Degradation Characteristics of Acridine during UV/chlorination Reaction

Abstract

Recently, pharmaceuticals, personal care products (PPCPs) and endocrine disrupting compounds (EDCs) have been detected at trace concentrations in water around the world. Even, several trace contaminants were detected in municipal wastewater treatment plant (WWTP) effluent and drinking water treatment plant (DWTP) that people are intake every day. Although these contaminants are present in trace concentrations, the environment and ecosystem can be negatively affected by continuous exposure. Acridine, a three-ring compound, is group of water contaminants with mutagenic and carcinogenic activity. Acridine has been used as a chemical intermediate in the manufacture of dyes and the synthesis of pharmaceuticals. Also, acridine is generated in diesel exhaust, coal burning, coal tar and coke-oven emissions. Especially, acridine can be formed as a degradation intermediate of carbamazepine (CBZ) using as pharmaceutical by such as biodegradation and UV/H2O2 reactions. According to increase of environmental threat by residual contaminants in water treatment processes, many techniques have been developed by previous studies. Advanced oxidation processes (AOPs), the techniques characterized by the generation of radicals, can be applied to water treatment processes. In this study, chlorination, UV photolysis and UV/chlorination reactions were conducted to remove acridine in water. The UV-C light more effectively removed acridine than UV-A and UV-B lights in water. Under the UV/chlorination reaction, acridine was more effectively removed than by UV photolysis and chlorination only reactions. During UV/chlorination reaction, 100 ng/L acridine was removed to 80% within 60 min and completely removed after 240 min. The removal efficiency of acridine was higher at lower pH condition. The chlorine dose was a significant factor in the degradation of acridine in UV/chlorination reaction. DOM can inhibit degradation of acridine in water. By-products of acridine during UV, chlorination and UV/chlorination reactions were confirmed by using mass spectrometer. Six acridine by-products were identified during UV photolysis reaction. Also, three acridine by-products was identified during chlorination and UV/chlorination reaction, respectively. By-products were generated when OH and Cl radicals degrade acridine during UV/chlorination reaction. Using time profiles of acridine by-products, the degradation pathway of acridine by-products was also proposed during UV photolysis, chlorination and UV/chlorination reaction. The results of our study can provide important information when the UV/chlorination reaction was conducted to remove acridine in WWTP and DWTP. Ultimately, this study is helpful to improvement in the public health though maintaining clean water.