Nanofiltration of Aqueous Dye Solution through the Diffused Rough Pores of a Carbonaceous–Kaolinite Amalgamation Membrane

Abstract

This study demonstrates a supported carbonaceous–kaolinite composite membrane that has a highly porous medium with prevalent submicron pores. These pores exhibit a diffused configuration assembled by carbonaceous (Cn) nodules and kaolin particles wrapped by a thin Cn sheath. The membrane was prepared by three steps: (i) applying an acrylic–kaolin coating to a porous stainless-steel tube; (ii) compressing the dried coated layer in an isopress chamber to ratchet the amalgamated coating layer; and (iii) conducting partial pyrolysis to achieve the Cn-kaolin membrane (CKM), exhibiting a rough and diffused CK amalgam frame inherited from the intense compression. The membrane displays attractive nanofiltration performance, that is, >95% rejection over 30 h and mean permeances of 4–10 L/h·m2·bar for the four probe dyes in water (50 ppm) with different molecular masses and charge types. The intricate and rough pore channels of the membrane agitate tiny turbulences amid the thin permeate streams, which drives an effective solute interaction with the pore walls. Solute retention occurred through entrapment along the pore walls, leading to a boundary layer, which assists further retention via dragging, circulating solute molecules, and transferring them to the retentate. The filtrate permeates through nanopores of the CK amalgam frame.

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