A core-shell structured diffusion-bubbling membrane for efficient oxygen separation: Formation and transport properties

The newly developed core-shell structured molten oxide membranes with fast combined diffusion-bubbling oxygen mass transfer and theoretically infinite selectivity are of technological interest because of their high separation efficiency. In this article, a core-shell structured molten V₂O₅–Cu₂O- based diffusion-bubbling membrane was prepared by one-step thermal treatment of initial CuO–25 wt.% Cu₅V₂O₁₀ ceramic composite in a chemical field (under an oxygen partial pressure difference across the composite) above copper vanadate peritectic transformation temperature (816°C). Oxygen fluxes through the membrane were measured at 830°C, using either gas mixtures (O₂ + N₂) with different oxygen concentrations or air as feed gas at the shell of the membrane and helium (He) as sweep gas. Oxygen flux through the membrane with a shell thickness of 0.15–0.61 mm was 3.8·10^–8–1.4·10^–7 mol/cm²/s under an oxygen partial pressure difference of 0.1 –0.75 atm, respectively. The effect of oxygen partial pressure on the thickness of the membrane shell is found. The relationship between membrane shell thickness, oxygen partial pressure difference across the membrane, and oxygen permeation flux through the membrane is established. Oxygen permeation flux through the dual-phase MIEC membrane shell is described in terms of the diffusion model. Oxygen permeation flux through the membrane core is described both within the framework of the stationary model and nonstationary model for uniform (the membrane thickness is much larger than the characteristic distance of bubble dynamic relaxation) and accelerated (the membrane thickness is comparable to the characteristic distance of bubble dynamic relaxation) bubble motion in a viscous oxide melt, respectively.