Hamadan University of Medical Sciences Journal of Research in Health Sciences 2228-7795 5 2 2005 12 29 Photo -Chemical Degradation of 2, 4- Dichlorophenoxyacetic acid (2, 4-D) in the Effluent 27 31 EN AJ Jafari S Marofi Journal Article 2011 07 04 Background: 2, 4-dichlorophenoxy acetic acid (2, 4-D) is well known as inexpensive herbicides but it can give rise to undesirable pollution. The objective of this investigation was to describe a photo-chemical system for degradation of 2, 4-D.Methods: A designed photolytic cell system was used in this study with a 150W or 400W UV lamp. A set of experiments was carried out at pH 1.5, 2.5, 3.5 and 4.5 to investigate the effect of pH on the degradation rate of 2, 4-D. The samples were collected and analyzed by UV spectrophotometer, and HPLC.Results: With a 150 WUV- source, the percentage degradation of 2, 4 -D after one hour was 3% while 60% of destruction was achieved using a 400W. The percentage degradation of 2, 4-D was 19% and 99.9% after 8 hours with a 150 W or 400 W UV lamp, respectively. The complete degradation of 2, 4-D was achievable with addition of hydrogen peroxide after 120 and 15 min using 150 W and 400 W UV lamp, respectively.Conclusion: This investigation finding shows that 2, 4-D is degradable in acidic pH of 2.5 or 3.5. In addition, 2, 4-D degradation can be achieved in wastewater by UV light and depends on intensity of lamp or present of H2O2 oxidant.