Th(NO3)2] solution so it needs to be precipitated as thorium hydroxide [Th(OH)2] to facilitate the next process. Precipitation of Th after SIR process is conducted with the aim to obtain optimum precipitation condition. The supporting resin used is amberlite XAD-16 with impregnated tributyl phosphate (TBP) extractant, dilute nitric acid (HNO3) as elution reagent, and ammonium hydroxide (NH4OH) as precipitation reagent. The observed parameters are the effect of pH and precipitation time on Th recovery. The results show that the optimum precipitation conditions of Th from monazite after SIR process is on pH 1.2 and 60 minutes time, resulting recovery of 84.74 % Th, 3.26 % U, 34,74 % RE, and 8.52 % PO4.

Homogeneous hydrolysis of thorium by thermal decomposition of urea

Thorium was precipitated homogeneously from a thorium nitrate solution by the thermal decomposition products of urea. The kinetics of the hydrolysis were studied at 90 and 100°C by pH measurement during the initial 5 h and the precipitation efficiencies of thorium and radium were measured over a 24 h period. Precipitation of the radium daughters was closely followed with the aim of co-precipitation of radium with thorium. The CO2 formed during urea decomposition dissolved in the solution, forming CO32− during the experiment upon reaching a sufficiently high pH level (>7). This allowed radium to co-precipitate partially, thus reducing the activity of the filtrate. After filtration or centrifugation, the precipitate is composed of nanocrystalline thorium dioxide (crystallite size ~10 nm), with weakly bound H2O and CO2.