Pengendapan Uranium pada Monasit Bangka sebagai Ammonium Diuranate (ADU) Menggunakan Gas NH3

ABSTRAK Monasit, sebagai produk ikutan penambangan timah, mengandung unsur-unsur logam tanah jarang (LTJ) serta unsur radioaktif seperti uranium (U) dan torium (Th). Penelitian dan pengembangan pengolahan monasit di Pusat Teknologi Bahan Galian Nuklir-Badan Tenaga Nuklir Nasional (PTBGN-BATAN) telah berhasil memisahkan LTJ sebagai senyawa hidroksida dengan recovery 85%. Unsur radioaktif U dan Th masing-masing diperoleh sebagai produk dalam bentuk konsentrat senyawa ammonium diuranate (ADU)/(NH4)2U2O7 dan torium hidroksida (Th(OH)4). Pada penelitian sebelumnya, pemisahan U sebagai ADU pada monasit dilakukan dengan proses pengendapan menggunakan larutan NH4OH. Pada penelitian, U ini akan diendapkan sebagai ADU menggunakan reagen gas NH3 dengan tujuan memperoleh kondisi optimum pengendapan. Umpan pengendapan berupa larutan (U,Th,LTJ) sulfat diperoleh dari proses pengolahan monasit secara basa yaitu dekomposisi menggunakan NaOH, pelarutan parsial menggunakan HCl, dan pelarutan total menggunakan H2SO4. Parameter yang diteliti meliputi pengaruh laju alir gas NH3, temperatur proses, dan waktu kontak terhadap recovery U. Hasil penelitian menunjukkan bahwa pada kondisi statis pH-7, kondisi optimum pengendapan U menggunakan gas NH3 adalah pada laju alir gas NH3 150 ml/menit, temperatur proses 30oC, dan waktu kontak 15 menit dengan recovery pengendapan U 100%, Th 99,97%, dan LTJ 99,93%. Hasil tersebut menunjukkan bahwa unsur U sudah terambil seluruhnya akan tetapi masih bercampur dengan unsur lain yaitu Th dan LTJ, sehingga diperlukan penelitian berikutnya untuk memperoleh U dengan kemurnian yang tinggi pada kondisi pH optimum.ABSTRACT Monazite, as a by-product of tin mining, contains rare earth elements (REE) and radioactive elements like uranium (U) and thorium (Th). The monazite processing Research and Development at the Center for Nuclear Mineral Technology-National Nuclear Energy Agency (PTBGN-BATAN) has succeeded in separating REE as a hydroxide compound with an 85% recovery. The radioactive elements U and Th are each obtained as a product in the form of concentrated compounds of ammonium diuranate (ADU)/(NH4)2U2O7 and thorium hydroxide (Th(OH)4). In previous studies, the separation of U as ADU in monazite was carried out by the precipitation process using NH4OH solution. In this research, U will be precipitated as an ADU using NH3 gas reagents to obtain precipitation optimum conditions. Precipitation feed in the form of (U, Th, REE) sulfate solution derived from the monazite processing using the alkali or base method, which includes decomposition using NaOH, partial dissolution using HCl, and total dissolution using H2SO4. The parameters studied include the effect of NH3 gas flow rate, process temperature, and contact time on U recovery. The results showed that on the static pH-7 condition, the optimum state of U precipitation using NH3 gas is at NH3 gas flow rate of 150 ml/minutes, processing temperature of 30oC, and 15 minutes contact time with precipitation recovery of U 100%, Th 99.97%, and REE 99.93%. These results indicate that U has been taken entirely but still mixed with other elements, which are Th and REE, so that further research is needed to obtain U with high purity on optimum pH condition.

Identifying surface morphological characteristics to differentiate between mixtures of U3O8 synthesized from ammonium diuranate and uranyl peroxide

In the present study, surface morphological differences of mixtures of triuranium octoxide (U3O8), synthesized from uranyl peroxide (UO4) and ammonium diuranate (ADU), were investigated. The purity of each sample was verified using powder X-ray diffractometry (p-XRD), and scanning electron microscopy (SEM) images were collected to identify unique morphological features. The U3O8 from ADU and UO4 was found to be unique. Qualitatively, both particles have similar features being primarily circular in shape. Using the morphological analysis of materials (MAMA) software, particle shape and size were quantified. UO4 was found to produce U3O8 particles three times the area of those produced from ADU. With the starting morphologies quantified, U3O8 samples from ADU and UO4 were physically mixed in known quantities. SEM images were collected of the mixed samples, and the MAMA software was used to quantify particle attributes. As U3O8 particles from ADU were unique from UO4, the composition of the mixtures could be quantified using SEM imaging coupled with particle analysis. This provides a novel means of quantifying processing histories of mixtures of uranium oxides. Machine learning was also used to help further quantify characteristics in the image database through direct classification and particle segmentation using deep learning techniques based on Convolutional Neural Networks (CNN). It demonstrates that these techniques can distinguish the mixtures with high accuracy as well as showing significant differences in morphology between the mixtures. Results from this study demonstrate the power of quantitative morphological analysis for determining the processing history of nuclear materials.

The Removal of Uranium From Simulated Ammonium Diuranate Filtrate by Nanofiltration

In this study, a simulated ammonium diuranate filtrate (ADUF) which was obtained by adding uranyl nitrate to a 35 g/L ammonium nitrate solution to adjust the uranium concentration to about 50 mg/L was treated by a nanofiltration process. Experiments were carried out on a plate membrane testing device with a trans-membrane pressure (TMP) range of 0.5 ∼ 3.0 MPa, a crossflow velocity range of 10 ∼ 50 cm/s and a temperature range of 5 ∼ 35 °C. The results show that NF270 membrane has good rejection property for uranium and excellent permeability for ammonium nitrate. The ammonium nitrate concentration in the permeate is about 32 g/L which means the reject ratio of ammonium nitrate is only about 10%. Though NF270 membrane shows good uranium rejection property, the corresponding permeate flux is very high. When the trans-membrane pressure is 1.5 MPa, the uranium reject ratio is 96.8% and the the corresponding permeate flux is about 80 L/(m2·h). It indicates a bright application prospect of nanofiltration process in the treatment of ADUF.