Electrochemical sensors based on track-etched membranes for rare earth and heavy metal ion detection

Electrochemical sensors were developed using track-etched polyethyleneterephthalate (PET TeMs) membranes modified by UV-initiated graft copolymerization to produce PET TeMs-g-p(NHMA-co-HEMA). The modification process, structural features and physicochemical properties of the resulting membranes were comprehensively characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Energy-Dispersive X-ray spectroscopy (EDX), UV-visible spectrophotometry (colorimetric method), gas permeability measurements and contact angle analysis. Optimal grafting conditions were achieved at a monomer concentration of 10% (NHMA : HEMA = 70 : 30), UV irradiation time of 60 min and UV lamp distance of 10 cm at a temperature of 38-40 °C. The modified membranes were subsequently used in an electrode system to determine Eu³⁺, Gd³⁺, La³⁺, Ni²⁺ and Pb²⁺ ions using square-wave anodic stripping voltammetry (SW-ASV). The sensors were evaluated over this concentration range of 1 × 10^-7-1 × 10^-4 for Ni²⁺, 0.5 × 10^-7-1 × 10^-5 M for Pb²⁺, 0.5 × 10^-6-5 × 10^-5 M for Eu³⁺, 0.5 × 10^-6-0.5 × 10^-4 M for Gd³⁺, and 1 × 10^-6-1 × 10^-4 M for La³⁺, with detection limits of 8.5 × 10^-7 M for Eu³⁺ (R ² = 0.96), 6.3 × 10^-6 M for Gd³⁺ (R ² = 0.975), 2.51 × 10^-6 M for La³⁺ (R ² = 0.96), 8.7 × 10^-7 M for Pb²⁺ (R ² = 0.98), and 7.4 × 10^-6 M for Ni²⁺ (R ² = 0.98). The results indicate a significant improvement in electrochemical performance due to the grafted PET TeMs-g-p(NHMA-co-HEMA) structure and the developed sensor demonstrates high applicability and stable performance for the detection of rare earth and heavy metal ions in tap water as well.