电化学催化氧化技术处理焦化废水的研究

【作者】 常欣；

【导师】 王博；

【作者基本信息】 陕西师范大学 ， 化学工艺， 2009， 硕士

【摘要】 当今,焦化厂在发展中国家蓬勃发展,并带来了大量的焦化废水。在炼焦过程中产生的焦化废水含有苯酚类物质、氰化物、硫氰化物和多环芳烃等多种高浓度有害物质,不仅会对生态环境造成严重污染,并且难以用常规方法处理。高级氧化技术（Advanced OxidationProcesses,AOPs）是众多水处理方法中的一项技术热点,AOPs反应机理目前普遍认为是自由基氧化机理,即利用复合氧化剂、光照射、电或催化剂等作用,诱发产生多种形式的强氧化活性物质（·OH、HO₂·、过氧离子等）,尤其是·OH,几乎可以无选择性地与废水中的任何有机污染物反应,彻底氧化污染物为CO₂、H₂O或矿物盐。本文研究采用电化学高级氧化技术处理焦化废水。论文的研究内容之一是在臭氧条件下,以高锰酸钾为催化剂以高岭土为载体进行的高级氧化法处理焦化废水。试验探讨了溶液的初始pH值、电流密度、催化剂用量等在多相电化学体系中对焦化废水降解效果的影响。实验表明,在常温常压及臭氧条件下,当体系初始pH为3,电流密度为30 mA·cm^-2时,处理焦化废水的COD降解率80 min内可达到92.5%。催化剂寿命研究表明,在催化剂使用三次后,依然保持它的催化活性。本部分还进一步讨论了经该法处理后水体的可持续性利用问题,实验以处理后水体定时定量灌溉于观赏性植物三叶草栽培土壤,通过研究三叶草叶绿素的日平均变化量,证明该法处理后的水体可完全用于植物灌溉。论文的研究内容之二探索了以高岭土为载体,采用焙烧法利用Fe和Mo制备改性高岭土催化剂,并成功地将其引入到环境科学领域进行水处理方面的研究。使用全自动X射线衍射仪、扫描电镜、红外可见光分光光度计及综合热分析仪对催化剂的结构、形貌及性能进行评价。研究表明,经过改性的高岭土在微观形貌和结构特征上均发生了较大的变化。制备的高岭土催化剂以无定型态存在,随着Al-O结构的缩合析出,层间键断裂,原高岭石结构被破坏,其微观形貌呈粒径较小的多孔性颗粒。最佳参数设计试验表明,该催化剂下在初始pH为6和电流密度为30 mA·cm^-2时,处理焦化废水的COD降解率90 min内可达到90.3%。在第二部分的基础上,论文的研究内容之三探索了以Fe、Mo和V制备改性高岭土为催化剂进行的高级氧化法处理焦化废水,并通过仪器分析比较了改性前后催化剂的结构、形貌和组成特征,以此为评价催化剂优劣的标准。通过对各种影响电化学高级氧化有机废水处理效果的因素如电流密度、pH值、铁离子和氯离子的存在等进行研究,期望得到降解焦化废水的最佳参数。试验表明对于难以处理的焦化废水,Fe₂O₃-MoO₃-V₂O₅负载高岭土是一种有效的催化剂,在常温常压及最佳试验条件下,可以使COD去除率在90 min内达到95.5%。本部分还进一步比较了改性高岭土催化剂存在的多相电化学体系和传统二维电化学体系,以及只有催化剂存在的多相体系的处理焦化废水的能力。研究表明,在相同对比实验条件下,高岭土改性电催化氧化焦化废水的处理效果优于单独二维电化学处理及单独使用催化剂的处理效果,处理焦化废水的COD降解率分别高出其他两个体系26.1%和62.2%。更多还原

【Abstract】 Nowadays, coke plants and coal gasification plants are available in developing countries, so a large volume of wastewater generated from the coking industry contains phenolic compounds, cyanide, thiocyanide and polynuclear aromatic hydrocarbons （PAHs）. The presence of these pollutants in water sources produces long-term environmental and ecological impacts, and which makes it difficult to treat the wastewater by conventional technologies. Advanced Oxidation Processes （AOPs） is the technical key points in treatment of wastewater. It is widely accepted that the mechanism of AOPs is the free radical oxidation mechanism. AOPs employ composite oxidant, irradiation, electricity or catalyst to produce kinds of strong oxydants （·OH, HO₂·, O₂^- ）. Expecially OH, it can degrade any organic pollutements to CO₂, H₂O or mineral salt. Coking wastewater was treated by AOPs in this article.The first part of this thesis is treatment of coking wastewater with AOPs which employ potassium permanganate as catalyst and use kaolin as carrier, in the presence of ozone. The article discussed the effect of parameters like initial pH, current density and catalyst dose on chemical oxygen demand （COD） removal rate with time. The study results showed that at 298 K and 1 atm in the presence of ozone, COD removal efficiency with coking wastewater of 92.5% was obtained in 80 min at pH 3 and 30 mAcm^-2 current density. Catalyst lifetime was also tested, and the results showed that catalyst activity still remained even if the catalyst was used three times. Further discussion about the sustainable use of the treated wastewater was made when using it to irrigate the ornament clover. The chlorophyll concentration of clover was selected as parameter to evaluate the using feasibility of the treated water. The steady amount of chlorophyll indicated that the treated wastewater could be applied to irrigation completely.The second part of this thesis is to use kaolin as carrier, synthesize Fe and Mo modified catalyst which was used in wastewater treatment. Catalyst was charactered by X-ray diffraction （XRD）, Fourier Transform Infrared Spectrometer （FT-IR）, Scanning electron microscope （SEM） and Thermo-gravimetric Analyzer （TGA）. Study indicated there’s a total difference in its micro-sized morphology and structure before and after the modification. The results showed that the previous structure of kaolin had almost disappeared, the stable Al-O ocatahedron structure in neat kaolin had broken, and the losses in crystallinity and the structure deformation. It existed large amount of micro-sized and loose particles. The study results showed that employing modified kaoln catalyst, COD removal efficiency with coking wastewater of 90.3% was obtained in 90 min at pH 6 and 30 mAcm^-2 current density.The third part of this thesis is treatment of coking wastewater with AOPs which employ Fe, Mo and V modified kaolin as catalyst, based on the second part study. Micro-sized morphology and structure of the catalyst were investigated before and after the modification. The effect of current density, initial pH, the presence of Fe³⁺ and Cl^- on COD removal rate with time were tested to find the optimal parameter combination. Experimental results showed that Fe, Mo and V modified kaolin was effectual catalyst in treatment of coking wastewater. In the presence of it at 298 K and 1 atm, COD removal efficiency with coking wastewater of 95.5% was obtained in 90 min at optimal parameter combination. The treatment results were compared using three different systems （multi-phase electrochemical system, traditional two-electrode electrochemical system and only catalyst existed system） to eliminate the pollutants with coking wastewater in this part. The study indicated that the COD degradation rate with coking wastewater under multi-phase electrochemical system was higher than that of two others by 26.1% and 62.2%.更多还原