| The traditional electrochemical oxidation and nano zero valent iron（nZVI）reduction were improvedand the advantage and disadvantage of the two methods on degradating Orange G dye wastewater wasanalysed.Based on the use of graphite plate as the anode, the traditional electrochemical oxidation method isimproved by the combination of coagulation and conventional electrochemical oxidation. The treatmenteffects in supporting electrolytes systems of NaCl, Na2SO4and NaCl&FeSO4·7H2O combinations werecompared. Meanwhile, effects of factors such as voltage, initial pH, concentration of electrolytes, spacingbetween electrodes and electrolysis time on the decolorization of Orange G and the degradation of COD inthe wastewater were also investigated. The results show that the decolorization of Orange G may mainlyowe to the oxidation of active chlorine, and the mineralization of Orange G may owe to the action of·OHgenerated during the electrolysis process. With the addition of FeSO4·7H2O, the coagulation function isenhanced, which further improves the treatment effect. Under the optimal decolorization conditions, thedecolorization rate of Orange G and the removal efficiency of COD are97.6%and56.3%, respectively.Moreover, biodegradability is significantly improved with the B/C (BOD/COD) increased from0.09to0.41. Besides, the removal efficiency of COD is increased gradually with the increase of reaction time. Thisresult indicates that the removal of COD is hysteretic with respect to the decolorization in Orange Gwastewater.With a graphite plate as anode, a further improvement of electrochemical oxidation method is done byusing electrochemical coagulation and internal-electrolysis coupling process method. Effects of factorssuch as NaCl, FeSO4·7H2O, initial pH, scrap iron and coke on the decolorization of Orange G and thedegradation of COD in the wastewater were investigated. Meanwhile, the treatment effect ofelectrochemical coagulation and innernal-electrolysis coupling process and their addition of individualtreatment effect were also compared. The results show that, under the same conditions, electrochemicalcoagulation and innernal-electrolysis coupling process for the decolorization of Orange G and thedegradation of COD in the wastewater is higher than each individual treatment effect. And the former for the degradation of COD is higher than the sum of the leter two, which shows that the coupling is synergy.With the addition of FeSO4·7H2O, the effect of decolorization and coagulation sedimentation are bothimproved, which making the following mud separation process more favourable. Under the optimaloperation conditions, the decolorization rate of Orange G and the removal efficiency of COD are98.3%and66.7%.A facile one-step method was developed to fabricate nano-scale Ni/Fe and SiO2, thus making a newkind of SiO2-coated nano-scale Fe/Ni particles. Compared with nano-scale Fe/Ni in terms of the pHapplication range and the dissolution of metal ion based on the study of decolorization of simulated orangeG dye wastewater. Meanwhile, the degradation process of Orange G dye, degraded by SiO2-coatednano-scale Fe/Ni, has been inferred. The results showed that the prepared SiO2coated nano-scale Fe/Nishowed highly reactive under a various pH condition. After reaching higher decolorization, the dissolvedquantity of iron ion and nickel ion kept at a comperatively low concentration in the solution, which will noteasy to cause secondary pollution. During the decolorization process, iron corrosion reaction isaccompanied by the release of metal ions. The nano-scale iron particles was consumed firstly, and then thenickel dissolved gradually into the solution by participating in the catalytic hydrogenation reaction. Afterthe decolorization efficiency increased up to maximum, the concentration of metal ions dropped graduallyfor the sake of transformation, adsorption, netting and precipitation. In the molecular structure of Orange G,the azo bond chromophore and the naphthalene ring structure is easily to be broken and then opened loop.However, the degradation of the benzene ring structure was slow and the ring was difficult to open. Thepepared SiO2coated nano-scale Fe/Ni improved the dispersibility of the nano-scale particles. In theprotective effect of silica films, the effect of catalytic hydrogenation of nickel nanoparticles and crossionreaction were given into full play, decreasing the benzene ring structure effectively.The comparison results of the improved electrochemical oxidation and nano zero valent iron reductionmethods show that the latter has a higher response rate than the former and easy to operate, thus, it issuitable for pretreatment of large quantities of wastewater, but the material is not easy to store. The latterhas a strong mineralization to pollutants, but the reaction time is longer and the power consumption islarger. Thus, it is suitable for depth treatment of a small amount of water. The proposal of the combinationof two methods for dyeing wastewater treatment can make up each other. |
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