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Acetaminophen is the most commonly used drug worldwide for relieving pain and fever. Consequently, it has been detected in groundwater in different areas of the world. In this study, acetaminophen removal from water using a dielectric barrier discharge (DBD) system, operated in the open air, was investigated. Our results show that treating water for only 0.5 min at 1, 5, 25, 50, 75 and 100 mg L–1acetaminophen concentration resulted in the removal of 98.85%, 99%, 89.16%, 42.84%, 33.86% and 32.87% of the initial acetaminophen amount, respectively. These removal rates increased significantly when the treatment duration was extended to 2 min, reaching 100%, 99.40%, 99.66%, 90.62%, 85.89% and 77.09% of the initial amount of acetaminophen at similar concentrations, respectively. The initial pH of the solution causes a negligible variation in the degradation of the acetaminophen; therefore, it was not found as an important parameter. The pH of the solution decreases during the plasma treatment. The final pH of different solution was always within 15%, regardless of the initial concentration. Optical emission spectroscopy of the DBD during operation revealed the prominent reactive species and possible reaction pathways. The acetaminophen removal efficiency of the DBD system used in this study for water treatment is higher than that reported for other systems employed in previous studies. Moreover, as the discharge is generated here in the open air, it is very cost-effective. Further studies are recommended to investigate DBD operated in open air for the removal of other organic pollutants from water.

Caffeine is a well-known central nervous system stimulant, which can cause anxiety, insomnia and nervousness. Domestic wastes of caffeinated drinks, beverages and chocolates are the major sources for entry of caffeine in the environmental system. Caffeine has been widely detected in natural water resources. The current study describes a method for efficient removal of caffeine from aqueous solution by a laboratory scale dielectric barrier discharge (DBD) in open air. Caffeine concentrations in various sample solutions were monitored by high-performance liquid chromatography, and the degradation products were identified by directly injecting the sample to mass spectrometer. The consequences of varied parameters such as input power, initial concentration and initial pH of the solution on the degradation of caffeine were investigated. Removal efficiency of caffeine from aqueous solution was 72.6% and 96.6% for the initial concentrations of 100 and 1 µg/mL, respectively, at initial pH 7 after 4 min treatment in DBD plasma system with 60 W input powers. Caffeine removal efficiency was less in acidic solutions (initial pH 4), and insignificant degradation was observed in alkaline solutions (initial pH 10). Furthermore, the degradation of caffeine was also enhanced by increasing the input power in DBD system. The DBD system used in this study has been considered to be fast, effective and economical. It was operated at atmospheric condition in open air without using catalyst, expensive gases or organic solvents, and significant degradation of caffeine was achieved in a short (4 min) treatment time.