ABSTRAK Pembuatan bead kitosan magnetik berikatan silang glutaraldehid telah dilakukan dan diaplikasikan pada penyerapan ion logam merkuri pada air limbah daerah pertambangan emas Manggamat, Aceh. Bead kitosan magnetik berikatan silang glutaraldehid dibuat dengan variasi komposisi kitosan, glutaraldehid, dan Fe yang bersumber dari proses isolasi pasir besi pantai Syiah Kuala Banda Aceh. Berdasarkan hasil penelitian, bead kitosan magnetik berikatan silang glutaraldehid yang terbaik diperoleh pada komposisi kitosan sebanyak 0,35 g, Fe sebanyak 0,5 g, dan glutaradehid sebanyak 0,01 g. Hasil Uji adsorpsi menunjukkan daya serap optimum diperoleh pada pH 4 dengan waktu kontak 80 menit. Isoterm adsorpsi bead kitosan magnetik berikatan silang glutaraldehid terhadap ion logam merkuri mengikuti model isoterm Langmuir dan Freundlich. Berdasarkan persamaan isoterm Langmuir diperoleh kapasitas adsorpsi maksimum (Qm) sebesar 13,192 mg/g. Selanjutnya bead kitosan magnetik berikatan silang glutaraldehid dapat diaplikasikan untuk penyerapan ion logam merkuri pada air limbah pertambangan emas dengan kapasitas penyerapan mencapai 96 %. Kata kunci: Kitosan Magnetik, ikat silang, glutaraldehid, isoterm adsorpsi ABSTRACT The preparation of glutaraldehyde crosslinked magnetic chitosan bead had been conducted and applied for mercury ions adsorption from gold mining area wastewater in Manggamat, Aceh. The glutaraldehyde crosslinked magnetic chitosan bead was prepared with variation of chitosan, glutaraldehyde, and Fe compositions which was isolated from iron sand of Syiah Kuala beach in Banda Aceh. Based on the study, the best glutaraldehyde crosslinked magnetic chitosan beads of were obtained at chitosan 0.35 g, Fe 3 O 0.5 g, and glutaraldehyde 0.01 g. The results of adsorption study exhibited optimal adsorption capacity on pH 4 with 80 minutes contact time. The adsorption isotherm of the glutaraldehyde crosslinked magnetic chitosan bead was fitted with Langmuir and Freundlich isotherm models. Based on Langmuir isotherm, the maximum adsorption capacity (Qm) was 13.192 mg/g. The glutaraldehyde crosslinked magnetic chitosan bead was applicable to adsorb mercury ions from gold mining wastewater with adsorption capacity reached 96%. Keywords: Magnetic chitosan, Crosslinking, glutaraldehyde, adsorption isotherm 4 3 O 4 3 3 O O 4 4