An assembled poly-4-vinyl pyridine and cellulose triacetate membrane and Bi2S3 electrode for photoelectrochemical diffusion of metallic ions

The transport phenomena across ion exchange membrane may be enhanced by applying various strengths inside or outside the system. The electrical current, generated by n-type semiconductor, is used to catalyse the separation of metal ions. The cation exchange membrane located between the two compartments allows both the separation and concentration of Mn+ (Ag+, Cu2+, Pb2+ and Ni2+). The flows of Mn+ from the aqueous solution to-and inside the membrane are monitored by the determination of the fluxes and the potentials. In this study, the four cations are investigated alone or in quaternary systems. From photoelectrochemical measurement, the gap of Bi2S3 is found to be indirect at 1.65 eV. The shape of photocurrent potential curve and the negative flat band potential (−1.02 VSCE) give evidence of n-type character. The conduction band (−1.25 VSCE) yields thermodynamically M2+ photoreduction and catalyzes the diffusion process. The photoelectrode Bi2S3 makes the flux twofold greater than that observed in the dark. In all cases, the potential of the electrode M2+/M in the feed compartment increases until a maximal value, reached at ∼100 min above which it undergoes a diminution. The membrane is more selective to Cu2+ and this selectivity decreases in the quaternary system.