Silver recovery from aqueous streams using ion flotation

Ion flotation was examined as an alternative method for the recovery of silver from dilute aqueous solutions containing complexing agents (thiosulphates). The dispersed-air flotation technique (laboratory micro-scale) was used for bubble generation, while the flotation experiments were performed using the cationic surfactant dodecylamine, (ethanol or water solutions); as a convenient frother, ethanol (0.5% v/v) was also added in most experiments. The main physicochemical parameters influencing the process, such as pH of the solution, concentrations of surfactant, of thiosulphate and of silver, as well as kinetic parameters, such as flotation time and gas flowrate, were evaluated. Employing the optimum defined conditions, high recovery of silver (approaching 100%) was obtained. The application of the proposed method for the treatment of spent solutions, generated after the development of X-rayed films, has also been examined.