Efficiency of hydroxyl radical formation and phenol decomposition using UV light emitting diodes and H₂O₂

Abstract

A novel process combining hydrogen peroxide (H2O2) and radiation emitted by ultraviolet light emitting diodes (UV LEDs) has been investigated. The UV LEDs were used as UV-C light sources emitting radiation in the range 257-277 nm for decomposition of the model substance phenol in water. In addition, the effect of H2O2 to phenol molar ratio and initial phenol concentration was examined. Two parameters, the decomposition efficiency of phenol and characterization of hydroxyl radical (HO*) production from H2O2 when illuminated with UV radiation, were selected to provide detailed information regarding the performance of the UV LEDs in the treatment process. A new concept was introduced to characterize and describe the production of HO* radicals produced when photons were absorbed by H2O2 molecules. The phenol decomposition efficiency at the initial concentration of 100 mg/L was the most pronounced at the lowest emitted wavelength. A significant correlation was found between the phenol decomposition efficiency and the photons absorbed by H2O2 (i.e. formation of radicals).

Increase of the anaerobic biodegradability of olive mill wastewaters through a pre-treatment with hydrogen peroxide in alkaline conditions

“…(Eqs. (1-3)), which, however, can be consumed by an excess of H 2 O 2 [3,7]. These considerations are in agreement with the findings of Crittenden et al [35], who observed an attenuation of the oxidation rate in response to a high peroxide dosage in a H 2 O 2 /UV system.…”

“…However, the acidic pH, high salinity, lack of nutrients, low biodegradability and elevated polyphenols concentrations make it necessary to perform an adequate pre-treatment [1][2][3][4]. For the removal of phyto-toxic and low-biodegradable compounds, many advanced oxidation techniques have been proposed [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Some of these, such as ultrasonic irradiation, photo-catalysis and electrochemical processes are quite profitable because there is no need for the addition of chemical reagents.…”

Biogas production from wet olive mill wastes pretreated with hydrogen peroxide in alkaline conditions

“…Indeed, in an alkaline environment, hydrogen peroxide decomposes according to a series of reactions with OH Radicals formation (reactions 5e6), which, however, can be consumed by excess H 2 O 2 (reaction 7) leading to less reactive radicals HO 2 . These species can react themselves with hydrogen peroxide restoration (reaction 8) [9,12]. The cyclical reactions are favoured by high initial peroxide doses, that, in the authors' opinion, probably reduces both the process speed and the stoichiometric ratio.…”

Bacterial mer operon-mediated detoxification of mercurial compounds: a short review

“…Mercury exists in nature mainly as cinnabar ores (Barnes and Seward 1997), and several of its compounds enter aquatic environment through leaching, washing of soils sediments and rocks by rain (Shrestha and Sillanpää 2008;Sillanpää 2009). In addition, artificial mode of mercury pollution includes leakage from landfills, sludge applications, and byproducts from chemical industries Vilhunen et al , 2011Rassaei et al 2009;Sillanpää and Rämö 2009). These byproducts and chemical waste are responsible for massive amounts of organic as well as inorganic forms of mercurial compounds released into environment as indicated in the report of National Research Council (2000).…”