Study on the degradation of methyl orange by UV-acetylacetone advanced oxidation system
Qirui Feng, Yuchao Tang, Kun Wang, Changnian Wu, Xianhuai Huang
Abstract
In recent years, Acetylacetone (abbreviated as AA) has garnered considerable scientific interest, particularly in the field of dye wastewater treatment due to its distinctive enol-keto structures. In this work,degradation of methyl orange(MO) by UV/AA process was explored. Effects of AA dosage, MO concentration, initial pH value and water matrices were investigated.Experimental results showed that under conditions of 298 K, a pH of approximately 5.73, a stirring speed of 1150 rpm, an initial MO concentration of 15 mg/L and an AA dosage of 0.5 mM, the decolorization rate reached nearly 98.4 % after 12 min of photolysis. The decolorization process fitted well with the pseudo-zero-order reaction model in the UV/AA system with an R 2 value greater than 0.990. The reaction rate increases as the pH decreases; at approximately pH 2.0, the decolorization rate is 99.3 % after 6 min, while at approximately pH 9.0, it is only 41.2 %. 10 mM HCO 3 ⁻significantly inhibit the system, 0.1 mM Cl⁻has a slight promoting effect at low concentrations but inhibits at high concentrations and NO 3 ⁻inhibits the reaction while SO 4 2- has minimal impact at a concentration of 0.1–10 mM .0.1 mM iron ions accelerated the reaction.The sodium citrate , a printing and dyeing auxiliary , has negative impacts on the MO degradation. Free radical capture experiments and Electron Paramagnetic Resonance (EPR) tests reveal that singlet oxygen (¹O 2 ) is the primary active species in the UV/AA system. UV-Vis absorption spectroscopy indicates that azo bonds are largely destroyed after 12 min, with a decrease in AA concentration as the reaction proceeds. Liquid chromatography-mass spectrometry (LC-MS) results suggest a possible conversion pathway for MO during the UV/AA advanced oxidation process .