Mass Transport of Dye Solutions through Porous Membrane Containing Tannic Acid/Fe³⁺ Selective Layer

Tannic acid (TA)-Fe³⁺ membranes have received recent attention due to their sustainable method of fabrication, high water flux and organic solutes rejection performance. In this paper, we present a description of the transport of aqueous solutions of dyes through these membranes using the transport parameters of the Spiegler-Kedem-Katchalsky (SKK) model. The reflection coefficient (σ) and solute permeability (PS) of the considered TA-Fe³⁺ membranes were estimated from the non-linear model equations to predict the retention of solutes. The coefficients σ and PS depended on the porous medium and dye molecular size as well as the charge. The simulated rejections were in good agreement with the experimental findings. The model was further validated at low permeate fluxes as well as at various feed concentrations. Discrepancies between the observed and simulated data were observed at low fluxes and diluted feed solutions due to limitations of the SKK model. This work provides insights into the mass transport mechanism of dye solutions and allows the prediction of dye rejection by the TFC membranes containing a TA-Fe³⁺ selective layer using an SKK model.