Recycling polystyrene and integrating graphite particles: A circular economy strategy for sustainable and enhanced electrochemical sensor manufacturing

The recycling of polystyrene (PS)-based cups for the additive manufacturing of sustainable, cost-effective, and high-performance electrochemical devices is presented here for the first time. In this approach, we integrated graphite (Gpt, a conductive material) within the PS matrix (a thermoplastic component) to design alternative conductive filaments for the production of new electrochemical sensors using a 3D pen (an easy-to-use and transportable tool). Various material ratios were examined, with the Gpt/PS (50:50) composition showing enhanced electrochemical performance without compromising printability. Structural, morphological, and thermal information on the proposed materials was accessed using Raman and infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The electrochemical features of the material were studied by electrochemical impedance spectroscopy and voltammetric measurements using model species such as [Fe(CN)₆]^3−/4−, hexaminruthenium (III) chloride, and dopamine, highlighting a charge transfer resistance (Rct) value of 1.5 kΩ and an elevated electroactive area of 49.3 mm² due to the electrical properties offered by Gpt. Additionally, a differential pulse voltammetry based method was developed for sulfanilamide antibiotic detection, a molecule of interest in various fields (pharmaceutical, food, and environmental). Noteworthy linear ranges (1–10 μmol L^-1 and 10–50 μmol L¹), a limit of detection (LOD) of 0.3 μmol L⁻¹, high intra- and inter-electrode precisions (RSD < 2.2 %), and selectivity even in the presence of other antibiotics were observed. When applied to real samples, such as pharmaceuticals, water, and milk, recoveries close to 100 % demonstrated the accuracy and reliability of the electrochemical analyses. These results validate the performance of the proposed 3D-printed sensor and underscore a sustainable electrochemical investigation in alignment with circular economy precepts.