Biosorption of silver from aqueous solutions using wine industry wastes

The potential of wine industry wastes (grape peel, seed, and stem) as alternative biosorbents to remove Ag from aqueous media was investigated in this work. Wine industry wastes were washed, lyophilized and pulverized to obtain the biosorbents. The powdered biosorbents were characterized in detail and several batch experiments were performed to found the most suitable conditions for Ag biosorption. Kinetic, equilibrium, and thermodynamic studies were also performed. The interactions Ag-biosorbent were elucidated by analyses before and after the biosorption. For all wastes, the maximum removal percentages were found using a biosorbent dosage of 3.0 g L-1 at pH of 7.0. The kinetic data were well represented by the pseudo-first-order model. The equilibrium was satisfactorily represented by the Sips model. The maximum biosorption capacities, found at 298K, were: 41.7, 61.4, and 46.4 mg g(-1) for grape peel, seed, and stem, respectively. Thermodynamically, the biosorption was a spontaneous, favorable, exothermic, and enthalpy-controlled process. The magnitude of H-0 indicated a physical sorption. These results showed that the wine industry wastes can be considered alternative efficient, low-cost, and eco-friendly biosorbents to remove Ag from aqueous media.