Healthcare Waste-Derived Pyrolytic Char as a Functional Porous Carbon Material for Electrochemical Sensing of Estriol

Abstract This study presents an integrated approach for the sustainable management of healthcare waste (HCW) through slow pyrolysis and the application of the resulting pyrolytic char (Pc) for electrochemical sensing of estriol (E3), an emerging contaminant, in environmental and pharmaceutical samples. Pc was produced by the pyrolysis of HCW at 400 °C and characterized by Brunauer–Emmett–Teller (BET) analysis, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Pc exhibited a mesoporous structure with a specific surface area of 6.9 m² g⁻¹, a pore volume of 0.026 cm³ g⁻¹, and an average pore diameter of 14.44 nm. Morphological analysis revealed a heterogeneous surface with a composition dominated by carbon (61.3%), oxygen (23.6%), silicon (9.6%), and aluminum (5.5%). A new conductive ink formulation was developed by modifying a commercial carbon-based ink with HCW-derived Pc, aiming to fabricate advanced and portable screen-printed electrodes for electrochemical E3 sensing. Pc proportions ranging from 1% to 10% were investigated. The sensor exhibited a high sensitivity of 58.5 nA L µmol⁻¹ and achieved a detection limit of 47.1 nmol L⁻¹ over a linear concentration range from 1.0 to 216.0 µmol L⁻¹. Recovery assays were performed in tap water, lagoon water, and pharmaceutical cream samples, yielding recoveries between 97.7% and 105.4% without the need for any sample pretreatment. These findings demonstrate that HCW-derived Pc is a promising, efficient, and sustainable sensing material for steroidal hormones, providing an integrated approach to waste valorization and environmental protection.