BIOLOGICAL FENTON'S DEGRADATION OF CHLORINATED ENDOCRINE DISRUPTING CHEMICALS BY AQUATIC PLANTS

摘要

Fenton reaction has been proven to rapidly degrade many persistent organic compounds via the hydroxyl radical formation. A study was performed to propose a new treatment method to decompose persistent chemicals such as dichlorodiphenyldichloroethane (p,p'-DDD) and pentachlorophenol (PCP) in water, utilizing endogenous hydrogen peroxide present in aquatic plants to proceed the biological Fenton reaction. Batch experiments were conducted using duckweeds (Spirodela polyrhiza and Lemma aoukikusa) as aquatic model plants and PCP and p,p'-DDD as persistent chemicals, respectively. Aquatic plants showed a small impact in removing PCP and p,p'-DDD. However, by adding 2.8 mM of iron (Fe~(2+)), there was a rapid removal of both chlorinated EDCs while at the same time consumption of endogenous hydrogen peroxide occurred. It was found that when the initial concentration of EDCs was low (100 μg/L), all EDCs were rapidly removed from water. Also, when the initial PCP concentration was high (5 mg/L), more than 80% of PCP was removed within two days. In addition, the concentration of endogenous hydrogen peroxide in duckweed plants decreased in parallel with PCP removal, as well as the increase of chloride ions formation in water - confirming the degradation of PCP. These results demonstrated that PCP and p,p'-DDD were oxidized through a biological Fenton reaction, and the hydrogen peroxide in aquatic plants was a key endogenous substance in treatment of refractory toxic pollutants.