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Removal of Nitramine Explosives in Aqueous Solution by UV-Mediated Advanced Oxidation Process in Near-Neutral Conditions

Khue Do Ngoc, Bach Vu Quang, Binh Nguyen Thanh, Minh Do Binh, Nam Pham Thi, Loi Vu Duc, Nguyen Hoa Thanh

Journal of Ecological Engineering

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2021

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Vol. 22, nr 6

232--243

EN

Explosive compounds are hazardous to the environment, posing a serious risk to human and animal health and the ecosystem. The primary goal of research was to compare the efficiency of UV/H2O2, photo-Fenton, electro (EO)/ UV/H2O2 processes at near-neutral pH (pH=6) on the degradation of nitramine explosives (NAs), such as hexogen (RDX), octogen (HMX), and tetryl (TET), in an aqueous solution. The effect of operational conditions, likely pH of the solution, initial H2O2 concentration, initial Fe2+ concentration, and solution temperature, was observed. The removal kinetics fit with first-order kinetics and were in the order: photo-Fenton >EO/UV/ H2O2 > UV/ H2O2. The results showed higher rate constant values for TET, RDX and HMX removal by UV/ H2O2 (k = 0.07778, 0.03791 and 0.03786 min-1), EO/UV/ H2O2 (k = 0.16599, 0.1475 and 0.08674 min-1) and photo-Fenton (k = 0.18018, 0.1501 and 0.09336 min-1) processes. Furthermore, TET, RDX and HMX were mineralized at 59.7%, 45.1%, and 25.1 %, respectively, under optimum conditions after 60 min of the photo-Fenton process. From the economic perspective, photo-Fenton only requires 2.132–4.113 kWh m-3 to completely reduce NAs. Finally, acute toxicity towards Vibrio fischeri was defeated after usage of near-neutral photo-Fenton. Thus, photo-Fenton at circum-neutral is promising for low-cost, eco-friendly and efficient processes for treating nitramine explosives in aqueous solutions.

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Treatment of Landfill Leachate by Using Fenton and Photo-Fenton Processes

Leszczyński J.

Journal of Ecological Engineering

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2018

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Vol. 19, nr 5

194--199

EN

The paper deals with the study on the use of the Fenton and photo-Fenton process for the treatment of landfill leachates from a stabilized landfill site. The effluents were characterized by pH of 8.1, color: 1320 mg Pt/L, COD of 1670 mg/L, of BOD5 155 mg/L, conductivity of 10.3 mS/cm, absorbance of UV254 0.332 and turbidity of 11 NTU. It has been shown that by using Fe(II) and hydrogen peroxide in the Fenton reaction, the organic compounds expressed as COD can be efficiently removed from the effluents. The process was carried out at various doses of H2O2 and Fe(II), using different reaction times in the Fenton process and different times of exposure in the photo-Fenton process. The best conditions for the Fenton process were obtained with a Fe/COD ratio of 1.4 and a H2O2/Fe molar ratio of 3.2. Under these conditions, the removal efficiency of COD was 85.8%. It was also shown that additional UV irradiation of leachate in the so-called photo-Fenton process and the use of appropriate hydrogen peroxide dosing conditions, can increase the effectiveness of COD removal. The maximum effect of COD removal in the photo-Fenton process was 70.7% at a dose of H2O2 3.3 g/L and a dose of Fe(II) of 0.6g Fe/L. An additional advantage of the photo-Fenton process is the ability to shorten the reaction time and reduce the dose of iron, which can thus reduce the amount of deposits generated.

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Fotodegradacja małocząsteczkowych WWA w warunkach reakcji Fentona

Kozak J., Włodarczyk-Makuła M.

Zeszyty Naukowe. Inżynieria Środowiska / Uniwersytet Zielonogórski

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2017

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nr 168 (48)

25--34

PL

Obecnie wiele uwagi naukowców i praktyków skupia się na technologiach oczyszczania ścieków, które mają za zadanie usuwać związki toksyczne i/lub trudno rozkładalne. Do związków tego typy należą WWA. Badania wykazały, że procesy zaawansowanego utleniania (AOP- advanced oxidation processes) mogą być stosowane do degradacji WWA. Jedną z metod AOP jest utlenianie z wykorzystaniem odczynnika Fentona. Modyfikacje tej reakcji zmierzają m.in. w kierunku poszukiwnia alternatywnych, niż H2O2 źródeł rodników hydroksylowych oraz wspomagania procesu utleniania promieniami ultrafioletowymi. Celem pracy było określenie efektywności fotoutleniania małocząsteczkowych WWA w oczyszczonych ściekach koksowniczych, w warunkach reakcji Fentona. Źródłem rodników hydroksylowych był nadtlenek wapnia CaO2, a proces wspomagano promieniami UV. Efektywność utleniania oceniono na podstawie analiz WWA w badanych próbkach przed i po procesie fotoutleniania. Jakościową i ilościową identyfikację WWA prowadzono z wykorzystaniem metody chromatografii gazowej w połączeniu z spektrometrią masową GC-MS. Badania wykazały, że w warunkach silnie utleniających następowała fotodegradacja badanych WWA. Spadek stężenia analizowanych węglowodorów był w zakresie od 0 do 96%. Badania wykazały, że nadtlenek wapnia może stanowić alternatywne źródło rodników hydroksylowych do degradacji WWA, obecnych w ściekach koksowniczych.

EN

Nowadays, the attention of many researchers and scientists is focused on wastewater treatment technologies which are designed to remove toxic and/or persistant compounds. PAHs belong to this type of compounds. Studies have shown that advanced oxidation processes (AOP-advanced oxidation processes) can be used for PAHs degradation. One of the AOP methods is oxidation using Fenton's reagent (Fe2+/H2O2). The aim of this modification is a search for alternative sources of hydroxyl radicals than H2O2 and support that processes by UV light.. The aim of the study was to determine the efficiency of photocatalysis of low molecular weight PAHs in pretreated coking wastewater under Fenton reaction conditions. The source of hydroxyl radicals was calcium peroxide and the process was supported by UV radiation. The oxidation efficiency was assessed on the basis of PAH analyzes in the pre-and post-oxidation samples. Qualitative and quantitative identification of PAHs was carried out using gas chromatography in combination with GC-MS mass spectrometry. The decrease in the concentration of the analyzed carbohydrates was in the range of 17 to 96%. Studies have shown that calcium peroxide can be an alternative source of hydroxyl radicals for the PAH degradation present in coke wastwater.