Activated carbon is porous carbon material, has a strong adsorption capacity,Widely used in air purification, wastewater treatment and other fields.The reactive nitric acid is placed in an environment to absorb radon gas, and then Y measurement is carried out, which can be pushed
Calculate the radon concentration in the environment.Activated carbon Y energy spectrum is one of the main methods for measuring radon.In 1957, Mirandajr "used activated carbon as an adsorber to measure radon concentrations in the atmosphere;Since then, many scholars have carried out a series of theoretical and experimental studies on the method of measuring radon on activated carbon, and it has been widely used in the study of radon release rate 23.
In 1986, Lin Lianqing et al. carried out radon measurement by activated carbon.
In 1993, China promulgated the national standard 5 for the method of measuring radon by activated carbon V energy spectrum. Since then, this method has been popularized and applied in China, and has achieved satisfactory results in the determination of radon release rate and radon concentration in air L6-8.The radon measurement by activated carbon mainly measures the energy spectrum peak of 2Pb or 21Bi, and the radon concentration value is calculated from the net peak area. This method can distinguish 2Rn daughters, which is convenient for attenuation correction, and has a strong anti-interference ability for other Y radiators (such as 2Rn and its daughters, etc.).However, it requires high energy resolution and low counting rate.
coconut shell based granular activated carbonThe theoretical basis, attenuation correction and standing time of this radon measurement method are discussed.
Combined Equations (5) and (10) can calculate the total amount of Pb and 21Bi atoms in activated carbon after adsorption for any length of time (i.e., the total number of activated carbon Y).Let n=0 in Equation (10), then the accumulation and attenuation of total atomic amount of 2Pb and 2Bi (total number of activated carbon Y) after the removal of activated carbon can be calculated in Equation (10).In fact, if thin layer activated carbon is used, the value of N should be equal to the product of the adsorption coefficient of activated carbon and radon concentration, while the radon adsorption coefficient of activated carbon mainly depends on the type of activated carbon and is affected by temperature, humidity and other factors.
When the radon adsorption coefficient of activated carbon is constant,n is proportional to the concentration of radon. In this case, Equation (10) represents the functional relationship among the total number of activated carbon V, radon concentration and adsorption (or exposure) time. Therefore, the concentration of radon in the environment can be calculated according to the total number of activated carbon and adsorption time.Simulation calculation and result analysis of total number of activated carbon According to Equations (5) and (10), a computer program can be written to calculate the relationship between the total number of Y in the process of radon adsorption on activated carbon and the relationship between the total number of Y after the removal of activated carbon and the change of time.
In order to verify the accuracy of the simulation calculation, two 12g activated carbon bags thickness of activated carbon ~ 1.5cm) were put into the container containing uranium ore, and then taken out after radon adsorption for 30 min and 85 min. After continuous measurement, the change curve of total Y number of activated carbon over time could be obtained.
According to the adsorption duration used in the experiment and the appropriate value of n (in the calculation process, when the adsorption duration is 30 min, n=480;
When the adsorption time is 85 min, take n-600), and the calculated theoretical curve is shown in FigureIt can be seen from the figure that the measured curve is in good agreement with the theoretical curve.Fig. 2 is the simulation result of the total number of Y taken out over time after activated carbon adsorbs 1 radon atom from the environment every second and continues to adsorb for 3 days.After the activated carbon was taken out, the total number of V reached the maximum after t time, and then the total number became smaller. After about 50 min, the total number of V decreased by a negative exponential function.
www.chinactivecarbon.comThe curve can be divided into a stationary area and a measuring area. The width of the stationary area (i.e. the duration of the stationary area) is set at (t+50) min, followed by the measuring area.
There is no obvious rule of counting in the standing zone. Should be avoided during this period of time.Total number of;The measurement area is counted by
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