Optimized electrospun Schiff-base alumoxane/PAN nanofibers for lead and cadmium adsorption: characterization & RSM analysis

This study details the preparation and evaluation of a nanofibrous composite adsorbent comprising polyacrylonitrile (PAN) as the polymer matrix and Schiff-base alumoxane (SBA), designed for the adsorption of heavy metal cations Pb²⁺ and Cd²⁺. The nanofibrous structure provides an extensive surface area for effective adsorption. Key factors such as solution pH, nanoparticle concentration, initial ion concentration, and contact time were systematically examined using response surface methodology (RSM) within a central composite design (CCD). The SBA/PAN nanocomposite nanofibers were synthesized through an electrospinning process, followed by a dip-coating technique, and subsequently characterized for their adsorption capabilities. The statistical analysis revealed that the model terms significantly influenced the adsorption process, with "Prob > F" values much less than 0.0500. The optimization of the process, achieved through the response surface optimization technique, led to a maximum removal efficiency of 97.22% for Pb²⁺ and 93.87% for Cd²⁺ under optimal conditions: initial ion concentration of 36.87 ppm, nanoparticle concentration of 4.02 wt.%, pH of 6.40, and a contact time of 69.11 min. Adsorption capacities of 35.84 mg/g for Pb²⁺ and 34.61 mg/g for Cd²⁺ were observed under these conditions. Reanalysis of isothermic and kinetic data confirmed Langmuir for Pb²⁺ and for Cd²⁺, with pseudo-second-order kinetics (R² > 0.99) indicating chemisorption as the dominant mechanism. These findings demonstrate the potential of SBA/PAN nanocomposite nanofibers as effective adsorbents for heavy metal removal from aqueous solutions.emoval from aqueous solutions.