ABSTRACT

The present work consisted in evaluating the effect of a natural plant reducer, gallic acid (GA), on the discolouration/oxidation of two azo dyes by Fenton processes (Fe³⁺/H₂O₂ and Fe²⁺/H₂O₂). A kinetic study was performed to better interpret the discolouration data at different temperatures. The 1st-order kinetic model presented the best fit for the experimental data of methyl orange discolouration, while the 2nd-order was better for chromotrope 2R. Due to the addition of GA and the temperature rise, there were increases in discolouration and in the reaction rate constant values. As a highlight, it was possible to verify the reduction of the apparent activation energy (Ea) due to the presence of GA. For example, Ea for discolouring methyl orange corresponded to 81.5 and 53.6 kJ.mol⁻¹ by Fe²⁺/H₂O₂ and Fe²⁺/H₂O₂/GA, respectively. Thus, it can be inferred that the GA reduces the energy barrier to increase the oxidation of dyes by Fenton processes.

摘要

目前的工作包括评估天然植物还原剂没食子酸 (GA) 对芬顿法对两种偶氮染料（Fe ³⁺ /H ₂ O ₂和 Fe ²⁺ /H ₂ O ₂ ）变色/氧化的影响。 ）。进行动力学研究以更好地解释不同温度下的变色数据。一级动力学模型最适合甲基橙变色的实验数据，而二级动力学模型更适合变色剂 2R。由于 GA 的添加和温度升高，变色和反应速率常数值增加。作为一个亮点，可以验证表观活化能的降低（Ea ) 由于 GA 的存在。例如，使甲基橙变色的Ea分别对应于Fe ²⁺ /H ₂ O ₂和Fe ²⁺ /H ₂ O ₂ /GA的81.5和53.6 kJ.mol ^{-1 。}因此，可以推断 GA 降低了能垒以增加芬顿工艺对染料的氧化。