Affinity filtration by a coating of pyrolyzed fish scale colloids on microfibres for removing phenol/quinone compounds from alcohols. Issue 5 (October 2021) - Ong, Pin Jin
Abstract: This study utilizes the elementary grains of fish scale to construct a filtration membrane, which manifests organic solvent nanofiltration (OSN) efficacy relying on a microflow-promoted adsorption percolation mechanism. Specifically, a colloidal suspension of Barramundi fish scales (BFS) in concentrated sulfuric acid was blended with polyvinyl alcohol (PVA) in aqueous medium. The resulting suspension was thereafter coated on two pieces of cellulose filtration paper (CFP), followed by sandwiching the two coating layers together. The resulting stacked sheet was then subjected to partial pyrolysis under slight compression to complete the membrane preparation. The resulting membrane possesses a fibrous matrix in which individual cellulose fiber is wrapped by a selective layer comprising of cubic-shaped grains that aggregate together and leave nano-crevices. The tortuous pores amongst the fibers act as permeation channels where the coating layer chafes with the permeate stream. The membrane offers high retentions (> 90%) for Sudan IV and Rose Bengal in solvent solutions of ethanol and isopropanol respectively. The assessments suggest that the membrane separation proceeds via a hybrid mechanism, by which convective feed flowing through the permeation channels disperses into the nano-crevices of the selective layer, where pore diffusion facilitates adsorption due to the increase in liquid-solid contact. In addition, the fact that liquid streams chafe with the rough selective layer amidst the permeation channels increases residence time. The friction, pore diffusion, adsorption and buildup mutually sustain the solute retention rates. Graphical Abstract: An affinity NF membrane derived from Barramundi fish scale presents potential to strip phenolic dyes from alcohol solvents via the selective adsorption-sustaining-adsorption mechanism, which critically relies on microflows penetrating the crevices of the selective layer that has a cobblestone-base-like structure. ga1 Highlights: A flat sheet membrane comprises micron-fibers with a selective sheath. Selective layer derive from fish scale colloid coating bound by polyvinyl alcohol. Coating is converted to an affinity selective layer via pyrolysis. Selective layer possesses fractal particles and nano interstitial voids. Separation relies on affinity adsorption and accretion of solutes.