Study On The Characteristic Of High Selective Purify Nitrogen Dioxide In Medical Nitric Oxide By Activated Carbon

Nitric Oxide (NO) was extensive used in clinical treatment when it was identified as an"endothelium derived relaxing factor". However, the inhaled NO (iNO) diluting from bottled gas has a little toxic gas of nitrogrn dioxide (NO₂) which is also existed in the product of NO starting from air arc discharge. In order to purify the NO₂ efficiently, activated carbon was used as the adsorbent to selectively adsorb NO₂ in NO. The mechanism of selective adsorption is discussed by the analysis of the pore structure and acid-basic surface functional groups. On the base, an adsorbent having the character of highly selective adsorption of NO₂ is developed. The research achievements are as follows:(1) In order to evaluated the adsorption character of NO₂ in NO using activated carbon, the assessment equations of adsorption capacity were designed by definite integral principle on the base researches of selective adsorption of NO₂ on the four activated carbon (1#, 2#, 3#, 4#). An automatic specific surface area and porosity analyzer was used to analysis the pore structure of activated carbon and the fractal dimension was calculated. The results showed that the adsorbent of 1# and 4# had the highly selective adsorption of NO₂ and it related to the highly specific surface. The fractal dimension illustrated that the rough level on the surface of activated carbon hadn't direct relation with the specific surface.(2) The results from the analysis of Boehm method showed that the surface functional groups on adsorbents were mainly acidic groups but little basic groups; 2# and 3# were mainly basic groups and acidic groups can hardly be found. It implied that the acidic groups may be more conducive to the adsorption of NO₂. However, this conclusion was different from the reports which were about the acidic groups were conducive to the adsorption of basic matter. In order to explain the phenomenon, dipole moment and bond order theory were used to resolve it for the first time. The mechanism may be the polarity of NO₂ was stronger than that of NO and the bond of N-O in NO₂ was more sensitive.(3) H₂O₂, HNO₃, NH₃·H₂O, NaOH were used to modify the activated carbon. It suggested that acidity modify was better than basic modify, acidity modify showed the better selectivity adsorption of NO₂. The analysis results of Boehm method and FTIR showed that the increase and decrease in the intensities of C=O stretching of non-aromatic carboxylic acid and lactone structures suggested that acidity intensified it but alkalescence weakened it. The acidity (oxidation) modify increases the acidic groups and the basic modify was in the same. The two kind of activated carbon treated by impregnation of Mg (NO₃)2 and high temperature treatment remained the character of NO adsorption but performed better with NO₂.(4) It was found that the desorption of activated carbon was easy to occurred because of the variation of temperature under normal temperature and pressure. The adsorption property of activated carbon after twice heating treatment was better than the first regeneration by H₂O₂.(5) The orthogonal experiment design was carried out to prepare the granular walnut shell activated carbon in 9 groups. Using the assessment of capacity, the best technological parameter were that 6:1 of shell/base, 600°C of activation temperature, 1h of activation time. After adsorption research, the activated carbon received that U=0.73, SU NO₂ ,NO=32.96 in the selective adsorption of NO₂ in NO, the ratio of NO₂/NO remaining around 2% in the period of 5.5h. In a word, the selective capability was better than the four kinds of activated carbon studied before.(6) The activated carbon molding by polyvinyl alcohol also had the high selective adsorption of NO₂ in NO. The ratio of NO₂/NO still satisfied the requirement of clinical treatment before 5500min during the period of 6060min for lifetime adsorption research.