ABSTRAK Mineral monasit sebagai mineral ikutan penambangan timah di Kepulauan Bangka Belitung mengandung unsur tanah jarang ringan, diantaranya Cerium (Ce), Lanthanum (La), dan Neodymium (Nd). Tujuan penelitian ini adalah untuk memperoleh konsentrat unsur tanah jarang karbonat melalui proses pengendapan dengan sodium karbonat (Na2CO3), serta menentukan pengaruh konsentrasi dan volume Na2CO3 terhadap recovery pengendapan Ce, La, dan Nd. Persiapan umpan dilakukan dengan mengikuti rute proses pengolahan monasit menggunakan metode basa meliputi tahapan dekomposisi, pelarutan, dan pengendapan unsur radioaktif. Recovery pengendapan tertinggi untuk Ce, La, dan Nd yaitu sebesar 10,84%, 7,81%, dan 2,68% pada penggunaan Na2CO3 dengankonsentrasi 30% wt dan volume 55 mL.ABSTRACT Monazite mineral as associated mineral of tin mining in Bangka Belitung Islands contains light rare earth elements like Cerium (Ce), Lanthanum (La), and Neodymium (Nd). The objective of this study is to obtain the concentrates of rare earth carbonate through the precipitation process with sodium carbonate (Na2CO3) and determine the effect of concentration and volume of Na2CO3 on the precipitation recovery of Ce, La, and Nd. The preparation of the feed solution was carried out by following the monazite processing route using the alkali method includes the stages of decomposition, dissolution, and precipitation of radioactive elements. The highest precipitation recovery for Ce, La, and Nd are 10.84%, 7.81%, and 2.68% respectively in the use of Na2CO3 with a concentration of 30% wt and a volume of 55 mL.