Biosorption of gold(III), palladium(II) and silver(I) from aqueous solution onto low-cost durio zibethinus husk

Abstract

Biosorption is one of efficient low-cost process of precious metal ions recovery from aqueous solution. This study investigated the biosorption of gold(III), palladium(II) and silver(I) ions from aqueous solution using Durio zibethinus husk (DZH) as a biosorbent. The DZH characterized by FT-IR (Fourier transform infrared) spectroscopy, showed that it has hydroxyl, carboxyl and phenolic groups, which have possibility to adsorb precious metal ions from aqueous solution. The ability of DZH was investigated using batch biosorption system. Several parameters were studied such as contact time, pH, adsorbent dosages, initial metal concentration, and temperature. The optimum conditions were achieved to give the adsorption percentage of 98.50, 93.88 and 67.18 (%) for gold(III), palladium(II) and silver(I), respectively. The experimental data was fitted very well the pseudo-second-order kinetic model for both of gold(III) and palladium(II), and pseudo-first-order kinetic model for silver(I), respectively. Experimental results were also analyzed by the Langmuir, Freundlich and Dubinin-Reduskevich isotherm equations at different temperatures. The results shows that the biosorption of gold(III), palladium(II) and silver was follow Langmuir isotherm model for all temperatures with the maximum biosorption capacity was obtained to be 500.00, 30.30 and 3.66 mg g-1, respectively. The fact that the Langmuir model fits the experimental data very well shows that the surface of DZH was homogeneous. The thermodynamic properties (?G°, ?H° and ?S°) were also studied at three different temperatures (30, 40 and 50oC). Negative value of ?H° for gold(III) and silver(I) confirmed the exothermic nature of adsorption processes, whereas the positive value of palladium(II) adsorption showed endothermic in nature. The activation energy (Ea) of the biosorption of gold(III), palladium(II) and silver(I) were estimated from the Arrhenius equation and found to be 21.15, 70.28 and 31.56 kJ mol-1, respectively, shows that all the metal studied was controlled by chemical mechanism since the value of activation energy more than 4 kJ mol-1. The verification of adsorbed gold(III) on DZH surface was done by Field emission scanning electron microscopy-energy dispersive X-ray (FESEM-EDX), indicating that the atomic percentage of gold was detected by 4.12 (%).