Adsorption of acid dyes using polyelectrolyte impregnated mesoporous silica

Cationic polyelectrolyte, PDDA (Poly(diallyldimethylammonium chloride)), was impregnated on mesoporous silica SBA-15 (PDDA/SBA-15) and amorphous conventional silica (PDDA/CS) supports. Acid dye adsorption characteristics, such as adsorption kinetics, adsorption isotherms, maximum adsorption capacity, and breakthrough curves of the prepared PDDA/SBA-15 and PDDA/CS adsorbents, were examined by batch and column adsorption techniques where the Acid Violet 17, Acid Red 44, and Acid Blue 45 were used as target adsorbates. PDDA/SBA-15 adsorbent showed fast adsorption kinetics of less than 10 min and much higher adsorption capacities compared to PDDA/CS due to large pore sizes, ordered cylindrical pore structures, and high amount of impregnated PDDA. Results from batch and column experiments showed that practical use of PDDA/SBA-15 adsorbent for effective removal of acid dyes from aqueous solution would be possible. Polyelectrolyte impregnation method was suggested as a simple method for the development of adsorbent with large pore diameters and efficient adsorption characteristics.     

Investigation of the photodegradation properties of iron oxide doped mesoporous SBA-15 silica

Mesoporous silica (SBA-15) and iron oxide incorporated silica (Fe₂O₃-SBA-15) were synthesized by co-operative self-assembly technique. Samples were characterized using nitrogen adsorption–desorption isotherm, electron microscopic and spectroscopic techniques. The results confirm the uniform distribution of pores, presence of metal oxides in the pores as well as in the surface of the mesoporous wall and oxidation state of iron in the Fe₂O₃-SBA-15. The photocatalytic degradation of methylene blue (MB), sulphorhodamine B (SR-B) and methyl orange (MO) by Fe₂O₃-SBA-15 was investigated. It was observed that Fe₂O₃-SBA-15 degraded 98 % of MB, 96 % of SR-B and 99 % of MO within 3 h after exposure to sunlight. SBA-15 does not exhibit any photocatalytic effect. These results demonstrate the potential of Fe₂O₃-SBA-15 for environmental pollution control.     

Cu/SBA-15 as adsorbent for propane/propylene separation

Samples of mesoporous silica SBA-15 were prepared under hydrothermal conditions where Cu cations were incorporated to the structure by impregnation in order to compare the adsorption behavior in the presence and absence of this element. The adsorption/desorption equilibrium isotherms of propylene, propane, and N₂ were measured to evaluate their usefulness in the propane/propylene separation. All the adsorption isotherms of SBA-15 measured in the absence of Cu cations were described by the Freundlich equation, while the adsorption isotherms of propane on Cu/SBA-15 were better represented by the Henry equation and those of propylene were satisfactorily described by the Langmuir model in the range P < 100 Torr. The adsorption uptake of propylene increased and that of propane decreased in Cu/SBA-15 as compared to the amounts observed in the SBA-15 sample. The presence of Cu atoms in the adsorbent lattice increased the selectivity towards propylene. Under some working conditions the adsorbed amount of propylene in Cu/SBA-15 sample was totally reversible and the propane uptake, negligible.     

TiO2-SBA-15的制备及其吸附脱硫性能

采用等体积浸渍法与过量浸渍法制备TiO2-SBA-15,以FCC汽油为原料,在间歇式反应器中对其吸附脱硫性能进行评价.结果表明,过量浸渍法制备的TiO2分散度较好,比表面积大;TiO2负载量（质量比）为20％,焙烧温度为500℃,吸附剂具有最高的吸附脱硫率,达42.54％,经3次再生,脱硫率仍在35％左右.     

Selective removal of sulfur compounds in city-gas by adsorbents

Silver nitrate impregnated on beta zeolite (BEA), mesoporous silica MCM-41 and SBA-15 (AgNO₃/BEA, AgNO₃/MCM-41, AgNO₃/SBA-15) were prepared to remove sulfur compounds selectively in city-gas, which contains tetrahydrothiophene and tert-butylmercaptane. Sulfur adsorption capacity was determined when the sulfur concentration of effluent gas in breakthrough test reached 0.1 ppm, which is acceptable sulfur concentration for hydrogen production in a reformer for fuel cells. As the AgNO₃ concentration in AgNO₃/BEA, AgNO₃/MCM-41, and AgNO₃/SBA-15 increased, their sulfur adsorption capacities also increased. Although microporous zeolite BEA has smaller pore volume and lower surface area than those of mesoporous silica MCM-41 and SBA-15, the sulfur adsorption capacity of AgNO₃/BEA was higher than those of AgNO₃/MCM-41 and AgNO₃/SBA-15. Adsorbed sulfur molecules per impregnated silver nitrate and the shape change of breakthrough curves depending on the adsorption temperature showed that not only chemisorption but also physisorption was involved in sulfur compounds adsorption on AgNO₃ impregnated adsorbent. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Adsorption of l-histidine over mesoporous carbon molecular sieves

Mesoporous carbon, CMK-3, was prepared by large pore hexagonal mesoporous silica SBA-15. The structural order and textural properties of all the materials were studied by XRD, HRTEM, and nitrogen adsorption. Adsorption of l-histidine (His) over various porous adsorbents such as CMK-3, SBA-15, and activated carbon was studied from solutions with different pH. His adsorption was observed to be pH dependent with maximum adsorption near the isoelectric point of the amino acid. CMK-3 showed a larger amount of His adsorption as compared to SBA-15 and the conventional adsorbent, namely activated carbon. CMK-3 registers the total adsorption capacity of ca. 1350 μmol g⁻¹ which is ca. 12 times higher than the adsorption capacity of SBA-15. This large difference could be mainly due to the stronger hydrophobic interaction between the non-polar side chains of amino acids and the hydrophobic surface of the mesoporous carbon as compared to mesoporous silica. The influence of ionic strengths on the adsorption of His was also studied and the results are discussed. Nitrogen adsorption of CMK-3 after His adsorption confirmed that His molecules are tightly packed inside the mesopores.     

短孔道介孔二氧化硅SBA-15对铀的吸附性能

以短孔道介孔二氧化硅SBA-15为铀吸附剂,考察吸附时间、初始液pH、初始浓度对吸附性能的影响,并分析了吸附动力学和吸附等温线以及吸附前后红外光谱变化。结果表明,初始液pH对吸附具有重要的影响,最佳吸附的pH值为6; 吸附在30 min即可达到平衡; 当初始浓度为100 mg·L^-1时,饱和吸附量为311 mg·g^-1;吸附量随铀溶液初始浓度的增大而增大,而吸附百分数则相反;吸附等温线符合Langmuir和Freundlich吸附模型,吸附动力学符合准二级动力学方程;吸附过程中起主要作用的基团是Si-OH和Si-O-Si。     

Adsorption of cationic dyes from aqueous solution using hydrophilic silica aerogel via ambient pressure drying

In order to remove the organic dyes of textile waste water, the silica aerogel was successfully prepared by using E-40 as a novel precursor and then dried in ambient pressure. The synthesized sample was verified by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). After calcining, the hydrophilic silica aerogel (HSA) was used as adsorbent to remove Methylene Blue (MB), Malachite Green (MG), and Gentian Violet (GV) from aqueous solution. The effects of initial concentration of dyes and adsorbent dosage on the adsorption process were examined. It was found that HSA showed excellent adsorption capacities, the maximum percentage of removal dyes could reach 98%. Herein, the Langmuir, Freundlich and de Boer-Zwikker isotherm modes were employed to discuss the adsorption behavior. The results indicated that the de Boer–Zwikker model can effectively describe the adsorption behavior. Besides, the HSA could be utilized as the recyclable adsorbent in degradation experiment, after five cycles, no obvious loss of adsorption capacity was found. As an efficient, low-cost, environmental friendly and recyclable adsorbent, silica aerogel is expected to be used for dyes removal.     

Reactive adsorption of sulfur compounds in diesel on nickel supported on mesoporous silica

Sulfur compounds in commercial diesel were selectively removed by reactive adsorption using metallic nickel nanoparticles supported on mesoporous silica. Nanosize nickel particles were supported on mesoporous silica SBA-15 and KIT-6 by impregnation of nickel nitrate and subsequent reduction. X-ray diffraction and transmission electron microscopy study revealed that the maximum nickel concentration achieved was 30 wt% for both the substrates, before particle agglomeration sets. Under these conditions, the best dynamic adsorption capacity observed was 1.7 mg/g at 10 ppmw S breakthrough level with a high sulfur diesel (240 ppmw) on 30 wt% Ni/SBA-15. For a low sulfur diesel (11.7 ppmw), the corresponding result was 0.47 mg/g for the same adsorbent at 0.1 ppmw S breakthrough level, which is suitable for fuel cell applications.     

Adsorption performance of mesoporous silicas towards a cationic dye. Influence of mesostructure on adsorption capacity

The dye adsorption performance of four mesoporous silicas with different structure and textural properties, MCM-41, MCM-48, SBA-15 and mesocellular silica foam (MCF), was studied and compared by using toluidine blue O (TBO) as dye model in aqueous solution. These materials were characterized by X-ray diffraction (XRD), small-angle X-ray scattering, nitrogen adsorption-desorption analyses, and transmission electron microscopy (TEM). The effect of some parameters such as adsorbent dosage, contact time, temperature, and pH on the TBO removal in aqueous solution was studied. Results showed that adsorption capacity raised when adsorbent dosage, contact time and pH solution were increased while an increase in temperature decreased the adsorption of TBO. Langmuir, Freundlich and Temkin isotherm models were employed to elucidate the adsorption mechanism while the adsorption rate data were analyzed according to the pseudo-first and second-order kinetic models. Results showed that adsorption of TBO onto MCM-48, SBA-15, and MCF fitted well the Freundlich isotherm model while the kinetic studies showed that adsorption process could be better described by the pseudo-second-order model for all mesoporous silicas. Finally, some solvents were evaluated to carried out dye desorption from the TBO-loaded mesoporous silicas founding that acetic acid was the most efficient.     

Direct synthesis of Cerium(III)-incorporated SBA-15 mesoporous molecular sieves by two-step synthesis method

Cerium(III)-incorporated SBA-15 (Ce-SBA-15) mesoporous molecular sieves were successfully synthesized by a two-step direct synthesis method in acid media, and characterized by XRD, UV–vis, ESR, TEM, N₂ adsorption and FT-IR. The Ce-SBA-15 samples prepared show highly ordered mesostructures with larger pore diameter, pore volume and uniform mesopore size distribution. The valence of cerium species incorporated into the frameworks of SBA-15 can be controlled by adjusting the pH value of the synthesis solution accurately. When the pH value of the solution is 6.0, Ce(III)-SBA-15 can be synthesized. If the pH value is higher than 6.0, the cerium species exist in the SBA-15 sample in form of Ce(IV). Moreover, it can be found that the two-step synthesis method is a feasible, effective and simple method to expand the pore size and the pore volume of SBA-15.     

Synthesis of mesoporous materials SBA-15 and CMK-3 from fly ash and their application for CO2 adsorption

A supernatant solution of silicate species extracted from coal fly ash in a power plant by alkali fusion was used in acidic condition to prepare a mesoporous silica SBA-15. The SBA-15 was used as a template for the synthesis of a mesoporous carbon CMK-3 using sucrose as a carbon source. Characterization of the produced mesoporous materials by XRD, N₂ adsorption-desorption, SEM, and TEM confirmed the formation of well-ordered hexagonal mesostructures. Textural properties were found close to those prepared by pure chemicals. SBA-15 after polyethyleneimine impregnation and CMK-3 were tested for carbon dioxide adsorption, successfully demonstrating the possibility of recycling the industrial waste product in a power plant into a useful adsorbent.     

Adsorption of cationic dyes from aqueous solution using hydrophilic silica aerogel via ambient pressure drying

In order to remove the organic dyes of textile waste water, the silica aerogel was successfully prepared by using E-40 as a novel precursor and then dried in ambient pressure. The synthesized sample was verified by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). After calcining, the hydrophilic silica aerogel (HSA) was used as adsorbent to remove Methylene Blue (MB), Malachite Green (MG), and Gentian Violet (GV) from aqueous solution. The effects of initial concentration of dyes and adsorbent dosage on the adsorption process were examined. It was found that HSA showed excellent adsorption capacities, the maximum percentage of removal dyes could reach 98%. Herein, the Langmuir, Freundlich and de Boer-Zwikker isotherm modes were employed to discuss the adsorption behavior. The results indicated that the de Boer-Zwikker model can effectively describe the adsorption behavior. Besides, the HSA could be utilized as the recyclable adsorbent in degradation experiment, after five cycles, no obvious loss of adsorption capacity was found. As an efficient, low-cost, environmental friendly and recyclable adsorbent, silica aerogel is expected to be used for dyes removal.     

Desulfurization of fuels by means of a nanoporous carbon adsorbent

Mesoporous carbon, CMK-3, was prepared using hexagonal Al-SBA-15 mesoporous silica, instead of SBA-15, as a template. The synthesized materials were examined via X-ray diffraction and N₂-adsorption. The mesoporous carbon was studied for its adsorption of dibenzothiophene (DBT) from petroleum fuels. The performance of this adsorbent was compared with SBA-15 and Al-SBA-15, through which CMK-3 showed higher sulfur adsorption capabilities due to a larger mesopore volume and a higher specific surface area. The uptake capacity for DBT followed the order CMK-3 > Al-SBA-15 > SBA-15. The results confirmed the importance of the adsorbent pore size and its surface chemistry for the adsorption of DBT from liquid phase.Langmuir and Freundlich isotherm models were used to fit equilibrium data for CMK-3. The equilibrium data were best represented by the Langmuir isotherm. Kinetic studies were carried out and showed the sorption kinetics of dibenzothiophene was best described by a pseudo-second-order kinetic model.     

过氧化氢溶液中痕量离子吸附分离用氨基功能化SBA-15的制备及性能

通过后接枝法制备了氨基功能化SBA-15介孔氧化硅(S-N),用于吸附过氧化氢溶液中的金属和阴离子及有机杂质制高纯过氧化氢.研究了接枝量对吸附剂结构和性能的影响并发现S-N中的氮含量随接枝剂用量增加而增加,最高为1.83％.S-N保留了高度有序的六方孔道结构,但比表面积和孔体积均随接枝量增加而下降.在过氧化氢溶液中,各...     

Removal of acid dyes from aqueous media by adsorption onto amino-functionalized nanoporous silica SBA-3

Adsorption of acid dyes on SBA-3 ordered mesoporous silica, ethylenediamine functionalized SBA-3 (SBA-3/EDA), aminopropyl functionalized SBA-3 (SBA-3/APTES) and pentaethylene hexamine functionalized SBA-3 (SBA-3/PEHA) materials has been studied. The structural order and textural properties of the synthesized materials have been studied by XRD, FT-IR and nitrogen adsorption-desorption analysis. The adsorption capacity of the adsorbents varies in the following order: SBA-3/PEHA > SBA-3/APTES > SBA-3/EDA > SBA-3. The SBA-3/PEHA is found to have the highest adsorption capacity for all acid dyes. The adsorption mechanism which is based on electrostatic attraction and hydrogen bonding is described. Batch studies were performed to study the effect of various experimental parameters such as chemical modification, contact time, initial concentration, adsorbent dose, agitation speed, solution pH and reaction temperature on the adsorption process. The Langmuir and Freundlich isotherm models have been applied and the Freundlich model was found to be fit with the equilibrium isotherm data. Kinetics of adsorption follows the second-order rate equation.     

磷酰基乙酸改性粉煤灰基SBA-15及选择性吸附稀土性能

以粉煤灰为硅源合成了介孔二氧化硅SBA-15，对其进行磷酰基乙酸（PAA）功能化改性制备了PAA-SBA-15吸附剂，对改性前后的吸附剂进行了XRD，N2-吸脱附、红外光谱表征。结果显示，改性后SBA-15的孔道保持高度有序。将PAA-SBA-15用于模拟溶液中稀土离子吸附，发现PAA-SBA-15对Eu3+、Gd3+、Tb3+、Nd3+和Sm3+的吸附容量分别可达18.6、23.2、21.9、22.6和20.2 mg/g。考察了竞争离子Ca2+、Mg2+、Al3+和Fe3+对稀土离子吸附的影响。结果显示，Fe3+的存在对PAA-SBA-15吸附稀土离子干扰性最强。吸附动力学和热力学结果显示，PAA-SBA-15对稀土离子的吸附符合准二级动力学和Langmuir等温吸附模型，吸附过程中化学吸附占主导作用。     

2-吡啶甲醛功能化SBA-15介孔材料的制备及其对Cr(Ⅲ)离子的吸附

通过席夫碱反应将2-吡啶甲醛成功嫁接到氨基化的SBA-15介孔分子筛上，本文获得了一种新型功能化SBA-15吸附剂（N-SBA-15）。采用傅里叶变换红外光谱、X射线衍射、元素分析、扫描电子显微镜、透射电子显微镜、X射线光电子能谱、热重分析和氮气吸附-脱附等手段对N-SBA-15的表面官能团、形貌、孔道结构和表面化学性质进行了详细的表征分析。利用N-SBA-15对水溶液中的Cr(Ⅲ)进行了吸附实验，其最大吸附容量为84.3mg/g。动力学分析和等温吸附研究结果表明，N-SBA-15对Cr(Ⅲ)的吸附过程符合准二级动力学模型和Langmuir模型。吸附热力学分析表明，该吸附过程是自发的吸热过程（?G<0、?S>0、?H>0）。吸附机理分析表明该吸附过程主要是由N-SBA-15表面有机官能团与Cr(Ⅲ)的配位作用实现的。而且，N-SBA-15吸附剂经过5次吸附-脱附测试，仍然对Cr(Ⅲ)具有较高的吸附容量。     

氨基功能化介孔硅吸附剂的制备及其对铬(Ⅲ)的吸附行为

采用3-氨丙基三甲氧基硅烷（APTMS）对SBA-15介孔硅进行改性,获得氨基功能化介孔硅吸附剂（NH₂-SBA-15）,从而赋予其螯合重金属离子的能力。利用XRD、SEM、TEM、EDX、TGA、BET和XPS等手段对吸附剂的表面形貌、孔道结构、元素分布和表面化学性质进行了表征。研究了NH₂-SBA-15吸附剂对水溶液中铬(Ⅲ)的吸附性能,分析了吸附动力学、吸附热力学和再生性能。结果表明,SBA-15吸附剂经过氨基功能化后,其原有的结晶结构没有明显变化,且对铬(Ⅲ)的吸附性能显著提高。NH₂-SBA-15对铬(Ⅲ)的吸附行为符合Langmuir等温吸附模型和拟二级吸附动力学方程。NH₂-SBA-15对铬(Ⅲ)的吸附过程主要依靠其表面—NH₂与铬(Ⅲ)的配位螯合作用,且为吸热过程。经过5次循环利用后,NH₂-SBA-15对铬(Ⅲ)的吸附率仍然保持在92%以上。该氨基功能化介孔硅吸附剂在吸附铬(Ⅲ)方面具有潜在的应用前景。     

载银介孔SBA-15吸附剂的制备及其对脂肪酸甲酯的吸附研究

以介孔分子筛SBA-15作为载体,在3-氨基丙基三乙氧基硅烷(APTS)对SBA-15表面修饰的基础上负载银离子制备Ag⁺-APTS/SBA-15吸附剂,采用氮气吸附-脱附、X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、透射电镜(TEM)、扫描电镜-能谱(SEM-EDS)对吸附剂进行表征,并将吸附剂应用于混合脂肪酸甲酯的分离以考察其吸附性能。氮气吸附-脱附、XRD和TEM分析结果可以看出,制备的吸附剂具有规则有序孔道结构;FT-IR数据显示,介孔SBA-15表面被APTS成功修饰;SEM-EDS结果表明,银离子成功负载到载体SBA-15上;对混合脂肪酸甲酯吸附研究表明,该吸附剂对不饱和脂肪酸甲酯(UFAMEs)吸附效果较好,且随着银离子负载量的增加以及UFAMEs双键数的增多,吸附效果增强;当银离子负载量为25%时,吸附剂对亚麻酸甲酯吸附率高达53.47%。