Pembuatan komposit α-Fe 2 O 3 vi ABSTRAK -bentonit telah berhasil dilakukan menggunakan metode solid state reaction dari bahan baku pasir besi pantai Syiah Kuala, Banda Aceh dan bentonit dari Kuala Dewa, Aceh Utara. Sintesis α-Fe dilakukan dengan cara ekstraksi pasir besi menggunakan asam klorida dan presipitasi menggunakan NH 4 OH pada pH 6. Komposit α-Fe 2 O -bentonit dipreparasi dengan mencampurkan α-Fe 2 O 3 3 dan bentonit dengan perbandingan 4:1 menggunakan ball mill selama 2 jam. Karakterisasi pasir besi dan komposit α-Fe 2 O -bentonit dengan XRD menunjukkan bahwa fasa dominan yang terdapat dalam pasir besi adalah magnetit (Fe 3 O 4 ) sedangkan dalam komposit adalah hematit (α-Fe 3 ) dan silika (SiO ). Aktivitas fotokatalitik komposit diuji pada degradasi zat warna indigo carmine pada berbagai variasi kondisi pH, massa fotokatalis, konsentrasi awal zat warna dan waktu radiasi. Hasil yang diperoleh menunjukkan bahwa aktivitas fotokatalitik komposit α-Fe 2 2 O -bentonit tertinggi diperoleh pada kondisi pH larutan 1, massa fotokatalis 250 mg dan konsentrasi indigo carmine 10 ppm dengan persen degradasi mencapai 91,480% setelah diradiasi dengan sinar ultra violet (UV) selama 60 menit. Komposit α-Fe 3 2 O -bentonit memiliki aktivitas yang lebih tinggi menggunakan radiasi sinar matahari (92,083%) dibandingkan dengan radiasi sinar ultra violet. Kata kunci : pasir besi, bentonit, fotokatalis, hematit, indigo carmine, komposit ABSTRACT Preparation of α-Fe 2 O 3 3 -bentonite composite has been successfully performed by solid state reaction method by using iron sand from coastal of Syiah Kuala, Banda Aceh and bentonite from Kuala Dewa, North Aceh as raw materials. The α-Fe was extracted from iron sand using hydrochloric acid and precipitated using ammonium hydroxide at pH 6. The α-Fe 2 O -bentonite composite was prepared by mixing α-Fe 2 O 3 3 and bentonite at 4: 1 ratio using ball mill for 2 hours. The XRD results showed that the dominant phase of iron sand was magnetite (Fe ), while in α-Fe 2 O 3 -bentonit composites the dominant phase were α-Fe 2 O . The photocatalytic activity was tested on degradation of indigo carmine dye at various condition of pH, photocatalyst mass, initial dye concentration and irradiation time. The results showed that the highest photocatalytic activity of α-Fe 3 -bentonite (%D = 91.480%) was obtained at pH of solution 1, 250 mg photocatalyst mass and concentration of IC 10 ppm after irradiated with UV light for 60 minutes. The α-Fe 2 O -bentonite composite has higher activity in sunlight irradiation (92,083%) than ultra violet rays. Keywords: iron sand, bentonite, photocatalyst, hematite, indigo carmine, 3 composite 2 2 O O 3 3 3 O 4 and SiO 2 O 3 2 2 O 3