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In this study, boron-doped magnetic mesoporous silica nanocomposite was prepared through the hydrothermal synthesis procedure followed by post modification with –NH2 groups. The higher surface area, more ordered mesoporous structure, and higher surface charge density obtained by boron doping and amino functionalization contributed to the use of nanocomposite for multipurpose application functions. When used as an adsorbent for light green (LG) anionic dye, boron-doped nanocomposite exhibited higher adsorption capacity (105.80 mg/g) compared to undoped nanocomposite (72.23 mg/g), while when used as a drug carrier for Doxorubicin (DOX), a sufficient drug loading capacity (48.0 mg/g) was obtained, which is also higher than that of undoped nanocomposite (30.3 mg/g). In terms of LG adsorption, the effects such as initial concentration, adsorbent dosage, time, pH, and temperature on the adsorption properties were investigated in detail. Adsorption kinetics, isotherms, thermodynamics, and reusability are discussed. The existence of small quantity of boron doping enhanced the surface charge density from 0.0393 to 0.2854 C/m2, which resulted in higher adsorption capacity for LG adsorption dominated by electrostatic attraction, and led to formation of silanol holes together with the –OH and –NH2 functional groups, which resulted in higher drug loading capacity for DOX adsorption dominated by hydrogen bonding. This promising result provides that boron-doped and –NH2 grafted magnetic mesoporous silica material can function as multipurpose adsorbent for various environmental applications. [ABSTRACT FROM AUTHOR]

In this study, magnetically separable Fe3O4-SiO2-mesoTiO2 nanocomposite has been synthesized for photodegradation of Methylene Blue (MB) and Rhodamine B (RhB) cationic dyes which have complex aromatic structures and are difficult to degrade into harmless products. By XRD analysis, it was determined that the magnetite phase of Fe3O4 was protected after coating with SiO2 interlayer and mesoTiO2 shell, and the anatase phase of TiO2 was formed. According to the N2-adsorption/desorption and VSM results, Fe3O4-SiO2-mesoTiO2 nanocomposite has a surface area of 197.8 m2/g, pore volume of 0.34 cm3/g and a pore size of 3.4 nm and has 3.8 emu/g saturation magnetization and negligible remnant magnetization and coercivity, which indicates its mesoporous and superparamagnetic character. The adsorption ability of RhB (16.86%) is lower than MB (23.32%), nevertheless, the photodegradation activity of RhB (99.06%) is higher than that of MB (97.52%). Photodegradation kinetics follows the pseudo-first order and the rate constants of photocatalytic reactions were calculated as 0.0422 and 0.0719 min−1 for MB and RhB, respectively. While the lower adsorption feature of RhB was resulted from steric hindrance, the higher photodegradation rate was explained by more radical scavenging effect. MB prefers to face the photocatalyst surface, whereas RhB prefers to focus on the aqueous phase, and based on scavenge results, RhB is more likely to encounter photoactive species (H2O2, h+ and ·O2−) than that of MB with ·O2− being the dominant active species. The synthesized Fe3O4-SiO2-mesoTiO2 photocatalyst could be reused three times with negligible photocatalytic loss in the photodegradation of both dyes. [ABSTRACT FROM AUTHOR]

Fe3O4-SiO2-NH2, Fe3O4-CTABSiO2-NH2 and Fe3O4-SiO2-CTABSiO2-NH2 magnetic adsorbents were successfully prepared and could be used effectively for the adsorption of Light Green from aqueous solutions. Unlike the first sample, mesoporous silica coatings were created using cetyltrimethylammoniumbromide micelles as molecular templates on superparamagnetic iron oxide in one sample, and on silica-coated iron oxide in the other sample to improve the adsorptive properties of the nanocomposites. The characterization by FT-IR, SEM/EDX, Zeta-potential, XRD, VSM, and N2-adsorption/desorption confirmed the production of mesoporous silica layer. Although coating processes with both silica and mesoporous silica layers led to a vaguely decrease in saturation magnetization of the Fe3O4-SiO2-CTABSiO2-NH2, the nanoparticles were protected with silica coatings for environment conditions and made more suitable for subsequent amino functionalization. The results determined from Batch adsorption experiments fitted to Langmuir isotherm model with maximum adsorption capacity (qmax) equal to 56.18, 196.08 and 227.27 mg g−1, for Fe3O4-SiO2-NH2, Fe3O4-CTABSiO2-NH2 and Fe3O4-SiO2-CTABSiO2-NH2, respectively, and it was seen from the kinetic results, the LG adsorption was identified by pseudo-second-order kinetics, revealing that LG adsorption process is homogeneous, monolayer and based on chemical interactions. According to the results, both silica and mesoporous silica coating strategy can play crucial role in improving the adsorptive properties of nanocomposites. [ABSTRACT FROM AUTHOR]

Multifunctional magnetic mesoporous nanocomposites are promising materials to remove the various pollutants from water due to the remarkable properties such as multiple binding sites, high surface area, and magnetic separation. Herein, we have developed a versatile nanocomposite, in which polydopamine (PDA) coated Fe3O4 nanoparticles are introduced during the synthesis of SBA-15 matrix for the first time to enhance adsorptive properties of hydrophilic magnetic mesoporous nanocomposite by combining the properties of high surface area, magnetization, and capability of interacting with more functional groups in one material. The resulting nanocomposite, Fe3O4@PDA@SBA-15, has been proved to be the effective sorbent for the removal of cationic dye, which can be ascribed to the functional groups of grafted PDA and the textural features of matrix SBA-15. On the other hand, after chemical modification via silanization of vinyltriethoxysilane (VTES), Fe3O4@PDA@SBA-15 nanocomposite turned to be a hydrophobic material, Fe3O4@PDA@SBA-15@VTES, which can adsorb oil with high adsorption capacity which could reach 8.83 times of its own weight. Moreover, both nanocomposites could be recycled by facile washing and drying processes. The materials provide a simple strategy for the preparation of multifunctional magnetic mesoporous nanocomposites satisfying various applications in water treatment. Highlights: The Fe3O4@PDA@SBA-15 hydrophilic nanocomposite was developed to enhance the adsorption of cationic dye. Nanocomposite turns to be a hydrophobic material (Fe3O4@PDA@SBA-15@VTES) that can adsorb oil. These materials with tunable properties satisfy various applications in water treatment. We offer a simple strategy to fabric multifunctional nanocomposites for dye and oil removal. Both nanocomposites are easily separated and regenerated owing to magnetic properties. [ABSTRACT FROM AUTHOR]

Fe3O4@SiO2@NH2 nanocomposite was prepared for highly effective adsorption of two anionic dyes one of which is triarylmethane dye (light green, LG) and the other is azo dye (brilliant yellow, BY). The characterization results demonstrated that superparamagnetic Fe3O4 nanoparticles were covered with silica and functionalized with amino groups successfully without losing magnetic character. The effects of adsorbent dosage, contact time, pH, temperature, and dye molecular structure on the adsorption were investigated. Acidic pH was better for both LG and BY, on the other hand, alkaline pH was favorable to some extent for LG in comparison with BY due to the contribution of stacking effect in addition to electrostatic attraction. Kinetic data demonstrated that the driving force for adsorption process could be explained by pseudo-second order mechanism in both systems. The equilibrium data were more compatible with Langmuir isotherm than those of Freundlich isotherm and the maximum adsorption capacities of Fe3O4@SiO2@NH2 calculated from Langmuir isotherm model for LG and BY at 30 °C and natural pH of the solution were 40.2 and 35.5 mg g−1. Thermodynamic calculations related to temperature dependence demonstrated that the adsorption process was spontaneous and exothermic. [ABSTRACT FROM AUTHOR]

Novel approach was developed towards the synthesis of heterogeneous mesoporous B-SBA-15-SOH acid catalysts. That is: B-SBA-15 materials were hydrothermally synthesized by using three different boron sources (boric acid, trisiopropylborate and potassium borohydride) and then post-synthetically functionalized with sulfonic acid to test their catalytic activity for the esterification of propionic acid with methanol. Mesoporous and amorphous character of the materials as well as the incorporation of the boron into the framework were verified by XRD, N-adsorption/desorption, ICP-OES, SEM and FT-IR techniques. All of the boron incorporated acid catalysts showed better activity than pure SBA-15-SOH for methyl propionate synthesis. Combining the advantageous of hydrothermal synthesis and post functionalization, the obtained B-SBA-15-SOH catalysts should present versatile catalytic properties in terms of both catalytic activity and reusability. Boron incorporation and post functionalization encourage the structural configuration, since the grafted catalytically active groups may experience similar environments and be isolated from each other. [ABSTRACT FROM AUTHOR]

The effect of calcination temperature on the structural and magnetic properties of Ni/SBA-15 nanocomposite prepared by reductant-impregnation method was studied using SBA-15 mesoporous silica as support. The structure, morphology and magnetic properties of the samples were characterized using X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectrometry, N adsorption/desorption (BET and BJH), vibrating sample magnetometer, and FT-IR. Characterization results showed the presence of crystalline phases characteristics of the Ni and/or NiO, and that the structural characteristics of the support were maintained after the impregnation of nickel ions followed by calcinations. Calcination process helps in crystallization and formation of the desired phase such as well crystalline NiO and Ni nano-particles. Moreover, this heat resulted in significant effects on different properties of the products such as the crystallite size, homogeneity, particle distribution, porosity, surface area and the sintering process. Magnetic measurements suggested that the magnetic properties in nanocomposites is probably the sum of two contributions: superparamagnetic and ferromagnetic one depending on the calcination temperature. Calcination at high temperatures affects both of the structural and magnetic properties of Ni/SBA-15. Because the location of the Ni particles depends on the pore size of the support, the uniformity of particle size was related to the interaction between the Ni particles and support. [ABSTRACT FROM AUTHOR]

The influence of poly(ethylene glycol) (PEG) and synthesis temperature in the synthesis of SBA-15-SOH was investigated to evaluate the catalytic activity in the esterification of propionic acid with methanol. The catalysts were characterized by means of surface and structure analyses; X-ray diffraction, FT-IR, scanning electron microscopy, Thermo-gravimetric and N adsorption/desorption techniques. It was found that, by the addition of PEG, the surface area and porosity of SBA-15-SOH increased, while the structure and size of mesopores remained unchanged. Nitrogen sorption measurements indicate that PEG introduces additional pores into the pore walls of SBA-15-SOH. Thus, a simple way of improving the porosity of mesoporous SBA-15-SOH was presented that could enhance transport of substrates through the porous system and allow the generation of stable mesoporous replicas, important for catalytic applications and also beneficial for replication and nanocasting purposes. [ABSTRACT FROM AUTHOR]

Esterifications of n-amyl alcohol with propionic acid catalyzed by macroporous (Amberlyst-15) and microporous (Dowex 50 W and Amberlite IR-120) polymeric ion-exchange resins were carried out between 333–348 K. When these catalysts were used as commercially available, Amberlyst-15 was observed to be the most effective catalyst with respect to rate constants, but after drying it became the less effective one. The reaction rate increased with increase in catalyst concentration and reaction temperature. Stirrer speed and different mesh sizes had virtually no effect on the rate under the experimental conditions. The effect of divinylbenzene content was examined for the microporous resin Dowex 50W, and the results showed that the propionic acid conversion decreased as the divinylbenzene content was increased. The rate data were correlated with a second-order homogeneous reaction model. The apparent activation energies, reaction enthalpies and entropy values were calculated for each catalyst. Reaction monitoring is simple and fast by volumetric method and the reproducibility of this method was the order of ± %2.54. [ABSTRACT FROM AUTHOR]