Journal of School of Public Health and

Background and Aim: 2,4-Dichlorophenol (DCP) is a compound  generated in a variety of industrial processes and also by chlorine disinfection of water polluted with phenolic compounds . Dumping of DCP into the environment and water resources is of great concern because of the compound's intense odor and toxicity. DCP is very soluble and resistant to biodegradability so it cannot be removed through conventional water and wastewater treatment processes. On the other hand, pollution prevention (P₂) strategies have not been able to resolve the problem.

Material and methods: In this study, one of the AOP_S named Fenton was used for DCP degradation. The method is based on simultaneous use of hydrogen peroxide and ferrous sulfate.

Results: Results of treatment with hydrogen peroxide and ferrous ion (as Fenton reagent ingredients) indicate that by oxidation of 50 mg/L DCP at 60 minutes contact time with iron concentration kept at 15 mg/L and various concentrations of H₂O₂ (50 and 100 mg/L), the efficiency of COD(Chemical Oxygen Demand) reduction would go up from 65% to 80% with higher concentrations of H₂O₂. We also determined the effect of various concentrations of ferrous ion on DCP oxidation rate. The results showed the prominent role of this ion in DCP treatment: increasing Fe concentration from 5 to 15mg/L produced a 60% reduction in COD occurred in 10 and 60 minutes contact times. Another conclusion was that the oxidation of DCP solutions by Fenton had a major effect on biodegradability so that BOD: COD ratios of these solutions increased significantly after this oxidation.

Conclusion: Pretreatment of waste containing dichlorophenol by the Fenton reagent can enhance the biodegradability of this chemical and perhaps of similar compounds in a short time interval.

Background and Aim: Problems related to conventional Fenton oxidation, including neccesity of having a low pH and production of considerable amounts of sludge, have prompted researchers to consider chelating agents to improve the pH operating range and iron nano-oxide particles to reduce excess sludge. The main objective of this study was to remove pyrene from contaminated soils by a modified Fenton oxidation method  at neutral pH.

Materials and Methods: Experiments were conducted using various concentrations of H2O2 (0-500 mM), iron nano-oxides (0-60 mM), reaction times (0.5-24 hours) and several chelating agents, namely, sodium pyrophosphate, ethylene diamine tetra-acetic acid, sodium citrate, fulvic and humic acids, to eliminate pyrene from soil (concentrations of 100-500 mg/kg).

Results: The efficiency of removal of pyrene at an initial concentration of 100 mg/kg was 99 % at the following reaction conditions: H2O2 and iron nano-oxide concentrations of 300 mM and 30 mM, respectively pH=3 and a reaction time of 6 hours. The initial pyrene concentration of 100 mg/kg decreased to 7 mg/kg at optimum conditions using sodium pyrophosphate as the chelating agent at pH 7.    

Conclusion: The modified Fenton oxidation method, using iron nano-oxide at optimum conditions as defined in this research, is an efficient alternative for chemical remediation or pre-treatment of soils contaminated wih pyrene at neutral pH.