Modifikasi silika terlapis pada bahan magnetik pasir besi dengan kitosan melalui penghubung 3-glisidoksipropil trimetoksisilan (GPTMS) untuk studi adsorpsi [AuCl4]-telah dilakukan. Bahan magnetik (BM) dipisahkan dari pasir besi menggunakan magnet eksternal kemudian dicuci dengan akuades dan larutan HF 10 %. Material BM-silika-kitosan-GPTMS (BMSiKG) disintesis melalui proses sol gel dengan menambahkan campuran BM dan natrium silikat ke dalam larutan kitosan-GPTMS. Pada penelitian ini perbandingan jumlah mol kitosan terhadap GPTMS divariasi 0:1; 1:0; 1:0,5; 1:1; dan 1:2. Produk dikarakterisasi dengan spektrofotometer Fourier Transform Infrared, X-Ray Diffractometer, Scanning Electron Microscopy dan Energy Dispersive X-Ray, analisis Termogravimetri, serta Vibration Sample Magnetometer. Selain itu produk diuji kestabilannya terhadap pengaruh pH. Adsorpsi [AuCl4]- pada produk dilakukan dalam sistem batch dengan variasi pH, waktu, dan konsentrasi. Adsorben dipisahkan dari larutan menggunakan medan magnet luar dan kadar [AuCl4]- yang tidak teradsorpsi dianalisis dengan Atomic Absorption Spectroscopy. Hasil karakterisasi menunjukkan bahwa material BMSiKG berhasil disintesis. Penggunaan GPTMS pada BM-silika-kitosan meningkatkan kestabilan material pada kondisi asam (pH 1-3). Hasil adsorpsi BM-silika-kitosan (BMSiK) dan BMSiKG terhadap [AuCl4]- mengikuti model kinetika pseudo orde-2 semu dan isoterm adsorpsi Langmuir dengan nilai tetapan laju adsorpsi dan kapasitas adsorpsi berturut-turut untuk BMSiK sebesar 4,1 x 10-3 g mg-1 menit-1 dan 149,25 mg g-1, sedangkan untuk BMSiKG adalah 1,99 x 10-3 g mg-1 menit-1 dan 94,34 mg g-1. Meskipun terjadi penurunan kapasitas adsorpsi, penggunaan GPTMS meningkatkan kestabilan produk pada kondisi asam.

Modification of silica coated on magnetic material iron sand with chitosan using a grafting agent of 3-Glycidoxypropyl trimethoxysilane (GPTMS) for adsorption of [AuCl4]- has been carried out. Magnetic materials (BM) from iron sand was separated using an external magnet and washed with aquades and HF 10 %. BM-silica-chitosan-GPTMS (BMSiKG) material was synthesized via sol gel process by mixing BM and sodium silicate with chitosan-GPTMS solution. In this research mol ratios chitosan to GPTMS were variated 0:1; 1:0; 1:0,5; 1:1; and 1:2. Product was characterized by Fourier Transform Infrared spectrophotometer, X-Ray Diffractometer, Scanning Electron Microscopy and Energy Dispersive X-Ray, Thermogravimetry Analysis, and Vibration Sample Magnetometer. Additionally, the effect of pH on the stability of the product has also been studied. The adsorption of [AuCl4]-on the product was done in a bacth system with variation of pH, time, and concentration. Adsorbent was separated using external magnet and concentration of [AuCl4]- not adsorbed was analized using Atomic Absorption Spectroscopy. Characterization result indicated that BMSiKG was succesfully synthesized. The addition of GPTMS on BM-silica-chitosan improved the stability of the material under acidic condition (pH 1-3). The result of BM-silica-chitosan (BMSiK) and BMSiKG adsorption to Au(III) according to pseudo second-order kinetic model and Langmuir isoterm with the value of adsorption rate constant and adsorption capacity for BMSiK are 4.10 x 10-3 and 149.25 mg g-1, for BMSiKG are 1.99 x 10-3 g mg-1 min-1 and 94.34 mg g-1 respectively. Even though decreasing the adsorption capacity, however the use of GPTMS as grafting agent improves the stability of the product under acidic condition.

Kata Kunci : silika, kitosan, pasir besi, GPTMS, adsorpsi