Continuous Supercritical CO₂ Process using Nanofiltration by Inorganic Membrane

Abstract

Nanofiltration using inorganic membranes was conducted to develop a continuous process in supercritical CO 2 . Inorganic membranes of various sizes (1, 5, 50, 300 kDa), materials (Al 2 O 3 /TiO 2 /ZrO 2 , Al 2 O 3 /ZrO 2 / TiO 2 ), and modules (one and three channels) were used for the experiments. The effects of fluid viscosity and density, membrane active layer thickness, number of channels, pore size, and the flux of a fluid were analyzed when supercritical CO 2 (sc-CO 2 ) passed through the membrane. In the case of PE6100 surfactant, it was confirmed that sc-CO 2 passed through the membrane at a flow rate and transmembrane pressure (∆P) greater than 10 mL/min and 0.04 MPa, respectively, although the size of the surfactant was larger than that of the membrane pore. The phenomena were proven to have been caused by the folding effect. In the case of microemulsions using NP-4 and H 2 O, it was confirmed that water adsorbed on the membrane surface passed through at ∆P greater than 0.7 MPa. Based on these findings, experiments were conducted to separate microemulsions and dispersions. The experimental results indicated that microemulsions achieved 47% separation efficiency and 90% surfactant recovery efficiency due to the displacement of metal ions through the water adsorbed on the membrane surface. Conversely, dispersions yielded high separation efficiency. Also, the correlation between the contaminant size and the membrane pore size was confirmed through SEM images.