Effective heavy metal removal from aqueous systems by thiol functionalized magnetic mesoporous silica

A thiol-functionalized magnetic mesoporous silica material (called SH-mSi@Fe₃O₄), synthesized by a modified Stöber method, has been investigated as a convenient and effective adsorbent for heavy metal ions. Structural characterization by powder X-ray diffraction, N₂ adsorption-desorption isotherm, Fourier transform infrared spectroscopy and elemental analyses confirms the mesoporous structure and the organic moiety content of this adsorbent. The high saturation magnetization (38.4 emu/g) make it easier and faster to be separated from water under a moderate magnetic field. Adsorption kinetics was elucidated by pseudo-second-order kinetic equation and exhibited 3-stage intraparticle diffusion mode. Adsorption isotherms of Hg and Pb fitted well with Langmuir model, exhibiting high adsorption capacity of 260 and 91.5 mg of metal/g of adsorbent, respectively. The distribution coefficients of the tested metal ions between SH-mSi@Fe₃O₄ and different natural water sources (groundwater, lake water, tap water and river water) were above the level of 10⁵ mL/g. The material was very stable in different water matrices, even in strong acid and alkaline solutions. Metal-loaded SH-mSi@Fe₃O₄ was able to regenerate in acid solution under ultrasonication. This novel SH-mSi@Fe₃O₄ is suitable for repeated use in heavy metal removal from different water matrices.     

Hybrid surfactant-templated mesoporous silica formed in ethanol and its application for heavy metal removal

With cetyltrimethylammonium (CTAB) and tetramethylammonium hydroxide (TMAOH) as hybrid surfactant templates, a mesoporous adsorbent (adsorbent C) was synthesized in ethanol via the integration of "One-step" procedure and "Evaporation-Induced Self-Assembly" procedure. During the synthesis, TMAOH served as the subsidiary structure-directing agent. Adsorbent C exhibited higher pore diameter (centered at 6.1 nm), BET surface area (421.9 m(2)/g) and pore volume (0.556 cm(3)/g) than the other two adsorbents only using P123 (adsorbent A) or CTAB (adsorbent B) as the surfactant. The adsorbents were also characterized by XRD and FTIR spectroscopy. The adsorption of copper, zinc, lead, iron, silver and manganese ions on adsorbent C was investigated by contrast tests with adsorbent A and B. The experimental data showed that adsorbent C possessed better adsorption properties than the counterparts. The order of adsorption capacity for six metal ions was Mn(2+)相似文献   

Synthesis and properties of dense bulks for mesoporous silica SBA-15 by a modified hydrothermal method

Dense SBA-15 bulks with mesoporous structure as well as powdered SBA-15 were successfully synthesized by the modified hydrothermal method. These SBA-15 bulks have the higher density of 1.16 to 1.19 g/cm³, compared to green density of 0.68 g/cm³ for the pellet from SBA-15 powder. Obtained SBA-15 bulks possessed extremely high BET surface area of 467 m²/g and mesopore of 4.0 nm in diameter The possibility of densification for SBA-15 bulks using this method was confirmed.     

Effective NH2-grafting on mesoporous SBA-15 surface for adsorption of heavy metal ions

Utilizing the reactions between toluene diisocyanate (TDI), silanol, and ethylenediamine (EDA), NH₂ groups were successfully grafted on mesoporous SBA-15 surface without any destroy to the mesostructure. TDI was employed as a ‘bridge’ molecule whose one NCO group was used to link SBA-15 surface silanols and the other one was left to link EDA. Such NH₂-grafting is highly effective for a high loading amount of NH₂ groups on SBA-15 because the special stepwise grafting can avoid amino/silanol and amino/amino interactions. Subjected to remove toxic heavy metal ions in aqueous solution, the obtained NH₂-SBA-15 showed very high adsorption rates 99.4%, 100%, 99.7%, 98.7% and 99.9% for Cu²⁺, Zn²⁺, Cr³⁺, Ni²⁺ and Cd²⁺, respectively, which should be attributed to the strong complexation reactions between metal ions and grafted NH₂ groups.     

Synthesis and characterization of mesoporous composite silica monolith

Coumarin4 (Cou4) was loaded into mesoporous silicon SBA-15 monolith channels by a simple postgrafting method at room temperature. The obtained Cou4/SBA-15 composite monolith was compared with the blank SBA-15 monolith. The investigation of X-ray diffraction, transmission electron microscopy (TEM), UV–vis and photoluminescence (PL) reveals the existence of cou4 in the channels of SBA-15 monolith. In addition, a red-shift and strong fluorescence in PL spectrum was observed from the composite monolith compared with that of Cou4 in C₂H₅OH solution. This is good for the new application of optical materials.     

Synthesis and application of a novel mesoporous SBA-15 sorbent functionalized by 2,4 dinitrophenylhydrazine (DNPH) for simultaneous removal of Pb(II), Cr(III), Cd(II) and Co(II) from aqueous solutions: Experimental design,kinetic, thermodynamic,and isotherm aspects

Heavy metal cations are the most common group of pollutants which significantly contribute to the pollution of aquatic systems. Among the heavy metal cations, lead, chromium, cadmium and cobalt are the most abundant cations present in wastewaters. In this work, a novel sorbent was synthesized via functionalization of chloro-mesoporous SBA-15 with 2,4- dinitrophenylhydrazine. The adsorbent was identified by various characterization techniques and then was used for adsorption of Pb(II), Cr(III), Cd(II), and Co(II). and then the response surface methodology was employed to study the influence, and interaction of different parameters. According to the results, the optimized adsorption capacity of 242.50, 214.72, 187.86, 166.46 mg/g was obtained respectively for the studied cations. furthermore, the sorption of cations was fast and the process achieve to equilibrium within 23.65, 20.31, 24.05 min for Pb(II), Cr(III), Cd(II) and within 19.88 min for Co(II). The adsorbent regenerated by a mixture of nitric acid and methanol could be recycled without losing a remarkable amount of capacity. The results analyzed with various isotherm models were best conformed to the Langmuir model.     

介孔炭材料及介孔炭/氧化硅复合材料对大分子有机污染物的吸附

介孔炭材料与活性炭相比具有较大的孔体积和孔径,高的比表面积以及规则的孔道结构,而介孔炭/氧化硅复合材料兼顾了活性炭与介孔材料的优点,因此在吸附大分子有机污染物方面有很好的应用前景。笔者综述了近年来介孔炭,负载/修饰后的介孔炭,介孔炭/氧化硅复合材料的制备和最新研究进展。在制备方面,根据其制备机理的不同可分为硬模板法和软模板法,制备出有序的介孔炭与介孔炭/氧化硅复合材料。在应用方面,重点介绍了介孔炭材料和介孔炭/氧化硅复合材料对大分子有机污染物的吸附性能。进而对介孔炭/氧化硅复合材料在吸附方面的应用进行了展望。     

Selective adsorption behavior of Pb(II) by mesoporous silica SBA-15-supported Pb(II)-imprinted polymer based on surface molecularly imprinting technique

In this study, a new Pb(II) ion-imprinted polymer (Pb(II)-IIP), which can be used for selective adsorption of Pb(II) from aqueous solutions, was successfully prepared based on the supported material of ordered mesoporous silica SBA-15 with the help of surface molecular imprinting technology. The prepared polymer was characterized by Fourier transmission infrared spectrometry, X-ray diffraction, transmission electron microscope and nitrogen adsorption-desorption isotherm. The results showed that the synthesized polymer possessed high ordered mesoporous structure. The adsorption behavior of the adsorbents for Pb(II) was investigated using batch experiments. The Pb(II)-IIP showed fast kinetics, high selectivity and satisfied adsorption capacity for adsorption of Pb(II). Under the optimum experimental condition, Pb(II) adsorption process over Pb(II)-IIP follows pseudo-second-order reaction kinetics and follows the Langmuir adsorption isotherm. In addition, the thermodynamic parameters calculated from the adsorption data suggested that the adsorption of Pb(II) onto Pb(II)-IIP was a spontaneous and exothermic nature of the process.     

Short-period synthesis of ordered mesoporous silica SBA-15 using ultrasonic technique

Mesoporous silica SBA-15 was synthesized from rice husk ash via the ultrasonic technique in the hydrolysis-condensation stage. The effect of the time period in this stage on the mesoporous silica SBA-15 structure and physical properties was investigated and compared with those of the SBA-15 prepared by the conventional technique. It has been shown that the ultrasonic technique can be successfully applied for the synthesis of mesoporous silica SBA-15 with highly ordered hexagonal pore-arrangement and narrow PSD within the much shorter hydrolysis-condensation period. The SBA-15 products synthesized via the ultrasonic technique for the time period of 3 h have higher specific surface area, total pore volume, and microporosity than those prepared by the conventional technique for the time period of 24 h.     

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.     

短通道介孔二氧化硅的制备与水蒸气吸附性能EI北大核心CSCD

在高速搅拌条件下调整分子组装过程的外界应力,制备出短通道(500~700 nm)、条棒状的有序介孔二氧化硅,研究不同模板剂脱除方式对介孔二氧化硅的水蒸气吸附性能影响,获得强化介孔二氧化硅吸附性能的方法。结果表明:在短通道、条棒状介孔二氧化硅的制备过程中模板剂脱除的温度对材料表面羟基浓度影响较大,选择萃取与低温煅烧相结合方法脱除模板剂,萃取4次,250℃煅烧脱除模板剂的材料水蒸气吸附性能最好,在实验条件下平衡吸附时间约为7.5 min,是商品SBA-15的78.95%;平衡吸附量0.73 g·g^(-1),是商品SBA-15的1.49倍。     

Solution plasma for template removal in mesoporous silica: pH and discharge time varying characteristics

The evaluation of the ability of solution plasma process, SPP, depending on the pH of the discharge solution and discharge time for template removal in mesoporous silica was described. In the synthesis of mesoporous silica, ternary surfactant system containing tri-block copolymer EO₂₀PO₆₉EO₂₀ (P123), sodium dodecylbenzene sulfonate (SDBS), and 1,1,2,2,3,3,4,4,4-nonafluoro-1-butyl sulfonate (NFBS) was chemically used for synthesis under acid condition via sol-gel method then SPP was employed for template removal. The ordered 2D hexagonal arrangement was observed by the evidence of high resolution TEM and the diffraction mode of X-ray. The efficiency of SPP depending on the pH of the discharge solution and discharge time was scientifically demonstrated as a function of BET surface area. In the case of pH dependence, it was achieved that the ability of template removal in acid and base solutions was clearly higher than those of such results in neutral solution. In the term of discharge time, moreover, the percentage of template removal comparing in the result of BET surface area increased as the increase in discharge time.     

Chemiluminescence immunoassay based on dual signal amplification strategy of Au/mesoporous silica and multienzyme functionalized mesoporous silica

A chemiluminescent dual signal amplification strategy for the determination of α-fetoprotein (AFP) was proposed based on a sandwich immunoassay format. Monoclonal antibody of AFP immobilized on the gold nanoparticles doped mesoporous SiO₂ (Au/SiO₂) were prepared and used as a primary antibody. Horseradish peroxidase (HRP) and HRP-labeled secondary antibody (Ab₂) co-immobilized into the mesoporous SiO₂ nanoparticles (HRP-Ab₂/SiO₂) were used as the labeled immunological probe. Due to the high ratio surface areas and pore volumes of the mesoporous SiO₂, not only the amount of AFP monoclonal antibody but also the amount of the modified HRP and Ab₂ in HRP-Ab₂/SiO₂ were largely increased. Thus the chemiluminescent signal was amplified by using the system of luminol and H₂O₂ under the catalysis of HRP. Under the optimal conditions, two linear ranges for AFP were obtained from 0.01 to 0.5 ng mL⁻¹ and 0.5 to 100 ng mL⁻¹ with a detection limit of 0.005 ng mL⁻¹ (3σ). The fabricated signal amplification strategy showed an excellent promise for sensitive detection of AFP and other tumor markers.     

Construction of the composites of nitrogen and sulfur-doped porous carbon and layered double hydroxides and the synergistic removal of heavy metal pollutants

Layered double hydroxides (LDHs) composites (NSPC@LDH) were successfully prepared on nitrogen and sulfur-doped porous carbon (NSPC) by a simple co-precipitation method. The synergistic effect between the modified porous carbon and LDH enhanced its adsorption performance. Compared with pure LDH, the composite had a larger specific surface area (188.78 m²/g) and pore structure with a smaller crystallite size (4.56 nm). The porous carbon carrier effectively mitigated the aggregation effect of LDH. The maximum adsorption capacities of NSPC@LDH for Zn²⁺ (100 ppm) and Cu²⁺ (100 ppm) were 125.7 mg/g and 137.5 mg/g, respectively, which were 2.85 and 2.39 times the original LDH. The XRD and XPS studies of the adsorbent after adsorption revealed that surface complexation and physical adsorption played a dominant role in the removal of Zn²⁺ and Cu²⁺, and the introduction of N, S heteroatoms provided more active centers for heavy metal ions. Moreover, after five desorption cycles, NSPC@LDH still exhibited high removal efficiency. The results indicated that the synthesized NSPC@LDH composites have great potential for removing Zn²⁺ and Cu²⁺ from aqueous solutions.     

Adsorptive removal of heavy metals from aqueous solution by treated sawdust (Acacia arabica)

The removal of Cr(VI), Pb(II), Hg(II) and Cu(II), by treated sawdust has been found to be concentration, pH, contact time, adsorbent dose and temperature dependent. The adsorption parameters were determined using both Langmuir and Freundlich isotherm models. Adsorption capacity for treated sawdust, i.e. Cr(VI) (111.61 mg/g), Pb(II) (52.38 mg/g), Hg(II) (20.62 mg/g), and Cu(II) (5.64 mg/g), respectively. Surface complexation and ion exchange are the major removal mechanisms involved. The adsorption isotherm studies clearly indicated that the adsorptive behaviour of metal ions on treated sawdust satisfies not only the Langmuir assumptions but also the Freundlich assumptions. The applicability of Lagergren kinetic model has also been investigated. The adsorption follows first-order kinetics. Thermodynamic constant (k_ad), standard free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were calculated for predicting the nature of adsorption. The percentage adsorption increases with pH to attain a maximum at pH 6 and thereafter it decreases with further increase in pH. The results indicate the potential application of this method for effluent treatment in industries and also provide strong evidence to support the adsorption mechanism proposed.     

Biosorption of heavy metals and uranium by starfish and Pseudomonas putida

Biosorption of heavy metals and uranium from contaminated wastewaters may represent an innovative purification process. This study investigates the removal ability of unit mass of Pseudomonas putida and starfish for lead, cadmium, and uranium by quantifying the adsorption capacity. The adsorption of heavy metals and uranium by the samples was influenced by pH, and increased with increasing Pb, Cd, and U concentrations. Dead cells adsorbed the largest quantity of all heavy metals than live cells and starfish. The adsorption capacity followed the order: U(VI)>Pb>Cd. The results also suggest that bacterial membrane cells can be used successfully in the treatment of high strength metal-contaminated wastewaters.     

盐酸小檗碱/介孔二氧化硅载体的制备与缓释行为研究

采用水热合成法制备了SBA-15和SBA-16两种介孔SiO₂载体材料,利用浸渍法将盐酸小檗碱(BBH)原料药负载于载体上,制备了载药BBH/SBA-15和BBH/SBA-16。通过多种表征方法对载药后材料的晶体结构、孔道结构等进行了测试,并研究了材料的载药、释药规律。结果表明,SBA-15和SBA-16的载药量分别为13.50%和3.45%。与BBH原料药相比,两种介孔SiO₂载体均能够延长药物的释放,具有缓释效果。但SBA-15的孔径(5.77nm)较大,释药存在突释现象;而SBA-16的孔径(3.95nm)较小,能够缓慢释放药物。     

Synthesis and characterization of ordered mesoporous silica by using polystyrene microemulsion as templates

A simple room temperature synthesis of pure mesoporous silica by using a homemade and functional template: polystyrene microemulsion is reported. The process consists of HCl-catalysed sol-gel reactions of tetraethyl orthosilicate (TEOS) in polystyrene microemulsion, followed by removal of the template via solvent extraction or calcining. X-ray diffraction, Transmission Electron Microscope and N₂ adsorption-desorption isotherms are then used to characterize the mesostructure. The results indicate that the synthesized mesoporous silica has a large BET surface area with more than 900 m²/g, large pore volume with more than 0.8 cm³/g and ordered mesopore-structure. This provides a possible way to control the meso-structure and pore size of mesoporous materials via potential functional templates.     

Preparation and characterization of vinyl-functionalized mesoporous SBA-15 silica by a direct synthesis method

Vinyl groups were used to functionalize the pore channels of mesoporous SBA-15 materials by the co-condensation of tetraethyl orthosilicate (TEOS) and triethoxyvinylsilane (TEVS) in the presence of poly(ethylene glycol)-B-poly(propylene glycol)-B-poly(ethylene glycol) (P123) surfactants under acidic conditions. The final materials were investigated in detail by means of FT-IR, XRD, TEM, solid state NMR and N₂ adsorption, in order to study the effect of vinyl concentration on their mesoscopic order and pore structure. The results show that vinyl groups are attached covalently to the pore wall of SBA-15 after modification. The mesoscopic architecture almost remains intact upon functionalization, with only a minor decrease of the intensity of (110) diffractions for the 20 mol% TEVS-functionalized samples, which still preserve a desirable pore structure, with a surface area of 883.7 m²/g, a pore volume of 0.98 cm³/g and a mean pore size of 4.4 nm.