Dye wastewater treatment: Photocatalysis and the synergies of photocatalytic oxidation with Fenton reagent

Photocatalysis and the synergies of photocatalytic oxidation with Fenton reagent were used to treat the dye wastewater of Beijing Fanbo Science & Technology Co., Ltd. Through the orthogonal experiment, the optimal conditions of photocatalysis were obtained. Under such conditions, the removal rate of COD_Cr was 63% while the removal rate of 'chromaticity' was 70%. In experiments on the synergies of photocatalytic oxidation with Fenton reagent, the optimal conditions were: H₂O₂ + FeSO ₄*7H₂O₂ = 12ml/L +1.7g/L, TiO₂ =12g/L, the reaction pH was 3, and the photo-aeration time was 90min. Under such conditions, the removal rate of the wastewater COD_Crreached 89.4% while the removal rate of the chromaticity was 98%, which was more than 50% improvement on simple photocatalytic oxidation. Dye wastewater may include dye production wastewater and the print/dyeing industry wastewater. At present, aromatic hydrocarbon and heterocyclic compounds are the primary components of the dyestuff and they have colour groups and polar groups. Dye developments mean that their structures are becoming more complex and their properties more stable. This brings greater difficulty to the treatment1 of print/dyeing wastewater. Dye wastewater has various characteristics such as the complex ingredients, high chromaticity, high COD_Cr and BOD, suspended matter and a wide range of water quality and quantity with hard to degrade substances. This wastewater is one of the more difficult to treat industry wastewaters. Take the CODCr of a dye user wastewater for example, it is usually between 500 and 1500mg/L while dye production wastewater is usually over 10 OOOmg/L. According to the literature and reports, the decolouration methods for the dye wastewater are mainly biological oxidation process, hydrocarbonylation (chemical oxidation, photocatalysis and microwave synergy), adsorption, coagulation and electrochemical technologies. Fenton reagents have become one much-discussed point. The Fenton method can be applied to the advanced disposal of the wastewater, the application of Fenton reagent and various improved systems in the wastewater disposal can be divided into two groups: one is solely as a disposal method to oxidize the organic wastewater; the other is used synergistically with other methods, such as coagulation sedimentation activated charcoal, biological process and photocatalysis. Beijing Fanbo Corporation is a fur chemical material company. Its wastewater is the typical acid dye production wastewater and contains leather chemical materials such as surfactants in high concentration and grease. The dyes typically have a M.Wt of 400 to 800 and are monosulphonic. The range of COD_Cr in the wastewater may be from 1500mg/L to 160 OOOmg/L and the ingredients complex. As a chemical provider to fur factories, the production wastewater from Fanbo Corporation not only has the same wastewater characteristics as that from the fine chemical industry, but also has the wastewater characteristics typical of leather production. This article has disposed of the dye wastewater from Beijing Fanbo Science & Technology Co., Ltd., by the synergy of photocatalytic oxidation with Fenton reagent and expected to solve the problems of dye wastewater, such as high COD_Cr, high chromaticity, hard degradation and high cost. The particular wastewater is considered to have a moderate COD and average levels of colour.