PELAPISAN MAGNETIT DENGAN HIBRIDA MERKAPTO-SILIKA UNTUK ADSORPSI SELEKTIF Au(III) DARI SISTEM MULTILOGAM Au(III)/Cu(II)/Ni(II)

Selective adsorption of Au (III) in multimetal systems Au(III)/Cu(II)/Ni(II) on mercapto-silica hybrid coated magnetite (MHMS) has been studied. MHMS was synthesized via sol-gel process using magnetite that obtained through coprecipitation of Fe 2+ /Fe 3+ salts mixture with NH4OH as precipitating solution, sodium silicate as a precursor of rice husk ash and 3-mercaptopropyltrimethoxysilane (MPTMS) as a source of thiol. MHMS was characterized by Fourier Transform Infrared (FTIR) Spectrophotometer, X-ray diffraction (XRD), Transmission electron micrograph (TEM), Gas Sorption Analyzer (GSA) BET method, and Vibrating Sample Magnetometer (VSM). Optimization of Au (III) adsorption was carried out as function of pH, contact time and concentration of ion. Adsorption kinetics was determined by pseudo-first order (Lagergren) and pseudo-second order (Ho) model, while the adsorption isotherm was analyzed studied by the Langmuir and Freundlich models. The adsorbed metal ions Au (III), Cu (II) and Ni (II) quantitatively calculated based on the difference of metal concentrations before and after adsorption were analyzed by AAS spectrophotometer. Similar work conducted for multimetal (Au(III)/Cu(II)/Ni(II)) system for evaluating the thermodynamic parameter. FTIR and XRD characterizations showed that MHMS have been successfully synthesized. The coating of magnetite could increase the particle size and reduced magnetic properties. Adsorption of Au(III) on MHMS is not affected by pH. Adsorption kinetics studies showed that the adsorption of Au(III) on MHMS fits to pseudo-second order model with adsorption rate constant is 1.37x10 -3 g.mg -1 min -1 . MHMS adsorbent shows a linear plot of Langmuir isotherm models with adsorption capacity of Au (III) is 125 mg/g. Adsorption on multimetal systems (Au(III)/Cu(II), Au(III)/Ni(II) and Au(III)/Cu(II)/Ni(II) shows that capacity of Au(III) is higher than that of Cu(II) and Ni(II) in multimetal systems. MHMS has high selectivity for Au(III) metal ions toward Cu(II) and Ni(II) ions