Alternative View of Chlorine Oxidation Stimulated by Longer Wavelength Light

作者：Izadifard M^*; Langford C H; Achari G

来源：Journal of Environmental Engineering (United States), 2016, 142(10): 04016048.

DOI：10.1061/(ASCE)EE.1943-7870.0001124

• Chlorine oxidants
• Hypochlorite
• Blue light emitting diodes
• Organic contaminants
• Sensitized degradation

Aqueous chlorine (Cl2, OCl-, Cl-) in combination with longer wavelength ultraviolet (UV) irradiation has been investigated as a potential advanced oxidation process (AOP) for water and wastewater treatment. The cases include bleaching of organic matter (NOM) and oil sands tailing pond water (OSPW) under sunlight irradiation. Surprisingly, low energy tail of OCl- (Amax at 290nm) has been postulated to be responsible for degradation of organic components. An alternative photoreaction, potentially more photon efficient, postulates absorption by strongly absorbing chromophores of target compounds present in water, which then undergo reaction in their excited states. This alternate hypothesis was tested in the current study under 440nm light-emitting diode (LED) irradiation, where chlorine species have no absorption, using Swannee River fulvic acid (SRFA), an oil sands process water, and by bleaching of a coumarin dye. All results show substantial enhancement of hypochlorite oxidation processes under irradiation of the various complex mixtures of organic chromophores at 440nm, where chlorine species offer no measurable absorbance that can compete with the organic chromophores in the complex mixtures. In the fulvic acid case, a known long-lived triplet excited state is a plausible active species that may be a contributor.

• 出版日期2016-10