Silver recovery by microbial electrochemical snorkel and microbial fuel cell
Mario Mitov, Elitsa Chorbadzhiyska, Ivo Bardarov, K.L. Kostov, Yolina Hubenova
Abstract
In this study, we demonstrate for the first time the use of the microbial electrochemical snorkel (MES) for silver recovery from aqueous solutions. For comparison, identical bioelectrochemical reactors in which the cathodes were connected through a 510 Ω load resistor (MFC) with the bio-anodes of well-acclimated sediment microbial fuel cells were operated at the same other conditions. Three different types of cathodes - silver foil, copper foil, and graphitized paper, were explored for silver recovery from AgNO3 solution. The data obtained show that the operation in MES mode is more advantageous than that in MFC mode in terms of both silver removal and recovery. The XPS analysis has proved that on the silver foil and graphitized paper cathodes the silver is recovered as Ag0 particles, while on the copper foil cathodes mixed Ag-Cu deposits are obtained due to the predominant electroless displacement of Cu by Ag+. The superiority of operation in MES mode was also confirmed by experiments performed with [Ag(S2O3)2]3- - containing solution, simulating exhausted photographic fixer. The total amount of silver was removed from the MES-catholyte for 24 hours, while during the operation in MFC mode a silver removal of 88.2±5.8 % was reached.