Adsorpsi Metilen Biru Pada Hidroksiapatit Dari Tulang Ikan Kakap MerahABSTRAKPenelitian yang bertujuan untuk mempelajari adsorpsi metilen biru pada hidroksiapatit yang diperoleh dari tulang ikan kakap merah (Lutjanus sp.) telah dilakukan. Tulang dikalsinasi dalam tanur pada 600, 800, dan 1000 oC, digerus, dan diayak dengan ayakan 100 mesh. Material tersebut selanjutnya digunakan dalam eksperimen adsorpsi dan data yang diperoleh dianalisis menggunakan model isoterm adsorpsi Langmuir, Freundlich, dan Dubinin-Raduskevich. Hasil penelitian menunjukkan bahwa semakin tinggi suhu kalsinasi, semakin rendah kapasitas adsorben untuk mengadsorpsi metilen biru. Energi adsorpsi yang dihitung berada dalam kisaran 0,84-1,14 kJ mol-1 yang mengindikasikan bahwa metilen biru teradsorpsi secara fisik pada adsorben dan adsorpsi cenderung mengikuti model isoterm adsorpsi Freundlich.Kata kunci: adsorpsi, hidroksiapatit, kakap merah, metilen biru Adsorption of Methylene Blue on Hydroxyapatite from Red Snapper Fish Bones ABSTRACTA research aimed to study the adsorption of methylene blue on hydroxyapatite obtained from red snapper fish bones (Lutjanus sp.) was performed. The bones were calcined in a furnace at 600, 800, and 1000 oC and ground to pass a 100 mesh sieve. The materials were used in the adsorption experiment and the data obtained were analyzed using Langmuir, Freundlich, and Dubinin-Raduskevich adsorption isotherm models. The results showed that the higher the calcination temperature, the lower the capacity of the adsorbent to adsorb methylene blue. Calculated adsorption energy which was in a range of 0.84-1.14 kJ mol-1 indicated that the dye was adsorbed physically on the adsorbent and the adsorption could be well described by Freundlich adsorption isotherm model.Keywords: adsorption, hydroxyapatite, red snapper, methylene blue