ABSTRAK: Tujuan penelitian adalah mempelajari karakteristik hidroksiapatit (TA) yang diekstraksi secara termal dan aplikasinya untuk adsorpsi ion selektif biru metilen. Karakteristik TA yang dipelajari adalah rasio Ca/P, kristalinitas dan ukuran partikel, keasaman dan kebasaan permukaan, situs aktif, serta luas permukaan. TA diekstraksi secara termal pada variasi suhu 400, 750, 950, dan 1100oC. Karakterisasi yield TA ditentukan secara gravimetri, Ca/P dianalisis secara laser induced breakdown spectroscopy (LIBS), kristalinitas dan ukuran kristal secara difraksi sinar-X (X-ray diffraction, X-RD), keasaman dan kebasaan permukaan ditentukan secara titrasi asam-basa, situs aktif secara fourier transform infrared (FTIR), serta luas permukaan secara spektrometri UV-vis dari methylene blue method. Sementara, jumlah ion selektif biru metilan yang teradsorpsi ditentukan secara spektrometri UV-vis. Hasil penelitian menunjukkan bahwa TA yang diekstraksi secara termal pada suhu 400oC paling baik karakteristiknya, yaitu rasio Ca/P paling mendekati standar (1,64 dibandingkan standar 1,67), berfasa kristal dengan ukuran rata-rata paling kecil (6,79 nm), jumlah situs aktif tertinggi (21,94 x 1020 situs/g), dan luas permukaan (Langmuir surface area) tertinggi (31,49 m2/gram) serta jumlah ion selektif biru metilen yang teradsorpsi rata-rata juga tertinggi yaitu 85,89%. TA tersebut potensial digunakan sebagai adsorben untuk ion biru metilen. Kata kunci: tulang sapi, hidroksiapatit, biru metilen, adsorpsi ABSTRACT: The aim of this research to study the characteristics of hydroxyapatite (TA) which was extracted thermally from bovine bone waste and its application to adsorption of methylene blue selective ions. Characteristics of TA were studied are Ca/P ratio, crystallinity and crystalline size, surface acidity and basicity, active sites, and Langmuir surface area. The TA is extracted thermally on temperatures variation of 400, 750, 950, and 1100oC. Characterization of Ca/P was done by laser induced breakdown spectroscopy (LIBS), crystallinity and crystalline size analyzed by X-ray diffraction (X-RD), surface acidity and basicity by acid-base titrations, fuctional groups by fourier transform infrared (FTIR), as well as Langmuir surface area with the methylene blue method analyzed by UV-vis spectrometric. Meanwhile, the amount of adsorbed methylene blue selective ions was determined by UV-vis spectrometric. The results showed that the TA extracted thermally at 400°C was the best characteristic, the Ca/P ratio was 1.64 closed to the standard (1.67), average crystalline size (6.79 nm), the highest amount of active sites (21.94 x 1020 sites/g), and the highest Langmuir surface area (31,49 m2/g) and the highest average amount of adsorbed methylene blue selective ions was 85.89%.