Construction of bimodal silsesquioxane-based porous materials from triphenylphosphine or triphenylphosphine oxide and their size-selective absorption for dye molecules

Phosphorus-containing porous materials from octavinylsilsesquioxane possessed unique bimodal structure and exhibited an excellent size-selective absorption for dye molecules.

Functionalization of mesoporous materials for lanthanide and actinide extraction

Recent advances in the field of functionalized mesoporous solid-phase sorbents designed for rare earth element and actinide separation/concentration could provide answers to limitations occurring in the industrial separation processes of these critical elements.

Synthesis of Mn₃O₄/CeO₂ Hybrid Nanotubes and Their Spontaneous Formation of a Paper-like, Free-Standing Membrane for the Removal of Arsenite from Water

One-dimensional nanomaterials may organize into macrostructures to have hierarchically porous structures, which could not only be easily adopted into various water treatment apparatus to solve the separation issue of nanomaterials from water but also take full advantage of their nanosize effect for enhanced water treatment performance. In this work, a novel template-based process was developed to create Mn3O4/CeO2 hybrid nanotubes, in which a redox reaction happened between the OMS-2 nanowire template and Ce(NO3)3 to create hybrid nanotubes without the template removal process. Both the Ce/Mn ratio and the precipitation agent were found to be critical in the formation of Mn3O4/CeO2 hybrid nanotubes. Because of their relatively large specific surface area, porous structure, high pore volume, and proper surface properties, these Mn3O4/CeO2 hybrid nanotubes demonstrated good As(III) removal performances in water. These Mn3O4/CeO2 hybrid nanotubes could form paper-like, free-standing membranes spontaneously by a self-assembly process without high temperature treatment, which kept the preferable properties of Mn3O4/CeO2 hybrid nanotubes while avoiding the potential nanomaterial dispersion problem. Thus, they could be readily utilized in commonly used flow-through reactors for water treatment purposes. This approach could be further applied to other material systems to create various hybrid nanotubes for a broad range of technical applications.

Rational design of nanomaterials for water treatment

The ever-increasing human demand for safe and clean water is gradually pushing conventional water treatment technologies to their limits. It is now a popular perception that the solutions to the existing and future water challenges will hinge upon further developments in nanomaterial sciences. The concept of rational design emphasizes on 'design-for-purpose' and it necessitates a scientifically clear problem definition to initiate the nanomaterial design. The field of rational design of nanomaterials for water treatment has experienced a significant growth in the past decade and is poised to make its contribution in creating advanced next-generation water treatment technologies in the years to come. Within the water treatment context, this review offers a comprehensive and in-depth overview of the latest progress in rational design, synthesis and applications of nanomaterials in adsorption, chemical oxidation and reduction reactions, membrane-based separation, oil-water separation, and synergistic multifunctional all-in-one nanomaterials/nanodevices. Special attention is paid to the chemical concepts related to nanomaterial design throughout the review.

Zirconia-Nanoparticle-Reinforced Morphology-Engineered Graphene-Based Foams

The morphology of graphene-based foams can be engineered by reinforcing them with nanocrystalline zirconia, thus improving their oil-adsorption capacity; This can be observed experimentally and explained theoretically. Low zirconia fractions yield flaky microstructures where zirconia nanoparticles arrest propagating cracks. Higher zirconia concentrations possess a mesh-like interconnected structure where the degree of coiling is dependant on the local zirconia content.

Chemical Insight into the Adsorption of Chromium(III) on Iron Oxide/Mesoporous Silica Nanocomposites

Magnetic iron oxide/mesoporous silica nanocomposites consisting of iron oxide nanoparticles embedded within mesoporous silica (MCM-41) and modified with aminopropyl functional groups were prepared for application to Cr(III) adsorption followed by magnetic recovery of the nanocomposite materials from aqueous solution. The composite materials were extensively characterized using physicochemical techniques, such as powder X-ray diffraction, thermogravimetric and elemental analysis, nitrogen adsorption, and zeta potential measurements. For aqueous Cr(III) at pH 5.4, the iron oxide/mesoporous silica nanocomposite exhibited a superior equilibrium adsorption capacity of 0.71 mmol/g, relative to 0.17 mmol/g for unmodified mesoporous silica. The aminopropyl-functionalized iron oxide/mesoporous silica nanocomposites displayed an equilibrium adsorption capacity of 2.08 mmol/g, the highest adsorption capacity for Cr(III) of all the materials evaluated in this study. Energy-dispersive spectroscopy (EDS) with transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) experiments provided insight into the chemical nature of the adsorbed chromium species.

Graphene-Diatom Silica Aerogels for Efficient Removal of Mercury Ions from Water

A simple synthetic approach for the preparation of graphene-diatom silica composites in the form of self-assembled aerogels with three-dimensional networks from natural graphite and diatomite rocks is demonstrated for the first time. Their adsorption performance for the removal of mercury from water was studied as a function of contact time, solution pH, and mercury concentration to optimize the reaction conditions. The adsorption isotherm of mercury fitted well with the Langmuir model, representing a very high adsorption capacity of >500 mg of mercury/g of adsorbent. The prepared aerogels exhibited outstanding adsorption performance for the removal of mercury from water, which is significant for environmental applications.

Hydrotalcite-TiO2 magnetic iron oxide intercalated with the anionic surfactant dodecylsulfate in the photocatalytic degradation of methylene blue dye

The new magnetic photocatalysts HT/TiO2/Fe and HT-DS/TiO2/Fe, modified with the anionic surfactant sodium dodecylsulfate (DS) were successfully synthesized in this work. Titanium dioxide (anatase) followed by iron oxide were deposited on the hydrotalcite support. Several catalyst samples were prepared with different amounts of titanium and iron. The photocatalysts were characterized by infrared and Raman spectroscopy, X-ray diffraction, scanning electron microscopy. Photocatalytic performance was analyzed by UV-visible radiation (filter cutoff, λ > 300 nm) of an aqueous solution (24 mg/L) of methylene blue (MB). The most efficient catalyst was obtained at an iron oxide:TiO2 molar ratio of 2:3. This catalyst showed high photocatalytic activity, removing 96% of the color and 61% of total organic carbon from the MB solution after 120 min. It was easily removed from solution after use because of its magnetic properties. The reuse of the HT-DS/TiO2/Fe23 catalyst was viable and the catalyst was structurally stable for at least four consecutive photocatalytic cycles.

New gel-like polymers as selective weak-base anion exchangers

A group of new anion exchangers, based on polyamine podands and of excellent ion-binding capacity, were synthesized. The materials were obtained in reactions between various poly(ethyleneamines) with glycidyl derivatives of cyclotetrasiloxane. The final polymeric, strongly cross-linked materials form gel-like solids. Their structures and interactions with anions adsorbed were studied by spectroscopic methods (CP-MAS NMR, FR-IR, UV-Vis). The sorption isotherms and kinetic parameters were determined for 29 anions. Materials studied show high ion capacity and selectivity towards some important anions, e.g., selenate(VI) or perrhenate.

Temperature based adsorption studies of Cr(vi) using p-toluidine formaldehyde resin coated silica material

A PTFR coated silica material was developed, characterised and applied for the treatment of hexavalent chromium.

Amidoxime functionalization of mesoporous silica and its high removal of U(vi)

Amidoxime-functionalized mesoporous silica has been prepared and applied to eliminate U(vi) from aqueous solutions.

EBT anchored SiO2 3-D microarray: a simultaneous entrapper of two different metal centers at high and low oxidation states using its highest occupied and lowest unoccupied molecular orbital, respectively

Simultaneous binding of two different metal centers, Zr(iv) and Tl(i) at the HOMO and LUMO, respectively, of the extractor (FSG-EBT).

Adsorption of Hg2+ by thiol functionalized hollow mesoporous silica microspheres with magnetic cores

Thiol functionalized hollow mesoporous silica spheres with magnetic cores were synthesized and found to be highly selective adsorbents of Hg²⁺.

New insights into the mesophase transformation of ethane-bridged PMOs by the influence of different counterions under basic conditions

The counterions are of crucial importance in determining the mesostructure and morphology of ethane-bridged PMO materials synthesized under basic conditions.

Removal of hazardous organics from water using metal-organic frameworks (MOFs): plausible mechanisms for selective adsorptions

Provision of clean water is one of the most important issues worldwide because of continuing economic development and the steady increase in the global population. However, clean water resources are decreasing everyday, because of contamination with various pollutants including organic chemicals. Pharmaceutical and personal care products, herbicides/pesticides, dyes, phenolics, and aromatics (from sources such as spilled oil) are typical organics that should be removed from water. Because of their huge porosities, designable pore structures, and facile modification, metal-organic frameworks (MOFs) are used in various adsorption, separation, storage, and delivery applications. In this review, the adsorptive purifications of contaminated water with MOFs are discussed, in order to understand possible applications of MOFs in clean water provision. More importantly, plausible adsorption or interaction mechanisms and selective adsorptions are summarized. The mechanisms of interactions such as electrostatic interaction, acid-base interaction, hydrogen bonding, π-π stacking/interaction, and hydrophobic interaction are discussed for the selective adsorption of organics over MOFs. The adsorption mechanisms will be very helpful not only for understanding adsorptions but also for applications of adsorptions in selective removal, storage, delivery and so on.

Anion selectivity in ion exchange reactions with surface functionalized ionosilicas

Mesoporous imidazolium functionalized ionosilicas have been investigated as anion exchange materials for the adsorption of oxo-anions in aqueous media. Pertechnetate exchange in the presence of competing anionic species revealed Hofmeister selectivity.

Amino-functionalized magnetic magnesium silicate double-shelled hollow microspheres for enhanced removal of lead ions

Both iron magnetic core and amino-group were put forward to functionalize the magnesium silicate hollow microspheres for a fast recoverable and high efficient absorbent of lead ions.

Evolution of tubular copper sulfide nanostructures from copper(i)–metal organic precursor: a superior platform for the removal of Hg(ii) and Pb(ii) ions

Room temperature synthesized porous mixed phase copper sulfide acts as an effective adsorbent for the removal of heavy metal ions from water.

Direct electrochemical analysis in complex samples using ITO electrodes modified with permselective membranes consisting of vertically ordered silica mesochannels and micelles

Herein we report a simple and cost-effective method for direct electrochemical detection of redox-active small organic analytes in complex media, such as soil dispersions, human serum and milk, without sample pre-treatment.

Structural study of hybrid silica bilayers from “bola-amphiphile” organosilane precursors: catalytic and thermal effects

Hybrid materials obtained upon acid or base-catalyzed hydrolytic condensation of bola-amphiphile organosilanes were carefully analysed by several experimental techniques.

Recent advances in hybrid periodic mesostructured organosilica materials: opportunities from fundamental to biomedical applications

Periodic mesoporous organosilica nanostructures functionalized with various active functional groups: from design to biomedical applications.

Dye–collagen interactions. Mechanism, kinetic and thermodynamic analysis

Dye–collagen interactions. Mechanism, kinetic and thermodynamic analysis.

Hydrophobic polydimethylsiloxane (PDMS) coating of mesoporous silica and its use as a preconcentrating agent of gas analytes

Mesoporous silica with mean pore size of ∼14 nm was coated by polydimethylsiloxane (PDMS) using a thermal deposition method. We showed that the inner walls of pores larger than ∼8 nm can be coated by thin layers of PDMS, and the surfaces consisting of PDMS-coated silica were superhydrophobic, with water contact angles close to 170°. We used the PDMS-coated silica as adsorbents of various gas-phase chemical warfare agent (CWA) simulants. PDMS-coated silica allowed molecular desorption of various CWA simulants even after exposure under highly humid conditions and, therefore, is applicable as an agent for the preconcentration of gas-phase analytes to enhance the sensitivities of various sensors.

Synthesis of highly phosphonic acid functionalized benzene-bridged periodic mesoporous organosilicas for use as efficient dye adsorbents

Periodic mesoporous organosilicas (PMOs) with benzene bridging groups in the silica wall were functionalized with a tunable content of phosphonic acid groups. These bifunctional materials were synthesized by co-condensation of two different organosilane precursors, that is, 1,4-bis(triethoxysilyl)benzene (BTEB) and sodium 3-(trihydroxysilyl)propyl methyl phosphate (SPMP), under acidic conditions using nonionic surfactant Brij-S10 as template. The materials exhibited well-ordered mesostructures and were characterized by X-ray diffraction, nitrogen sorption, TEM, TGA, FTIR, and solid-state NMR measurements. The materials thus obtained were employed as adsorbents to remove different types of dyes, for example, cationic dyes methylene blue and phenosafranine, anionic orange II, and amphoteric rhodamine B, from aqueous solutions. The materials exhibited a remarkably high adsorption capacity than activated carbon due to their ordered mesostructures, a large number of phosphonic acid groups, and high surface areas. The adsorption was mainly governed by electrostatic interaction, but also involved π-π stacking interaction as well as hydrogen bonding. The adsorption kinetics can be better fitted by the pseudo-second order model. The adsorption process was controlled by the mechanisms of external mass transfer and intraparticle diffusion. The materials retained more than 97% dye removal efficiency after use for five consecutive cycles.