Fabrication of ceramic nanofiltration membrane for organic solvent separation

Abstract

Organic Solvent Nanofiltration (OSN) separates solutes dissolved in organic solvents, which has benefits such as low energy consumption and ease of scale-up than conventional separations such as solvent extraction. OSN membranes are generally made of various polymers, thus, unstable at high temperatures and swelled in specific organic solvents. Recently, ceramic nanofiltration membranes (CNM) have been proposed as a potential solution to overcome the limitations of polymeric OSN due to the high mechanical, thermal, and chemical stability. However, the current preparation methods for CNM cannot be applied for mass production at low cost. In this study, OSN membranes with a precisely controlled molecular weight cutoff (MWCO) were prepared by the filtration coating of ceramic membrane and tested for separating oil and pharmaceutical products. In this study, the various size of γ - Al2O3 nanoparticles are prepared by the sol-gel method (NPs), then loaded into the pores and on the surface with 10 bar of transmembrane pressure and 15 cm/s of the cross-flow velocity. The fabricated CNM(f-CNM) has a coating layer with a thickness of 2 μm, permeability of 49 LMH/bar, and MWCO of 2,000 Da, whereas the commercial CNM(c-CNM) fabricated with repeated coating process has four coating layers with permeability of 21 LMH/bar, and MWCO of 2,000 Da. In order to investigate the potential applicability of f-CNM for OSN, f-CNM is applied for thermal and solvent resistance cases, which is hardly applied to polymeric OSN membranes. For the recycling of used lubricants, the experiment was conducted at high temperature for reducing viscosity of used lubricants. The performance of the f-CNM with regard to the concentration of heavy metals (Cd2+, Pb2+, Cr+, and As2+) is below the regulation of recycling lubricants in Korea during the treatment of used lubricants. Also, the separation of antibiotics (Daptomycin, DAP) in Dimethylformamide (DMF) was conducted. DAP synthesis is carried out in diverse organic solvents such as trifluoroacetic acid, DMF, methanol, etc. f-CNM is also applied in DAP synthesis, especially downstream processing. After the f-CNM separation system, DAP in DMF was removed over 90% on permeate side with the f-CNM and 6.6 times recovered on the retentate side with the fabricated CNM. Overall, this work indicated the relatively simple and scalable fabrication process of CNM that has a high potential in practical applications for organic solvent permeation.