Adsorption of a Mixture of Daily Use Pharmaceuticals on Pristine and Aged Polypropylene Microplastics

The main goal of this study is the examination of polypropylene (PP) microplastics (MPs) as possible carriers of daily use pharmaceutical compounds. The selected compounds can be separated into three groups: (i) antibiotics (Trimethoprim, Metronidazole, Indomethacin, Isoniazid), (ii) anti-inflammatories (Ketoprofen, Diclofenac), and (iii) anti-hypertensive (Valsartan). Two types of PP MPs (virgin and UV-aged) were used in the experimental procedure, and the effect of time and the effect of the initial concentrations of the drugs were examined. The impact of various environmental factors such as pH, salinity, and natural organic matter were also explored. The last two factors were studied using real aqueous matrices such as wastewater and seawater. According to the obtained results, the highest uptake was observed in indomethacin (9.3 mg/g) and diclofenac (7.3 mg/g), owing to their physiochemical properties. Aged particles showed enhanced adsorption ability in accordance with the existing literature, as their adsorption capacity was between 0.5-1.5 times greater than that of the virgin ones. Regarding the desorption of compounds from the virgin and aged PP MPs at three different pH values, diclofenac and indomethacin exhibited the highest desorption capacity, while alkaline conditions favored the desorption ability of PP MPs for most of the target compounds.