Abstract:

In this work, an electro-Fenton system with a graphite cathode, a Ti/IrO$_{2}$-RuO$_{2}$ anode, iron-carbon particles and nano-Fe$_{3}$O$_{4}$ heterogeneous catalysts was developed for phenol wastewater and coal liquefaction wastewater. In a 3D electrode/electro-Fenton (3D-EF) reactor coupled with iron-carbon particle catalysts, the removal rate of phenol reached 100${\%}$ in 1 h, and the removal rate of chemical oxygen demand (COD) reached 80${\%}$ in 5 h. That was higher than those in heterogeneous catalytic electro-Fenton (HEF) coupled with nano-Fe$_{3}$O$_{4}$ catalysts. The results indicated that the optimum reaction conditions were controlled as follows: initial pH=3, 2 mm$<d<$5 mm particle size, 10 g (33 g/L) particle dosage, and 1 400 mg/L initial COD concentration. After 5 h of the reaction, high treatment efficiency of coal liquefaction wastewater was obtainedin the 3D-EF system.The removal efficiency of COD was approximately 40${\%}$, and B/C was 0.44. UV spectrum, 3D fluorescence spectroscopy and Fourier transform infrared spectroscopy were used to investigate variation of dissolved organic matters before and after degradation process. The results show that single ring aromatic compounds in coal liquefaction wastewater is easy to degrade, and removal of COD in wastewater are mainly from degradation of phenolic compounds.

Key words: 3D electrode/electro-Fenton (3D-EF), phenol, coal liquefaction wastewater, chemical oxygen demand (COD) removal rate