HIDROTALSIT Mg-Al-NO3 SEBAGAI ADSORBEN UNTUK PUNGUT ULANG LOGAM EMAS DARI LARUTAN [AuCl4]-; GOLD RECOVERY FROM [AuCl4]- SOLUTION USING Mg-Al-NO3 HYDROTALCITE AS ADSORBENT

MUH. NUR KHOIRU WIHADI, Sri Juari Santosa

2014 | Disertasi | PROGRAM STUDI S2 KIMIA

The Mg-Al-NO3 hydrotalcite (HT-NO3) has been investigated as a potential adsorbent of [AuCl4]- ion. The HT-NO3 was prepared by Mg/Al molar ratio of 2:1 using co-precipitation method at pH 10.0 and characterized by the Fourier transform infra red spectroscopy (FT-IR), the X-ray diffraction (XRD) and the thermal analysis. Gold sources were prepared from HAuCl4 stock solution and waste central processing units (CPUs). The leaching study of CPUs was carried out by H2O2 30% and H2SO4 4 M mixture solution and aqua regia. Batch adsorption experiments were performed to investigate the effect of various experimental parameters such as pH, contact time, concentration, selectivity, and addition of the competitors of [Fe]3+ and [Cr2O7]2-. It was found that the optimum pH reached at pH 3 with average adsorption of equilibrium achieved at 300 min in all experiments. The adsorption kinetics of [AuCl4]- ion in single, binary, and multi component solutions were followed pseudo second order rate equation. The adsorption capacities of HT-NO3 to [AuCl4]- ion from Langmuir isotherm analyses were 1.104 x 10-4 mol/g (21.74 mg/g) for single solution, 0.725 x 10-4 mol/g (14.29 mg/g) and 0.806 x 10-4 mol/g (15.87 mg/g) for binary mixture of [Fe]3+ and [Cr2O7]2- ions and 1.410 x 10-4 mol/g (27,78 mg/g) for multi component solution with [Fe]3+ and [Cr2O7]2- ions. The desorption of [AuCl4]- ion from HT-NO3 was studied at room temperature using [OH]- ion as an anion exchanger. Furthermore, the reduction experiments were investigated by varying pH and molar ratio using reducing agents such as natrium citrate, ascorbic acid and tannic acid. The UV-VIS spectra showed that difference reducing agent influenced appeared surface plasmon resonance (SPR) in gold colloid formation. Gold recovery through adsorption-desorption and reduction processes were 0.043 mmol/L of 0.140 mmol/L (30.71%) and 1.476 mmol/L of 3.859 mmol/L (38.25%) for multi component solution of Au/Fe(III)/Cr(VI) and CPUs, respectively.

Kata Kunci : hydrotalcite, adsorption, desorption, reduction, recovery