Efficient removal of diclofenac and phosphate anions from aqueous solutions using electrospun quaternized chitosan/poly(vinyl alcohol) fibrous membranes

In this study, chitosan (CS) was first grafted with [3-(methacryloylamino)propyl] trimethylammonium chloride (MAPTAC) with the help of the free radical initiator ammonium cerium(IV) nitrate, and mixed with poly(vinyl alcohol) (PVA) to prepare fibrous membranes by electrospinning. After that, the quaternized membranes were cross-linked with glutaraldehyde (GA), named g-CS/PVA/GA, and were applied to efficiently adsorb diclofenac (DCF) and phosphates in aqueous solutions. Conditions for the preparation of such electrospun fibrous membranes were first optimized by inspecting the surface morphology using field emission scanning electron microscopy (FE-SEM), and then the textural properties and chemical composition of as-prepared fibrous membranes were determined. Batch contact-time experiments revealed that the adsorption of DCF and phosphates on the fibrous membrane reached equilibrium within 6–8 h. Moreover, the prepared membranes exhibited the highest adsorption ability for DCF and phosphates at an equilibrium pH of 9.5 and 6.0, respectively, highlighting the crucial role of the anionic forms of DCF and phosphates. Under such an equilibrium pH, the adsorption isotherms revealed that the adsorption capacities of DCF and phosphates, expressed as total phosphorus (P), on the fibrous membranes with a mass ratio of MAPTAC to CS of 5 were 369.5 and 57.6 mg/g, respectively, at 25 °C. More than 82.7 % of DCF and 75.6 % of phosphates of the original amounts of adsorption remained after five repeated adsorption-desorption tests. That is, the prepared g-CS/PVA/GA fibrous membranes possessed good reusability and provided promising potential for the removal of anionic species from dilute solutions.