Novel mesoporous Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript>/CTAB–SiO<Subscript>2</Subscript> as an effective adsorbent for the removal of amoxicillin and tetracycline from water

The current study was carried out to investigate the efficiency of using magnetic mesoporous of cetyltrimethylammonium bromide-functionalized silica-coated magnetite for removing amoxicillin (AMX) and tetracycline (TC) from tap water, river water, and medical wastewater as real samples. The properties of the synthesized adsorbent were characterized through transmission electron microscopy (TEM), scanning electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectroscopy, vibrating sample magnetometry, pH_pzc, and also Brunauer, Emmett, and Teller (BET) methods. The BET surface area and the average diameter of mesoporous Fe₃O₄/SiO₂/CTAB–SiO₂ in accordance with TEM were 157.8 m² g^?1 and around 55 nm, respectively. In batch tests, the adsorption parameters, including the initial concentration, contact time, pH of solution, ionic strength, and adsorbent dose, were analysed. The experimental adsorption data were modelled using different classical and recently developed models. According to the results, the maximum adsorption capacities of AMX and TC on mesoporous Fe₃O₄/SiO₂/CTAB–SiO₂ were found to be 362.66 and 220.70 mg g^?1, respectively. Also, the results indicated that AMX and TC loaded on the adsorbent could be easily desorbed with 0.1 mol L^?1 HNO₃⁺ acetonitrile (1:1, v/v) and the adsorbent showed good reusability for the adsorption of the drugs studied.     

Self-assembly,microstructure and photoluminescence properties of nanocomposite mesoporous silica loaded with In2O3 and In2O3–SnO2

Abstract

The mesoporous nanocomposite fabricated by self-assembly has many unique properties compared with the original materials. In₂O₃ (IO) and In₂O₃–SnO₂ (ITO) in mesoporous silica were studied in the present paper. They were self-assembled in a nanoscale mesoporous silica by an adsorption–annealing process. The composite of IO and ITO in mesoporous silica was characterised by transmission electron microscopy, atomic force microscopy and nitrogen sorption isotherms. Photoluminescence spectra of the samples were measured by a fluorescence spectrophotometer. The results show that the composite was synthesised from IO and ITO in a nano-scale mesoporous silica with assembly structure, and bulk mesoporous silica is easier to be loaded by the particles than the sheet one, but the specific surface area decreases with increasing atomic weight of the substances loaded in silica mesoporous. The results also show that the mesoporous composite doped with some substance may enhance the effect of photoluminescence. For instance, the mesoprous composite of IO/SiO₂ has an enhancement in the effect of photoluminescence, and that of the mesoprous nanocomposite of ITO/SiO₂ is greater. Mesoporous nanocomposite is a promising photoluminescence material in the application to industry.     

The size-controllable synthesis of nanometer-sized mesoporous silica in extremely dilute surfactant solution

10–60 nm-sized mesoporous silica particles with ordered or worm-like pore structures were controllably synthesized in extremely dilute surfactant solution, and the lowest concentrations of TEOS and CTAB were 12.45 mM, 1.52 mM, respectively. The synthesis of nanometer-sized Al-incorporated mesoporous silica particles (Al-MS) was also performed under the similar conditions. Compared to the mesoporous silica without doping of aluminum, those Al-incorporated silica particles have a certain textural mesoporosity. The results indicate that the size and pore structure of mesoporous silica can be adjusted by changing the concentration of reactants. The mesoporous silica nanoparticles, including Al-MS, were characterized by transmission electron microscopy (TEM), small-angle X-ray diffraction (SAXRD), as well as nitrogen adsorption/desorption techniques. It was suggested that the formation of the mesoporous silica nanoparticles could be attributed to the deposition of self-assembled silicate micelles.     

The use of mesoporous silica in the removal of Cu(I) from the cyanidation process

This research proposed the use of a mesoporous silica material (SiO₂) as a Cu(I) adsorbent in a pre-treatment of cyanide effluents employed in gold and silver extraction. Two copper sources were employed: a [Cu(CN) _X ]^?(X+1) standard solution, and a cyanide solution obtained from an ore of Peña de Bernal, Chihuahua, México, which was named Cu(I)–CN–PB. Mesoporous silica removes around 90 % of the Cu(I)–CN at 30 min in Cu(I)–CN solutions with 50 ppm of the metals; while, in a solution with a high concentration of copper (311 ppm), around 52 % was removed. The adsorption dates were adjusted following the Langmuir model; obtained a maximum adsorption capacity (Q ₀) of 8.01 mg g^?1 and a separation factor (R _L) lower than one, which indicates a favorable thermodynamic adsorption process of Cu(I)–CN by SiO₂. However, a similar copper removal capability and low selectivity was observed when Cu(I)–CN–PB was employed as the copper source. Therefore, a modification on the silica’s surface with phenyl groups was performed, in order to enhance the metallic ion selectivity. IR spectroscopy and TGA/DTA analysis confirmed the coupling of organic groups; on the other hand, nitrogen adsorption indicated a decrease on the BET surface area of the silica at 76 %, a modification of the silica structure was observed with the formation of two pore diameter (3.6 and 5.37 nm); ¹³C CP-MAS NMR indicated two different chemical shifts that corresponded to the phenyl groups on the two different pores observed. Phenyl groups enhance the selectivity for copper in the cyanide effluent, increasing the removal to 99 %.     

Synthesis and characterization of ordered mesoporous silica using rosin-based Gemini surfactants

As structure-directing agents, the molecular structure of surfactants is critical for determining the properties of prepared mesoporous materials. Using dehydroabietic acid as a starting material, a series of rosin-based Gemini surfactants (abbreviated as R-n-R, n = 3, 6, 8 and 10, indicating the carbon atom number contained in the spacer) were synthesized and applied as templates in the preparation of ordered mesoporous silica. The structures and morphologies of the samples were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and N₂ adsorption–desorption. The R-n-R surfactants feature rigid tricyclic hydrophobic groups with large volumes, which are beneficial for the formation of a three-dimensional cubic phase. Furthermore, the spacer length was found to have a tremendous effect on the structure of the prepared mesoporous silica materials. The head group of R-3-R, which has a short spacer, is excessively charged, leading to silica nanoparticles with an irregular morphology and a rather low BET surface area. With longer spacer lengths, R-6-R, R-8-R and R-10-R are conducive to generating silica nanoparticles with a novel dumbbell-like morphology and with higher BET surface areas of 1171, 1096 and 1186 m² g^?1, respectively. The results demonstrate the particularities of the Gemini surfactant structure in the preparation of mesoporous silica nanoparticles with novel morphologies, and the details of the molecular interactions that occur in the condensation of silicate anions are also revealed.     

Phosphate adsorption on aluminum-coordinated functionalized macroporous–mesoporous silica: Surface structure and adsorption behavior

In this study, Al(III)-coordinated diamino-functionalized macroporous–mesoporous silica was synthesized and characterized by X-ray diffraction, N₂ adsorption–desorption, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy. Because of well-defined and interconnecting macroporous–mesoporous networks, the resulting adsorbent (MM-SBA) exhibited a significantly better phosphate adsorption performance and faster removal rate, as compared with the mesoporous adsorbent (M-SBA). Based on the Freundlich and Langmuir models, the phosphate adsorption capacity and the maximum adsorption capacity of MM-SBA were 7.99 mg P/g and 23.59 mg P/g, respectively. In the kinetic study of MM-SBA, over 95% of its final adsorption capacity reached in the first 1 min; whereas that of M-SBA was less than 79%.     

High surface area ordered mesoporous carbon for high-level removal of rhodamine B

We report the synthesis of ordered mesoporous carbons (OMCs) with high surface area by the variation of mass ratio of tetraethylorthosilicate (TEOS) to resol, followed by carbonization and removal of silica. The obtained OMCs were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, N₂ adsorption and desorption analysis, Zeta potential and Fourier transform infrared spectroscopy. Results reveal that the OMCs were transformed from ordered to disordered structure at high mass ratio of TEOS/resol. A typical sample of OMCs possesses very high specific surface area of 1906 m² g^?1 and large pore volume of 1.8 cm³ g^?1. The OMCs as adsorbent show an ultrahigh-level adsorption capacity for the removal of toxic dye Rhodamine B (1028 mg g^?1) in the short contact time (60 min). The adsorption follows pseudo second-order kinetics with rate constant 2.5 × 10^?4 g mg^?1 min^?1, showing rapid adsorption properties. The OMCs can be reused; though the adsorption capacity seems to decrease somewhat after each cycle tested over 10 reuse cycles, it might be affected by the chemisorptions. The adsorption mechanism study reveals that the adsorption proceeds with hydrogen bonding between hydrogen atom of carboxylic group at OMCs and electronegative element (nitrogen) of RhB. It is concluded that the surface area and pore volume of the OMCs is tuned by the variation of mass ratio of TEOS to resol which is also demonstrated to have ultrahigh adsorption capacity for the model RhB dye.     

Efficient desulfurization of fuel with functionalized mesoporous carbon CMK-3-O and comparison its performance with mesoporous carbon CMK-3

In this work, a functionalized mesoporous carbon (CMK-3-O) was synthesized after oxidation with nitric acid and was used to adsorb dibenzothiophene (DBT) from model oil for the first time. Then, its performance was compared with that of CMK-3. The functionalized mesoporous carbon, CMK-3-O, showed better a capacitance performance for DBT adsorption than that of CMK-3. The maximum adsorption capacity was obtained for functionalized mesoporous carbon at optimum conditions with 6 M HNO₃ aqueous solution and 30 min contact time. The physical and structural properties of CMK-3-O and CMK-3 were investigated with X-ray diffraction method (XRD), N₂ adsorption–desorption isotherm, FT-IR, and elemental analysis (CHNO). Results of the elemental analysis showed that the oxygen and nitrogen content has increased and the carbon content has decreased through oxidation treatment. The effects of various factors on the adsorption process (such as temperature, amount of adsorbent, contact time, and concentration) of DBT were studied. CMK-3-O showed a maximum adsorption capacity of 86.96 mg DBT g^?1 of CMK-3-O at optimized conditions (temperature, 25°C; adsorbent dosage, 20 g L^?1; contact time, 60 min), which was a higher adsorption capacity of that observed for CMK-3 (57.47 mg DBT g^?1 of CMK-3). Kinetic studies have revealed that the adsorption of DBT can be described by a pseudo-second-order rate equation. Equilibrium data showed that adsorption process was best represented by the Langmuir model. The results also illustrated the fact that the regenerated adsorbent afforded 64.3% of the initial adsorption capacity after the two regeneration cycles.     

Adsorption kinetics, isotherm, and thermodynamics of Hg2+ to polyaniline/hexagonal mesoporous silica nanocomposite in water/wastewater

A nanocomposite of polyaniline/hexagonal mesoporous silica (PAN/HMS) was prepared and characterized by BET analysis, transmission electron microscopy, and FT-IR spectra. Batch adsorption results showed that PAN/HMS had high affinity to Hg²⁺ in aqueous solutions. Various factors affecting the adsorption capacity such as contact time, temperature, absorbent dosage, pH, and initial concentration of Hg²⁺ ions were investigated. The adsorption kinetics for the Hg²⁺ showed that the adsorption reached equilibrium within 8 min and adsorption rates followed the pseudo-second-order rate law, indicating chemical sorption as the rate-limiting step of the adsorption mechanism. Sorption of Hg²⁺ to PAN/HMS agreed well to the Langmuir adsorption model at different ionic strengths with the maximum adsorption capacity of 843 mg g^?1 (I = 1000 mg L^?1) at pH 10. Thermodynamic studies revealed that the adsorption of Hg²⁺ ions was spontaneous, exothermic processes with an increase of entropy. The recovery of the Hg²⁺ from the adsorbent was found to be more than 88 % using H₂SO₄ (0.1 M), and the ability of the absorbent to be reused was investigated.     

In situ incorporation of nickel nanoparticles into the mesopores of MCM-41 by manipulation of solvent-solute interaction and its activity toward adsorptive desulfurization of gas oil

In this contribution, different amounts of nickel were incorporated into the mesopores of MCM-41 via an in situ approach. A hydrophobic nickel precursor was incorporated into the nanochannels of mesoporous silica by manipulation of solvent-solute interaction. The synthesized material was characterized using X-ray diffraction, nitrogen physisorption, temperature programmed reduction, and transmission electron microscopy. The results implicate the formation of MCM-41 with well-ordered hexagonal structure and establish also the presence of nickel nanoparticles inside the nanochannels of mesoporous silica. Adsorptive desulfurization of gas oil was conducted using the nickel-incorporated MCM-41 samples. The effects of nickel concentration, temperature of process and feed flow rate on the desulfurization process were examined. The MCM-41 containing 6 wt.% of nickel had both the highest breakthrough sulfur adsorption capacity and total sulfur adsorption capacity, which were 0.69 and 1.67 mg sulfur/g adsorbent, respectively. The breakthrough sulfur adsorption capacity was almost regained after reductive regeneration of spent adsorbent. The obtained results suggest that the method applied for the synthesis of Niy/MCM resulted in formation of well-dispersed, accessible and small nickel nanoparticles incorporated into the pores of MCM-41 which might be an advantage for adsorption of refractory sulfur compounds from low sulfur gas oil.     

Co3O4 doped over SBA 15: excellent adsorbent materials for the removal of methyleneblue dye Pollutant

Nanosized cobalt oxide particles are incorporated into SBA 15 mesoporous silica materials and are effectively used for the first time as adsorbent materials for aquatic dye pollutant removal. Cobalt is found to exist in its Co₃O₄ spinel structure as evident from FTIR and X-ray diffraction studies. The best weight ratio of metal loading to show excellent adsorption of methyleneblue is found to be 10 wt% Co over the support. There, Co₃O₄ spinel nanoparticles lie inside the pores of mesoporous silica. Further increase in the percentage of metal loading decreases the adsorption capacity which may be due to the agglomeration of nanoparticles over the silica support as evident from TEM photographs. Cobalt-doped systems of the present study, having good adsorption capacity of methyleneblue, are prepared via impregnation of cobalt nitrate over SBA 15 in aqueous medium. Here, we introduce a new SBA 15-based system for the fast removal of aquatic dye pollutants which is highly economical for industrial applications.     

功能化SBA-15介孔材料的制备及其吸附性能研究

硅基介孔材料因其特有的特性,被用于去除废水中重金属离子的吸附剂.为了提高对目标污染物的吸附容量, 本文采用一步法和两步法制备了氨基或巯基功能化SBA-15介孔材料,利用傅里叶红外光谱仪、场发射扫描电镜、X射线衍射仪和氮气吸附脱附表征测试了材料的化学组成、微观形貌和物相结构.测试结果显示经功能化处理后的样品成功地接枝氨基或巯基功能基团.研究发现,经功能化处理后,材料的骨架结构及介孔孔道均未被破坏,但有序性下降且出现少许团聚,物性参数也有一定程度下降,功能化材料对Zn²⁺、Pb²⁺、Cr³⁺和Cu²⁺的吸附率均有大幅度提高.经氨基或巯基功能化后,SBA-15介孔材料对水体中重金属离子的吸附率有很大提高,但一步法制备的功能化硅基介孔材料因模板剂去除不彻底而影响了对重金属离子的吸附效率,两步法制备的功能化硅基介孔材料对重金属离子的吸附效果更好,说明本文的功能化硅基介孔材料工艺是可行有效的,但两步法合成的功能化介孔材料具有更好的吸附效果.     

TiO2负载硅铝陶瓷介孔球对甲基橙吸附和光催化 降解的研究

：以自制硅铝陶瓷介孔球为基体,经溶胶凝胶法制备TiO2溶胶并将其负载于硅铝陶瓷介孔球表面,用于甲基橙溶液的吸附和光催化降解,再利用扫描电子显微镜、X射线衍射仪、傅里叶变换红外光谱仪和可见分光光度计对样品的表观形貌、晶体结构、吸附和光催化性能等进行表征和测定。研究结果表明：TiO2是以粗糙度较高的多层膜包覆于硅铝陶瓷介孔球表面且TiO2为锐钛矿晶型;在黑暗条件下,硅铝陶瓷介孔球和TiO2负载硅铝陶瓷介孔球对甲基橙仅起到吸附作用,且两者的吸附性能较接近;但在紫外光照条件下,TiO2负载硅铝陶瓷介孔球对甲基橙除有吸附作用外还表现出较好的光催化降解活性。     

Silver-containing mesoporous bioactive glass with improved antibacterial properties

The aim of the present work is the study of the bacteriostatic/bactericidal effect of a silver-containing mesoporous bioactive glass obtained by evaporation-induced self-assembly and successive thermal stabilization. Samples of the manufactured mesophase were characterized by means of transmission electron microscopy and N₂ adsorption/desorption at 77 K, revealing structural and textural properties similar to SBA-15 mesoporous silica. Glass samples used for bioactivity experiments were put in contact with a standardized, commercially available cell culture medium instead of lab-produced simulated body fluid, and were then characterized by means of X-ray diffraction, field emission scanning electron microscopy and Fourier transform infrared spectroscopy. All these analyses confirmed the development of a hydroxyl carbonate apatite layer on glass particles. Moreover, the investigated mesostructure showed a very good antibacterial effect against S. aureus strain, with a strong evidence of bactericidal activity already registered at 0.5 mg/mL of glass concentration. A hypothesis about the mechanism by which Ag affects the bacterial viability, based on the intermediate formation of crystalline AgCl, was also taken into account. With respect to what already reported in the literature, these findings claim a deeper insight into the possible use of silver-containing bioactive glasses as multifunctional ceramic coatings for orthopedic devices.     

Synthesis of a mesoporous silica hollow microsphere using polyvinyl alcohol

A mesoporous silica hollow microsphere was synthesized in the presence of polyvinyl alcohol for the first time. The synthesized material was characterized by various instrumental techniques such as small-angle X-ray scattering, scanning electron microscopy, transmission electron microscopy, N₂ adsorption measurement and Fourier transform infrared spectroscopy. I have succeeded in incorporating an Ultraviolet ray absorber, 2, 2´, 4, 4´ tetrahydroxy benzophenone by mixing it after synthesis. However an attempt to incorporate by mixing before synthesizing it changes the morphology. In addition to polyvinyl alcohol, the use of other polymers such as polyvinyl pyrrolidine and polyethylene glycol also changes the morphology into dry leaves or fibers.     

One-step synthesis of hydrophobic mesoporous silica ellipsoidal particles with a bimodal mesopore system

Highly CH₃-functionalized mesoporous silica ellipsoidal particles with bimodal mesopore structure were prepared via a one-step route using polymethylhydrosiloxane (PMHS) and tetraethoxysilane (TEOS) with triblock copolymer P123 as template under acidic conditions. N₂ adsorption–desorption, XRD, HRTEM, SEM and ²⁹Si MAS NMR were used to characterize the obtained material. The introduction of PMHS into the synthetic system led to the formation of a bimodal mesopore system consisting of framework mesopores of ∼7.2 nm and textural mesopores of ∼29.4 nm. The two scale pores were directly observed in HRTEM images and indirectly proved by the two-step increase in N₂ adsorption–desorption isotherm. Also, PMHS played an important role in morphology controlling and organic functionalization, ensuring monodisperse ellipsoidal particle morphology and high CH₃ functionalization degree of the mesoporous silica product. Subjected to removing highly diluted nonylphenol from aqueous solution, the hydrophobic bimodal mesoporous silica ellipsoidal particles showed high adsorption performance.     

Preparation of polyelectrolyte-functionalized mesoporous silicas for the selective adsorption of anionic dye in an aqueous solution

Polyelectrolytes (PDDA, poly (diallydimethylammonium chloride)) functionalized mesoporous silica adsorbent (PDDA/MS) was prepared and characterized by N₂ adsorption, transmission electron microscopy (TEM) and zeta potential. The PDDA/MS showed ordered pore structure and the surface charge was successfully converted from negative to positive by PDDA functionalization. The adsorption capability of the prepared adsorbents was evaluated using nine different dye solutions with positive, neutral and negative charges. For the comparison purpose, commercial silica (CS, Davisil) and granular activated carbon (GAC), which are conventionally used as adsorbents, were also treated by PDDA impregnation. The batch adsorption experiments showed that the PDDA/MS exhibited the highest selective adsorption capacity of negative acid dye dissolved in an aqueous solution. Taken together, the results of this work indicate that polyelectrolyte functionalization of the inorganic surface could be a simple and suitable method for the surface modified adsorbent and the PDDA/MS suggested in this study could be used for the effective removal of acid dye from aqueous solutions.     

葡萄糖醛酸功能化双介孔硅对胆红素的高效吸附研究

胆红素是由衰老及异常红细胞被吞噬、血红蛋白分解代谢产生的一种生物活性物质。采用具有小孔径和较大孔径两种介孔孔道的双介孔硅作为基底材料,并用葡萄糖醛酸对双介孔硅进行功能化,以实现对胆红素的选择性吸附。研究了吸附时间、温度、初始浓度、血清蛋白、离子强度对胆红素吸附的影响。实验结果表明,葡萄糖醛酸化双介孔硅对胆红素的吸附快速、高效,吸附平衡为15 min,最大吸附量为(246.78.3)mg/g,血清蛋白的存在对胆红素吸附的影响不大。胆红素吸附符合二级吸附动力学模型和Langmuir等温吸附模型。     

Fumed silica/polymer hybrid nanoparticles prepared by redox-initiated graft polymerization in emulsions

Hybrid particles comprising aggregated fumed silica nanoparticles as the core and hydrophobic polymers existing around the nanoparticles were prepared by ‘grafting from’ polymerization in emulsions. The emulsion polymerization employed cetyltrimethylammonium bromide (CTAB) as a cationic surfactant and sodium dodecyl sulfate (SDS) as an anionic surfactant, respectively, to stabilize the emulsion polymerization. The polymerization was initiated by the redox reaction between ceric ion Ce(IV) and the amine groups on the surfaces of aminated fumed silica nanoparticles that were modified by 3-aminopropyltriethoxysilane. Infrared spectroscopy and thermogravimetric analysis demonstrated that both poly(methyl methacrylate) (PMMA) and polystyrene (PS) were successfully grafted onto the fumed silica surface. The type of surfactant greatly affected the grafting ratio, monomer-to-polymer conversion, and morphology of the product. When CTAB was used as the surfactant, both the grafting ratio and monomer-to-polymer conversion were lower than when SDS was used, but transmission electron microscopy and light scattering analysis indicated that most of the resultant particles were sub-100 nm hybrid nanoparticles with a non-spherical shape and particles sizes of 75–90 and 57–85 nm for PMMA and PS-grafted fumed silica, respectively. Whereas, when SDS was used as the surfactant, the particles agglomerated to form large irregular clusters or even networks, possibly due to the electrostatic attractions between SDS and Ce(IV) and/or the aminated fumed silica nanoparticles in aqueous solution.     

Synthesis of mesoporous hydroxyapatite nanoparticles using a template-free sonochemistry-assisted microwave method

A facile template-free sonochemistry-assisted microwave method was successfully developed for the synthesis of mesoporous hydroxyapatite nanoparticles (MHN) in a short time. The prepared MHN were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and N₂ adsorption–desorption isotherms. TEM images showed a clear rod-like morphology with length of 50–100 nm and width of about 20 nm. XRD and FTIR indicated a typical hydroxyapatite phase with high crystallinity. N₂ adsorption–desorption isotherms revealed an irregular mesoporous structure. Judging from the values calculated from N₂ isotherms, the specific surface area and pore volume obviously decreased after the sintering process. In a typical example, the specific surface area, pore volume, and pore size of MHN before and after calcination were 79.74 m²/g, 0.46 cm³/g, 2.7 nm and 45.41 m²/g, 0.22 cm³/g, 2.8 nm, respectively. In addition, MHN could be synthesized in a period of time as short as 10 min. Further investigation indicated that microwave radiation played a dominant role in the emergence of mesoporous structure, while ultrasound irradiation acted as a supporting role. Based on the above results, a possible mechanism of formation of mesoporous hydroxyapatite has been proposed.