**2.1 Methodology for the transference of Ag (I)**

All products used had analytical grade and were used as received. The device used for this work is shown in Figure 1 and comprises a two-compartment cell, divided by a microfiltration membrane.

Fig. 1. Cell used for the recovering of silver, the membrane is located in between the two compartments

The feed phase was composed by different concentrations of AgNO3 (from 25 to 100 mg L-1) at various HNO3 concentrations (from 0.1 to 1 mol L-1). The stripping phase was composed by a solution of ascorbic acid and its concentrations were changed from 0.2 to 1.5 mol L-1. The feed and stripping solutions were added to compartments 1 and 2, respectively. The cell was then covered and the system was stirred. Aliquots were taken from both sides at several different times and, finally; Ag (I) content was analyzed by atomic flame absorption using a Perkin-Elmer Analyst 200 flame atomic absorption spectrometer. The pH of both the feed and stripping solutions was measured with the help of a combined glass electrode using a Methrom potentiometer (Titrino 716). The ascorbic acid's quantitative determination in both compartments was performed by Iodometry using a standard solution of iodine and starch as an indicator of endpoint.

The microporous membrane used, was a polyvinylidene difluoride (PVDF) hydrophilic membrane with 75% porosity, 125 µm thickness and average pore size of 0.22 µm (Millipore). During reduction of the silver ions, the membrane is used as a support for the metallic silver formations.

After every experiment, the membrane was removed from the system and the water was eliminated by evaporation. Subsequently, the membrane was weighed to determine the variation with respect to its initial weight.

The characterization of the metallic silver particles was carried out with a SEM (Scanning Electronic Microscope) Hitachi S-3000N coupled to an EDAX InCAx-sight analyzer. Contact angle of the microporous membrane with ascorbic acid solutions and Ag (I) in HNO3 solutions was measured using the CAM 200 from KSV Instruments Ltd. This unit has a measuring range of 0° to 180°, with an uncertainty of ± 0.1°.
