Development and characterization of PAN/GO-tyrosine hollow fiber membranes for enhanced heavy metal adsorption and SPME-spectrophotometric detection

Abstract

PAN-based fiber membranes have attracted significant attention owing to their potential in heavy metal removal. However, they show low selectivity, poor hydrophilicity, and low adsorption efficiency, which limits their performance. In the present investigation, PAN/GO-Tyr hollow fiber (PAN/GO-Tyr HF) membranes were fabricated via the phase inversion of PAN/GO, and subsequent grafting of tyrosine was done via self-polymerization to the surface of the membrane. FESEM characterization showed significant changes in the morphology of PAN/GO-Tyr HF, such as the presence of thumb-like pores in the outer layer of the membrane. AFM results of PAN/GO-Tyr HF revealed a more homogeneous surface with low roughness. Results of derivative and cumulative BJH adsorption showed that micropores in the structure of PAN/GO-Tyr HF were in the size range below 20 Å, while PAN/GO HF had a higher percentage of mesopores with larger pores. Furthermore, BET analysis showed that PAN/GO-Tyr HF had more complex pores, greater surface area, and larger hysteresis behavior. A detailed assessment was conducted on the impact of surface alterations on several adsorption processes as well as adsorption kinetics characteristics. Adsorption kinetics fitted better with the pseudo-second order model and confirmed multiple layer adsorption mechanism and chemisorption process. Finally, the fabricated hollow fiber was used as an adsorbent for SPME-spectrophotometric detection. The adsorbent demonstrated good linearity and correlation coefficients over the concentration ranges of 0.005–4.0 ppb (r² = 0.989), 0.01–10.0 ppb (r² = 0.974), 0.003–2.0 ppb (r² = 0.999) and 0.05–1.0 ppb (r² = 0.989) and detection limits of 0.004, 0.005, 0.002 and 0.01 ppb for As³⁺, Cu²⁺, Sn²⁺ and Pb²⁺, respectively. Furthermore, reusability of the membrane was evaluated for six adsorption–desorption cycles.