Research Of Decomposition Of Polycyclic Aromatic Hydrocarbons (PAHs) On Microwave Energy

Polycyclic Aromatic Hydrocarbons (PAHs) are the hydrocarbons that have two or more benzene ring in its molecule. They are the ubiquitous organic pollutant in the environment. They have very poor water-solubility, can inhibit the growth of microorganisms, and have the special ringed stable structure, so that they cannot be assimilated by microorganisms for energy, and are constantly accumulating in the environment. In the meantime, PAHs have very good fat-solubility and can be bio-enriched and bio-magnified by microorganisms. So the more being the top of the food chain, the more the life-forms are likely to have the high concentration of PAHs in their body. Thus humankind on the top of the food-chain may have the highest concentration of PAHs in their bodies.In recent years, the PAHs pollution control has been of a great of interest all over the world. World Health Organization (WHO) has studied out that the permitted highest concentration of 6 representative PAHs (namely fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(b)pyrene, indeno(1, 2, 3-cd) pyrene and benzo(ghi)perylene) in drinking water is 0.02μg/L. The Chinese health standards of drinking water has set that the concentration of benzo(a)pyrene in the drinking water ought to be less than 0.01μg/L. Environmental Protection Agency(US EPA) has listed out 16 prior pollutants PAHs (PPPAHs) and ordained that their total concentration cannot be more than 0.2μg/L.PAHs are produced when organic substance deficiently combusts or pyrogenates in reductive ambience. PAHs are severely threatening human being's health because their metabolized product in organism can strongly cause the aberrance, cancer and mutation. Thus their source, their distributing, their harmfulness, their physical and chemical properties, their analytical methodology and their decomposingmethodology are presented in the first chapter in this dissertation, and according to above discussions, taking decompositions of naphthalene, anthracene, pyrene and pentacene for instance, a method for decomposing PAHs with microwave energy is put forward, and this is the main significance and content of this dissertation.TLC analytical method for naphthalene, anthracene and pyrene is established in chapter 2. The conditions of TLC for naphthalene, anthracene and pyrene such as visualization reagent, developing agent are selected. Rf value of naphthalene, anthracene and pyrene are determinated. The better separating conditions between other ingredient and them are attained.The microwave decomposing resultants of reaction of naphthalene and anthracene are analyzed with TLC, ultraviolet spectrophotometric method and RP-HPLC. RP-HPLC analyses indicate that naphthalene and anthracene cannot be better decomposed only by microwave without auxiliary decomposing reagent under such simple conditions. But PAHs such as naphthalene, anthracene, can be rapidly, thoroughly decomposed by microwave under the action of auxiliary decomposing reagent such as H2O2, O3. After microwave decomposing method and auxiliary decomposing reagent have been selected, the effect of microwave and auxiliary decomposing reagent to the decomposing percentage is determined. The result shows that naphthalene cannot be decomposed by H2O2 and traditional heating method. But the decomposing percentage on H2O2 and microwave for naphthalene is 99.02% determinated with RP-HPLC and is more 85.1% with ultraviolet spectrophotometric method. The decomposing percentage is 99.4% determinated with ultraviolet spectrophotometric method under same conditions. The decomposing percentage on O3 and microwave is 86.3% for naphthalene and 100% for anthracene determinated with ultraviolet spectrophotometric method. This method can efficiently, rapidly decompose aqueous PAHs without the slashing conditions such as acid, alkali, high temperature, and high pressure. So it is evidently superior to the traditional method.The decomposing conditions of pyrene and pentacene are researched according to the analogical method in chapter 4 and 5. Pyrene cannot be decomposed by microwave and H2O2 or O3. On the contrary, it can be thoroughly done by chloric auxiliary decomposing reagent under the same conditions. 4352mg/L aqueous pyreme can be thoroughly done by microwave when the chlorine concentration is 3.66mg/L. Pentacene can be easily decomposed and the aqueous pentacene can be thoroughly done by microwave without any other conditions. It can be concluded that the linear PAHs become more and more labile and are more and more easily decomposed along with the increasing benzene ring. In the meantime, if PAHs have the same benzene ring, the unfolding PAHs are more active and more easily decomposed.The microwave decomposition of the true waste water sample from printing and dying industry is researched in chapter 6. Printing and dying waste water CODo value has lowered from 102 mg/L to 16.7mg/L on microwave and O3. So the better decomposing results are attained.In conclusion, the decomposing method for waste water with microwave and auxiliary decomposing reagent is rapid, thorough, and very economical.In the end, the resultants from microwave decomposition of naphthalene and anthracene have basically been determinated by GC-MS. CO2 and HCOOH have all been found in the mixture of resultants from both two.