【作者】 邹学权；

【导师】 汪大翚；

【作者基本信息】 浙江大学 ， 环境工程， 2008， 博士

【摘要】 氯酚类有机化合物种类繁多，是一类典型的水体“三致”污染物，其降解及消除一直受到广泛的关注，采用吸附方法去除氯酚也一直是人们的研究热点。活性炭具有高度发达的孔隙结构和极大的比表面积，对分子具有极强的吸附能力，是目前最常用的吸附材料之一。为了适应不同的吸附要求，需要对活性炭进行不同性质的改性处理，以调整活性炭的孔隙结构和表面化学性能，活性炭的微波改性就是一种近年来比较流行的改性方式，同时，由于微波加热具有加热速度快、选择性强、可直接作用到样品上等特点，国内外学者已将微波加热技术应用于活性炭再生工艺并就此展开了大量研究。本文主要对微波技术在氯酚水处理活性炭的改性和再生中的应用进行了深入研究，考察微波改性和再生对活性炭吸附性能的影响，并与其它改性方式与再生方法进行了比较，借助N₂等温吸附、元素分析、XPS、XRD、FTIR、SEM、Boehm滴定等手段研究了活性炭改性与再生前后表面结构与化学变化规律，同时通过2，4-DCP等温吸附实验，考察了活性炭改性与再生前后对2，4-DCP的吸附性能，并结合表征分析，探讨了活性炭微波辐照改性与再生对2，4-DCP吸附的影响机理；本文最后还考察了炭载金属对2，4-DCP分解的影响。结果表明：1、微波改性后活性炭对2，4-DCP的吸附性能增强，最大饱和吸附量增幅在12．5％左右；2，4-DCP在改性前后活性炭上的吸附模式发生了变化，由原先的Langmuir吸附转变为Freundlich吸附。活性炭微波处理后比表面积变化不大，孔容略有缩小，孔径分布变化不大，只是向小孔方向发生稍微的移动；改性后活性炭表面氧含量大幅减少，石墨化程度提高，C=O含量增多，碱性以及疏水性能增强。2、渗氮改性后活性炭对2，4-DCP的吸附能力增强明显，增幅可达22．70％，而氧化处理的活性炭则吸附性能减弱，其中浓硝酸改性活性炭吸附性能最弱；活性炭渗氮改性后比表面积与孔容均变大，而H₂O₂改性活性炭则变化不大，但在孔隙结构方面得到了部分改善，主要是由于H₂O₂的氧化腐蚀打通了封闭的细小微空，积累孔容也略有增加；HNO₃处理活性炭总孔容与比表面积均大幅下降，因为高浓度硝酸的强氧化作用使得活性炭的微孔结构坍塌；活性炭经氧化处理后，样品中氧元素含量迅速升高，表面酸性增强，COOH含量大幅提高，π-π^*作用显著增强，而渗氮处理则与之作用相反。3、用间歇实验方法对渗氮和微波改性活性炭测得的吸附平衡数据和吸附动力学数据分别用Freundlich方程和拟二级动力学方程进行拟合，相关度较高；通过对热力学参数的计算可知这两种改性活性炭对水中2，4-DCP的吸附是放热的自发进行的过程，尽管活性炭渗氮和微波改性后其表面化学性质的变化有利于2，4-DCP在其上的化学吸附，但整个吸附过程仍是由物理吸附主导。4、经过一次微波再生后的活性炭对2，4-DCP的吸附能力较原始活性炭有一定的提高，而再生3次和6次的活性炭对2，4-DCP吸附性能则明显降低，这种吸附性能的变化与再生活性炭孔隙的变化有关，同时也受到活性炭表面化学性质的影响；随微波功率与微波辐照时间的增加，吸附于活性炭表面的2，4-DCP的去除率增加；2，4-DCP在再生过程中一部分发生脱附，绝大部分通过热解方式去除，热解过程中形成的积炭容易堵塞活性炭孔隙结构，造成活性炭孔容、比表面积下降，影响其对2，4-DCP的再吸附能力。5、微波再生技术具有与常规加热方式再生更优越的性能，不仅再生耗时少，而且可以保持活性炭原有孔隙结构。经过多次微波再生后，活性炭对2，4-DCP的吸附容量仍保持在相当高的水平；而电加热再生容易造成活性炭孔隙坍塌，一方面使活性炭孔隙结构不利于2，4-DCP的吸附，另一方面也造成了活性炭再生过程中炭损耗量的增加。6、炭载铁催化剂对2，4-DCP的微波降解具有更高的反应活性。负载金属均以单质与氧化物共存的形式均匀附着在活性炭载体表面，其中铁的氧化物及铁在高温下与表面碳原子形成的羰基铁等都是可以强烈吸收微波的物质，在微波场中升温迅速，利于2，4-DCP的降解；而铜的存在对微波具有反射作用，不利于2，4-DCP的微波降解。更多还原

【Abstract】 Chlorophenols are mainly produced in chemical industries, such as pesticide,petroleum refineries, plastics and wood preservation. Chlorophenols and related compoundsare carcinogenic, mutagenic and resistant to biodegradation, so their discharge leads to thecontamination of soils, surface and ground water and living organisms. Many efforts havebeen made for the treatment of chlorophenol-rich wastewater, the adsorption process givesthe best results as it can be used to remove different types of them. Takes the advantages ofgood opening structure and huge surface area, activated carbon （AC） has excellentadsorption capacity and becomes the most common adsorption materials. In order to getdifferent adsorption characteristic, AC will be modified by means of different physical andchemical processes to change its pore structure and surface chemistry. Microwave treatmentis one of the most popular method for AC modification, at the same time, as microwaveheating takes advantages of instantaneous heating, energy and time consuming, a lot ofresearches have been carried out regarding the application of microwave in AC regenerationboth at home and abroad.This dissertation focused on the modification of AC used for the treatment ofchlorophenois and its regeneration by using microwave technology. The adsorptionperformance of 2, 4-DCP onto microwave modified and regenerated activated carbon （AC）were investigated by comparing its adsorption ability with traditional AC modified orregenerated in other ways. Regularity for the change of the surface physicochemicalcharacters was studied with kinds of measurement thchnologies such as N₂ isothermadsorption, elemental analyzer, XPS, XRD, FTIR, SEM and Boehm titration. Theadsorptive ability of 2, 4-DCP on modified and regenerated ACs were characterized with 2,4-DCP isothermal adsorption. Combined with the above analysis of the surface chemistries,the effect mechanisms for the adsorption of 2, 4-DCP on modified and regenerated ACswere studied in details. At last, the activities of AC supported copper and iron catalysts for 2,4-dichlorophenol （2, 4-DCP） decomposition were studied in the presence of microwaveirradiation. Results show that: 1. After microwave modification, the adsorptive capacity of AC is improved, theamplitude is about 12.5%, and the adsorption isotherm model is changed from Langmuirequation to Freundlich equation after modification. Modified AC has little change in thesurface area, modest shrink on pore volume and a little change in pore size distribution,compared with the virgin AC. MW treatment of AC eliminate the oxygen-contained sufacefunctional groups, result in the decrease of surface oxygen content and the increase ofsurface basicity and hydrophobicity, as well, its surface C=O content and graphitizingincreases.2. The adsorption capacity of AC increases rapidly after the modification of nitrogendoping, the amplitude is about 22.70%, while oxidation treatment decreases its adsorptionability, especially when it was modified by nitric acid. With nitrogen doping treatment, thesurface area and pore volume of carbon increased, while with H₂O₂ treatment, the porestructure is somewhat improved, which suggests that the modest oxidizing corrosion openup the enclosed tiny hole. With high concentration HNO₃ treatment, the surface area andpore volume of carbon decreases, for the strong oxidation probably obstruct the entrance ofmicropore. After oxidation, surface oxygen content and acidity of AC increases, whilenitrogen doping treatment gives the contrary effects.3. Equilibrium and kinetic data of 2, 4-DCP adsorption onto nitrogen doping andmicrowave modified ACs gained from batch experiments were fitted to Freundlichequations and pseudo-second-order kinetic model respectively, and the results are verifiedto fit the adsorption data well. The thermodynamics constants of these two adsorptionprocess were estimated, which show that the adsorption of 2, 4-DCP is exothermic andspontaneous, although the chemisorption capability of ACs are enhanced after microwavemodification and nitrogen doping treatment, the adsorption studied here are assigned to aphysisorption mechanism.4. Adsorptive capacities of AC increases more or less after one adsorptionregenerationcycle, afterwards, the adsorptive capacity slowly decreases. This phenomenonnot only related to the textual change of regenerated AC but also affected by the variety ofits surface chemistry. The removal rate of 2, 4-DCP are enhanced with the increase ofmicrowave power and irradiation time. Most of them are removed by pyrolysis, only a little of them are removed through desorption.5. Microwave regeneration offers the advantage over conventional regeneration notonly for its time and energy consuming but also for its maintaining the porosity of AC. Theadsorptive capacities of microwave regenerated AC can maintain relatively high level afterseveral adsorption-regeneration cycles, whereas conventional heating can’t give the soundresult because the porous structure blockage of regenerated AC, on the other hand, the massloss of AC is also higher during conventional heating regeneration.6. Elemental copper and iron are found highly dispersed on the surface of AC in theform of elment and oxide. AC-supported iron catalyst shows desirable activity in thedecomposition of 2, 4-DCP. Powder iron and its oxide are suggested to adsorb microwaveirradiation more intensively, so the temperature of catalyst bed rises more quickly, whilecopper brings the negative effect.更多还原