Degradation of 2, 4-D acid using Mn2+ as catalyst under UV irradiation

Abstract

In this paper, the oxidative degradation of 2, 4-dichlorophenoxyacetic acid (2, 4-D) using Mn 2+ /H 2 O 2 reagent under UV irradiation was studied. The results show that 2, 4-D was degraded more completely in Mn 2+ /H 2 O 2 solution than traditional Fenton solutions. The effects of the concentration of Mn 2+ , H 2 O 2 and pH were also investigated. And under the optimal condition of 2 Mn c + 1.48×10 −4 mol/L, 2 2 H O c 8.99×10 −5 mol/L and pH 3.38, the formation of • OH was the most, both the decomposition rate of H 2 O 2 and the degradation rate of 2, 4-D were the fastest. In addition, the photoreaction process was monitored using spin-trapping electron paramagnetic resonance (EPR), and the results indicated that the oxidative process was predominated mainly by the hydroxyl radical (• OH) gennerated in the system.

Phenol degradation by Fenton-like process

“…The addition of Mn 2+ -MnSO 4 .H 2 O to the Fenton process, transforming it into Fenton-like, provided good efficiencies on the phenol degradation, according to what is suggested by Goldstein et al (1993) and Huang et al (2009), fact that may be verified by the significant positive quadratic effect ( Fig. 1) …”

“…3), which indicates that, if Mn 2+ is increased, the degradation efficiency is decreased. The lowest degradation efficiencies observed in a global view, using an initial pH of 5 in relation to the initial pH of 3, is a result, possibly, to the fact that in a less acidic environment, the reaction Mn 2+ + H 2 O 2 → Mn 3+ + OH • + OH − , quoted by Huang et al (2009), may be harmful, justifying, therefore, the lowest global efficiencies observed. It may be possible to observe, within the time intervals tested on this experiment, that there was a linear and quadratic effect of reaction time.…”

“…About the possibility of two electron oxidation of manganese, Jacobsen et al (1998) and Deguillaume et al (2004) proposed the reaction H 2 O 2 + Mn 4+ , would generate as product Mn 2+ + 2H + + O 2 . In acid medium (greater [H + ], result from the previous reaction), the reaction Mn 2+ + H 2 O 2 → Mn 3+ + OH • + OH − would occur (Huang et al 2009). Depending on the H 2 O 2 concentration, and the oxidation potential Mn 2+ to Mn 4+ , there could be one cycle, there would be an increased consumption of H 2 O 2 , so that there was degradation of organic compounds because the nonselectivity hydroxyl radicals or decrease the efficiency degradation.…”

“…Kao et al (2015) using Bio-electro-Fenton microbial fuel cell, concluded that the performance with Fe 2+ is better than in the case of with Mn 2+ . Huang et al (2009) using Mn 2+ as catalyst under UV irradiation, concluded that manganese can be an effective catalyst.…”

Degradation Kinetics of Reactive Brilliant Red X-3B Dye by UV/Mn²⁺/H₂O₂/Micro-Aeration

“…Fernandez et al [12] studied the degradation of Orange II by using Mn 2+ and the results indicated that Mn 2+ had a good catalytic activity like Fenton regents. Huang et al [13] studied the oxidative degradation of 2, 4-dichlorophenoxyacetic acid (2, 4-D) using Mn 2+ /H 2 O 2 reagent with UV irradiation; the results showed that 2, 4-D was degraded completely. In this paper, reactive brilliant red X-3B (X-3B) solution was used as a dyestuff wastewater, and was treated by UV/Mn 2+ /H 2 O 2 /micro-aeration, and the intrinsic kinetics of degradation was studied.…”