Interaction effects of various reaction parameters on the treatment of sulfidic spent caustic through electro-photo-Fenton

In this research, the interaction effects between pH (range from 2 to 5), temperature (20–60 °C), current density (5–20 mA/cm 2 ), hydrogen peroxide per chemical oxygen demand H 2 O 2 COD (0.2–0.75), and reaction time (45–135 min) for spent caustic wastewater treatment were assessed through electro-...

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Bibliographic Details
Published inInternational journal of environmental science and technology (Tehran) Vol. 16; no. 11; pp. 7165 - 7174
Main Authors Nasr Esfahani, K., Farhadian, M., Solaimany Nazar, A. R.
Format Journal Article
LanguageEnglish
Published Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2019
Subjects
Aquatic Pollution
Earth and Environmental Science
Ecotoxicology
Environment
Environmental Chemistry
Environmental Science and Engineering
Original Paper
Soil Science & Conservation
Waste Water Technology
Water Management
Water Pollution Control
Electro-photo Fenton
AOP
RSM
Wastewater treatment
Sulfidic spent caustic
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Summary:In this research, the interaction effects between pH (range from 2 to 5), temperature (20–60 °C), current density (5–20 mA/cm 2 ), hydrogen peroxide per chemical oxygen demand H 2 O 2 COD (0.2–0.75), and reaction time (45–135 min) for spent caustic wastewater treatment were assessed through electro-photo-Fenton oxidation process by using response surface methodology. The optimum conditions for Esfahan oil refinery’s spent caustic wastewater treatment with an experimental COD removal of 97% were obtained at 4.5 (pH), 60 °C, 16.6 mA/cm 2 , 0.69 ( H 2 O 2 COD ), and 80 min. The interaction effects of hydrogen peroxide with pH; hydrogen peroxide with temperature; and temperature with reaction time were considered essential, which indicated the dependency among the factors. However, the interaction effect between pH and hydrogen peroxide was found so significant for chemical pollutant removal due to the activity of both iron ions and hydrogen peroxide. The pH reduction step of spent caustic (pH < 5) could lead toward the COD removal of 45% in the form of hydrogen sulfide gas. Complementary tests were run on the precipitated chemical sludge at optimal conditions to find organic contaminants, which indicated the chemical sludge mainly contains FeSO 4 and Na 2 SO 4 . It was shown that advanced oxidation process for the degradation of contaminants was efficient and pollutants did not add to the sediment in the sludge phase. Graphical abstract
ISSN:1735-1472
1735-2630
DOI:10.1007/s13762-018-2126-8