共查询到19条相似文献,搜索用时 140 毫秒
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活性炭的吸附性能与其表面化学密切相关,本研究为讨论活性炭表面氧化改性对其Cr(Ⅵ)吸附特性的影响,分析了Cr(Ⅵ)吸附过程与活性炭表面化学性质的关系,阐释吸附机理。结果表明,与未改性活性炭相比,硝酸氧化改性后活性炭对溶液中Cr(Ⅵ)的吸附性能提高,且改性后活性炭的比表面积和孔容积降低,表面的羧基、内酯基和酚羟基等酸性含氧官能团的数量增多。改性活性炭对Cr(Ⅵ)的吸附过程可用Langmuir、Freundlich、D-R和Temkin4种吸附模型模拟,吸附动力学数据与拟二级动力学模型吻合。采用X射线光电子能谱(XPS)表征了改性前后活性炭的表面化学性质。Cr(Ⅵ)在活性炭上的吸附机理主要为静电吸引、还原和配位络合等,与Cr(Ⅵ)发生络合作用的是活性炭表面含氧官能团。 相似文献
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本文主要研究活性炭表面氧化对其吸附二苯并噻吩性能的影响。将活性炭在不同低温下氧化制得表面氧化活性炭,用静态吸附法进行了二苯并噻吩在初始及氧化活性炭上的吸附等温线,应用Langmuir方程对吸附等温线进行拟合,用漫反射红外谱(DRIFTS)表征活性炭表面含氧基团,用Boehm滴定测定活性炭表面官能团含量,讨论了活性炭表面化学性质对其吸附二苯并噻吩的影响。结果表明:活性炭表面酸性含氧基团对二苯并噻吩的吸附有重要影响,酸性含氧基团越多,其吸附量越大。低温气相氧化活性炭提高了活性炭表面酸性含氧基团,提高了其对二苯并噻吩的吸附。氧化温度越高,其表面含氧基团含量越多,其对二苯并噻吩的吸附量也越大。Langmuir吸附等温线可适用于描述二苯并噻吩在活性炭表面上的吸附。 相似文献
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采用H2O2和HNO3作为氧化剂,对市售煤基活性炭表面进行化学改性,探究活性炭表面官能团随氧化剂浓度的变化规律及其对甲烷吸附的影响。结果发现,硝酸氧化增加了活性炭表面的酸性官能团,碱性官能团降低,双氧水氧化使活性炭表面的内酯基含量明显增加,酸性官能团不利于活性炭对甲烷的吸附,而碱性官能团有利于甲烷的吸附。 相似文献
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兰炭因其固定碳和化学活性高,且保留了低变质煤丰富的微孔结构,是一种优质且廉价的活性炭原料。但兰炭末制成的兰炭基活性炭具有孔径分布无序、表面化学性质局限等缺点,限制了其应用效果,而化学法改性可以弥补这一不足。笔者研究对比了无机酸和有机酸改性对兰炭基活性炭孔隙结构和表面化学性质的影响。常温下,分别用硝酸、磷酸、草酸和乙酸溶液对水蒸气活化制备的兰炭基活性炭进行改性,采用碘吸附试验、N2吸附/脱附试验、扫描电子显微镜和Boehm滴定等方法考察改性过程对活性炭孔隙结构和表面化学性质的影响,并对焦化废水进行吸附,分别研究了吸附剂投加量、吸附时间和转速对吸附效果的影响,用Langmuir和Freundlich模型模拟等温吸附过程。结果表明:改性后的兰炭基活性炭表面亲和力大的活性点由于受到酸的刻蚀发生了扩孔作用,导致其碘吸附值、比表面积和孔结构参数均降低,又因为活性炭边缘的高活性碳原子遇酸氧化后会结合氧原子形成含氧官能团,故表面含氧官能团含量升高,且氧化性越强的酸,结合的氧原子越多,硝酸改性后含氧官能团升高最明显,含量是改性前的2.41倍。焦化废水吸附试验表明,经酸改性后的兰炭基活性炭对焦化废水的吸附效果明显优于改性前,其中无机酸改性较有机酸更好,硝酸改性效果最佳,COD去除率比改性前最多可提升31.34%。这是因为焦化废水中污染物的主要是有较大分子量和分子直径的有机污染物,而酸改性使兰炭基活性炭平均孔径增加,中大孔比例提升,这有利于大分子有机污染物被吸附,而且改性后活性炭表面所增加的含氧官能团也提高了对污染物的亲水性和对极性有机物的亲和力。等温吸附试验表明,318 K条件下,50 m L焦化废水中加入4 g硝酸改性兰炭基活性炭吸附90 min后,COD去除率可达86.79%,吸附过程符合Langmuir模型。 相似文献
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《炭素技术》2014,(3)
以玉米秸秆为原料,在不同热解条件下制备活性炭,再运用BET模型和Boehm滴定法测定活性炭孔隙结构和表面性质,并选取性能较优的活性炭进行NaOH改性,研究其改性前后对甲醛的吸、脱附性能和表面结构与表面化学性质变化。结果表明:在最优热解参数60 min、650℃制备的玉米活性炭经NaOH改性后可使其对甲醛饱和吸附时间延长62%,饱和吸附量提高133.33%,比表面积增加3.02%,微孔容积增大0.6%,脱附峰面积和峰高明显增大,且其表面碱、酸性官能团含量分别提高了11.85%、5.51%,说明NaOH改性能提高活性炭的表面碱、酸性官能团含量,增大活性炭比表面积与孔径,从而提高其对甲醛等极性物质的吸附能力。 相似文献
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活性炭广泛应用在工业废气的吸附、脱硝脱硫中,然而,传统活性炭微孔结构较少、孔隙分布不均匀、孔道内灰分较多造成阻塞等,脱硝脱硫效率不理想;在应用前常常需要通过改性手段处理活性炭来扩大其比表面积,提升孔隙率,改善表面官能团与掺杂原子的种类和数量,以此来提升吸附性能。综述了活性炭脱除废气中SO2和NOx的机理,研究了物理改性、化学改性对活性炭比表面积、孔结构、表面官能团等理化性质的影响,以及改性方法对活性炭吸附、脱除烧结废气中NOx/SO2效率的影响规律,展望了用于处理废气脱硝脱硫的活性炭改性趋势。 相似文献
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活性炭表面改性及其对Cr(Ⅵ)吸附性能的研究 总被引:12,自引:0,他引:12
分别用HNO3、H2SO4以及HNO3加乙酸铜溶液对活性炭进行了表面改性处理,测定了它们的表面化学性能,研究了改性活性炭对Cr(VI)吸附性能的影响。实验结果表明:通过上述改性,活性炭表面官能团数量发生了显著改变,特别是羧基增加较多;通过改性后的活性炭对Cr(Ⅵ)吸附性能有所提高。 相似文献
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以生物质柞木为原料,采用不同活化法制备具有不同结构特征的柞木基活性炭,利用N2吸附、FT-IR、XPS、XRD、Raman光谱等表征手段对活性炭的微结构特性进行解析,探究活化方式对活性炭微结构性能的影响;微结构与超级电容器性能的构效关系。研究表明: KOH和H3PO4-KOH法制备的活性炭微孔发达,炭结构表面缺陷位与杂原子丰富,在低电流密度下表现出更高的比电容;H3PO4-KOH法制备的活性炭具备更宽的微介孔分布与孔道连通性,使其具有更好的电容保持率;CO2、H3PO4和H3PO4-CO2法制备的活性炭介孔发达,微孔体积小,孔道连通性差,炭结构相对完整,裸露于炭结构表面的缺陷与杂原子相对较少,尽管电容保持率较高,但比电容较低。因此,高性能的超级电容器活性炭电极应具有发达的微孔结构、较宽的微介孔分布、通畅的微介孔连通结构,同时含有更多的裸露于炭结构表面的结构缺陷与杂原子基团,从而提高超级电容器的能量密度。 相似文献
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通过椰壳活性炭对模拟硫酸盐松节油进行液相吸附脱硫的研究,考察了活性炭的结构和表面化学对活性炭吸附的影响。通过Gaussian03计算模拟油中各化合物的化学硬度,根据软硬酸碱理论解释表面化学对该吸附过程的影响。同时考察了活性炭吸附过程的热力学性质。结果表明,由于吸附体系中的二甲基二硫醚和莰烯的化学硬度相接近,活性炭表面的含氧官能团的变化对吸附性能影响不大,但活性炭比表面积和孔结构的变化对吸附性能的影响较为明显;等温吸附平衡数据符合Freundlich等温吸附模型,热力学数据显示该活性炭吸附过程是一个放热、混乱度降低的自发物理吸附过程。 相似文献
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Modifications of commercial activated carbons by chemical treatment with HNO3 or HCl and HF and the adsorption behavior of simple aromatic compounds (aniline, pyridine, phenol, and benzene) on activated carbon and modified activated carbon were investigated. The results show that the textural properties change a little after these modifications, but the surface acidity (mainly oxygen‐containing groups) of activated carbon modified with HNO3 increases greatly. The effect of ash of activated carbon on adsorption of the organic compounds mentioned above is insignificant. However, addition of surface acidity (mainly surface oxygen‐containing groups) decreases the adsorption capacity of compounds significantly. The adsorption uptake of compounds on activated carbon with oxidation of HNO3 is low possibly due to dispersive interaction, water cluster blocking, or competition between water and compounds adsorbed on activated carbon's surface because of hydrophilic increase of the activated carbon surface. The solubility of aromatic compounds in water has an important effect on the adsorption capacity of activated carbon. qm and KL (Langmuir adsorption parameters) for the aromatic compounds vary similarly. 相似文献
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Mohammad Asadullah Mohammad Shajahan Kabir Mohammad Boshir Ahmed Nadiah Abdul Razak Nurul Suhada Abdur Rasid Airin Aezzira 《Korean Journal of Chemical Engineering》2013,30(12):2228-2234
Activated carbons have been prepared from jute stick by both chemical and physical activation methods using zinc chloride and steam, respectively. They were characterized by evaluating surface area, iodine number, pore size distribution, and concentration of surface functional groups. The chemically activated carbon largely featured micropore structure, while the physically activated carbon mainly featured macropore structure. The specific surface area of chemically and physically activated carbons was 2,325 and 723 m 2 /g, while the iodine number was 2,105 and 815mg/g, respectively. The concentration of surface functional groups was determined by Boehm titration method, which suggested that different types of surface functional groups are randomly distributed on chemical activated carbons, while it is limited for physical activated carbon. The microporosity along with surface functional groups provided a unique property to chemically activated carbon to adsorb Methylene Blue dye to a large extent. The adsorption of dye was also affected by the adsorption parameters such as adsorption time, temperature and pH. Comparatively, higher temperature and pH significantly facilitated dye adsorption on chemically activated carbon. 相似文献
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Structural characterization of N-containing activated carbon fibers prepared from a low softening point petroleum pitch and a melamine resin 总被引:1,自引:0,他引:1
The incorporation of heteroatoms like N in activated carbons is of interest to modify the surface chemistry of the materials and, then, to improve their behavior as catalyst or catalyst support. In this work, N-containing activated carbon fibers have been prepared using a petroleum pitch with a low softening point and an N-containing resin. The novelty of the preparation method is that it involves the steps used in the synthesis of activated carbon fibers, i.e. spinning, stabilization, carbonization and activation. The materials have been characterized with techniques such as XPS and UPS, which allows us to follow the changes in both the chemical state of N species and the valence band structure of the carbon samples during the preparation steps. 相似文献
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C Selomulya V Meeyoo R Amal 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1999,74(2):111-122
The removal mechanisms of Cr(VI) from water using different types of activated carbons, produced from coconut shell, wood and dust coal, were investigated in this project. Different types of activated carbons have different surface characteristics. The coconut shell and dust coal activated carbons have protonated hydroxyl groups on the surface (H‐type carbons), while the surface of the wood‐based activated carbon has ionised hydroxyl groups (L‐type carbons). The adsorption kinetics of chromium onto the activated carbons at pH values ranging from 2 to 6 were investigated. It was found that the optimum pH to remove total chromium was 2 for wood‐based activated carbon, while for coconut shell and dust coal activated carbons, the optimum pH was around 3–4. The difference in the optimum pH for different activated carbons to remove Cr(VI) from water can be explained by the different surface characteristics and capacity of the activated carbons to reduce Cr(VI) to Cr(III). © 1999 Society of Chemical Industry 相似文献