Magnetite as a heterogeneous electro Fenton catalyst for the removal of Rhodamine B from aqueous solution

Abstract

This paper deals with the investigation of Rhodamine B (RhB) dye removal characteristics of the heterogeneous electro Fenton (EF) process using laboratory prepared Fe₃O₄. Throughout the experiment graphite–graphite electrolytic systems with the electrodes having a surface area of 25 cm² were used. Removal efficiencies of Fe₃O₄ prepared at various Fe²⁺ : Fe³⁺ ratios were found to be close to the same range and Fe₃O₄ with 2 : 1 ratio was selected for further experiments. The effects of solution pH, catalyst concentration, voltage, electrode spacing etc. on dye removal efficiency were analysed to determine the optimal operating conditions. The experiment results indicated that 97.3% of RhB was removed within 180 min of electrolysis from a solution containing 10 mg l⁻¹ of RhB at pH 3 with a catalyst concentration of 10 mg l⁻¹, an applied voltage of 8 V and an inner electrode spacing of 4 cm. It was also found that addition of anions negatively affected the efficiency of the electrolytic system and followed the order CO₃²⁻ ∼ Cl⁻ > SO₄²⁻ > NO₃⁻ > HCO₃⁻. The reusability of magnetite highlights the practical applicability of heterogeneous EF process over homogeneous EF processes. Also, compared to the Fenton process, the optimal catalyst concentration required for the EF process was much less. From the present study, it can be concluded that heterogeneous EF process using Fe₃O₄ is an alternative method for dye removal from aqueous solution.