This study aimed to develop magnetic Fe₃O₄/sugarcane bagasse activated carbon composite for the adsorption of arsenic (III) from aqueous solutions. Activated carbon (AC) was prepared from sugarcane bagasse by chemical activation using H₃PO₄ as an activating agent at 400 °C. To enhance adsorption capacity for arsenic, the resultant AC was composited with Fe₃O₄ particles by facile one-pot hydrothermal treatment. This method involves mixing the AC with aqueous solution of iron (II) chloride tetrahydrate, polyvinyl pyrrolidone (PVP), and ethanol. Batch adsorption experiments were conducted for the adsorption of As (III) onto the composite. The effects of pH, adsorbent dosage, and contact time on the arsenic adsorption were studied. The result showed that the composite could remove the arsenic from the water far more effectively than the plain AC. The highest percentage of arsenic removal was found at pH at 8, adsorbent dose of 1.8 g/L, and contact time of 60 min. Langmuir and Freundlich adsorption isotherm was used to analyze the equilibrium experimental data. Langmuir model showed the best fit compared to the Freundlich model with a maximal capacity of 6.69 mg/g. These findings indicated that magnetic Fe₃O₄/sugarcane bagasse AC composite could be potentially applied for adsorptive removal of arsenic (III) from aqueous solutions.

Real-time monitoring of membrane degradation is critical for enhancing the durability and reliability of proton exchange membrane fuel cells (PEMFCs). Chemical degradation of the Nafion® membrane results in the release of fluoride ions (F⁻), making F⁻ concentration a direct and quantifiable indicator of membrane health. This study presents a fluoride ion sensing system capable of continuous, in situ detection using a LaF₃ crystal-based ion-selective membrane paired with an Ag/AgCl reference electrode and integrated with a low-threshold metal-oxide semiconductor field-effect transistor (MOSFET) for signal amplification. A miniaturized bipotentiostat was used as a power supply for I-V outputs, enabling high-resolution tracking of dynamic fluoride ion fluctuations. Both a commercially available sensor and a lab-fabricated LaF₃-based sensor demonstrated stable reversible, and sensitive responses across a wide concentration range. The system effectively captured real-time changes in F⁻ concentration associated with membrane degradation, validating its suitability for operando diagnostics. The compact design, low power requirements and consistent performance of the sensor support its potential for miniaturization and direct integration into PEMFC stacks. Such embedded monitoring would enable continuous non-invasive assessment of membrane condition, early detection of degradation and predictive maintenance, ultimately extending fuel cell service life and operational efficiency.