A highly recyclable nanoadsorbent based on carbon nanosphere-decorated polymer nanofibers for effective cationic dye removal

Abstract

The use of carbon nanomaterials in wastewater treatment often necessitates additional processes such as filtration and separation post-treatment, due to their high dispersion in aqueous media, which complicates their separation. To address these challenges, this study proposes a two-step approach: firstly, carbon nanospheres (CNSs) are synthesized from glucose via a hydrothermal process; secondly, CNSs are incorporated into electrospun polyvinyl alcohol nanofibers (PVA NFs). The PVA NFs act as a versatile host for CNSs, which provide effective adsorption sites on the fiber surface. The CNS@PVA NF composite offers a promising solution for creating highly efficient and easily separable adsorbents. The average diameter of the nanofiber composite was 318.61 ± 71.27 nm, in contrast to 257.14 ± 53.42 nm for pristine PVA. The CNS@PVA NF composite membrane demonstrated superior adsorption performance compared to pristine PVA NFs. With the incorporation of CNSs, the adsorption capacity underwent a remarkable increase from the initial 96.03 mg g⁻¹ for the PVA NFs to an impressive 405 mg g⁻¹ for the CNS@PVA NFs. The adsorption process followed the Langmuir and pseudo-second-order models, indicating a monolayer adsorption mechanism. Thermodynamic parameters, including changes in Gibbs free energy, entropy, and enthalpy, confirmed the spontaneous and endothermic nature of the adsorption process. Electrostatic, hydrogen bonding, and π–π interactions mediate the adsorption of CV dye by the CNS@PVA NFs. This study introduces a promising approach for fabricating reusable and easily separable nanofibrous adsorbents tailored for the removal of cationic dyes.