Fabrication and characterization of xanthan gum nanofibers reinforced with thiosemicarbazide: adsorption of Pb²⁺ from an aqueous medium

Abstract

In this study, electrospinning was used to fabricate xanthan gum (XF) and thiosemicarbazide/xanthan gum (TXF) nanofibers crosslinked with ferric ions for effective Pb²⁺ adsorption. The produced nanofibers were investigated using several physicochemical methods. Both XF and TXF demonstrated thermal stability up to 800 °C, with mass losses of 79% and 75%, respectively. TXF had a surface area of 153.4 m² g^-1 and point of zero charge at pH 6.7. ATR-FTIR analysis revealed the existence of surface chemical functional groups such as -NH₂, -NH, and -C[double bond, length as m-dash]S owing to thiosemicarbazide reinforcement. XF and TXF displayed maximum adsorption capacities of 211.65 and 289.18 mg g^-1 at pH 6, 2.0 g L^-1 nanofiber dose, 22 °C, and after 40 min of contact shaking time. The adsorption process was investigated using several nonlinear adsorption models as well as by desorption and reusability investigations. Thermodynamics examination demonstrated the spontaneous, endothermic physisorption of Pb²⁺ onto XF and TXF. Ethylenediaminetetraacetic acid was selected as the most efficient eluent for Pb²⁺ removal from the nanofiber surfaces, with desorption efficiencies of 100% and 97% for XF and TXF, respectively. TXF and XF revealed remarkable sustainability, with reductions in adsorption capacities of only 7% and 12% of the initial removal efficiency after 10 cycles of adsorption/desorption, respectively. As a solid adsorbent for the removal of heavy metal cations, the produced TXF nanofiber demonstrated great sustainability and environmental friendliness.