非沥青粘结剂煤基活性炭制备及水处理的应用研究

发布时间：2018-08-19 21:03

【摘要】：煤基活性炭由于其丰富的孔结构及巨大的比表面积，可有效地去除常规水处理工艺无法解决的溶解性有机物（DOM）。因此，在微污染水深度处理方面获得广泛应用，且发展前景十分广阔。目前，煤基活性炭的工业生产过程中，在添加大量的煤焦油沥青作为粘结剂的工艺中，环境污染严重，而采用新型非沥青有机粘结剂的工艺中，由于高成本使得活性炭生产难度增加。针对以上问题，本文以廉价的煤炭为主要原料，采用课题组自主研发的廉价高效洁净非沥青粘结剂，通过水蒸汽活化、氧化-催化制备、活性炭处理微污染水以及吸附动力学对煤基活性炭的性能进行了系统的研究，取得的主要研究成果与结论如下： 1.非沥青粘结剂煤基活性炭的优化制备操作条件：炭化温度650℃，炭化时间45min，活化温度880℃，活化时间180min，水蒸汽流量0.04mL·(min·g)-1，在此条作下制得的活性炭碘值853.8mg/g，炭收率44.5%，比表面积684.3m2/g，总孔体积0.3852cm3/g，微孔体积0.2455cm3/g，中孔体积0.1362cm3/g，属于中微孔发达型煤基活性炭。 2.原煤经空气和HNO3氧化后，其内部形成碳-氧C（O）微晶耐热大分子结构化合物，且羰基（C=O）、醚基（C-O-C）和硝基（-NO2）等含氧官能团均有明显的增加。（002）衍射峰强度随着空气温度的升高而逐渐减弱，随HNO3浓度的增大而呈现先减弱后增强的变化，在空气温度240℃和HNO3浓度10%处出现最弱，由于炭化的交联与聚合作用，炭化料的石墨化程度大为降低。HNO3氧化后炭化料收率为71.0%，较空气氧化后的67.5%有所提高。当空气氧化温度为240℃，碘值出现最大值875.3mg/g，炭收率55.4%，灰分含量41.3%；当HNO3氧化浓度为10%时，碘值出现最大值970.7mg/g，炭收率38.8%，灰分含量24.2%。 3.原煤经过氧化后，煤基活性炭表面的C与O的赋存形式发生明显变化。其中C主要以石墨碳和烷基碳（C-C）为主，两者之和占总碳含量的70%以上。经空气氧化后，制得活性炭中石墨碳、酚醚碳和羰基碳含量均有较大的增幅，烷基碳和羧基碳含量均减小，羟醚氧的含量增加21.7%，羧基氧含量减小19.1%；经HNO3氧化后，活性炭中烷基碳和羧基碳含量大幅度减小，酚醚碳含量增加，羟醚氧和羧基氧含量分别增加37.0%和40.0%，羰基氧含量减小36.3%。 4.随着催化剂添加量的增加，煤基活性炭的碘值先增加后减小，灰分含量呈现先减小后增加的趋势。添加KNO3制得活性炭的碘值均高于其他两种硝酸盐，灰分含量均低于其他两种硝酸盐。当添加15%的KNO3时，活性炭碘值出现最大1184mg/g，灰分含量出现最小27.43%。 5.不同硝酸盐对制备高性能活性炭的催化活性不同，其顺序为：KNO3NaNO3Fe(NO3)3。由于硝酸盐经炭化后部分的晶体产物（K2O、Na2O2和Fe3C等）与气体产物（O2和NO等）对煤中分子产生不同程度的破坏，，导致炭化料的石墨化程度下降。其中催化机理分为两个部分，一部分硝酸盐在炭化过程中释放出O2和NO，对煤内部支链分子进行氧化，另一部分由于炭化产生的金属氧化物在水蒸汽活化反应过程中起到催化作用，生成大量的孔隙结构。 6.通过UV-VIS分析，非沥青粘结剂煤基活性炭对微污染水中的烷烃、芳香烃和杂环等小分子有机物具有较好的吸附效果，液相吸附等温线符合非均匀Freundlich吸附模型：q=2.36488·c1.16011，其下限吸附容量较大，吸附容量指数较小，更适合处理水中浓度较低的有机物。其处理微污染水的优化条件为：吸附时间150min，投加量2.5g/L，pH值7.80，处理温度50~60℃，在该条件下对初始浓度为9.66mg/L的微污染水处理时，水样中COD和UV254去除率分别可达到83.76%和97.78%。 7.活性炭吸附微污染水中小分子有机物的平衡吸附量均随吸附时间和温度的增加而增大，吸附动力学能够很好地符合伪二级动力学方程模型，反应速率表达式：K=499.49·exp(-25310/RT)，其中活化能Ea=25.31kJ/mol，指前因子A=499.49g·(mg·min)-1，且以物理吸附为主。
[Abstract]:Coal-based activated carbon can effectively remove dissolved organic matter (DOM) which can not be solved by conventional water treatment process because of its rich pore structure and huge specific surface area.
At present, in the process of industrial production of coal-based activated carbon, the environmental pollution is serious in the process of adding a large number of coal tar pitch as binder, but in the process of using new non-asphalt organic binder, it is difficult to produce activated carbon because of the high cost. The performance of coal-based activated carbon (CBAC) was systematically studied by steam activation, oxidation-catalysis preparation, activated carbon treatment of slightly polluted water and adsorption kinetics. The main research results and conclusions are as follows:
1. The optimum preparation conditions of coal-based activated carbon without asphalt binder are as follows: carbonization temperature 650 C, carbonization time 45 min, activation temperature 880 C, activation time 180 min, steam flow rate 0.04 mL ((min g) - 1. Under this condition, the iodine value of activated carbon 853.8 mg/g, carbon yield 44.5%, specific surface area 684.3 m2/g, total pore volume 0.3852 cm3/g, micropore volume 0.2 455cm3/g, mesopores volume 0.1362cm3/g, belongs to medium microporous developed coal based activated carbon.
2. The carbon-oxygen C(O) microcrystalline heat-resistant macromolecule structure compound was formed in the raw coal oxidized by air and HNO_3, and the oxygen-containing functional groups such as carbonyl group (C=O), ether group (C-O-C) and nitro group (-NO2) all increased obviously. (002) The diffraction peak intensity decreased gradually with the increase of air temperature, and then increased with the increase of HNO_3 concentration. The graphitization degree of the carbonized material is greatly reduced due to the cross-linking and polymerization of carbonization. The yield of carbonized material is 71.0% after oxidation, which is higher than 67.5% after air oxidation. When the air oxidation temperature is 240 C, the maximum iodine value is 875.3 mg/g, the carbon yield is 55.4%, and the ash content is increased. 41.3%. When the HNO_3 oxidation concentration was 10%, the iodine value reached a maximum of 970.7 mg/g, the carbon yield was 38.8%, and the ash content was 24.2%.
3. The occurrence of C and O on the surface of coal-based activated carbon changed obviously after the oxidation of raw coal. C was mainly composed of graphite carbon and alkyl carbon (C-C), which accounted for more than 70% of the total carbon. After air oxidation, graphite carbon, phenol ether carbon and carbonyl carbon content in activated carbon increased greatly, alkyl carbon and carboxyl carbon content increased. The content of hydroxyether oxygen increased by 21.7% and the content of carboxyl oxygen decreased by 19.1%. After HNO3 oxidation, the content of alkyl carbon and carboxyl carbon in activated carbon decreased greatly, the content of phenol ether carbon increased, the content of hydroxyether oxygen and carboxyl oxygen increased by 37.0% and 40.0% respectively, and the content of carbonyl oxygen decreased by 36.3%.
4. With the increase of catalyst dosage, the iodine value of coal-based activated carbon increases first and then decreases, while the ash content decreases first and then increases. The iodine value of activated carbon prepared by adding KNO3 is higher than that of the other two nitrates, and the ash content is lower than that of the other two nitrates. The content was minimum 27.43%.
5. Different nitrates have different catalytic activities for the preparation of high performance activated carbon. The sequence is: KNO3NaNO3Fe (NO3) 3. The graphitization degree of carbonized materials is decreased because the crystalline products (K2O, Na2O2, Fe3C, etc.) of nitrates and gaseous products (O2, NO, etc.) destroy the molecule in coal in varying degrees. There are two parts: one part of nitrate releases O2 and NO during carbonization, oxidizing branched chain molecules in coal, and the other part of metal oxides produced by carbonization play a catalytic role in steam activation reaction, resulting in a large number of pore structures.
6. Through UV-VIS analysis, the coal-based activated carbon with non-asphalt binder has better adsorption effect on small molecular organic compounds such as alkanes, aromatic hydrocarbons and heterocycles in slightly polluted water. The adsorption isotherm of liquid phase conforms to the non-uniform Freundlich adsorption model: q=2.36488.c1.16011, which has larger lower adsorption capacity and smaller adsorption capacity index, so it is more suitable for treatment. The optimum conditions for the treatment of micro-polluted water are as follows: adsorption time 150 min, dosage 2.5 g/L, pH 7.80, treatment temperature 50-60 C. Under these conditions, the removal rates of COD and UV254 in the water sample can reach 83.76% and 97.78% respectively when the initial concentration of 9.66 mg/L is treated.
7. Equilibrium adsorption capacity of activated carbon for small molecule organic compounds in slightly polluted water increases with the increase of adsorption time and temperature. Adsorption kinetics is in good agreement with pseudo-second-order kinetic equation model. The reaction rate expression is K=499.49.exp(-25310/RT), in which activation energy Ea=25.31kJ/mol, pre-exponential factor A=499.49g ((mg min))-1 and the activation energy Ea=25.31kJ/mol. Physical adsorption is the main method.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703;TQ424.11

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