The increasing carbon emissions from various fossil fuels have led to the search for efficient and clean energy sources to replace them. Proton exchange membrane fuel cells (PEMFCs) are a promising alternative, but the use of platinum as a catalyst material poses challenges due to its limited resources and low abundance. This study proposes an efficient method for platinum recovery while retaining spent membranes. The membrane and catalyst were separated using isopropanol, and the spent membrane was dissolved in a 50% ethanol solution to prepare the precursor for subsequent membrane regeneration. Hydrochloric acid (HCl) was used as the leaching agent, and the experimental parameters such as HCl concentration, H₂O₂ concentration, contact time, and operating temperature were optimized to achieve the highest platinum leaching rate. Finally, through isothermal leaching experiments, the leaching mechanism was investigated using the shrinking core model, indicating the involvement of both surface chemical and inner diffusion mechanisms in the platinum leaching process, primarily controlled by the inner diffusion mechanism. Under optimal conditions, the platinum leaching rate was about 90%, and the activation energy of the reaction was calculated to be 6.89 kJ/mol using the Arrhenius equation.

Calcium carbonate (CaCO₃) particles have attracted increasing attention as a promising material for drug delivery systems. In this study, coral remains were utilized as a raw material for a novel drug carrier. A series of pre-treatment and parameter experiments were conducted to synthesize sub-micron spherical CaCO₃ particles. The CaCO₃ particles exhibited uniform size distribution, with the minimum mean size being only 344 nm. The effects on the CaCO₃ crystal phases and particle sizes were also discussed in this study. Drug loading experiments were also conducted to assess the feasibility of the CaCO₃ drug carrier. We loaded TRITC-Dextran into CaCO₃ particles for the simulation experiments. The loading capacity reached up to 9.6 wt.%, which was as high as common drug carriers such as liposomes. In this study, we aimed not only to tackle the local environmental issues caused by coral remains, but also to synthesize a suitable drug carrier for cancer therapy using the outstanding properties and low cost of CaCO₃.