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Synthesis of silica coated on iron sand magnetic materials modified with mercapto was carried out through a sol-gel method. This study aims to obtain adsorbent material that has magnetic properties. The purpose of this research are gift magnetic proprties of adsorbent. It was easy access to the separation of the adsorbent after the adsorption process in aqueous system. Modified silica surface with mercapto group provides spesific and selective for soft metals according to hard soft acid base (HSAB) principle. Solution of Na₂SiO₃ as a silica precursor were coated on the surface of iron sand magnetic materials (MM) that has been activated by acid. Silica which have been coated on MM then modified with compound 2- mercaptobenzimidazole as a functional group of mercapto (-SH). The compound 2- mercaptobenzimidazole does not have a functional group of silanol (≡Si-OH) and siloxane (Si- O-Si) to bind to the functional group on silica surface. Therefore, chloropropyltrimethoxysilane (CPTMS) was added as a link between silica and 2-mercaptobenzimidazole. Chloropropyltrimethoxysilane (CPTMS) was reacted with 2-mercaptobenzimidazole as mixture I then mixed into silica which has coated MM as mixture II by sol-gel process. Material characterization was carried out by Fourier Transform Infrared (FTIR) spectrophotometer, X- ray diffractometer (XRD) and Vibrating Sample Magnetometer (VSM), and the stability of coated magnetite against acid. The characterization results showed that synthesized adsorbent of MM/SiO₂/SH was successful. Coating of iron sand magnetic material with silica modified mercapto increases the stability of the acid and decreases the magnetic properties.