树枝状硅基纳米粒子对重金属去除研究进展

树枝状介孔二氧化硅纳米粒子(DMSNs)独特的三维中心辐射状孔道结构使其具有出色的比表面积和孔体积,表面硅羟基官能团可作为功能化活性位点。已有研究表明,DMSNs基新型吸附剂材料能够替代传统二氧化硅材料(如MCM-41和SBA-15),对重金属离子具有优异的去除作用。综述总结了DMSNs基新型吸附剂材料的功能化方法,比较了其和功能化MCM-41或SBA-15对不同重金属离子(Pb²⁺、Cr⁶⁺、Hg²⁺等)和放射性金属离子(U(Ⅵ)、Th(Ⅳ)等)的吸附性能,以期为设计具有优越重金属离子去除能力的DMSNs基新型吸附材料提供理论指导。     

APTES改性介孔硅的制备及对重金属离子的吸附性能研究

以介孔二氧化硅为原材料,将3-氨基丙基三乙氧基硅烷(APTES)改性接枝到介孔硅表面,对改性介孔二氧化硅进行表征分析。介孔硅具有较高的比表面积,而APTES中的氨基具吸附重金属功能,使得氨基改性介孔硅吸附重金属离子的功能更强。探讨了介孔硅对重金属的吸附性能,考察氨基功能化介孔硅吸附剂对重金属镉离子(Cd~(2+))、铅离子(Pb~(2+))、铜离子(Cu~(2+))的选择吸附作用。实验结果表明,吸附时间8h以上,介孔硅和改性介孔硅对Cd~(2+)的吸附量分别为0.14、0.15mg/g,对Pb~(2+)的吸附量分别为0.14、0.15mg/g,对Cu~(2+)的吸附量分别为0.13、0.15mg/g;在温度为25℃,震荡时间为24h的条件下,改性介孔硅对Pb~(2+)吸附性能最好,吸附量为0.13mg/g,其次是Cu~(2+)为0.02mg/g,最后是Cd~(2+)为0.01mg/g,说明在3种金属的混合溶液中,改性介孔硅对Pb~(2+)有良好选择吸附性。     

巯基功能化介孔氧化硅的合成及其对Pb(Ⅱ)的吸附

采用直接模板法,以三嵌段共聚物P123作为模板剂,酸性条件下制备出了具有规则孔道结构的介孔氧化硅.用有机硅烷MPTMS对其进行后续功能化,引入了对Pb2 离子有吸附能力的巯基基团.通过HRTEM、FTIR和N2吸附脱附等测试手段对功能化前后氧化硅的结构进行表征,结果表明,巯基功能团接枝在介孔氧化硅孔道内壁.吸附实验结果显示,巯基功能化氧化硅对水中Pb(Ⅱ)离子具有选择吸附性.当铅与铜、镉离子摩尔比为1:5时,巯基功能化材料对其吸附的分配系数之比分别为KdPb2 /KdCu2 =13.1和KdPb2 /KdCd2 =9.2.在Cu2 、Cd2 离子摩尔浓度相同时,此功能化介孔材料对Cd2 的吸附能力大于对Cu2 的吸附能力.     

巯基改性SBA-15的制备及其对Cr6+的吸附

环境中存在的重金属铬对人体健康有严重的危害, 本研究采用水热共缩聚法制备了一种对Cr ⁶⁺有较高吸附能力的介孔材料SBA-15-SH。经红外光谱证实, 通过使用改性硅源3-巯丙基三甲氧基硅烷, 对SBA-15成功实现了巯基改性。经扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察, 所制备的材料呈棒状, 具有均匀的孔道结构, 孔径约为7 nm。将制备材料用于重金属Cr ⁶⁺的吸附, 研究了吸附时间、环境温度、Cr ⁶⁺溶液pH和初始浓度以及吸附剂用量对吸附剂吸附性能的影响。研究表明: 该材料吸附Cr ⁶⁺的平衡吸附时间约10 min, 吸附过程符合Langmuir方程与伪二级动力学模型。当Cr ⁶⁺溶液pH为4.0、吸附温度在25~45 ℃时, 介孔材料SBA-15-SH对Cr ⁶⁺吸附量最大, 达到6.85 mg/g。将本方法用于自来水和工业废水中Cr ⁶⁺的吸附, 回收率介于95%~105%之间。     

巯基功能化短孔道有序介孔材料HS-Zr-Ce-SBA-15的合成及吸附性能

以P123为模板剂,正硅酸乙酯（TEOS）为硅源,氧氯化锆和硝酸亚铈为无机前驱盐,3-巯基丙基-三甲氧基硅烷（MPTMS）为硅烷化试剂,通过一步共缩聚法合成了巯基功能化短孔道有序介孔材料HS-Zr-Ce-SBA-15（HS-ZCS）。采用红外光谱（FT-IR）、小角X射线衍射（LXRD）、透射电镜（TEM）、扫描电镜（SEM）、N2吸附/脱附、热重分析（TG）等手段对HS-ZCS进行了表征。结果表明MPTMS成功地引入到有序介孔材料上,HS-ZCS仍保持了类似于传统SBA-15高度有序的二维六方相介孔结构。对罗丹明6G的吸附实验表明,这种功能化短孔道介孔材料表现出比传统的长孔道SBA-15有更好的传输能力。     

简单中和法制备二茂铁介孔SBA-15复合材料

采用一种新颖的简单中和法,利用羧基二茂铁中的羧基与含有氨基的介孔材料SBA-15作用,将二茂铁成功引入介孔SBA- 15孔道中,避免了二茂铁催化剂与催化产物不易分离,重复使用寿命低及腐蚀污染严重的问题.此方法步骤简单,反应条件温和,也可用于制备其他的介孔基复合材料.通过傅立叶红外光谱分析、X射线衍射分析、透射电镜及能谱分析、N2吸附一脱附实验和热-质谱分析表征了样品的性能,实验结果表明,二茂铁与介孔材料SBA-15结合良好.     

氨基化修饰介孔Fe_3O_4@SiO_2@mSiO_2磁性吸附剂的制备及吸附性能的研究

以Fe_3O_4为磁核,中间包覆一层SiO_2,再以十六烷基三甲基溴化铵(CTAB)为模板剂形成介孔二氧化硅,并以3-氨丙基三乙氧基硅烷(APTES)为表面官能团化基团,对介孔磁性材料表面进行氨基官能团化。通过XRD、TEM、FT-IR对磁性纳米粒子及核壳式磁性纳米复合粒子进行了表征分析。研究了氨基功能化介孔磁性纳米粒子对水中Cu(Ⅱ)的吸附性能。考察了接触时间、溶液的pH值、初始浓度、吸附剂用量对吸附效果的影响,并对其吸附动力学和吸附等温线进行了研究。同时考察了负载了重金属离子的吸附材料用酸溶液超声处理后循环使用的吸附效率。结果表明,二级动力学模型比一级动力学模型更适合于描述吸附剂对Cu(Ⅱ)的吸附动力学行为,说明吸附过程为化学吸附;其对Cu(Ⅱ)的吸附可用Langmuir吸附等温模型进行较好地描述,说明吸附为单分子层吸附,其对Cu(Ⅱ)的最大吸附量为120 mg/g;最大吸附发生在pH值为5.0,t=120 min时。且吸附剂解吸再生4次后,吸附率还能达到68.75%,说明所制备的氨基功能化磁性纳米材料具有较高的吸附容量,是一种潜在的能高效吸附、可再生利用的去除废水中重金属离子的吸附材料。     

介孔炭作为加氢脱硫催化剂载体材料的研究

以介孔硅SBA-15为模板,焦糖和呋喃醇为碳源,通过多种浇注法制备介孔炭材料.采用低温氮吸附、透射电镜和X射线小角衍射分析模板及介孔炭的织构.结果显示合成的介孔炭成功地复制了SBA-15的结构.以制备的介孔炭作载体担载钴钼合成了加氢脱硫催化剂,利用X射线能谱、透射电镜能量分布谱及一氧化氮化学吸附评估了催化剂的活性及活性点分布,结果表明介孔炭担载的催化剂活性高于活性炭担载的同类催化剂.     

镧(Ⅲ)对SBA-15分子筛改性研究

借助水热法,利用三嵌段共聚物聚(1,2-亚乙基二醇)-嵌段-聚(丙二醇)-嵌段-聚(1,2-亚乙基二醇)为模板剂,正硅酸四乙酯为硅源,强酸性条件下制备了分子筛SBA-15.分别以水及水+乙醇为介质采用LaCl₃溶液与煅烧的主体材料SBA-15分子筛固-液相交换法,制备了La-(SBA-15)复合材料.利用化学分析、粉末XRD、N₂吸附技术、IR评价了制备方法的有效性及对SBA-15分子筛孔结构的影响.结果表明,镧已并入SBA-15分子筛中,SBA-15内表面上的硅羟基团是镧进入的主要位置,部分客体在分子筛孔道内.制得的材料La-(SBA-15)保持高度有序的介孔二维六角结构,不改变载体SBA-15的介孔孔道结构.此外,考察了La-(SBA-15)产物的发光现象.     

复合介孔材料的结构与催化性能

以三嵌段共聚物P123为模板剂、正硅酸乙酯为硅源,在强酸和水热条件下合成了介孔分子筛SBA-15,用胺丙基三乙氧基硅烷对分子筛进行功能化。运用X射线衍射、傅里叶红外光谱,N_2吸附-脱附以及透射电子显微镜等手段对功能化前后的介孔分子筛进行了表征。以甘氨酸法制备草甘膦工艺为模型反应进行的催化性能分析表明:该介孔分子筛对该反应具有较高的催化性能。     

Synthesis of novel thiol-functionalized mesoporous silica nanorods and their sorbent properties on heavy metals

Novel thiol-functionalized mesoporous silica nanorods (MSNRs) were synthesized through a base co-condensation method, in which two organoalkoxysilanes, tetraethoxylsilane (TEOS) and bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT), were used as silica precursors simultaneously. TESPT was firstly used for both morphology control and inner surface functionalization of mesoporous silica hybrid materials. The microstructures as well as porous character of the MSNRs were characterized by means of SEM, XRD, TEM and N₂ sorption measurements. Infrared spectrum analysis and heavy metal ions (Ag⁺ and Cd²⁺) adsorption measurements were carried out to confirm the functionalized framework of MSNRs.     

Functionalized silica materials synthesized via co-condensation and post-grafting methods

Mesoporous silica particles have been prepared with functionalized precursors, used either in situ co-condensation process or as post-synthesis grafting agents, in order to deliver surface functionalisation. Aminopropyl, mercaptopropyl, vinyl and hexyl organosilanes were used as funtionalized precursors, tetraethyl orthosilicate as the base silica precursor material, hexadecyl-trimethylammonium bromide (CTAB) as directing agent and water-ethanol mixture as solvent, with ammonia catalyst. The aim was to explore the effect of various recipes on the structural properties of the composite materials. The samples’ microstructures have been evaluated using nitrogen sorption and small angle neutron scattering. Ordered mesoporous structures were obtained, for almost all synthesis conditions, after the solvent-extraction of the template agent. Only in one case, for the materials functionalized by mercaptopropyl groups in co-condensation route, disordered amorphous structure was obtained. All samples functionalized by post-grafting presented well-ordered mesoporous structures. The results have potential use for easy design of sorbent materials for drug loading or pollutant adsorption applications.     

Adsorption performance of VOCs in ordered mesoporous silicas with different pore structures and surface chemistry

Ordered mesoporous silicas with different pore structures, including SBA-15, MCM-41, MCM-48 and KIT-6, were functionalized with phenyltriethoxysilane by a post-synthesis grafting approach. It was found that phenyl groups were covalently anchored onto the surface of mesoporous silicas, and the long-range ordering of the mesoporous channels was well retained after the surface functionalization. The static adsorption of benzene and the dynamic adsorption of single component (benzene) and bicomponent (benzene and cyclohexane) on the original and functionalized materials were investigated. As indicated by the adsorption study, the functionalized silicas exhibit improvement in the surface hydrophobicity and affinity for aromatic compounds as compared with the original silicas. Furthermore, the pore structure and the surface chemistry of materials can significantly influence adsorption performance. A larger pore diameter and cubic pore structure are favorable to surface functionalization and adsorption performance. In particular, the best adsorption performance observed with phenyl-grafted KIT-6 is probably related to the highest degree of surface functionalization, arising from the relatively large mesopores and bi-continuous cubic pore structure which allow great accessibility for the functional groups. In contrast, functionalized MCM-41 exhibits the lowest adsorption efficiency, probably owing to the small size of mesopores and 1D mesoporous channels.     

Preparation of poly (vinyl alcohol)/silica composite nanofibers membrane functionalized with mercapto groups by electrospinning

Membranes of poly vinyl alcohol (PVA)/silica functionalized with mercapto groups are synthesized by electrospinning. Scanning electron microscopy (SEM) studies showed that the fiber diameters are in the range of 200-300 nm. The thickness of nanofiber decreases with an increase in calcination temperature. The results of Fourier transform infrared (FTIR) indicated that PVA/silica nanofibers are functionalized by mercapto groups via the hydrolysis poly-condensation method. N₂ adsorption-desorption showed that organic molecules can be removed completely when the PVA/silica composite fibers are calcinated at 800 °C. The fibers calcinated at 800 °C were pure inorganic silica species with a mesoporous structure. These mercapto groups functionalized PVA/silica nanofibers have a great potential application in the field of adsorption of heavy metal ions.     

Cu(II) complexes imobilized on functionalized mesoporous silica as catalysts for biomimetic oxidations

Mesoporous HMS silica was synthesized and functionalized with 3-aminopropyl-triethoxysilane (APTES) by a post-synthesis method. HMS and NH₂-HMS supports were used for immobilization of two Cu(II) biomimetic complexes ([Cu(acac)(phen)(H₂O)](ClO₄), [Cu(acac)(Me₂bipy)](ClO₄)) or laccase enzyme. Mesoporous structure of the support; functionalization of silica surface, structure of ligands, and Cu complexes; and their immobilization were evidenced by XRD analysis, N₂ adsorption–desorption, SEM microscopy, TGA-DTA, IR and UV–Vis spectroscopy, and elemental analysis. The results confirm the structural integrity of the mesoporous hosts and successful anchoring of the metal complexes over the supports. For comparison, copper-substituted mesoporous silica (Cu-HMS) by using dodecylamine as structure-directing agent was also synthesized. All the synthesized materials were tested for their catalytic activity on the oxidation of 4-aminoantipyridine, 2,2′-azinobis (3-ethyl-benzothiazoline)-sulfonic acid (ABTS) with air, as well as in liquid phase oxidation of anisole and phenol with hydrogen peroxide. In order to verify the complex biomimetic activity, the Trametes versicolor laccase was immobilized by adsorption in the same supports.     

Development of chemically engineered porous metal oxides for phosphate removal

In this study, the application of ordered mesoporous silica (OMS) doped with various metal oxides (Zr, Ti, Fe and Al) were studied for the removal of (ortho) phosphate ions from water by adsorption. The materials were characterized by means of N₂ physisorption (BET), powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM). The doped materials had surface areas between 600 and 700 m² g⁻¹ and exhibited pore sizes of 44–64 Å. Phosphate adsorption was determined by measurement of the aqueous concentration of orthophosphate using ultraviolet–visible (UV–vis) spectroscopy before and after extraction. The effects of different metal oxide loading ratios, initial concentration of phosphate solution, temperature and pH effects on the efficiency of phosphate removal were investigated. The doped mesoporous materials were effective adsorbents of orthophosphate and up to 100% removal was observed under appropriate conditions. ‘Back extracting’ the phosphate from the doped silica (following water treatment) was also investigated and shown to have little adverse effect on the adsorbent.     

Periodic mesoporous organosilicas (PMOs): past, present, and future

Periodic mesoporous organosilicas (PMOs) represent a new class of organic-inorganic hybrid materials suitable for a broad range of applications such as chromatography, catalysis, sensing and microelectronics. Unlike in organic functionalized mesoporous silica phases obtained via grafting or co-condensation procedures the organic groups in PMOs are direct parts of the 3D framework structure, thus giving raise to enormous possibilities to tune their chemical and physical properties in designated ways by varying the structure of the precursors. In this review the distinctive features of PMOs are discussed, the latest developments concerning compositions, structures, morphologies and potential applications are figured out and finally a brief outlook of future aspects is given.     

Preparation of highly ordered Fe-SBA-1 and Ti-SBA-1 cubic mesoporous silica via sol-gel processing of silatrane

Silatrane prepared from fumed silica and triethanolamine (TEA) was used as a precursor for the sol-gel synthesis of M-SBA-1 (M = Fe and Ti) at room temperature using cetyltrimethylammonium bromide as a template, and dilute solutions of ferric chloride and titanium glycolate as metal sources. Powder X-ray diffraction (XRD) showed the mesoporous materials to be well-ordered cubic structures, while N₂ adsorption/desorption measurements yielded high surface areas. Diffuse reflectance UV-visible spectroscopy demonstrated that iron (Fe³⁺) and titanium (Ti⁴⁺) were incorporated in the framework of the calcined materials to loadings of 6 wt.% Fe and 10 wt.% Ti without perturbing the ordered mesoporous structure.     

Functional mesoporous silica nanoparticles for the selective sequestration of free fatty acids from microalgal oil

A series of 2d-hexagonally packed mesoporous silica nanoparticle material with 10 nm pore diameter (MSN-10) covalently functionalized with organic surface modifiers have been synthesized via a post-synthesis grafting method. The material structure has been characterized by powder X-ray diffraction, electron microscopy, and nitrogen sorption analyses, and the free fatty acid (FFA) sequestration capacity and selectivity was investigated and quantified by thermogravimetric and GC/MS analysis. We discovered that aminopropyl functionalized 10 nm pore mesoporous silica nanoparticle material (AP-MSN-10) sequestered all available FFAs and left nearly all other molecules in solution from a simulated microalgal extract containing FFAs, sterols, terpenes, and triacylglycerides. We also demonstrated selective FFA sequestration from commercially available microalgal oil.     

Silica nanoparticles functionalized with a thermochromic dye for textile applications

The aim of this work was the fabrication of mesoporous silica nanoparticles functionalized with thermochromic dye for further incorporation onto textiles. The nanosilicas were prepared under alkaline conditions in the presence of the surfactant hexadecyltrimethylammonium chloride and functionalized with the organosilane dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (C18-NTMS). The dye was incorporated onto the mesoporous silica nanoparticles by two different methods: co-condensation and post-grafting, i.e. by adding the dye during or after the synthesis of the nanosilica, respectively. The morphology, particle and pore size, chemical composition, and textural properties of the silica nanoparticles were characterized by scanning electron microscopy (SEM), dynamic light scattering, N₂ adsorption isotherms at ?196 °C, Fourier transform infrared spectroscopy and thermogravimetry. The silica nanoparticles prepared with and without dye presented spherical shape (by SEM) and particle size ranging from 15 to 40 nm. The infrared spectra revealed the characteristic bands of silica and organosilane (in the cases where it was used). The prepared materials presented colour change when submitted to different conditions. The thermochromic dye-functionalized nanosilicas were efficiently immobilized into cotton fabric and tests were performed to verify the washing fastness. After washing, a slight decrease on the amount of silica was noticed, but much of it remained on the textile. The functionalized textiles presented a colour change within different conditions.