Effect of cysteine using Fenton processes on decolorizing different dyes: a kinetic study

Area of Science:

• Environmental Chemistry
• Catalysis
• Oxidation Processes

Background:

• Homogeneous Fenton processes (Fe2+/H2O2 and Fe3+/H2O2) are used for dye degradation.
• Cysteine is an amino acid with known Fe3+-reducing activity.

Purpose of the Study:

• To investigate cysteine's role as a reducing mediator in Fenton processes for dye degradation.
• To evaluate the impact of cysteine on hydroxyl radical production and pro-oxidant properties.

Main Methods:

• Homogeneous Fenton reactions with varying catalysts (Fe2+, Fe3+) and the addition of cysteine.
• Decolorization of diverse dyes including Methyl Orange, Phenol Red, Safranin T, Rhodamine B, Reactive Black 5, and Reactive Yellow 2.
• Kinetic modeling and activation energy analysis at varied temperatures.

Main Results:

• Cysteine significantly enhanced dye decolorization, particularly in Fe3+-catalyzed reactions.
• The presence of cysteine increased hydroxyl radical (HO•) production.
• Reaction rate constants improved with cysteine addition, and activation energy (Ea) decreased for Safranin T decolorization.

Conclusions:

• Cysteine acts as an effective reducing mediator, improving Fenton-based dye decolorization.
• Cysteine lowers the energy barrier of Fenton reactions, leading to enhanced degradation efficiency.
• The findings support cysteine's application in advanced oxidation processes for dye removal.