Rhodamine B wastewater degradation by graphite-graphite electro-Fenton system

Electro-Fenton with graphite-graphite as the electrodes was applied to degrade wastewater containing Rhodamine B (RhB). Both the influencing factors and mechanism were investigated. The effects of various operating factors including potentials, initial solution pH, Fe²⁺ concentration, electrode plates spacing were systematically investigated in order to obtain the optimized conditions for degradation of RhB under four levels orthogonal test of five factors. The optimum values were as follows: potential2 V, initial pH=2.5, Fe²⁺ concentration 0.1 mmol/L, electrode plates spacing 4 cm. The removal rate of RhB could reach to 98.59% under the optimum conditions. Three-dimensional fluorescence, HPLC-MS, UV were used to detect intermediate products of RhB during Electro-Fenton. Results showed that the absorbance at 554 nm by UV was almost zero, but fluorescence peak still existed. Removal rate of TOC was 33.3%. Certain intermediate products that have fluorescence did not completely remove. Results from HPLC-MS proved that the following intermediate products produced in the Electro-Fenton, likeC₂₆H₂₇O₃N₂ (m/z=415), C₂₄H₂₃O₃N₂(m/z=387) et al.