Removal Of Two Kinds Of Pesticide EDCs In Water By Ozone, Ozone/Hydrogen Peroxide Methods

From the end of 20th to the beginning of this century, a kind of pollutants which has existed fora long term, but have not been paid attention by the public——Endocrine Disrupting Chemicals(EDCs), gradually becomes the hotspot of environment science. At present, the amount of EDCswhich have been validated is 70 kinds, 60% of which are pesticides and their metabolizedsubstances. Recent years, pesticide EDCs are detected incessantly in both groundwater and surfacewater, even including some forbidden ones. They are hard to effectively removed by general watermanage techniques, hence investigating the means and methods of removing this kind of pollutantshas important significance.The origin,categories,harm and mostly remove approaches of pesticide EDCs aresummarized in this thesis. On the basis of which, two kinds of pesticide EDCs——methomyl andatrazine——are chosen to fumble their optimized reaction condition that removed by ozone,ozone/hydrogen peroxide techniques separately, also the influence of different water qualities anddegradation dynamics, including the direct and indirect oxidation. The degradation production ofthe two organic substances are analysized, then their possible approaches are brought forward. Keycontent and conclusions as follows:(1)The effects of H₂O₂ quantity,pH,temperature and the original concentration of organicsubstances on oxidating methomyl and atrazine are worked over. The concentration of methomyl is3mg/, quantity of ozone is 30mg/l, room temperature(25℃), pH is 9.0, the highest removal ofmethomyl approaches 90%; the concentration of atrazine is 2mg/l, quantity of ozone is 7.5mg/l,H₂O₂/O₃ molar ratios is 0.75, room temperature(25℃), pH is 7.5～8.5, the highest removal ofatrazine is 96.4%; along with the accretion of organic substances original concentration, theremovels of two substances both depressed, but the quantities of utterly removal are increasedlargely;(2)Under the same condition, the removal of methomyl on the background of tap water(non-regulated pH) is higher12% than pure water; along with the concentration increase of HAand hydrogen carbonate, their restrain effect on methomyl removal increases. When theconcentration of HA is 10mg/l, the removal of methomyl is just 38.6%; when the concentration ofhydrogen carbonate is 2.4mmol/l, the removal is 68.4%, decreased for 20% than without hydrogen carbonate;(3) The removal of atrazine on the background of tap water (non-regulated pH and mole ratioof H₂O₂/O₃ is 0.6) is higher 5% than pure water; compared with 86.1% which is the removal ofatrazine without HA, the removal of atrazine is 87.2% when the concentration of HA is 0.5mg/l;when the HA concentration is 5 mg/l, the removal is just 30.2%; when the concentration ofhydrogen carbonate is 2.4mmol/l, the removal decreases into 73.8%;(4)The direct and indirect oxidation dynamics are investigated separately by adding freeradical depressor TBA and competitively reacting with phenol. The results show that directoxidation is the main process of methomyl degradation, its proportion in total oxidation is 15.8%;the indirect oxidation is the main process of atrazine degradation, its proportion in total oxidation is95.8%;(5)Integrated the results of HPLC,IC,GC-MS and LC-MS, the products of methomyl andatrazine are analysed. It is guessed that methomyl is be likely to transform into nitrate,carbondioxide and water; the main products of atrazine are DIA, DEA and OHA, and the possibledegradation approach of atrazine by ozone/hydrogen peroxide oxidation.