Study On Photochemical Degradation Of P-nitroaniline

Photochemistry, as one of the important branches of chemistry, is focusing on the research of interaction between light and matter. Photochemistry involves the wavelength range of light for 100¹000 nm. The comprehensive study on photochemistry in different water is of realistic significance for further understanding the whole photochemical research field. As Marine organic photochemistry (MOP) has a close relationship with other subjects such as marine biology and marine ecology, so the research on MOP is very important. The research on different water organic photochemistry can help to understand the removal patterns of organic pollutants in different water.P-nitroaniline(PNA), one of nitroaniline derivatives, is an important compound used as an intermediate of precursor in the manufacture of organic synthesis, such as p-phenylenediamine, azo dyes, antioxidants, fuel additives, corrosion inhibitors, pesticides, antiseptic agents, medicines for poultry and pharmaceutical synthesis. PNA released directly through PNA production or utilization process is highly toxic. PNA has been found to be harmful to aquatic organisms and may cause long-term damage to the environment. Therefore, it is necessary to conduct research on its photodegradation in seawater and to understand its effect on natural environment.We systematically studied the photochemical reaction of PNA and assessed its ecotoxicity to environment, and the results were showed as follows:1. Photoreaction kinetic behaviorMost photoreactions showed first-order reaction kinetic behavior. Under different experimental conditions, the rate constants (k) varied from 0.0004 min^-1 to 0.0443 min^-1.2. Many factors in the experiments would influence the photodegradation:(1) Light source: The photolysis rate of PNA was faster under 500W high pressure mercury lamp than under 300W high pressure mercury lamp, indicating that the photodegradation of PNA was greatly influenced by light intensity. (2) Initial concentration: The photolysis rate of PNA in aqueous solution decreased along with increasing PNA concentrations ranging from 5 to 8 mg/L.(3) Temperature: The photolysis rate of PNA in diluted water increased along with increasing temperature from 20℃to 50℃.(4) Media: When the initial concentration of PNA was 6 mg/L, the rate constant in the three media was in the following order: NSW > ASW > DW.(5) Heavy metal ions: In three different aquatic media, four metal ions including Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺ displayed different roles.(6) Methanol and H₂O₂: The addition of these two compounds has a great impact on the photolysis rate of PNA.(7) Nitrate and nitrite: Both nitrate and nitrite(0.1 mg/L⁴ mg/L) showed the promoting effects on photochemical degradation of PNA in the dosage range studied.(8) Photosensitizer: The selected photosensitizer– humic acid could accelerate the photoreactions of PNA.