凹凸棒石/炭复合吸附材料研究进展

近年来,黏土矿物/炭复合吸附材料因具有来源丰富、结构可控和性能稳定等特点,成为碳基复合吸附材料研究热点之一。凹凸棒石是一种天然含水富镁铝硅酸盐黏土矿物,独特的孔道结构和一维棒晶使其成为理想的吸附材料和载体材料。本文综述了凹凸棒石/炭复合吸附材料的研究进展,围绕自然资源的高值化和废弃物的资源化利用,着重介绍了利用凹凸棒石脱色废土构筑环境友好型凹凸棒石/炭复合吸附材料的方法及再生应用进展,总结比较了不同方法制备复合吸附材料的形貌和性质及其对不同类型污染物的去除效果,并展望了凹凸棒石/炭复合吸附材料的未来发展方向,以期为黏土矿物/炭复合材料的研发及其在环境修复领域中的应用提供技术支撑。     

凹凸棒土固载N-杂环卡宾催化安息香缩合反应

本文将五种不同的NHCs催化剂前体接枝到凹凸棒土表面，制备了五种负载型NHCs催化剂。通过FT-IR、元素分析、BET和SEM对五种催化剂进行了表征，表征结果表明NHCs催化剂前体成功地固定在凹凸棒土表面。进一步的实验结果表明，这些负载型NHC可以作为安息香反应的有效催化剂。接着探究了这些负载型催化剂催化安息香反应的优化条件。结果发现，当BTBCl@ATP(催化剂B, 1 mmol%咪唑盐)作为催化剂，0.4当量NaOH作为碱，2ml CH3OH作为溶剂，在110℃油浴中，在Ar气氛中反应8小时，收率最高。在此优化条件下，负载型NHCs催化剂可以催化多种芳香醛的安息香反应，产率为61-86%。催化剂的重复使用实验表明，这些负载型催化剂可以简单地从反应体系中分离出来，重复使用四次后，这些负载型催化剂的催化活性没有明显下降。     

Three-dimensional g-C3N4/MgO composites as a high-performance adsorbent for removal of Pb(II) from aqueous solution

ABSTRACT

A novel, three-dimensional material of g-C₃N₄/MgO was prepared by pyrolysis method. The adsorption behavior for Pb(II) onto g-C₃N₄/MgO was systematically investigated. The adsorption experiments confirmed that the g-C₃N₄/MgO exhibited remarkable adsorption performance owing to its rough morphology and abundant active sites on the surface. The maximum adsorption capacities for Pb(II) reached to 220.3, 226.2 and 235.1 mg/g at 308 K, 318 K and 328 K, respectively. The optimum adsorbent dosage was 1.0 g/L. The adsorption kinetics and isotherm could be well described by the pseudo-second-order model and Langmuir isotherm model, respectively. The adsorption process was spontaneous and endothermic.     

Expanded graphite as a support for Ni/carbon composites

Expanded graphite decorated with nickel oxide particles (EG_NiO) has been synthesized through electrochemical oxidation of natural graphite in an aqueous nickel nitrate solution followed by a heat treatment. EG_NiO was used to prepare nickel/carbon composites using two techniques: (a) hydrogen reduction of nickel oxide particles loaded on the expanded graphite surface and (b) pyrolysis of coal tar pitch-impregnated EG_NiO blocks. The EG_NiO as well as the nickel/carbon composites have been characterized by X-ray diffraction, scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy and selected area electron diffraction.     

Thiol-functionalized magnetite/graphene oxide hybrid as a reusable adsorbent for Hg2+ removal

A thiol-functionalized magnetite/graphene oxide (MGO) hybrid as an adsorbent of Hg²⁺ was successfully synthesized by a two-step reaction. It exhibited a higher adsorption capacity compared to the bare graphene oxide and MGO due to the combined adsorption of thiol groups and magnetite nanocrystals. Its capacity reached 289.9 mg g^-1 in a solution with an initial Hg²⁺ concentration of 100 mg l^-1. After being exchanged with H⁺, the adsorbent could be reused. The adsorption of Hg²⁺ by the thiol-functionalized MGO fits well with the Freundlich isotherm model and followed pseudo-second-order kinetics.     

Insights into high-efficient removal of tetracycline by a codoped mesoporous carbon adsorbent

Adsorbents with simple preparation and high surface area have become increasingly prevalent for the removal of organic contaminants. Herein, a carbon nanoplate codoped by Co and N elements with abundant ordered mesoporous (Co/N-MCs) was applied as an adsorbent for tetracycline removal. Taking integrated advantages of ordered mesopores on carbon-based structures and N-doping inducing the strengthened π–π dispersion and generation of pyridinic N, as well as cobaltic nanoparticles embedded in carbon nanoplates, the Co/N-MCs was tailored for high efficiently absorbing tetracycline via π-π interaction, Lewis acid-base interaction, metal complexation and electrostatic attraction. The Co/N-MCs had the advantages of high surface area, porous structure, plenty adsorption sites, and easy separation. As such, the as-prepared Co/N-MCs adsorbents significantly enhanced tetracycline removal performance with a maximum adsorption capacity of 344.83 mg·g^-1 at pH 6 and good reusability, which was finally applied to removal tetracycline from tap water sample. Furthermore, the adsorption process towards tetracycline hydrochloride could be well attributed to the pseudo-second-order kinetic and Langmuir isotherm models. Compared with traditional carbon-based adsorbents, it owns a simpler synthesis method and a higher adsorption capacity, as well as it is a promising candidate for water purification.     

Sulfated zirconia as a novel and recyclable catalyst for removal of olefins from aromatics

A novel sulfated zirconia (ZrO₂/SO₄^2 −) catalyst was prepared and the catalytic property of this catalyst was compared with active clay and zeolite (USY) in removing olefins from aromatics. Pyridine-FTIR indicated that the abundance of Lewis acid centers on sulfated zirconia is a vital factor for its excellent catalytic activity. N₂ adsorption analysis shows that sulfated zirconia is a promising mesopore catalyst material. The superior catalytic performance as well as efficient reusability demonstrated that sulfated zirconia possesses bright application prospects in industry.     

β-Cyclodextrin functionalized graphene oxide: an efficient and recyclable adsorbent for the removal of dye pollutants

A novel method for the preparation of β-cyclodextrin grafted graphene oxide (GO-β-CD) has been developed. The GO-β-CD was characterized by Fourier transform infrared spectroscopy, ¹³C NMR spectroscopy, Raman spectroscopy and thermogravimetric analysis. The ability of GO-β-CD to remove fuchsin acid from solution was also studied. The GO-β-CD had an excellent adsorption capacity for fuchsin acid and could be recycled and reused. The adsorption capacities of GO-β-CD for other dye pollutants such as methyl orange and methylene blue were also investigated. The absorption capacities for the three dyes are in the order: fuchsin acid>methylene blue>methyl orange.     

Copper oxide nanoblades as novel adsorbent material for cadmium removal

A wide variety of new materials and their hybrids have emerged as novel adsorbents to help resolve contamination of heavy metals in water resources. In this research, copper oxide (CuO) nanoblades were synthesized in high yield using a facile chemical method. These synthesized CuO nanoblades were characterized for their topological, morphological, structural, optical, and chemical behavior using a variety of techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infra red (FTIR) spectrometry, Raman spectroscopy, and UV–Visible spectroscopy. The in-depth investigation confirmed that the blade-shaped synthesized nanomaterial was in pure CuO form. The synthesized nanoblades were 3–4 nm thick and 70–200 nm in length with consistent dots of 3 nm at one side on every blade. The performance of these nanoblades was further evaluated and optimized for cadmium (Cd) removal in relation to the parameters solution pH, contact time, and adsorbent/adsorbate dose. Their cytotoxicity was also assessed for probable utilization at the industrial/commercial level. CuO nanoblades showed a maximum adsorption capacity of 192.30 mg/g for Cd (adsorbent dose: 0.5 mg/ml) and exhibited a best fit for Langmuir isotherm with R² value of 0.99 and b =0.007. This is the first report for chemical synthesis of copper oxide nanoblades followed by their utilization for removal of cadmium ions with such high adsorption capacity.     

Para-magnetic polyvinylbutyral particles containing activated carbon as a new adsorbent

In this study, a new type of magnetic particle was prepared in a uniform and spherical form for the range of 750 w m <D p <1000 w m from commercially available polyvinylbutyral (Mowital B30H, Hoechst), magnetite, and activated carbon using solvent evaporation technique. Magnetite (D p <5 w m) was successfully embedded in the adsorbent particles. The surface and cross-sectional views of p -magnetic particles were investigated with a Scanning Electron Microscope (SEM). The intensity of magnetization was measured with a vibrating-sample magnetometer. The adsorption studies of phenol and chromium (Cr(VI)) onto the adsorbent particles were carried out batch-wise. The effects of activated carbon and magnetite percentages on the adsorption capacity were investigated, and different initial adsorbate concentration and pH values were examined. Desorption experiments were carried out with different concentrations of NaOH, and it was determined that approximately 95% of adsorbed ions were desorbed. It was concluded that the para-magnetic polyvinylbutyral particles containing activated carbon and magnetite could effectively be used in the adsorption of organic and inorganic pollutants.     

Coal based magnetic activated carbon as a high performance adsorbent for methylene blue

Coal based magnetic activated carbons (MACs) were prepared by using the two-stage carbonization and activation of coal in the presence of Fe₂O₃ as the magnetic source. Compared with the single-stage carbonization and activation, the two-stage temperature method was found to be efficient for the preparation of MACs with the high specific surface area and good magnetic properties in a lower alkali/carbon ratio. The as-synthesized MACs at optimized conditions exhibited specific surface areas of up to 2075 m²/g and optimal saturation magnetization of as high as 15.02 emu/g. Moreover, as an adsorbent, the efficiency of removing methylene blue (MB) from aqueous solutions is excellent. Based on MB adsorption behaviors at various conditions, including initial dye concentration, contact time and temperature, MACs prepared at optimized conditions exhibited a maximum equilibrium MB adsorption capacity of 871 mg/g. The data of adsorption kinetics and isotherms could be well fitted by using the pseudo-second-order equation and the Freundlich model. Importantly, MACs can be separated and recovered easily by applying a magnetic field. Therefore, the coal-based magnetic activated carbons might be a promising candidate of high efficiency, low cost for removal of organic dyes.     

Graphene oxide based carbon composite as adsorbent for Hg removal:Preparation,characterization, kinetics and isotherm studies

The presence of Hg in the aqueous media is known to cause severe health issues in both humans and animals.Many technologies and especially adsorbents have been applied for its removal.In this study,a graphene oxide-carbon composite (GO-CC) as a new adsorbent was prepared by sol gel procedure and characterized using field emission scanning electron microscopy,BET and EDX.The effects of different variables including solution pH,contact time,adsorbent dose and GO ratio in adsorbent matrix on the removal capacity of Hg were studied.The isotherm data correlated well with the Langmuir isotherm model.Further analysis recommended that the Hg2+ adsorption process is governed by the intra-particle and external mass transfer,in which the film diffusion was the rate restrictive step.The presented composite has maximum absorption capacity,qmax of 68.8 mg· g-1,which is comparable with carbon based adsorbent reported in the previous publications.(C) 2017 The Chemical Industry and Engineering Society of China,and Chemical Industry Press.All rights reserved.     

Nanographite-reinforced carbon/carbon composites

Carbon/carbon composites (C/Cs) with nanographite platelets (NGP) filler in a matrix derived from phenolic resin were produced. Different weight concentration (0.5, 1.5, 3, 5 wt.%) NGP were introduced by spraying the NGP during the prepreg formation. The NGP-reinforced C/Cs were characterized for effect of NGP concentration on microstructure, porosity, interlaminar shear strength (ILSS), flexural, ultrasonic and vibration damping behavior. At 1.5 wt.% NGP C/C, the highest values of ILSS observed was 10.5 MPa (increased by 22%), flexure strength of 142.4 MPa (increased by 27%), flexural modulus of 59.2 GPa (increased by 68%) and porosity of 18.8% (reduced by 17.5%) in comparison to neat (without NGP) densified C/C. Ultrasonic testing revealed an average increase of 15% through the thickness Young’s modulus of NGP-C/C; (3.12 GPa at 1.5 wt.% NGP). A 20% average decrease in the damping ratio of the first four modes of vibration was observed in 1.5 wt.% NGP densified C/C. At low concentration (⩽1.5 wt.%) the NGP filled in the pores, cracks and debonded interface but at concentration higher than 1.5 wt.% NGP lost their effectiveness due to agglomeration. The required cycles for desired density/properties are projected to be less compared to neat C/C due to less porosity observed in ⩽1.5 wt.% NGP concentration C/C.     

活性炭基吸附剂脱除硫化物的研究

以煤质活性炭为载体,采用旋蒸浸渍法负载碱性金属氧化物,制备了活性炭基吸附剂,用于脱除气体中的硫化物,包括硫化氢、丙硫醇和噻吩。采用X射线衍射分析、孔容及比表面积分析对制备的吸附剂进行了表征,对吸附剂脱除硫化氢、丙硫醇、噻吩等3种硫化物的脱硫性能和反应热效应进行了评价,并考察了空速对反应热效应的影响。试验结果表明:制备的活性炭基吸附剂可以有效脱除硫化氢、丙硫醇、噻吩等3种硫化物,穿透硫容达到50%以上;空速在考察的25~120 h-1时,反应热效应随空速的增加呈线性增加的关系,实际工况下的使用空速不宜超过100 h-1。     

Activated carbon derived from macadamia nut shells: an effective adsorbent for phenol removal

In this study, activated carbon based on the waste macadamia nut shells (MAC) was investigated for potential use as an adsorbent for phenol removal. The pseudo second-order kinetic model best described the adsorption process. The extent of the phenol adsorption was affected by the pH solution and the adsorbent dosage. Equilibrium data fitted well to the Langmuir model with a maximum adsorption capacity of 341 mg g^?1. The calculated thermodynamic parameters suggested that the phenol adsorption onto MAC was physisorptive, spontaneous and exothermic in nature. Phenol desorption from loaded adsorbent was achieved by using 0.1 mol L^?1 NaOH, ethanol (100 %) and deionized water.     

Oxidation resistance of a gradient self-healing coating for carbon/carbon composites

A gradient self-healing coating consisting of three layers, SiC-B₄C/SiC/SiO₂, was examined as a multilayer protection for carbon/carbon composites. The inner layer was made of B₄C and β-SiC, the middle layer was a SiC based layer, and the outer layer was SiO₂ as an airproof layer. Both inner and middle layers were produced to be diphase structure by a pack cementation technique, and the outer airproof layer was prepared by hydrolyzing tetraethylorthosilicate. SEM and EDS investigations showed that the coating had a compositional gradient between B₄C and SiC. The coating showed great self-healing properties from 500 °C to 1500 °C. The weight loss rate of the coated composites was less than 1.3% after 50 h at 1500 °C, and coating represented excellent thermal shock resistance at 1500 °C. The oxidation kinetics of coated carbon/carbon composites showed that the Arrhenius curve consisted of three parts with two broken points at about 700 °C and 1100 °C, and the three parts corresponded to three different self-healing mechanisms in different temperature regions.     

Surfactant-modified bentonite as adsorbent for the removal of humic acid from wastewaters

The effectiveness of surfactant-modified bentonite (SMB) in removing humic acid (HA) from wastewaters was evaluated. Hexadecyl trimethylammonium (HDTMA) chloride was used to modify the surface of the clay mineral. The SMB exhibits very high adsorption potential for HA and at pH 3.0 more than 99% removal was achieved from an initial concentration of 25 μmol/L. The experimental kinetic data were analyzed using the pseudo-first-order kinetic model. Adsorption occurs through film diffusion at low as well as at higher concentrations and temperatures. The adsorption of HA using SMB was an exothermic process. HA adsorption was found to decrease with increase of ionic strength due to the formation of outer-sphere surface complexes on SMB. The equilibrium isotherms were determined and data were analysed using the Langmuir isotherm model. The maximum adsorption capacity, Q° was 73.52 μmol/g with binding constant, b = 0.155 L/μmol at 30 °C and pH 3.0. The adsorbent was suitable for repeated use (more than 3 cycles) without any noticeable loss of capacity.