| Polycyclic aromatic hydrocarbons (PAHs) represent a class of carcinogenic, teratogenic and mutagenic and ubiquitous persistent organic pollutants in environment. With the rapid development of modern industry, the burning of fossil fuels and industrial wastewater discharge and other factors, the pollution of the PAHs in water and soil are more and more serious, which are difficult to be eliminated by conventional treatment processes. The Fenton’s reagent is one of the efficient ways to remove such almost non-degradable pollutants.In this paper, the following three aspects of optimal design for PAHs degradationin water and soil by Fenton oxidation were studied.(1) Taking polycyclic aromatic hydrocarbons (fluorene, phenanthrene, fluoranthene and pyrene) as the object of this study, the degradation rates of fluorene, phenanthrene oxide, fluoranthene and pyrene in water by Fenton’s reagent were examined, and the experimental conditions including reaction time, solution pH, FeSO4 concentration, H2O2 concentration and citric acid concentration were optimized. The results showed that under the conditions of the experimental substrate concentration of 0.05 mg·L-1, the reaction time of 12 h, FeSO4 concentration of 5.21 mmol·L-1, H2O2 concentration of 51 mmol·L-1, citric acid concentration of 1 mol·L-1, and the solution pH value of 3.0, the oxidative degradation rates of fluorene, phenanthrene, fluoranthene and pyrene were as high as 101.59%, 103.37%,100.98% and 99.42%, respectively. When citric acid concentration was 40 mol/L, the best buffing effect reached.(2) Taking four kinds of PAHs, Fluorene, phenanthrene, fluoranthene and pyrene as target pollutants and grade hydrogen peroxide (30%),28% FeSO4 solution and 10% citric acid as main agents, the study on oxidative degradation of four kinds of PAHs in simulated polluted water using Fenton’s reagent was carried out, and the reaction factors were optimized. The results showed that after using 10% citric acid to adjust the pH of the solution, all the degradation rates of four kinds of PAHs increased. In addition, citric acid also had some buffing effect, and the higher concentration of citrate, the better the buffing effect during 24 h. When sodium citrate was added in simulated polluted water as a buffer to optimize reaction conditions, the results showed that the optimum experimental conditions were the substrate concentration experiment of 0.1 mg·L-1, the reaction time of 48 hours, iron adding ratio of 1/18 and the target hydrogen peroxide concentration of 1%, and all the oxidative degradation rates of the four kinds of PAHs were above 95%.(3) Fenton oxidation technology has been widely used for soil remediation. In this paper four low-ring PAHs, fluorene, phenanthrene, fluoranthene and pyrene were chose as the target pollutants. Simulated contaminated soil was prepared and the contents of four kinds of PAHs in contaminated soil samples were 346.49 mg·kg-1,513.12 mg·kg-1,314.67 mg·kg-1 and 427.08 mg·kg-1, respectively. Through laboratory simulation experiments, the factor optimization of Fenton oxidative degradation of PAHs in contaminated soil samples was conducted. In addition, because of the extensive distributions of PAHs in contaminated soil, and the violent nature of Fenton oxidation, in this experiment citric acid was choosen as a buffer solution to adjust the pH and prolong Fenton oxidation reaction time, resulting in the best degradation effect under the reaction conditions. The results showed that the optimum conditions of the Fenton’s reagent for oxidative degradation of PAHs in soil were the soil-water ratio of 2:1, the 10% citric acid dose of 50 μL, pH of 3.0,30% H2O2 concentration of 11%, iron adding ratio of 1/8 (28% FeSO4 dose of 2.63 mL) and the reaction time of 24 h. |
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