| The presence of phenolic and dye wastewater in the environment create acute toxicity to the organism and hence treatment of them are essential before the disposal. For the past few years, electrochemical method appears to be a most potential technology for the treatment of wastewater for its unique merit such as high efficiency, pollution free and realization of automation. In this paper, three-dimensional electrochemical reactor coupling E-Fenton degradation of phenol and Orange Ⅱ was investigated with graphite as the main cathode and anode, and three kinds of bentonite-based various iron species (Fe-Bent) as the particle electrodes. The main research contents and results are as follows:(1) The degradation of phenol by the 3D/E-Fenton process was investigated with the bentonite modified by Fe2(SO4)3 as the particle electrodes. The effect of preparation conditions such as Fe:Bent mass ratio, calcination temperature, calcination time and electrochemical operating parameters such as particle electrodes dosage, initial pH, initial concentration of phenol, electrolyte concentration, current density, space of anode and cathode were investigated. Batch experiments showed that 70.34% and 57.11% of phenol removal and chemical oxygen demand (COD) removal were obtained at the condition of mFe:mBent=1:3, calcination temperature 200℃, calcination time 4 h, Fe2O3-Bent dosage 2.0 g, initial pH 3, current density 125 mA/cm2, phenol initial concentration 100 mg/L, space of anode and cathode 1.0 cm and Na2SO4 concentration 0.05 mol/L, respectively.(2) Fe0-Bent was synthesized using a rapid method employing NaBH4 as the reducing agent and polyvinyl alcohol (PVA) as the capping agent. Some parameters such as the mass ratio of Bent and iron, NaBH4 concentration, PVA concentration and proportion of ethanol vs water were investigated. Then orthogonal method was used to confirm the optimum preparation conditions. The results showed that 90.36% and 69.08% of phenol removal and COD removal were obtained at the condition of mFe:mBent=1:5, NaBH4 concentration 0.25 mol/L, PVA concentration 0.74 mg/ml and the proportion of ethanol vs water was 3:7. The effect of pH on phenol removal was also investigated, and the phenol removal maintained at 86.11%-92.36% in the range of pH 3-10. However, it should be noticed that even at neutral pH,90.36% phenol removal still achieved in 180 min, indicating that the Fe0-Bent particle electrodes can be used in a wide pH range.(3) The degradation of Orange Ⅱ by 3D/E-Fenton system was investigated. The Fe-T-Bent particle electrodes were synthesized using a rapid and completely green method employing aqueous green tea extracts as both the reducing and capping agent. Some parameters, such as the preparation conditions (iron species and aging time) and electrochemical operating parameters (Fe-T-Bent dosage, initial pH, initial concentration of Orange Ⅱ, current density, electrolyte of different kind and concentration) were investigated. Batch experiments showed that 98.89% and 71.57% of decolorization and COD removal were obtained at the condition of Fe(NO3)3 concentration 0.1 mol/L, aging time was 30 min, Fe-T-Bent dosage 0.5 g, Orange II concentration 100 mg/L,I=0.3 A,0.05 mol/L Na2SO4 and initial solution pH of 6.4. And Fe-T-Bent had good stability and reusability for usage repeatedly.(4) SEM, XRD, FT-IR, XRF and BET were used to confirm that the iron had been immobilized on the bentonite successfully.(5) Fe concentration in solution was determined spectrophotometrically (absorbance measurement at 510 run) by 1,10-phenanthroline method, and ·OH was determined based on UV-vis spectroscopy with salicylic acid as scavenger. In addition, the relationship between iron concentration and ·OH was also discussed.(6) The degradation of wastewater in 2D,3D and 3D/E-Fenton were investigated, which could be used to determine the contribution of direct oxidation and indirect oxidation qualitatively.(7) By evaluating the evolution of instantaneous current efficiency (ICE), the results showed that the 3D/E-Fenton system exhibited higher efficiency for wastewater degradation than that of 2D system. |
PDF Full Text Request