Fabrication and Pb2+ Adsorption Properties of Fibrous Cation-Exchange Materials from Waste Polystyrene

Polystyrene (PS) is widely used in small plastic products, contributing significantly to the amount of plastic waste generated worldwide. Thus, the development of simple and practical strategies to prepare high-value-added products from waste PS is of great importance. In this study, fibrous cation-exchange materials (PS-SO₃H) were prepared by sulfonating waste PS and evaluated in terms of their heavy-metal-ion adsorption properties. The PS-SO₃H fibers demonstrated excellent Pb²⁺ adsorption, with a maximum adsorption capacity (q_max) of 240 mg/g at pH 4–5. Fourier transform infrared spectroscopy and scanning electron microscopy confirmed the successful introduction of sulfonic acid groups into the PS fibers and formation of a porous surface, which enhanced the availability of adsorption sites. Mixed-ion adsorption experiments (Cd²⁺, Cu²⁺, Zn²⁺) revealed the greatest affinity for Pb²⁺ owing to its large ionic radius and high charge density. Adsorption followed a second-order kinetic model, and the Langmuir isotherm yielded a q_max of 256.41 mg/g. Fixed-bed column experiments indicated that the height-to-diameter ratio significantly influenced adsorption. The Bohart–Adams and BDST models effectively predicted column performance. Desorption tests showed 1.0-N HNO₃ achieved over 90% desorption efficiency. The results demonstrate the potential of PS-SO₃H fibers as efficient adsorbents for Pb²⁺ removal, indicating applications in wastewater treatment and environmental remediation.