Anna Goi

Hydrogen peroxide photolysis, Fenton reagent and photo-Fenton for the degradation of nitrophenols: a comparative study

The kinetics of the degradation of seven nitrophenols (2-nitrophenol, 4-nitrophenol, 2,5-dinitrophenol, 2,6-dinitrophenol, 2,4-dinitrophenol, 2-methyl-4,6-dinitrophenol, 4-methyl-2,6-dinitrophenol) with the Fenton reagent, photo-Fenton, and hydrogen peroxide photolysis was investigated. The efficiency and operating costs for the studied treatments were evaluated and compared. The Fenton reagent was found to be the most efficient and the cheapest way for the nitrophenols (NPs) degradation. The formation of nitrate as a result of mineralisation of organically bounded nitrogen was observed during the treatment of NPs with studied treatment processes. The degrees of organically bounded nitrogen conversion to nitrate after 90% degradation of NPs with the Fenton, photo-Fenton and hydrogen peroxide photolysis were 51-67%, 85-90%, and 50-60%, respectively. According to Daphnia magna acute toxicity test, the Fenton treatment led to complete detoxification of NPs.

A study of toxicity, biodegradability, and some by-products of ozonised nitrophenols

Abstract Treatment performances of ozonation applied for the degradation of nitrophenols (NPs) were assessed in terms of biodegradability improvement, and toxicity reduction. Among the by-products formed during the ozonation of 4-nitrophenol and 2,4-dinitrophenol at initial pH 9.5 4-nitrocatechol, p-quinone, and hydroquinone were identified. The by-products of NPs ozonation were much more biodegradable than NPs. The degree of organically bounded nitrogen conversion to nitrate was 66–100% at pH 2.5 and 38–87% at initial pH 9.5. The reduction of ozone consumption and acceleration of NPs degradation rate was achieved during the ozonation of NP mixture at initial pH 9.5. According to Daphnia magna acute toxicity test, a complete detoxification of ozonised solutions was achieved. Thus, ozonation can be applied as a very effective treatment method for detoxification and biodegradability improvement of NPs containing wastewater. The achieved biodegradability improvement and detoxification of treated NPs supports the potential use of ozonation to improve the capacity of conventional biological treatment to remove these toxic and poorly biodegradable compounds.

Polychlorinated biphenyls-containing electrical insulating oil contaminated soil treatment with calcium and magnesium peroxides.

Calcium and magnesium peroxides were applied for the treatment of soil contaminated by polychlorinated biphenyls-containing electrical insulating oil (Aroclor 1016). The removal of PCB-containing electrical insulating oil was achieved with the addition of either calcium peroxide or magnesium peroxide alone and dependent on dosages of the chemical. A 21-d treatment of 60% watered soil with the moderate addition (chemical/oil weight ratio of 0.005/1) of either calcium peroxide or magnesium peroxide resulted in nearly complete (96 ± 2%) oil removal, unsubstantial increase in soil pH and almost no changes in oxygen consumption and dehydrogenase activity, making it suitable for the soil decontamination.

Fenton Process for Landfill Leachate Treatment: Evaluation of Biodegradability and Toxicity

The single Fenton or the Fenton process implemented in combined scheme as a posttreatment after the ferric chloride coagulation was applied for leachate collected from a real waste disposal site. Depending on the ratios of H2 O2 /chemical oxygen demand, H2 O2 / Fe2+ , and pH, the Fenton oxidation or both the Fenton oxidation and the Fenton coagulation were involved in chemical oxygen demand reduction. The implementation of ferric chloride coagulation as a pretreatment stage or acidification of raw leachate did not result in the improvement of chemical oxygen demand reduction efficacy of the following Fenton process comparing with that obtained by the direct Fenton treatment of raw leachate. The direct Fenton treatment with a higher (3/1) H2 O2 /chemical oxygen demand ratio applied to raw leachate without pH preadjustment ( H2 O2 / Fe2+ =10/1 ) , produced more oxidized organic compounds (measured as dissolved organic carbon/chemical oxygen demand ratio), more biodegradable by-products (measured as a 7-day ...

Combination of Ozonation and the Fenton Processes for Landfill Leachate Treatment: Evaluation of Treatment Efficiency

Single processes such as ozonation, ozone/hydrogen peroxide, Fenton and several combined treatment schemes were applied for leachate collected from a waste disposal site. The implementation of combined Fenton and ozonation processes resulted in the highest chemical oxygen demand removal (77% from initial value) among all the treatment methods applied, while biodegradability improvement was observed during the Fenton pre-treatment only. Some decrease of chemical oxygen demand was obtained during the single ozonation or combined schemes including ozone resulting in slight if any biodegradability improvement. The addition of hydrogen peroxide to ozonation did not enhance chemical oxygen demand, dissolved organic carbon or biochemical oxygen demand removal compared to ozone alone. Ferric chloride coagulation used as a pre-treatment stage did not improve subsequent chemical oxygen demand removal by ozonation or the Fenton processes. Taking into account the effective chemical oxygen demand, dissolved organic carbon removal and biodegradability improvement the single Fenton process seems to be a preferable treatment method for the leachate treatment. Some reduction in toxicity to Daphnia magna was observed after the application of the studied treatment methods.

Fenton treatment efficacy for the purification of different kinds of wastewater

The Fenton chemistry comprises both the classical Fenton reagent and its modification, so-called Fenton-like techniques, which have received great attention as a promising technology for wastewater treatment. In the present study real wastewater from different sources (leachate from oil shale semicoke landfill, pharmaceutical effluents from medical ointment production, municipal landfill leachate and wastewater originated from food-processing) were treated by means of Fenton/Fenton-like systems. The effectiveness of wastewater treatment was assessed by COD removal. Additionally, biodegradability improvement (BOD7/COD) and acute toxicity reduction of investigated wastewater samples were observed. The application of the Fenton chemistry to wastewater samples with different origin resulted generally in 70% or higher COD removal. Thus, the Fenton could be effectively applied both as a single treatment method and pre-treatment step to improve subsequent biodegradability of wastewater effluents.

Ozonation and Fenton Treatment for Remediation of Diesel Fuel Contaminated Soil

The chemical treatment (ozonation and the Fenton) was applied for remediation of diesel fuel contaminated sand and peat. The chemical treatment of diesel adsorbed in peat resulted in lower diesel removal and required higher addition of chemicals than the chemical treatment of diesel in sand matrix. The reduction of absorbance at 254 nm gave evidence of aromatics degradation during the chemical treatment. Short-chained linear alkanes (C11–C18) were more effectively removed than branched (pristane + phytane) alkanes and long-chained linear alkanes (C19–C26) in both sand and peat. A rough estimation and comparison of chemical oxidation treatment (chemicals and energy) costs indicated that the low additions and costs of chemicals make the Fenton and Fenton-like treatment more cost-effective than ozonation. The application of combined chemical + biological treatment may increase the effectiveness of soil remediation and economical feasibility.

Cost Effectiveness of Ozonation and AOPs for Aromatic Compound Removal from Water: A Preliminary Study

The capital and operating costs for several aromatic compounds (phenanthrene, 2,4-dimethylphenol, 2,4,6-trichlorophenol, nitrobenzene) removal from polluted groundwater using ozonation and advanced oxidation have been estimated on the basis of the laboratory experiments in semibatch conditions. The pollutants initial concentration was in the range of 0.01–1.0 mM. In the calculations the polluted groundwater flow rate was taken 40 m3/h with the initial pH = 7.0. It is shown that polluted groundwater purification from the aromatic pollutants with the initial concentration in the range of 0.01–1.0 mM using ozonation and advanced oxidation is economically feasible.

Use of hydrogen peroxide and percarbonate to treat chlorinated aromatic hydrocarbon-contaminated soil

AbstractThis study compared treatment methods that utilised a liquid carrier of hydrogen peroxide and a solid carrier, percarbonate, for p-dichlorobenzene, p-chloro-m-cresol and p-chlorothymol degradation in the soil. The targeted chlorinated aromatic contaminants in the soil degraded to a certain level when treated with the liquid hydrogen peroxide, but the removal efficacy was not dependent on the dosage. In contrast, an increase in the percarbonate dosage enhanced the contaminant removal. Supplementary ferrous iron was more effective for the treatment that employed the liquid carrier of hydrogen peroxide than the treatment employing the solid carrier. Although acidic pH conditions (initial pH of 2.5) favoured contaminant degradation using liquid hydrogen peroxide, the treatment involving percarbonate resulted in more effective contaminant removal without any soil pH pre-adjustment. Therefore, the solid carrier of hydrogen peroxide, percarbonate, was concluded to be an effective alternative to the liqui...

Effect of iron ion on doxycycline photocatalytic and Fenton-based autocatatalytic decomposition

Doxycycline plays a key role in Fe(III)-to-Fe(II) redox cycling and therefore in controlling the overall reaction rate of the Fenton-based process (H2O2/Fe(III)). This highlights the autocatalytic profile of doxycycline degradation. Ferric iron reduction in the presence of doxycycline relied on doxycycline-to-Fe(III) complex formation with an ensuing reductive release of Fe(II). The lower ratio of OH-to-contaminant in an initial H2O2/Fe(III) oxidation step than in that of classical Fenton (H2O2/Fe(II)) decreased the doxycycline degradation rate. The quantum yield of doxycycline in direct UV-C photolysis was 3.1 × 10(-3) M E(-1). In spite of doxycycline-Fe(III) complexes could produce the adverse effect on the doxycycline degradation in the UV/Fe(III) system some acceleration of the rate was observed upon irradiation of the Fe(III)-hydroxy complex. Acidic reaction media (pH 3.0) and the molar ratio of DC/Fe(III) = 2/1 favored the complex formation. Doxycycline close degradation rates and complete mineralization achieved for 120 min (Table 1) with both UV/H2O2 and UV/H2O2/Fe(III) indicated the unsubstantial role of the reduction of Fe(III) to Fe(II) in UV/H2O2/Fe(III) system efficacy. Thus, factors such as doxycyclines ability to form complexes with ferric iron and the ability of complexes to participate in a reductive pathway should be considered at a technological level in process optimization, with chemistry based on iron ion catalysis to enhance the doxycycline oxidative pathway.