印染废水处理技术综述

印染废水处理技术综述内容摘要：

gradation products of these anic pounds are relatively less toxic and in some cases, these are almost , polluted water is of almost no use, but if these anic pounds are degraded to smaller fragments, then this treated water may be used for washing, cooling, irrigation and cleaning purposes[1]. One of the heavy metals that has been a major focus in water and waste water treatment is chromium and the hexavalent form of it has been considered to be more hazardous due to its carcinogenic properties [2]. Chromium has been considered as one of the toxic pollutants and because of its carcinogenic characteristics, it has been bee a serious health problem. Extensive use of chromium results in large quantities of chromium containingeffluents which need sufficient treatments[3]. Various methods have been proposed for the treatments of wastewater containing nickel as well as copper in wastewater, such as chemical precipitation, reverse osmosis, ion exchange,electrolysis, adsorption and photocatalysis. Removal of Ni (II) and Cu (II) from wastewater can effectively remove by photocatlysis [4]. Commonly applied treatment methods for color removal from dyecontaminated effluents consist of various processes involving biological, physical and chemical decolorization methods [5]. Conventional treatments of dye effluents include biological oxidation and adsorption. Although less expensive than other approaches, biological treatment is ineffective for decolorization because the dyes are toxic. Adsorption onto activated carbon transfers most of the contaminant from the wastewater to the solid phase. This method therefore requires further disposal of the sludge. In recent years, advanced oxidation processes (AOPs) and electrochemical methods have been developed to treat the contaminants of drinking water and industrial effluents. Advanced oxidation processes almost all are based on the generation of reactive species such as hydroxyl radicals (•OH) which degrade a broad range of anic pollutants quickly and it is claimed that there are other species involved, the active species responsible for the destruction of contaminants in most cases seems to be the hydroxyl radical (•OH) which is unstable and quite reactive. Due to the instability of •OH radical, it must be generated continuously ―in situ‖ through chemical or photochemical reactions[6]. Common AOPs involve Fenton, Fentonlike, photoFenton39。 s processes, ozonation, photo chemical and electrochemical oxidation, photolysis with H2O2 and O3, high voltage electrical discharge (corona) process, TiO2 photocatalysis, radiolysis, wet oxidation, water solutions treatment by electronic beams or γbeams and various binations of these methods [711]. Compared with other oxidation processes ,processes using Fenton type reagent are relatively cheap, easily operated and maintained [12]. Fenton prpcess, one of the most effective processes for the removal of anic pollutants from aqueous solutions [1315], involves the application of ferrous salts and hydrogen peroxide to produce hydroxyl radical according to the following scheme of reactions [16]: Fe2+ + H2O2 → Fe3+ + OH– + •OH (1) Fe2+ +•OH → Fe3+ + OH– (2) Fe3+ + H2O2 → FeO2H2+ + H+ (3) FeO2H2+ → Fe2+ + •O2H (4) Fe2+ + •O2H → Fe3+ + •O2H (5) Fe3+ + •O2H → Fe2+ + O2 + H+ (6) H2O2 + •OH → H2O + •OOH (7) Dye degradation： Dye + H2O2 → Intermediates +H2O (8) Dye + •OH → Intermediates (9) Intermediates + H2O2 → CO2 + H2O + Degradation Products (10) Intermediates + •OH → CO2 + H2O + Degradation Products (11) When a Fentonlike reagent is used, the sequence of reaction begins with reaction (3). There are many bibliographic sources which report that Fenton reagent is more effective than Fentonlike reagent[17]. Due to slow dissociation rate in the dark, the generation of hydroxyl radicals was reduced. It is obvious that the most effective AOPs for treating dye solutions is a UVenhanced H2O2/Fe2+ and H2O2/Fe3+ solutions [18]. The high removal efficiencies of this method can be explained by the fact that oxidation reaction are coupled to coagulation occurring due to the presence of ferrous/ferric cations, thus these metallic ions play a double role as a catalyst and a coagulant in the process. Moreover, in the Fenton process the hydrogen peroxide reacting with ferrous ions forms a strong oxidizing agent (hydroxyl radical), whose oxidation potential is higher than that of ozone ( Vpared to ). In Fentonlike reaction, ferric ions react with H2O2 to produce ferrous ions at very slow rate (k= – M–1s–1) few ferrous ions can be formedand thus induce the Fenton reaction. Therefore, only one process with Fe3+/ H2O2 reaction will dominate[19]. In this study, UV irradiated Fenton reagent (photoFenton process) and also UV irradiation Fentonlike reagent (photoFentonlike process) were applied for the minimization of anic content of colored synthetic wastewaters. Reactive azo dye, C. I Reactive Red 12 with azo chromophore was used as model anic pollutants. Investigations were carried out in order to establish optimal operating conditions,( pH , concentration of dye ,concentration of H2O2, and concentrations of Fe +2 and Fe+3 ions) for the degradation of study dye in model colored wastewaters. MATERIALS AND METHODS Series of experiments were conducted in order to find optimal conditions for study the photodegredation of reactive textile dye from wastewaters. The sample of reactive textile dye . Reactive Red 12 (Cibacron BrilliantRed BA ) with azo chromophore from (CIBA Geigy), was used as model pollutant . Their structures is depicted below : Other reagents namely, hydrogen peroxide ( 30% w/v ), FeSO4 .7H2O , Fe2(SO4)3 . 9H2O, NaOH and HCl were of grad from Merck . The effect of initial pH on treatment efficiency of azo dye was investigated. This was done。