Study on the regeneration of activated carbon adsorbed with radon by using a deep depressurization method

Abstract

Objective: To develop a heating-free, rapid, and efficient method for the regeneration of activated carbon by introducing deep depressurization. Methods: A validation experimental setup was designed to systematically investigate the impacts of various desorption methods, durations, and conditions on the desorption effectiveness of activated carbon with adsorbed radon and water. Consecutive repetitive and expanded experiments were carried out. Results: The combination of continuous ventilation and deep depressurization was proved the most effective in the desorption of activated carbon. Considering factors such as overall energy consumption and time, the optimal desorption duration for activated carbon was determined at 2 ​h. Reducing the relative humidity of radon-laden air and increasing the desorption environmental temperature significantly enhanced the desorption rate. Under a temperature range of 24–25°C, a relative humidity range of 5%–15%, and a flow rate of 0.3 ​L/min, a desorption rate of 85% was achieved for 122.5 ​g of activated carbon after 2 ​h of desorption. Moreover, the desorption results remained stable throughout 10 repetitions. Further experiments on a kilogram-scale activated carbon bed demonstrate that under a vacuum level meeting the requirement for moisture evaporation and an appropriate flow rate, the desorption rate of the activated carbon reached that of a smaller activated carbon bed, independent of the shape of the activated carbon bed. Conclusion: The deep depressurization method shows great promise as a rapid and efficient online method for the regeneration of activated carbon with adsorbed radon and water.

Keywords

• Radon
• Activated carbon
• Deep depressurization
• Desorption