载铜介孔碳CMK-3的制备及其对苯酚的吸附-催化氧化性能

通过一种简易的方法在介孔碳CMK-3的孔道内负载氧化铜粒子制备Cu/CMK-3复合物,利用粉末X射线衍射、氮气吸附-脱附、透射电镜等手段对其进行表征.结果表明,氧化铜均匀地分散在CMK-3孔道中,CMK-3在负载氧化铜后仍有较大的比表面积.考察了载铜CMK-3对水中苯酚的吸附和低温干法催化氧化苯酚性能.吸附和循环使用结果表明,Cu/CMK-3对水中苯酚具有较大的吸附量和良好的催化氧化效率.热重-质谱(TG-MS)联用测试结果表明,吸附的苯酚在180℃左右开始被催化氧化为CO2和水,此时不会造成苯酚的脱附和介孔碳CMK-3的烧蚀.     

双孔道管状有序介孔炭对维生素B12的吸附缓释性能

通过纳米铸型法,以硅基介孔分子筛SBA-15为模板,糠醇为碳源,草酸作为聚合催化剂合成了具有双孔道管状有序介孔炭CMK-5.利用粉末X射线衍射(XRD)、扫描电子显微镜(SEM)和氮气物理吸附法等对其结构进行了表征.结果表明合成的CMK-5具有有序结构,比表面积和孔容积分别高达1856 m2·g-1和2.10 cm3·g-1,在3.1和5.5nm具有集中的双孔分布.由于独特的双孔道结构特点,CMK-5在120 min内快速吸附维生素B12至平衡,吸附量高达943 mg·g-1,远高于商用活性炭.CMK-5吸附维生素B12后可以直接用于缓释,动态缓释浓度维持在～9 mg·L-1,适用于维生素B12分子在人体内的缓释.     

Kinetics and Thermodynamics of Adsorption of VB12 onto Mesoporous Carbon Coated with PMMA

Ordered mesoporous carbons CMK-3, CMK-1 coated with poly(methyl methacrylate)(PMMA)(CMK-3- PMMA and CMK-1-PMMA) and pristine mesoporous carbons CMK-3, CMK-1 were employed to adsorb vitamin B12(VB12) from water solution. Adsorption isotherm and kinetics of adsorption were investigated via batch experi- ments. It was found that the adsorption capacity of VB12 at 30, 40 and 50 °C can reach 688.2, 572.4 and 428.7 mg/g, respectively. The adsorption isotherm can be described by Langmuir model. The pseudo first- and second-order kinetic models were employed to fit the dynamic adsorption. It was found that the dynamic adsorption follows the pseudo second-order model. The thermodynamic equilibrium coefficients obtained at different temperatures were used to evaluate the thermodynamic constants ΔG0, ΔH0 and ΔS0. The negative value of Gibbs free energy, ΔG0 indicates that the adsorption occurred via a spontaneous process. The increase in the value of –ΔG0 with increasing temperature indicates that higher temperatures were favourable to the sorption process. The enthalpy values of ΔH040 kJ/mol(66.36 kJ/mol and 56.43 kJ/mol) for CMK-3-PMMA and CMK-1-PMMA confirm that chemisorption were involved in the adsorption process. This is consistent with the IR spectra and is another evidence for the formation of hydrogen bond between PMMA in the pore of CMK-3 and VB12.     

介孔碳CMK-3对苯酚的吸附动力学和热力学研究

研究了介孔碳CMK-3对苯酚的吸附性能, 与传统商用活性碳(CAC)进行了比较, 结果表明, CMK-3比CAC的吸附量大、吸附速率快、达到平衡时间短, 是一种较好的吸附剂. 同时探讨了介孔碳CMK-3对苯酚的吸附热力学和动力学特征. CMK-3对苯酚的吸附行为可用Langmuir和Freundlich等温式进行描述, 相关性都较好, 但更符合Freundlich经验公式. 分别采用模拟一阶反应和二阶反应模型考察了吸附动力学, 并计算了这些动力学模型的速率常数. 模拟二级反应模型和实验数据之间有较好的相关性. 分别计算了热力学参数ΔG0, ΔS0和ΔH0, 结果表明, CMK-3对苯酚的吸附过程是吸热和自发的.     

维生素B12与12-钨磷酸相互作用的双波长共振瑞利散射光谱及其分析应用

建立了一种双波长共振瑞利散射光谱测定维生素B12的新方法. 在pH=1.0的HCl介质中, 维生素B12(VB12)与12-钨磷酸(TP)形成摩尔比为3:1的离子缔合物, 导致双波长共振瑞利散射(DWO-RRS)、 二级散射(SOS)和倍频散射(FDS)光谱显著增强, 其最大散射波长分别位于330和370 nm(RRS), 608 nm(SOS)和386 nm(FDS). 在一定范围内, 3种散射增强(ΔIRRS, ΔISOS和ΔIFDS)均与VB12的浓度成线性关系. 该方法具有较高的灵敏度, RRS, SOS和FDS法对VB12的检出限(3σ)在2.0~7.6 ng/mL之间. 研究了反应条件和共存物质的影响, 结果表明, 该方法具有良好的选择性. 据此, 提出了简便、 快速、 准确且高灵敏测定痕量VB12的光散射新方法, 适用于片剂和尿样中VB12的测定. 还对反应机理和散射光谱增强的原因进行了讨论.     

二氧化碳/甲烷/氮气二元混合物在有序介孔碳材料CMK-3 中的吸附和分离

采用分子模拟与吸附理论研究了天然气成分在有序介孔碳材料CMK-3上的吸附和分离.巨正则系综蒙特卡罗(GCMC)模拟表明,CH4和CO2气体的较优存储条件分别为208 K、4 MPa和298 K、6 MPa,其最大超额吸附量分别为10.07和14.85 mmol· g-1.基于双位Langmuir-Freundlich (DSLF)模型,使用理想吸附溶液理论(IAST)预测了不同二元混合物在CMK-3中的分离行为,发现吸附选择性Sco2/CH4与ScH4/N2比较接近,在298 K和4 MPa下约等于3,而N2-CO2体系中的CO2吸附选择性较高,可达到7.5,说明CMK-3是一种适合吸附和分离天然气组分的碳材料.     

介孔碳材料CMK-3的合成及其吸附性能研究——介绍一个综合化学实验

介绍一个集物理化学、分析化学和无机化学为一体的综合实验——介孔碳材料CMK-3的合成及其吸附性能研究。实验通过合成具有高比表面积的介孔碳材料CMK-3,运用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和氮气吸附/脱附技术表征材料的形貌和多孔结构;考察了介孔碳材料CMK-3对水溶液中次甲基蓝染料分子的吸附性能。     

化学气相沉积法合成Fe/CMK-5及其对溶菌素的吸附性能

以SBA-15为模板,二茂铁为碳源,利用化学气相沉积(CVD)法合成了Fe/CMK-5复合材料.用粉末X射线衍射、低温N2吸附、热重分析、透射电镜等对复合材料进行了表征.结果表明复合材料中碳以CMK-5结构存在,Fe颗粒均匀地分布在CMK-5的骨架中,通过调节CVD时间可改变Fe/CMK-5的结构参数.在pH值为11的缓冲溶液中研究了Fe/CMK-5系列复合材料对溶菌素(lysozyme)的吸附性能,考察了溶菌素在Fe/CMK-5孔道内部的结构稳定性以及在不同pH值溶液中的泄露量.     

维生素B12在玻碳电极上的伏安行为及测定

在以0.1 mol/L KCl为支持电解质、pH 4.56的Britton-Robinson缓冲溶液中,维生素B12在玻碳电极上于-0.68 V(vs. Ag/AgCl)处产生灵敏的还原峰,该峰的电化学还原反应机理为具有吸附特性的不可逆过程.当VB12的浓度较低、搅拌吸附时间较长且扫描速度较快时电极反应可完全由吸附态的VB12所控制,在电极上的吸附模式符合Frumkin等温式.VB12浓度在5×10-9～ 5×10-8 mol/L范围内与还原吸附峰电流呈线性关系,据此对VB12样品进行测定,取得了较好的结果.     

有序介孔碳CMK-3的化学活化及储氢性能

选用KOH、NaOH、H3PO4对有序介孔碳CMK-3进行了活化,通过X射线衍射、低温氮吸附-脱附等对样品进行了表征,发现活化后样品的结构发生了巨大的变化。有序介孔碳CMK-3的有序性逐渐降低,比表面积明显增大,2 nm介孔明显增多。讨论了CMK-3和KOH质量比、活化温度、不同活化剂对活化效果的影响。储氢测试表明活化能够明显提高CMK-3的储氢性能,77K、100 kPa时的储氢性能高达2.32wt%。     

Structural and sorption properties of carbon replicas obtained by matrix carbonization of organic precursors in SBA-15 and KIT-6

We have carried out a comparative study of matrix carbonization of some organic precursors (sucrose, polydivinylbenzene, polyphenol-formaldehyde, polyacrylonitrile, acetonitrile) in SBA-15 and KIT-6 silica mesoporous molecular sieves. We have shown that carbon mesoporous molecular sieves of the CMK-8 type, obtained in KIT-6 mesopores, have better adsorption characteristics due to the features of the three-dimensional cubic structure, the larger pore volume and thickness of the walls of the framework. The maximum micropore volume is observed in CMK-3 and CMK-8, obtained by carbonization of polyphenol-formaldehyde and polydivinylbenzene, while the greatest specific surface area is observed on carbonization of sucrose, where the maximum hydrogen adsorption capacity is achieved at a level of ∼1.4 wt.% (77 K, 1 atm). We show that the mesopore surface coverage by hydrogen in carbon mesoporous molecular sieves increases as the degree of graphitization increases.     

Biomaterial immobilization in nanoporous carbon molecular sieves: influence of solution pH, pore volume, and pore diameter

The adsorption of lysozyme (Lz) onto nanoporous carbon molecular sieves with various pore diameters has been studied at different solution pH values. All the adsorption isotherms have successfully been correlated by the Langmuir equation. The amount of adsorbed Lz depends on the solution pH as well as on the specific pore volume and pore diameter of the adsorbents. The maximum adsorption was observed near the isoelectric point of the Lz (pI approximately 11), suggesting that suppression of electric repulsion between the enzymes plays an important role in the adsorption process. Moreover, the amount adsorbed depends on the pore size and pore volume of the nanoporous carbon adsorbents, indicating that the Lz molecules are adsorbed inside the mesopores. CMK-3-150 shows a larger amount of Lz adsorption as compared to CMK-3. The increased Lz adsorption capacity of CMK-3-150 may be due to the larger pore volume and pore diameter as compared to that of CMK-3. The unaltered structural order of the nanoporous adsorbents after the adsorption has been confirmed by the physicochemical characterization techniques such as XRD and N(2) adsorption. In addition, FT-IR spectroscopic studies confirm that the Lz used in this study is stable even after the adsorption on the nanoporous carbon. These results indicate that nanoporous carbon has superior water stability and thus is a more appropriate adsorbent for biomaterials than nanoporous silica.     

Surface functionalization of ordered mesoporous carbons--a comparative study

Hexagonally structured mesoporous carbons C15 and CMK-5 and cubically structured carbon C48 were synthesized using ordered silica SBA-15 and MCM-48 as templates and carbon precursors of different structures. The surfaces of these ordered carbons were chemically functionalized by employing an approach, in which the selected diazonium compounds were in situ generated and reacted with the carbon frameworks of the mesoporous carbons. The aromatic organic molecules containing chlorine, ester, and alkyl groups were covalently attached to the surface of these ordered mesoporous carbons. The presence of functional groups on the modified carbons was confirmed with Fourier transform infrared spectroscopy, thermogravimetric analysis, and nitrogen adsorption. The BET-specific surface area and the pore width of ordered carbons were significantly reduced, whereas the primary structure of these ordered carbons and their unit cells were intact. Basically, the density of grafted functional groups is related to the specific surface area of the sample, particularly the surface area of mesopores. The surface functionalization reaction takes place only on the external surface of carbon C15, while it occurs on both of the internal and external surface of CMK-5 carbon with the nanopipe structure. The presence of the micropores in CMK-5 carbon should be responsible for its lower grafting density because the small micropores are inaccessible in the reaction. It was also proposed that the preferred adsorption/reaction in C48 may be related to the observed unsymmetrical degradation of the XRD patterns for the functionalized C48 samples. The chemical modification process considerably reduced the primary mesopores in these ordered carbons by approximately 1-1.5 nm, affording carbons with micropores in the cases of C15 and C48, and mixed micropores and small mesopores in the case of CMK-5. A grafting density of approximately 0.9-1.5 micromol/m(2) was achieved under current research.     

Effect of the chemical and structural modification of CMK-3 mesoporous carbon molecular sieve on hydrogen adsorption

The effect of the conditions of postsynthetic modification of CMK-3 carbon mesoporous molecular sieves on their structural and adsorption properties was studied. The specific surface, volume, pore size, and hydrogen adsorption are markedly enhanced upon activation of CMK-3 by thermal, steam, and chemical treatment using H₂, CO₂, H₂O₂, and HNO₃. Analysis of the occupancy density of the mesopore surface indicated increased hydrogen adsorption capacity of the hydrogen-activated carbon surface of CMK-3. Hydrogen adsorption is increased from 1.20 to 2.23 mass % at 1 atm and 77 K by steam treatment. This effect may be employed to create efficient carbon MMS adsorbents, including composite adsorbents, for the accumulation and storage of hydrogen at high pressure (adsorption >6 mass %).     

Effect of the conditions of the matrix carbonization of sucrose on the structure and adsorption properties of mesoporous carbon materials

A study was carried out on the effect of the conditions of the matrix carbonization of sucrose in MCM-48 and SBA-15 silica mesoporous molecular sieves on the structure and adsorption properties of the resultant CMK-1 and CMK-3 mesoporous carbon molecular sieves. CMK-3 was found to be a structurally similar replica of SBA-15. An exact replica is not formed in the case of MCM-48. This failure is attributed to considerable deformation of the matrix during the carbonization process due to the bicontinuous pore system and thinner framework walls. This is probably related to transformation of the carbon material into a low symmetry product upon detemplating of the C/MCM-48 composite (dissolution of the silica). Mesoporous carbon materials were obtained with good adsorption structure features. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 365–370, November–December, 2008.     

CO2 adsorption by activated templated carbons

Highly porous carbons have been prepared by the chemical activation of two mesoporous carbons obtained by using hexagonal- (SBA-15) and cubic (KIT-6)-ordered mesostructured silica as hard templates. These materials were investigated as sorbents for CO(2) capture. The activation process was carried out with KOH at different temperatures in the 600-800°C range. Textural characterization of these activated carbons shows that they have a dual porosity made up of mesopores derived from the templated carbons and micropores generated during the chemical activation step. As a result of the activation process, there is an increase in the surface area and pore volume from 1020 m(2)g(-1) and 0.91 cm(3)g(-1) for the CMK-8 carbon to a maximum of 2660 m(2)g(-1) and 1.38 cm(3)g(-1) for a sample activated at 800°C (KOH/CMK-8 mass ratio of 4). Irrespective of the type of templated carbon used as precursor or the operational conditions used for the synthesis, the activated samples exhibit similar CO(2) uptake capacities, of around 3.2 mmol CO(2)g(-1) at 25°C. The CO(2) capture capacity seems to depend on the presence of narrow micropores (<1 nm) rather than on the surface area or pore volume of activated carbons. Furthermore, it was found that these porous carbons exhibit a high CO(2) adsorption rate, a good selectivity for CO(2)-N(2) separation and they can be easily regenerated.     

Adsorption of aqueous alkylphenol ethoxylate surfactants by mesoporous carbon CMK-3

Mesoporous carbon, CMK-3, was prepared using hexagonal SBA-15 mesoporous silica as the template and the adsorption of nonylphenol ethoxylates (NPE) onto CMK-3 was investigated. The adsorption process was well described using pseudo-second-order kinetics. At initial NPE concentrations of 107 and 530 mg l(-1), the adsorption rate constants were found to be 5.6 x 10(-3) and 8.7 x 10(-4) g mg(-1) min(-1), indicating that a higher initial concentration or adsorption amount resulted in a lower adsorption rate. NPE adsorption onto CMK-3 fitted a Langmuir-Freundlich model and the maximum amounts of NPE absorbed at 15, 25, and 35 degrees C were 923, 720, and 463 mg g(-1), suggesting an elevated adsorption capacity of CMK-3 for NPE with decreased adsorption temperature. In addition, increasing adsorption temperature led to the change of the adsorption model from the Langmuir-Freundlich to the Langmuir model. N2 adsorption results showed that the adsorption of NPE led to a decrease in the mesopore volume of CMK-3. However, the pore width of NPE-loaded CMK-3 was found to be identical to that of CMK-3.     

Adsorption of hydrogen isotopes on micro- and mesoporous adsorbents with orderly structure

The equilibrium and dynamic adsorption data of H(2) and D(2) on different micro- and mesoporous adsorbents with orderly structure including 3A, 4A, 5A, Y, and 10X zeolites; carbon CMK-3; silica SBA-15; and so forth were collected. Critical effect of the nanodimension of adsorbents on the adsorption behavior of hydrogen and its isotopes is shown. The highest adsorption capacity was observed at pore size 0.7 nm, but equal or even larger isotope difference in the equilibrium adsorption was observed at larger pore sizes, whereas the largest isotope difference in the dynamic adsorption was observed at 0.5 nm. The adsorption rate of D(2) is larger than that of H(2) in microporous adsorbents, but the sequence could be switched over in mesoporous materials. Linear relationship was observed between the adsorption capacity for hydrogen and the specific surface area of adsorbents although the adsorbents are made of different material, which provides a convincing proof of the monolayer mechanism of hydrogen adsorption. The linear plot for microporous adsorbents has a larger slope than that for mesoporous adsorbents, which is attributed to the stronger adsorption potential in micropores.     

有序介孔炭的合成及液相有机大分子吸附性能研究

分别采用有序介孔氧化硅SBA-15和NaY分子筛为硬模板合成了系列有序介孔炭OMC和微孔炭CFY. N₂静态吸附测试表明, 所合成的介孔炭具有丰富的介孔结构和集中的介孔分布. 以亚甲基蓝为探针分子, 研究其在有序介孔炭OMC和微孔炭CFY上的吸附行为. 研究结果表明, 有序介孔炭中大于3.5 nm的大介孔孔容是决定亚甲基蓝吸附容量和吸附速率的关键因素. 吸附动力学理论研究表明, 准二级动力学方程可以很好地描述亚甲基蓝分子在介孔炭上吸附动力学行为.