Determinants of natural zeolite clinoptilolite adsorption capacity for removing NO2

Background: NO2 is a poisonous gas that potential to cause major threat to human being health and the environment, as a result, removing this gas from environment seems to be essential.

Methods: The study aimed to remove this gas from environment using Iranian natural zeolite, clinoptilolite. After crushing and preparing two sizes of 1 and 2 mm zeolite they were activated in 380 to 420 ºC for 20 minutes. NO2 was produced by reaction of copper (Cu) and nitric acid (HNO3) and diluted with enough air to achieve desired concentration. A laboratory reactor set with different concentration of NO2 (20, 30, and, 45 ppm), flows through the zeolite absorbent bed was prepared. Different parameters affected No2 absorption, such as concentration, height, and diameter of zeolite bed, zeolite granulation, and activation temperature were examined.

Results: In different condition, the adsorption range of the zeolite for NO2 was varied from  0.35% W for 2mm granulation and the 20 ppm concentration to 1.5% W using 1mm granulation and 45 ppm concentration of NO2. Activation temperature of 420 ºC for 20 min was the best condition removing NO2. Efficiency of 1mm granulation was higher than 2mm.

Conclusion: Reducing parameters such as height and diameter of zeolite bed decreased but increasing concentration of gas flow increased adsorption capacity of zeolite. Using Iranian zeolite in gas masks still not recommended.