Analysis of aerosol collection by water droplets using Raman spectroscopy and ultrasonic levitator

This study investigates the ability of water droplets to capture ambient aerosol particles. It assesses the feasibility of using water droplets to effectively collect airborne radioactive waste generated by laser ablation during the decontamination of surface-fixed radioactive materials. Cerium dioxide (CeO2) particles, used to simulate radioactive material, are coated around a rotating cylinder and continuously ablated with a focused laser beam to produce CeO2 aerosols. These aerosols are then injected with a controlled air flow speed toward a water droplet suspended in an ultrasonic levitator, simulating the process of aerosol collection by a single water droplet without any mechanical contact. Raman spectroscopy is employed to quantify the aerosol collection efficiency of the levitated water droplet based on the intensity of Raman shifts obtained from the collected CeO2 aerosols during the delivery of the aerosol-laden airflow. The study confirms that CeO2 aerosols within the delivery airflow can be effectively captured by the levitated water droplet, primarily via interception and inertial impaction mechanisms. It also demonstrates that Raman spectroscopy accurately identifies the presence of CeO2 aerosols within water and correlates the intensity of Raman spectral shifts with the concentration of collected CeO2 aerosols. Therefore, Raman spectroscopy can be used to monitor real time aerosol collection performance during the decontamination process.