Research On Improved Active Activated Carbon Radon Measurement Method Based On Dynamic Adsorption Model

According to the United States Environmental Protection Agency(EPA)in 2003,radon is a major cause of lung cancer second only to smoking,and the main cause of lung cancer among non-smokers.Radon gas also has some valued applications in addition to its health hazards,such as measuring the concentration of radon underground to help determine whether there are uranium deposits in the area;monitoring the change of radon concentration in underground water can facilitate prediction of earthquake.Therefore,measurement of radon has become an important research topic.Among the numerous existing radon measurement methods,active activated carbon radon measurement method has acquired extensive attention in recent years due to its advantages,such as short sampling time and low cost.In this paper,we used Yoon-Nelson model to analyze the dynamic adsorption process of radon by activated carbon(AC),put forward an improved active AC radon measurement method according to the analysis results and previous research on active AC measuring radon,and deduced the calculation formula of two important parameters(scale factor and minimum adsorption time)in this method.Improved active AC radon measurement method utilizes the proportional relation between the amount of radon absorbed and the radon concentrations after the adsorption saturated to measure radon concentrations,it has overcome the disadvantages of existing methods,including the dependence to AC adsorption efficiency(adsorption efficiency up to 100%)and the influence of temperature on the adsorption efficiency,etcThe break-through curve of dynamic adsorption of radon in activated carbon is measured in the experiment.We studied the influence of temperature,gas flow rate and dosage of AC on dynamic adsorption break-through curve,and on the two important parameters of Yoon-Nelson dynamic adsorption model(half break-through time τ and k value).In our experiments,we found that the half break-through time τ decreased with the rise of temperature,and did not change with the radon concentration.It was inversely proportional to the gas flow rate,and proportional to the amount of AC.The k value of the break-through curve increases with the rise of temperature in a good linear relationWe calculated the minimum sampling time under different conditions with the half break-through time τ and k value acquired in the dynamic adsorption experiment.We studied the influence of temperature,gas flow rate and dosage of AC on minimum sampling time,and provided the method to determine the sampling time.The linear relationship between the counting rate and radon concentration was verified and the effectiveness of the method was proved by improved active AC radon measurement experimentation at different radon concentrations.We obtained the scale factor(1.05932 Bq·m-3·cpm-1)under the reference temperature(20 ℃).The temperature modification formula of the scale factor was obtained by experimentation,the formula was compared with the theoretically derived formula,the difference between the two coefficients in two formulas is less than 7%,which proves the correctness of the theoretical analysis.