Study On Radon Absorption Characterisitcs Of Liquid Nituogen Modified Activated Carbon

Radon(222Rn)is a natural radioactive gas and the main source of natural radiation to humans.The World Health Organization(WHO)believes that radon and its progeny are the second leading cause of lung cancer in humans.For the purpose of people's health,radon prevention and control are required in places with high radon levels,such as indoor buildings,mines,and underground facilities.Common methods for preventing radon include ventilating radon,blocking radon on wall paint,and removing radon by adsorption filtration.In some places that are not convenient for ventilation,it is an effective means to reduce radon by adsorbing and filtering to reduce the radon in the local space.In the design of this adsorption radon removal device,the processing capacity and volume of the equipment are limited by the adsorption radon performance of the adsorption material.This research is based on the modification of coconut shell activated carbon with excellent radon absorption performance in order to obtain a more efficient radon absorption material.In this paper,we have designed three modification schemes: liquidnitrogen immersion modification,liquid nitrogen immersion evaporation parallel modification,and low temperature nitrogen flushing modification.The liquid nitrogen immersion time,liquid nitrogen immersion evaporation times,and low temperature nitrogen flushing time and The relationship between the modification effect,and the static method for measuring the adsorption coefficient is preferably used as the measurement method of the adsorption material's radon absorption performance,and the method is improved so that the measurement result can more reflect the true situation of the material's radon absorption ability.The results showed that radon absorption showed that the continuous carbon nitrogen immersion and evaporation 4 times had the best modification effect of activated carbon,and its kinetic adsorption coefficient K(L/g)was increased by more than 30% compared with the raw material.The study preliminarily analyzed the reasons for the improved performance,and took scanning electron microscope images of the samples before and after modification.The samples were subjected to N2adsorption-experimental desorption to analyze the pore structure and pore size distribution.The specific surface area,average pore size,and total pore volume did not change much.The increase in the number of micropores with a pore size of 0.54 nm has a significant positive correlation with the change in radon absorption performance.The poresize of the sample is modified by immersion in liquid nitrogen 4 times.The specific surface area has been increased by more than 20%.On the basis of liquid nitrogen immersion and evaporation modification,large-scale production experiments were attempted,and an experimental platform for large-scale modification of activated carbon was designed.The initial expansion of the experiment enlarged the single-modified conditions of activated carbon in equal proportions,resulting in 4 immersion and evaporation The activated carbon's radon absorption capacity was increased by 17%,which was lower than that of small-scale modification experiments.The impact of external conditions such as temperature,humidity,and air pressure on the modification of liquid nitrogen in large-scale modification still needs further discussion.The liquid nitrogen modified activated carbon method has the advantages of simple process,short modification period,and low cost,and has application value.