Synthesis of N’-(3-trimethoxysilylpropyl)diethylentriamine modified silica (SiO2(RHA)-TMPDT) for adsorption of gold(III)

The synthesis of N’-(3-trimethoxysilylpropyl) diethylentriamine modified silica (SiO2(RHA)-TMPDT) has been done. The silica source precursor was sodium silicate (Na2SiO3) obtained rice hull ash (RHA) and N’-(3-trimethoxysilylpropyl) diethylentriamine (TMPDT) was used as modifier. Furthermore, SiO2(RHA)-TMPDT were characterized using Fourier transform infrared (FTIR) spectrophotometer, scanning electron microscope (SEM-EDX), thermogravimetric analyzer (TGA) and surface area analyzer (SAA). Adsorption was carried out using batch system with pH variation, contact time and initial concentration of gold (III). FTIR spectra of SiO2 (RHA)−TMPDT showed peaks at 1057, 1471 and 2908 cm-1 confirming Si-O-Si, NH2 and C-H stretching, respectively. SEM-EDX analysis showed the presence of C and N elements of 46.5 and 2.1%, respectively. TG analysis was characterized by a mass loss of 10.57% at (480-900) °C indicating the release of organic groups from TMPDT. Material of SiO2 (RHA)-TMPDT has surface area and pore diameter of 54.679 m2/g and 38.386 Å, respectively. The optimum adsorption of gold (III) on SiO2(RHA)-TMPDT was obtained at pH of 3.0. The kinetic study shows that the adsorption of Au (III) ion follows pseudo-2nd order. The study of adsorption isotherm of gold (III) on SiO2(RHA)-TMPDT follows Freundlich with an adsorption capacity of 1301 mg/g. The selectivity of Au3+/Zn2+, Au3+/Cu2+, Au3+/Fe3+ were 1.021, 0.164 and 0.113, respectively.