| Nowadays, organic drugs are in an enormous use in human life and industry. These chemical drugs have played an important role in antibacterial sterilization. However, their waste has been detected with non-ignorable dose in the environment, including in the atmosphere, soil sediments and surface water. These compounds would lead to chronic or acute toxicity for human heath and other organisms in the environment. Present studies have shown that pharmaceuticals and personal care products(PPCPs) are difficult to be depredated. Their existence form and degradation in the nature show complex. As new types of organic pollutions, PPCPs and some POPs pesticide draw widely attention recently.In this article we selected triclosan, personal care products additives, antibiotic drug levofloxacin, and organochlorine pesticides lindane as the research object to investigate their transformation in the environment. High oxidant OH radicals was chosen as initiator. Its degradation mechanism under the condition of OH radical exists was focuses on, which can provide calculation basis for environmental degradation and waste management. Density Functional Theory in quantum chemistry was employed to calculate relative reactions. MPWB1K/6-311+G(3df,2p) //MPWB1K/6-31+G(d, p) methods were selected to compare degradation pathways of three drugs. Kinetic studies were also performed. Some important conclusions are made:1. Chemical Conversion Pathways and Kinetic Modeling for the OH-initiated Reaction of Triclosan in Gas-phaseTriclosan, a widely used antimicrobial additive in personal care products, has drown peoples attention for a long time. To study the mechanism and kinetic property of trilosan in the environment, density functional theory and the canonical variational transition state theory are employed. Addition and abstraction pathways were taken into consideration. Their probable transformation were calculated. OH radicals could oxide triclosan to produce phenols, aldehydes. They also have the potential to convert to PCDD/Fs and PCBs. The energy barriers and reaction heat illustrate the probable pathways and the toxicity would be strengthened in such pathways. In addition, thermochemistry is calculated. The consequent ratio of kadd/ktotal and kabs/ktotal at 298K are 0.955 and 0.045, respectively. OH radical addition reactions are proved to be predominant.2. Investigation of lindane photocatalytic chain reaction mechanism in the atmosphereOn the basis of existing smoke box experiment, photodegradation in the atmosphere was investigated. With OH radicals as initiator, quantum chemical method was employed to calculate the chain reaction of lindane in the air. Degradation mechanism and reaction heat data are acquired. Results show that OH can’t leave the chain structure directly in the process of dechlorinating. Reasonable pathway is to break C-Cl bond first.3. The OH the degradation mechanism of levofloxacin in water researchAdvanced oxidation methods is one of the most efficient water treatment methods to treat levofloxacin. Using high OH-free radical oxidation activity and oxidation reduction potential can effectively remove the antibiotics in the water. Research on OH radical degradation of levofloxacin helps to provide more accurate data to support advanced oxidation technology. Article respectively to calculate the Ozzie and Harriet addition of levofloxacin and oxidation degradation, finding out the optimal degradation path. |
PDF Full Text Request