Degradation of 4-Clorophenol By Electro-Fenton Using Electrodes of Graphite

Electrochemical Advanced Oxidation Processes (EAOP) have been proposed like alternative processes for the treatment of industrial wastewater this is due to their high effectiveness in removing toxic organic compounds, low operating costs and minimum consumption of chemical reagents.

In this work the main purpose is to find the better conditions to degradate an organic compound in this case 4-Clorophenol by Fenton´s reaction.

Electrolytic System. Electrochemical cell is   an undivided glass cell of 1 Liter. The electrodes (anode and cathode) are made of graphite. An oxygen flow of 50 mL*min^-1 feeds with a diffuser to electro-generate hydrogen peroxide (H₂O₂) in situin the cathode.

The diffuser, furthermore of provide oxygen also generates a bubble matrix which increase the velocity of mass transfer from the ions situated in the electrolyte to the electrodes surface.

For applying constant current is necessary a power supply which maintaining a current at 0.2 A.  In this case the support electrolyte is Na₂SO₄ 0.05 mol*L^-1, this solution was adjusted to pH=3.0 with sulfuric acid.  

With the above conditions, an experiment with a volume of 900 mL of electrolyte solution were conducted to electro-generate H₂O₂. The determination of the concentration of H₂O₂was followed by spectrophotometry UV-Vis at λ=408nm in an equipment HACH DR 500.

Knowing that is possible to electro-generate H₂O₂ in situ in this electrochemical cell it was decided to carry out Fenton´s reaction. For this purpose the ions Fe²⁺were obtained from an iron piece which was placed within the cell and it was not connected to the circuit.

To prove the catalytic activity of iron (Fe²⁺) and the oxidizing power of the radicals hydroxyls generated by Fenton´s Reaction, was added 4-Clorophenol to the electrolyte solution, maintaining the same reaction conditions of the electro-generation of H₂O₂. The degradation of 4-Clorophenol was followed by the determination of Total Organic Carbon (TOC) with an equipment Shimadzu TOC-L.

Results show that the solution initial concentration is 59.39 mg*L^-1 of TOC which decrease until 33.26 mg*L^-as result of 3 hours of treatment by Electro-Fenton reaction, this is a 43.8% of remotion from initial concentration of 4-Clorophenol. This implies that this process must be improve to mineralize completly organic compounds and reduce treatment time.

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