Fabrication of Novel Electrospun Polyacrylic Acid/Chitosan Nanofibers for Organic Dye Adsorption from Aqueous Solution

Abstract

Background: In this study, electrospun nanofibrous composites made of polyacrylic acid (PAA) and chitosan (Chi), specifically at a 70:30 weight ratio, are successfully fabricated, characterized, and evaluated for performance. These composites are designed to adsorb methylene blue (MB) dye from aqueous solutions with high efficiency. Methods: The high surface area required for better adsorption kinetics was provided by uniform, bead-free nanofibers with an average diameter of 276.15 ± 108.20 nm, which were produced using optimized electrospinning conditions. The material’s applicability was validated by structural and surface characterizations: Zeta potential examination indicated the fibers were negatively charged (-21.5 ± 4.78 mV), allowing for robust electrostatic contact with the cationic MB dye, while Fourier-transform infrared (FTIR) analysis confirmed successful polymer interaction by typical peak shifts. By exhibiting pseudoplastic (shear-thinning) behavior, which is essential for steady fiber creation, rheological evaluations provided additional support for the procedure. Results: The composite performed well under ideal batch adsorption conditions (pH 6, 25ºC), attaining a removal efficiency of over 90% and a maximum adsorption capacity (Qm) of 78.125 mg/g. While isotherm modeling demonstrated a better fit with the Langmuir model [(coefficient of determination (R2 = 0.9789)], confirming monolayer adsorption on homogeneous sites, kinetic analysis significantly supported the pseudo-second-order model (R2 = 0.9859), suggesting that chemisorption is the rate-limiting phase. Performance was dose-dependent, and at a starting concentration of 200 mg/L, capacity increased to surpass 65 mg/g. Also, 50 - 60% of the total capacity was caught by the quick initial adsorption in the first two hours, and equilibrium was reached in around eight hours. Conclusions: All of these quantitative findings point to the polyacrylic acid-chitosan (PAA-Chi) composite nanofibers as a practical, affordable, and extremely effective adsorbent that provides a long-term way to treat wastewater that contains cationic organic dyes.