Polyaminated electrospun chitosan fibrous membranes for highly selective removal of anionic organics from aqueous solutions in continuous operation

In this study, the fibrous membranes were fabricated from chitosan (CS)/poly(vinyl alcohol) (PVA) polymers by electrospinning and were then cross-linked by glutaraldehyde (GA). After that, the fibrous membranes were soaked in a mixture of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and branched polyethylenimine (PEI) for polyamination. The as-prepared membranes were used for the removal of two model organics methyl orange (MO) and tetracycline (TC) from dilute solutions. Morphological, physicochemical, and textural properties of the prepared fibrous membrane were characterized. It was observed that the adsorption of MO and TC on the fibrous membranes reached equilibrium within 20 h. More importantly, the membranes showed the highest adsorption for MO and TC at pH 4.0 and 8.0, respectively, which highlighted the role and importance of the anionic forms of the organics. At such a specific pH, adsorption isotherms revealed that the maximum capacity of MO and TC reach 70.8 and 16.0 mg per gram of the membrane at 25 °C. To highlight the selective adsorption of anionic organics on the prepared membranes, a basic dye methylene blue (MB) was used as a binary pair with MO or TC in the solution. Under the conditions studied, the removal of MO and TC was comparatively high up to 43.6% and 27.5%, respectively, from continuous filtration-adsorption experiments within 24 h; however, the removal of MB was only 1–2%. The present results demonstrated that the prepared PEI-grafted fibrous membranes were reusable and could provide high selectivity toward anionic pollutants in dilute solutions.