Nitrate-induced Photodegradation of Colorants and the Corresponding Mechanisms Study.

In this paper, we first report effects of impact parameters on the oxidation property of photoinduced nitrate anion via degradation of multifarious colorants and indicators. While no degradation efficiencies are observed with respect to photoinduced nitrite instead of nitrate in the experiment. Several fundamental aspects regarding the effects of different structures of colorants, types of nitrate salt, illumination time and dosage of nitrate ion on the oxidation property were explored. The spectral evolution of UV-vis absorption was also investigated along with the degradation kinetics. Remarkably, this photoinduced nitrate ion played a major role in the fine oxidation property, and cations with greater extent of hydrolyzation would give rise to a more enhanced oxidation performance. The photodegradation of methyl orange and rhodamine B follows the zero-order and first-class dynamic equation, respectively. The maximum absorption peaks of dyes in visible light shifts towards shorter wavelengths as the illumination time increases. •OH radicals generated from photoinduced aqueous nitrate and •O2- originated from the reaction of •NO32- with dissolved oxygen were examined by EPR measurements, and they played a significant role in the photooxidation performance. This finding may provide new insights for treatment of industrial wastewater with good economic benefit and has potential application values in the field of photoreaction and photocatalysis. [ABSTRACT FROM AUTHOR]