Preparation, characterization and kinetics study of chitosan/PVA electrospun nanofiber membranes for the adsorption of dye from water

In this study, chitosan (CS) nanofibers with two different degrees of deacetylation (DDA) were first successfully fabricated from its solution in 1% aqueous acetic acid solution by mixing with poly(vinyl alcohol) (PVA) solution at a weight ratio of 50/50 via the electrospinning method. Then, the CS/PVA membranes were further modified by glutaraldehyde vapor. The prepared nanofibers were characterized by field electron scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), the tensile test, the contact angle test, the weight loss test and the adsorption test for Congo red (CR). SEM analysis showed defect-free nanofibers and a uniform diameter distribution, with an average diameter of 100-125 nm. Subsequently, FTIR spectroscopy, XRD and TGA indicated that the modified CS/PVA membranes had a relatively higher thermal stability, because the thermal decomposition temperature of the unmodified CS/PVA membranes (similar to 250 degrees C) increased to a higher temperature (similar to 300 degrees C) for the modified CS/PVA. The nanofiber membranes after modification possessed better mechanical tensile properties. The membranes with lower DDA had a relatively higher tensile strength, which can withstand the maximum tensile strength of up to 6.36 MPa. Furthermore, the resulting membranes showed excellent hydrophilicity and kept their stability in distilled water, acidic, and basic media for 20 days. In the adsorption study, the maximum adsorption capacity of the membrane for CR was 358 mg/l in the optimum operating conditions of 25 degrees C, pH = 6, 0.3 g membrane and 50 ml of 100 mg/l CR solutions. The resulting nanofibers membranes showed a better fitting to the Langmuir isotherm model and pseudo-second-order kinetic model.