Medical masks depolymerized with acidic deep eutectic solvents and applications for oil absorption

The disposal and utilization of discarded masks have gained social attention, especially during the COVID-19 pandemic. The need to explore environmentally friendly ways to minimize their negative impacts and convert them into valuable materials is crucial. Deep eutectic solvents (DESs), which are known for their desirable green chemistry attributes, offer an attractive strategy for polymer processing. In this study, four model DESs—constituting hydrogen bond acceptors like choline chloride or benzyltriethylammonium chloride and donors such as oxalic acid or p-toluenesulfonic acid monohydrate—were selected to process polypropylene surgical masks after preliminary screening. The DESs were characterized using infrared spectroscopy and evaluated for basic physicochemical properties like viscosity, conductivity and pH values. A continuous heating strategy was developed to improve the treatment process, and the contribution of DES on the degradation was evaluated through microscopic structure examination, fluffiness, density, and particle metrics analysis. Gel permeation chromatography was also used to analyze the degraded products. The resulting powders form of mask material was then explored for gasoline and diesel fuel adsorption. The modified material showed up to 4.06-fold improvement in adsorption capacity, with maximum uptake of approximately 40 g/g. Oil adsorption reached equilibrium in 10 to 15 min, and the powder material also exhibited enhanced oil retention and reuse after desorption. This research provides a feasible strategy for recycling polypropylene-based medical waste and encourages the development of effective oil sorbents from waste masks.