Selective separation of methylene blue from MB/AY61 mixtures using a non-fluorinated PVA–CA membrane coupled to activated carbon

Selective dye separation from complex aqueous mixtures remains challenging due to competitive interactions and weak mass transfer driving forces. In this study, a non-fluorinated poly(vinyl alcohol)–cholic acid (PVA–CA) polymer inclusion membrane was developed for selective transport of methylene blue (MB) from binary mixtures containing Acid Yellow 61 (AY61). FTIR, SEM, and TGA analyses confirmed successful incorporation of cholic acid and formation of a porous membrane structure favorable for mass transfer. Transport experiments showed complete rejection of AY61, while MB exhibited high selective permeation, especially in binary systems, driven by interfacial adsorption phenomena. To enhance transport performance, an olive-mill-wastewater-derived activated carbon (1383 m 2 ·g −1 surface area, 1.141 g MB·g −1 capacity) was introduced into the receiving phase, increasing permeability and diffusion coefficients by up to 22% and 127%, respectively, through a pseudo-infinite sink effect that reduced back diffusion and sustained the transmembrane concentration gradient. Colorimetric analysis indicated largely reversible MB adsorption on the membrane, supporting regeneration, and a preliminary cost estimate placed the adsorbent contribution at only a few thousandths of a US dollar per gram of MB recovered. This hybrid membrane–adsorption system offers an efficient, low-cost, and scalable strategy for selective dye separation and wastewater treatment, while minimizing secondary pollution and improving operational stability.