磁性催化剂的制备及其对染料废水降解适应性工艺的研究

【作者】 张红；

【导师】 李剑超；

【作者基本信息】 陕西师范大学 ， 环境科学， 2012， 硕士

【摘要】 水污染问题一直以来是一个极大的环境污染问题,尤其是高浓度的印染废水,它不仅会导致水体富营养化、扰乱水生生物的生长,还是一种美学污染。纺织印染废水的水质比较复杂,是难处理的工业废水之一。它具有水量大、有机污染物含量高、色度深、碱性大、等特点。CWPO是一种有效处理高浓度、有毒、有害废水的高级氧化技术,对高效催化剂的研究是CWPO技术广泛应用的一个关键部分。活性炭因其良好的特性被广泛的应用于饮用水净化、城市污水及工业废水的深度处理中。随着现在水质变化的日益复杂,活性碳本身的特性已不足于应对。因此将活性炭改性处理,研制出对污染物高效、深度净化的功能活性炭是降低活性炭使用成本、扩大其使用范围、提高其利用效率的有效途径。活性炭改性主要是通过一些物理、化学处理。其中在金属溶液中浸渍就是改善活性炭的孔分布和表面化学环境,提高催化性能的一种重要方法。但其在实际应用中存在分离困难的问题,传统的过滤分离容易引起筛网堵塞或活性炭的流失。因而磁分离作为一种简单高效的分离方法,逐渐被研究应用于水处理中。把磁性物质与粉末活性炭复合在一起制成磁性活性炭,就可解决粉末炭的分离问题。本文把活性炭和铁锰氧化物进行复合,制成复合吸附剂磁性活性碳MAC,并采用混合浸渍焙烧法,用Cu(NO3)2溶液对磁性材料进行改性,制备出磁性催化剂MCAC,对染料进行催化湿式氧化处理,破坏染料分子和结构。实验对材料制备过程中的各影响因素进行讨论,得到最佳的磁性催化剂,以期最大限度的利用材料的催化性能来对模拟染料废水直接紫进行处理。此外,在传统的CWPO过程中,温度对染料的降解具有重要的影响,而一般对反应体系的升温都是通过水浴加热的方法先对溶液相进行升温,再传递至固液界面,使染料进行降解,如果能极大的提高反应界面的温度,染料的降解效率将会更高,而磁热法就是解决这一问题的关键。因此,在本实验中搭建了磁热装置对磁性材料的磁热性能及磁热法对染料的降解性能进行了研究讨论。主要结论如下：(1)用30ml、0.6mol/L Cu(NO3)2浸泡24h,并在600℃下焙烧1h所得的材料在湿式催化氧化法中表现出良好的磁性能和催化性能；通过AC、MAC和MCAC材料的XRD图谱的对比分析可知,经浸渍焙烧后在MCAC材料表面形成的主要金属氧化物为铜铁氧化物CuFe2O4,并且通过MCAC材料的连续5次使用的XRD图谱分析得知MCAC材料表面的活性组分CuFe2O4的化学稳定性很好,有助于材料的长期稳定使用。(2)在本试验中,溶液中催化剂H202的最佳浓度为5.22mol L-1(30%H2O2浓度1.6ml)；反应的平衡时间约为60min,5小时后的去除率可达86.05%；随着温度的上升,染料的去除率不断上升,但当反应温度达到45℃以上时,去除率上升的速度趋于缓慢,本实验选择45℃为最佳反应温度；H+的存在使得反应体系中的H202被分解成OH.自由基,自由基浓度越大催化氧化反应速率越高,染料去除率也越高；当反应体系中有盐浓度存在时,染料的去除率随着NaCl浓度的升高而升高,随着Na2SO4浓度的升高而降低。(3)在添加双氧水的反应体系中,连续使用5次的材料对染料的去除率影响不大；在没有双氧水添加的反应体系中,反应以吸附作用为主,染料的去除率有明显的变化。表明MCAC催化剂具有良好的可重复使用性；此外,脱附再生实验表明,适量浓度的NaOH(10mL,1.5mol L-1)对材料的第一次脱附率为93.94%。而且其他两次实验所得的脱附率的值与第一次的相差不大,表明磁性催化材料MCAC具有较好的可再生性和稳定性。(4)从动态试验可以看出,在8h以前,染料的去除率都在90%以上,最高可达99.50%.通过计算得出,MCAC材料对模拟染料的去除率为34mg g-1。(5)为了考察材料的磁热性能以及磁热法对染料的降解特性的影响,试验采用实验室自制的磁反应装置。通过对磁反应过程的能量流向图的分析得出,磁热量与溶液温度的变化值ΔTw之间存在着线性关系,溶液温度的变化值ATw的值越大,材料表面的升温ΔTA的值就越大；试验中选用蒸馏水代替染料废水作为进水溶液,在自制的磁反应装置中进行流化床试验。结果显示出水最高温度为45.9℃后趋于平稳,溶液温度的变化值ΔT约为20℃。反应的热平横时间约为23min。定性的推导可知,材料表面的温度要远远高于溶液相的温度；磁性填料MCAC的质量越大,达到热平衡时获得的出水温度较高,出水的热平衡时间越长；填充材料的粒径对对出水温度和热平衡时间的影响不明显；填料粒径较小进水温度较高高,获得染料的出水效果较好。更多还原

【Abstract】 Water pollution is continuously a environmental problem attracting much more attention. Especially dye wastewater is a high density waste water contain large volumes of organic matters from dye production and application industries, it was not only cause water eutrophication, disturb the growth of aquatic organisms, but also maybe a aesthetic pollution.CWPO is a kind of effective oxidation technology of wastewater with high concentration and poisonous, the key problem of which is a high-effective catalyst research. Recent years, activated carbon has increasingly been used in dye wastewater treatment because of the excellent adsorption properties. Adsorption effect was proven to be markedly ineffective for handling wastewater containing synthetic dyes. It based on physical processes, although effective for color removal in many cases, merely transfer pollutants to the other media causing secondary waste. While, the above limitation can be overcomed by the exploration research of the more effective materials of modified activated carbon, which has been proposed in current development of water treatment. The overall efficiency of modified activated carbon can reduce the cost of activated carbon and improve its utilization. Much research effort has been launched on the modification of activated carbon. Impregnating AC in the metal ion solution is one of good methods, which improve the surface pore size distribution and chemical activity, even the catalytic properties of modified AC catalysts. In catalytic wet peroxide oxidation (CWPO) process, the catalysts are used to generate hydroxyl radicals in the presence of hydrogen peroxide for the oxidation of wastewater with high organic content. Whereas, the materials utility also limited by the difficulty of solid-liquid separation. The traditional filtrated separation can easily lead to mesh blocked and the loss of activated carbon. To overcome these drawbacks, magnetic separation, as a simple and efficient separation method, has gradually been studied and used in water treatment. The magnetic activated carbon, which was prepared by incorporating magnetic particles on powdered activated carbon, can be manipulated by external magnetic field. Thus the separation problem can be solved. Moreover, it can provide a potential advantage to the materials’recovery and reuse in this process. The objective of this study is to prepare a catalytic material with good magnetism for use in CWPO. By incorporation of manganese ferrite particles (MnFe2O4) on AC surface to prepare the magnetic activated carbon (MAC). Then the MAC was impregnated with copper ion solution at various concentrations and followed by calcination. The obtained catalysts were used in the CWPO of synthetic dye wastewater containing Direct violet (D-BL). Meanwhile, the effect factors have been discussed in the MCAC preparation process and the dye decoloration process. Magnetism, stability and reusability of the catalyst were also tested.In addition, temperature is an important effect factor on dye degradation. The temp of reaction system is generally heating in water bath, first heating to solution phase and then transfer to solution-liquid interface in the traditional CWPO. If can greatly increase the reaction temperature of the interface, the degradation of the dye efficiency will be higher. The magneto caloric method is the key to solve this problem. Therefore, in this lab built magnetic hot devices on magnetic material thermal properties and magnetic hot magnetic method of the degradation of the dye performance discussion. The results show that:(1)By incorporation of manganese ferrite particles (MnFe2O4) on activated carbon surface, the magnetic activated carbon (MAC) was prepared, and the MAC was impregnated with copper ion solution at various concentrations and followed by calcination to obtain MCAC. The MCAC presented an effective activity in decoloration of synthetic dye wastewater containing Direct Heliotrope (D-BL). The SEM/EDX observation identified the metal element were well dispersed and bound in the carbon matrix. The XRD patterns of the MCAC also verified that CuFe2O4as the main catalytic phase play roles in reaction. The H2O2dosage is the important factor to dominate the decoloration rate in CWPO process. The experimental results also showed that the materials have good magnetism under the optimum preparation conditions.(2) In the static CWPO experiment of the decomposition of Direct Heliotrope (D-BL), MCAC catalysts can obtain decoloration percentages of86.05%in5h at45℃, when the solid/liquid is1/300(g/mL) with H2O2dosage of5.22mol L-1. The pH plays a more important effect in the H2O2oxidation process and H2O2decomposed to-OH Radical by the existence of H+. Besides, dye decoloration rate increased gradually with the increase of NaCl salinity, while the reaction system with added Na2SO4was just the opposite. (3) In addition, desorption experiment proved that MCACs has good reproducibility and stability, as well the most of the adsorbed dyes can be desorbed by1.5moL L-1NaOH solution. In the reaction system without adding H2O2, the dye decoloration rate decreased gradually in5cycles. While, in the experiment with adding H2O2, the decoloration rates are basically remain steady, implying directly that the MCAC possessed good reusability.(4) The continuous filtering experiment shows the decoloring ability of MCAC on Direct violet (D-BL) is34mg g-1, and the highest percentage can up to99.50%(5) In order to investigate the magnetic thermal property of the material and magnetic thermal degradation characteristic of the dyes, the laboratory-made magnetic reactor was made. The energy flow diagram of magnetic reaction shows that, there is a linear relationship between the change in the value of temperature of the solution and the magnetic heat. And the higher values of temperature of solution, the greater temperature of the material surface will be. Besides, the distilled water as the feed solution in homemade magnetic reactor shows that water maximum temperature was45.9℃, which was increased about20degree, and the thermal equilibrium time is about23min. The qualitative derivation shows the surface temperature is much higher than that of the solution phase. In addition, higher temperature of effluent water and longer thermal equilibrium time can be reached in the greater quality of the magnetic filler MCAC. Size of the filler material on the water temperature and the thermal equilibrium time is not obvious, but better dying effluent solution can be acquire by smaller particle size and higher influent water temperature.更多还原