活性炭负载纳米零价铁诱发芬顿反应降解甲基橙的研究

发布时间：2018-01-24 19:26

本文关键词： 活性炭纳米零价铁芬顿效能机制　出处：《哈尔滨工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：非均相Fenton氧化技术具有H_2O_2利用率高、p H适用范围广和催化剂可再生等优势,一直是难降解有机废水领域的研究热点。随着纳米技术的发展,基于纳米零价铁(nanoscale zero-valent iron,nZVI)的非均相Fenton技术受到了广泛关注。但是nZVI的胶体性质决定了它易因团簇而降低活性,因此人们开始研究nZVI的固定化和其催化性能。本研究通过对活性炭负载纳米零价铁制备非均相Fenton催化剂,建立nZVI活性炭/H_2O_2非均相Fenton体系,以典型的偶氮染料甲基橙为目标污染物进行研究,探讨体系处理难降解有机物的可行性和有效性。本文通过对活性炭酸碱改性、负载次数进行优选,得到优选的nZVI活性炭制备条件,并对成品进行表征;其后,考察了优选所得nZVI活性炭对甲基橙降解效能的影响因素以及强化手段,并探讨了体系的作用机制。通过研究发现,以酸洗活性炭为载体,碳热法负载一次所得nZVI活性炭的载铁量较高,载铁稳定性及循环利用效果最佳。载铁后,活性炭密度未发生明显变化,比表面积略有增加。活性炭所载铁颗粒为纳米级零价铁,平均粒径为38.25 nm。对甲基橙进行实验,结果表明甲基橙初始浓度为15 mg/L时最佳实验条件为:初始pH为3,nZVI活性炭投加量为3 g/L,过氧化氢用量为11.76mmol/L,反应210 min后去除率达到93.78%。EDTA的投加可以强化非均相Fenton体系。在pH=7条件下投加100 mg/L EDTA时,可使甲基橙的去除率提升10.55%。不同体系去除甲基橙的结果表明,将nZVI负载于活性炭上能显著提高甲基橙的去除效果。nZVI活性炭/H_2O_2体系属于非均相Fenton反应,其作用机制包括两个方面:一是活性炭的吸附作用,二是nZVI诱发的Fenton氧化作用,二者协同作用,提高了单独作用的效能。活性炭对甲基橙的动态吸附过程符合Freundlich模型,其吸附行为以多层吸附为主,吸附过程符合准二级动力学方程,内扩散和膜扩散是吸附速率的控制步骤。nZVI活性炭催化分解H_2O_2的研究表明,H_2O_2浓度、nZVI活性炭投加量、初始pH均会影响分解速率,通过动力学分析可知其对于[nZVI活性炭]和[H_2O_2]满足二级反应动力学,速率常数k=0.202 3 g/(L·min)。
[Abstract]:Heterogeneous Fenton oxidation technology has the advantages of high utilization ratio of H _ S _ 2O _ 2 and wide application range of H _ 2O _ 2 and regeneration of catalyst. With the development of nanotechnology, nanoscale zero-valent iron is based on nanoscale nanoscale. The heterogeneous Fenton technology of nZVI has attracted much attention, but the colloidal properties of nZVI make it easy to degrade its activity due to the cluster. Therefore, people began to study the immobilization of nZVI and its catalytic performance. In this study, heterogeneous Fenton catalysts were prepared by nano-zero-valent iron supported on activated carbon. The heterogeneous Fenton system of nZVI activated carbon / H _ 2O _ 2 was established and the typical azo dye methyl orange was used as the target pollutant. The feasibility and effectiveness of the system in treating refractory organics were discussed. In this paper, the preparation conditions of nZVI activated carbon were obtained by modifying the acid-base of activated carbon and the times of loading, and the finished product was characterized. After that, the factors affecting the degradation efficiency of methyl orange were investigated and the mechanism of the system was discussed. It was found that the acid-pickled activated carbon was used as the carrier. The results showed that the nZVI activated carbon loaded by carbothermal method had higher iron load, and the stability of iron loading and recycling efficiency were the best. After loading iron, the density of activated carbon did not change obviously. The specific surface area was slightly increased. The iron particles contained in activated carbon were nano-scale zero-valent iron with an average particle size of 38.25 nm. The experiments were carried out on methyl orange. The results show that the optimum experimental conditions for the initial concentration of methyl orange are as follows: the initial pH is 3nZVI activated carbon dosage is 3 g / L. The amount of hydrogen peroxide was 11.76 mmol / L. The removal rate reached 93.78% after 210 min reaction. The heterogeneous Fenton system could be strengthened with the addition of 93.78% EDTA. When 100 mg/L EDTA was added to the system under the condition of pH=7. The removal rate of methyl orange was increased by 10.55%. The results of different systems showed that the removal rate of methyl orange could be increased by 10.55%. Loading nZVI on activated carbon can significantly improve the removal efficiency of methyl orange. NZVI activated carbon / H _ 2O _ 2 system belongs to heterogeneous Fenton reaction. The mechanism includes two aspects: one is the adsorption of activated carbon, the other is the Fenton oxidation induced by nZVI. The dynamic adsorption process of activated carbon to methyl orange accords with the Freundlich model, the adsorption behavior is mainly multi-layer adsorption, and the adsorption process accords with the quasi-second-order kinetic equation. Internal diffusion and membrane diffusion are the control steps of adsorption rate. The study on the catalytic decomposition of H _ 2O _ 2 by using nZVI activated carbon showed that the concentration of H _ 2O _ 2 was increased. The initial pH will affect the decomposition rate, and the kinetic analysis shows that the initial pH can affect the decomposition rate. [NZVI activated carbon and. [H _ 2O _ 2 satisfies the second-order reaction kinetics with a rate constant of 0.202 3 g / L 路min ~ (-1).
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703

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