【作者】 陈秋强；

【导师】 吴平霄；

【作者基本信息】 华南理工大学 ， 环境工程， 2010， 硕士

【摘要】 在现代,合成染料广泛应用于印染工业,因此产生了大量的印染废水。近年来,高级氧化技术(AOPs)由于其在均相或异相体系中可以产生高氧化活性的羟基自由基而被用于偶氮染料的废水处理。然而,在均相Fenton体系中,铁离子溶于水中,处理后的水体中的残留铁含量通常超过10 mgL-1 ,因此需要后续处理。这就增加了处理成本,同时也产生二次污染的问题,制约了均相Fenton体系的工业应用。为了克服这些缺陷并合成可循环利用的催化剂,越来越多的研究致力于发展异相Fenton催化剂,例如铁膨润土,铁离子交换沸石和铁负载树脂等。许多研究报道铁离子插层的柱撑矿物作为异相Fenton催化剂可有效对偶氮染料去色和矿化。一直以来异相photo-Fenton体系在紫外光降解活性染料废水的应用都备受关在。然而,紫外光只占到达地球的太阳光中的3～5%,而人工紫外线设备通常消耗大量的电能。因此,异相photo-Fenton体系的发展方向主要是制备可有效利用太阳光或可见光的催化剂。在本文中,我们通过离子交换的方式,即使用羟基铁离子交换矿物层间的可交换阳离子,制备了异相photo-Fenton催化剂,并用于研究其对偶氮染料X-GN的去色和矿化性能。本研究探讨了不同降解体系对X-GN的降解效果,以及不同实验参数对异相photo-Fenton体系的降解效果的影响,包括pH条件,H2O2浓度,催化剂投加量,初始X-GN浓度和反应温度。同时分析了TOC去除率并作了降解动力学研究。本研究工作表明铁柱撑蛭石、铁柱撑蒙脱石作为一种异相photo-Fenton催化剂在处理工业染料废水中有很大的应用潜力。本研究的主要结论如下:1.本研究制备了新型的异相photo-Fenton催化剂——铁柱撑蛭石(Fe-VT)。使用激光粒度分析,X射线粉末衍射分析(XRD),X射线粉末荧光分析(XRF),比表面积分析(BET),电子显微镜扫描(SEM)和X射线电子能谱分析(XPS)对Fe-VT进行表征。结果表明低聚合度的羟基铁进入了蛭石的硅片层。在紫外光照射下,在pH =3,温度为30oC, 3.92 mM H2O2以及0.5g/L Fe-VT投加量的实验条件下,75 min后Fe-VT对100 ml的X-GN的去色率为98.7%,TOC去除率为54.4%。同时,原子吸收光谱分析(AAS)结果表明最大铁溶出量小于1 ppm。动力学研究表明,X-GN的去色符合一级动力学方程。其良好的光催化性能和低浓度铁离子溶出量表明铁柱撑蛭石是一种有很大应用潜力的处理染料废水的催化剂。2.使用Fe-Mt/ H2O2作为异相photo-Fenton反应剂在可见光下(λ≥420 nm)对活性艳橙X-GN的去色和矿化。对Fe-Mt的表征结果((XRD、FTIR、XRF、BET、XPS、UV–vis光谱)表明,通过柱撑过程小分子羟基铁成功地进入了矿物的层间域。通过重复使用催化剂和逸出的铁离子浓度探讨Fe-Mt的稳定性。催化实验结果表明,在可见光照射下,在温度为30℃, pH =3.0, H2O2 =4.9mmol/L及0.6 g/L催化剂投加量的条件下,140 min后Fe-Mt对X-GN的去色率为98.6 %。同时,Fe-Mt重复使用3次后去色率仍高于90%。研究过程使用卤钨灯作为可见光光源,表明可见光可有效应用于异相photo-Fenton体系。更多还原

【Abstract】 Nowadays, synthetic dyes are consumed broadly in textile industries and large volumes of dye wastewater are produced. Advanced oxidation processes (AOPs) have been widely applied to deal with azo dye wastewater in recent years, which are characterized by the generation of highly oxidative hydroxyl radicals (?OH) in the homogeneous or heterogeneous phase. However, iron ions which act as catalyst are dissolved in water in the homogeneous Fenton process. Remained iron ions in the treated water normally exceed 10 mg L-1 and need to be removed. This adds to the cost as well as secondary pollution, thus limiting its industrial application. To overcome such limitations and to synthesize reusable catalysts, efforts have been made to develop hetero-Fenton catalysts, such as Fe-treated laponite, iron exchanged zeolite and iron-loaded resin. Many researchers have reported that pillared clays intercalated by iron cations have been used as active heterogeneous Fenton catalysts in decoloration and mineralization of azo dyes.Attention has been focused on the application of a heterogeneous photo-Fenton process to the photodegradation of reactive dye wastewater under UV irradiation. However, the ultraviolet band occupies only 3～5% of the solar light energy that reaches the earth, while artificial ultraviolet apparatus typically consumes large quantities of electrical power. Therefore, it is accepted that an important issue in the heterogeneous photo-Fenton process is to develop catalysts which efficiently use sunlight or visible light irradiation instead of UV as the light source.In this study, iron pillared vermiculite, which was obtained by exchanging the interlayer cations of layered clays with hydroxyl iron ions, was developed as a photo-heterogeneous catalyst in the decoloration and mineralization of the azo dye X-GN. Decoloration of X-GN by different processes was discussed, and the effects of parameters in heterogeneous photo-Fenton process such as solution pH, H2O2 concentration, catalyst dosage, initial X-GN concentration and reaction temperature, were evaluated, to elucidate their effects on the photocatalytic degradation of X-GN. TOC removal and degradation kinetics were also investigated. The present study reveals that iron pillared vermiculite and iron-pillared montmorillonite have great potential as heterogeneous photo-Fenton catalysts for the treatment of industrial dyeing wastewater.The conclusions are as follows:1. In the present study, a novel heterogeneous photo-Fenton catalyst was prepared by iron-pillared vermiculite (Fe-VT). The catalyst Fe-VT was characterized by Laser particle size analyzer, X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer-Emmett-Teller (BET), Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) methods. It was found that hydroxy-Fe of low polymerization degree intercalated into the silicate layers of vermiculite successfully. Under the following experimental conditions: 100mg/L reactive brilliant orange X-GN (named as X-GN) solution, pH 3, 30oC, 3.92 mM H2O2 and 0.5g/L Fe-VT dosage, 98.7% decoloration and 54.4% TOC removal could be achieved with 75 min UV irradiation. The kinetics results showed that decoloration kinetics of X-GN was well fitted by a pseudo-first order equation. In addition, the maximum dissolved iron, determined by atomic absorption spectrophotometer (AAS), was less than 1 ppm. Hence, taking into account the favorable photocatalytic properties and low leaching of iron ions, iron-pillared vermiculite is a promising catalyst for dye wastewater treatment.2. Decolorization and mineralization of reactive brilliant orange X-GN was investigated under visible light irradiation (λ≥420 nm) by using Fe-Mt / H2O2 as the heterogeneous photo-Fenton reagent. The characterization results (XRD、FTIR、XRF、BET、XPS、UV–vis diffuse spectra) of Fe-Mt suggested that small-sized hydrolyzed iron successfully intercalated into the interlayer spaces of the clay via pillaring. The stability of the Fe-Mt catalyst was evaluated according to the decolorization efficiency for X-GN with used catalyst from previous runs and the concentration of iron ions leached from the solid structure into the reaction solution. The catalytic results showed that at a reaction temperature of 30℃, pH 3.0, 4.9mmol/L H2O2 and 0.6 g/L catalyst dosage, 98.6 % discoloration of X-GN were achieved under visible irradiation after 140 min treatment. Furthermore, decoloration efficiency was till higher than 90% after the catalyst Fe-Mt being used for 3 cycles. A halogen lamp as light source has demonstrated that visible radiation can be successfully used for a heterogeneous photo-Fenton process.更多还原