| Refinery wastewater has large capacity of drainage and complex pollution component. The discharge of water quality could not satisfy with the national discharge standard after dealing with the “Old Three Sets” treatment technology, so the advanced treatment of refinery wastewater is very necessary, advanced oxidation is one of the effective methods of the advanced treatment to deal with the organic wastewater with low biodegradability. This paper studies the photocatalytic oxidation technology of refinery wastewater, and oxalic acid is introduced in the system to solve the problem of the traditional photo-Fenton technique with more iron sludge production and limited p H.The goethite photocatalyst was prepared by the precipitation method. The effects of source of Fe3+, reaction mode, aging temperature and time on the preparation of goethite were studied. In addition, X ray diffraction(XRD) and scanning electron microscope(SEM) were employed for the characterization of crystal phase and micro morphology of the goethite synthesized in terms of varied parameters, by which the best preparation condition was determined. The photocatalytic degradation performance of the goethite was investigated with using bisphenol A(BPA) as the target contaminant.The results indicated that the highly crystalized and uniform rodlike goethite was made by adding Na OH into Fe(NO3)3 and aging under the condition 60 oC for more than 12 h,while the BPA removal efficiency could be achieved more than 90%. Compared with the traditional photo-Fenton system, the UV/goethite/H2O2 system could not only broaden the usable range of p H of utilization, but also reduce the usage amount of hydrogen peroxide and decrease the processing cost.An oxalic acid-enhanced Fenton-like(goethite/H2O2/oxalic acid) process in the UV irradiation was studied by the degradation of bisphenol A(BPA) in wastewater. This paper examined the influence of different influence factors. The maximum BPA removal efficiency was about 96.4% at p H 6 when the BPA initial concentration was 10 mg/L,oxalic acid dosage was 0.33 mmol/L, goethite dosage was 0.7 g/L and H2O2 dosage was 5.5 mmol/L. Moreover, the catalyst had a good stability and reusability. The BPA removal rate maintained 90% after five reaction cycles. Kinetic model was studiede on the basis of erperimental data. The reaction is relatively well consistent with the pseudo second-order rate equation. The corresponding reaction constant was 0.0225L/( mol·min) and the half-life was 4.44 min.Comparison of the different BPA removal rate and·OH formation amount under different conditions, the reaction mechanism which the oxalic acid promotes the reaction of goethite photocatalytic oxidation was discussed. The result showes thatsynergistic effect exists between the goethite and H2O2, and this can significantly improve the BPA removal rate under UV irradiation. The introduction of the oxalic acid could promote the decomposition of H2O2 and accelerate the generation of ·OH, hence could further improve the BPA removal rate.The dynamic experimental equipment of the oxalic acid-enhanced Fenton process in the UV irradiation to handle the refinery wastewater was designed. The dynamic experimental equipment included pretreatment process and photoreaction process. The best conditions were found by optimizing the process conditions. The results showed that the TOC removal efficiency was about more than 70% at p H 6 when the oxalic acid dosage was 0.11 mmol/L, Fe2+dosage was 0.11 g/L and H2O2 dosage was 6.6 mmol/L after 15 min pretreatment. The adding of the pretreatment process could improve the TOC removal rate and reduce the dosage of H2O2. |
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