The Effectiveness And Mechanism Of Removing PCNB By Ozonation In Water

The bubble column reactor was choosed to study the effectiveness and mechanism of ozonating p-chloronitrobenzene(pCNB)in distilled water,and the intermediates of the ozonation was detected and determined in order to review the influence of ozonating on the biodegradability of pCNB.The effect of ozone adding mode,the initial pH value,the alkalinity,the humics or the catalyst hydrogen peroxide on removing pCNB was separately studied.The research manifested that,the removal percent at 25th minute were 55.8% and 50.15% separately for one-off and intermittent adding mode,and so the former mode was little better than the latter;the increase of pH value was conducive to removing pCNB,and the removal percent increased as a result of it.For example,the percent were 38%,43% and 51.4% separately corresponding the pH value 5.41,6.47 and 7.6;when the adding alkalinity were 0mg/L,20mg/L,40mg/L,80mg/L,120mg/L and 200mg/L,the removal percent were separately 43%,57.5%,28.8%,27.9%,33.4% and 34.1%;when the humics adding amount were 0mg/L,1.14mg/L and 2.27mg/L,the removal percent were 21.18%,27.17% and 18.81%;and at last the effect of the catalyst hydrogen peroxide was also studied,and when the adding amount were 0mg/L,0.26mg/L, 0.52mg/L,1.03mg/L,1.55mg/L and 2.07mg/L,the pCNB removal percent at 15th minute were 17%,54%,76%,77%,78%,86%; the pCNB removal percent at 20th minute were 26%,82%,90%,92%,92%,93%.The best mol ratio of hydrogen peroxide and ozone was between 0.38 and 0.75.The intermediates of ozonating pCNB were detected and determined,and the result manifested that,the main intermediates of ozonating pCNB were carboxylic acids.In the ozonating reactions,the substitution of hydrogen atom,chloro radical,or nitro radical in the phenol ring by hydroxyl took place first,accompanied by the creation of hydroxybenzenes and benzoquinnes,and followed by the cleaving of organic ring to form carboxylic acids.The degradation of carboxylic acids carring more atoms leaded to formic acids and finally to carbon dioxide. Ozonation made for the biodegradation of pCNB in...