Preparation And Application Of Bamboo Charcoal Enriched By Radon High Selective Adsorption

There is an urgent need for the control and treatment of radioactive aerosols inthe air of closed environment,such as defense industry,civil underground facilities and so on.The screening and preparation of radon and other radioactive aerosol purification and separation materials has been one of the important research fields at home and abroad.At present,activated carbon is often used as radon adsorption enrichment material.However,due to the low porosity（<2 nm）of activated carbon,its saturated adsorption capacity is limited.In this paper,bamboo charcoal based adsorptionand enrichment materials were prepared from fast-growing Phyllostachys pubescens,and activated bamboo charcoal based highly selective adsorption and enrichment materials were prepared by chemical activation method,and the radon adsorption and enrichment treatment was verified.The main results are as follows:（1）The iodine adsorption value is often used as an index to measure the adsorption performance of activated carbon.The iodine adsorption value of 8-year-old bamboo charcoal based adsorption enrichment material prepared by carbonization at 900℃is the highest,reaching 436.64 mg/g;The results showed that the adsorption properties of carbon based materials and carbon based materials from different parts of bamboo were similar,and the iodine adsorption values were 436.64 mg/g and 446.79 mg/g,respectively.The results of SEM,specific surface area and XRD show that the size and number of graphite microcrystals increase with the increase of carbonization temperature;With the increase of carbonization temperature,the specific surface area first increased and then decreased.The specific surface area of bamboo charcoal based adsorption enrichment material prepared at900℃was the largest,which was 95.9 m³/g.When the carbonization temperature is low,the bamboo charcoal based adsorption enrichment materials initially form a dense pore structure,and the average pore size is small.With the increase of carbonization temperature,the pore structure of bamboo charcoal based adsorption enrichment materials gradually expanded,even collapsed.In the experiment of radon adsorption,the highest amount of radon adsorption is 6.03 Bq/g.（2）The specific surface area of the activated bamboo charcoal based high selective adsorption and enrichment materials was the largest,which was 794.57 m²/g,and the radon adsorption capacity reached 48.78 Bq/g.After KOH activation,the secondary activation with activator will further expand the pore size.The specific surface area of the highly selective adsorption and enrichment materials based on activated bamboo charcoal is1129.17 m²/g,and the radon adsorption capacity is 100.87Bq/g.It is found that the active bamboo charcoal based highly selective adsorption enrichment materials with large surface area,rich micropores and small average pore diameter have more advantages in radon enrichment.The relationship between the specific surface area and radon adsorption of the activated bamboo carbon based highly selective adsorption enrichment materials is in accordance with the equationγ=exp(34.2-⁵³⁸¹³¹_χ+17080..₃⁵)（R²=0.958）;The relationship between average pore size and radon adsorption is in accordance with the equationγ=19.26+57021.98·0.09445^χ（R²=0.917）;The relationship between micropore and radon adsorption is in accordance with the equation（?）（R²=0.917）.（3）The adsorption and enrichment of radon by adsorption materials is influenced by many environmental factors.The equilibrium radon adsorption of bamboo charcoal based adsorption and enrichment materials was 2.01 Bq/g,59.13 Bq/g and 30.37 Bq/g respectively.The results of the simulation show that the adsorption process is in accordance with the quasi first-order kinetic model（R²=0.985）,and it is physicaladsorption.With the increase of radon concentration,the adsorption of radon from bamboo charcoal based adsorption and enrichment materials,coconut shell active carbonmaterials and highly selective bamboo charcoal based adsorption enrichment materials all showed an increasing trend.Through the fitting of isotherm adsorption model,itwas found that the adsorption behavior was in line with Freundlich model（R²=0.994）,and multi-layer adsorption behavior occurred.The results show that the amount ofradon adsorption of bamboo charcoal based adsorption and enrichment materials,active bamboo charcoal based high selective adsorption and enrichment materials and coconut shell activated carbon materials are reduced from 2.01 Bq/g,59.13 Bq/g,30.37 Bq/g to 1.83 Bq/g,56.43 Bq/g,56.43 Bq/g,respectively,due to the plugging of the binder to the void 27.74 Bq/g.The results of the 50cycles showed that the radon adsorptioncapacity of bamboo charcoal based adsorption and enrichment materials,active bamboo charcoal based high selective adsorption enrichment materials and coconut shell active carbon materials decreased from 2.01 Bq/g,59.13 Bq/g,30.37 Bq/g to 1.39 Bq/g,49.79 Bq/g and 24.36 Bq/g respectively;The radon adsorption capacity of the formed bamboo charcoal based adsorption and enrichment materials,the high selective adsorption materials and the formed coconut shell active carbon materials decreased from 1.83 Bq/g,56.43 Bq/g,27.74 Bq/g to 1.38Bq/g,48.47Bq/g and 22.67 Bq/g respectively.