Porous Polymers Based on 9,10-Bis(methacryloyloxymethyl)anthracene-Towards Synthesis and Characterization

Porous materials can be found in numerous essential applications. They are of particular interest when, in addition to their porosity, they have other advantageous properties such as thermal stability or chemical diversity. The main aim of this study was to synthesize the porous copolymers of 9,10-bis(methacryloyloxymethyl)anthracene (BMA) with three different co-monomers divinylbenzene (DVB), ethylene glycol dimethacrylate (EGDMA) and trimethylpropane trimethacrylate (TRIM). They were synthesized via suspension polymerization using chlorobenzene and toluene served as porogenic solvents. For the characterization of the synthesized copolymers ATR-FTIR spectroscopy, a low-temperature nitrogen adsorption-desorption method, thermogravimetry, scanning electron microscopy, inverse gas chromatography and size distribution analysis were successfully employed. It was found that depending on the used co-monomer and the type of porogen regular polymeric microspheres with a specific surface area in the range of 134-472 m²/g can be effectively synthesized. The presence of miscellaneous functional groups promotes divergent types of interactions Moreover, all of the copolymers show a good thermal stability up to 307 °C. What is important, thanks to application of anthracene derivatives as the functional monomer, the synthesized materials show fluorescence under UV radiation. The obtained microspheres can be used in various adsorption techniques as well as precursor for thermally resistant fluorescent sensors.

Adsorption and membrane separation for removal and recovery of volatile organic compounds

Volatile organic compounds (VOCs) are a crucial kind of pollutants in the environment due to their obvious features of severe toxicity, high volatility, and poor degradability. It is particularly urgent to control the emission of VOCs due to the persistent increase of concentration and the stringent regulations. In China, clear directions and requirements for reduction of VOCs have been given in the "national plan on environmental improvement for the 13th Five-Year Plan period". Therefore, the development of efficient technologies for removal and recovery of VOCs is of great significance. Recovery technologies are favored by researchers due to their advantages in both recycling VOCs and reducing carbon emissions. Among them, adsorption and membrane separation processes have been extensively studied due to their remarkable industrial prospects. This overview was to provide an up-to-date progress of adsorption and membrane separation for removal and recovery of VOCs. Firstly, adsorption and membrane separation were found to be the research hotspots through bibliometric analysis. Then, a comprehensive understanding of their mechanisms, factors, and current application statuses was discussed. Finally, the challenges and perspectives in this emerging field were briefly highlighted.

Adsorption of Carvone and Limonene from Caraway essential oil onto Tunisian montmorillonite clay for pharmaceutical application

To explore a novel kind of green composite material having excellent antibacterial, antifungal ability and specific-targeting capability for pharmaceutical uses, a novel kind of bio-composite was prepared using sodium purified clay as carrier of Caraway essential oil (CEO). Gas chromatography-mass spectroscopy (GC-MS) analyses of CEO reveals that Carvone (68.30%) and Limonene (22.54%) are the two major components with a minimum inhibitory concentration (MIC) value equal to 125 mg/mL against Staphylococcus (S) aureus bacteria and Candida albicans fungi. Clay from Zaghouan was purified and characterized by X-ray Photoelectron Spectroscopy (XPS), X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR) and N₂ adsorption-desorption (BET method). Results obtained by chromatograph equipped with a flame ionization detector (GC-FID) show that the concentration of 130 mg/mL of essential oil and 5 h of contact with the purified clay are the optimal conditions for the bio-hybrid formation. The pseudo-second-order model can describe the kinetic study of the adsorption of Carvone and Limonene on sodium montmorillonite, and the adsorption isotherms have been established to the Langmuir type. Limonene registers a maximum adsorption value equal to 3.05 mg/g of clay however Carvone register the higher amount of adsorption (19.98 mg/g) according to its polarity and the abundance of this compound in the crude CEO. X-ray diffraction, Fourier transformed infrared spectroscopy, elemental analyses (CHN) and X-ray fluorescence characterization valid the success adsorption of CEO in sodium montmorillonite surface. The purified clay/CEO hybrid (purified clay/CEO) combined the advantages of both the clay and the essential oil used in exerting the antibacterial and antifungal activity, and thus, the composite has a double antibacterial and antifungal activity compared to the separately uses of inactive clay and CEO, suggesting the great potential application in pharmaceutical treatments.

Enhancement Properties of Zr Modified Porous Clay Heterostructures for Adsorption of Basic-Blue 41 Dye: Equilibrium, Regeneration, and Single Batch Design Adsorber

Zirconium porous clay heterostructures (Zr-PCH) were synthesized using intercalated clay minerals by zirconium species with different contents of zirconium. The presence of zirconium and silica species was confirmed by X-ray diffraction, X-ray fluorescence, and magic-angle spinning nuclear magnetic resonance. The insertion of zirconium improved the thermal stability, the specific surface area with a maximum of 950 m²/g, and the acidity concentration of 0.993 mol of protons per g of solid. These materials were used to adsorb the basic blue-41 from aqueous solution. The adsorption efficiency was examined at different conditions, with a maximum adsorbed amount of 346 mg/g as estimated from Langmuir model. This value was dependent on zirconium content in the PCHs. The adsorption process was found to be favorable and spontaneous. The efficiency of the spent materials was maintained after five reuse cycles with a decrease by 15% of the original value for a particular Zr-PCH material with a Zr content of 6.82%. Single stage batch adsorber was suggested using the mass balance equation and Langmuir isotherm model. The amount of PCH materials required depended on the target percentage of adsorption at specific volume and initial concentration of the basic-blue-41 dye solution.

Clay-Supported Metal Oxide Nanoparticles in Catalytic Advanced Oxidation Processes: A Review

Advanced oxidation processes (AOPs) utilizing heterogeneous catalysts have attracted great attention in the last decade. The use of solid catalysts, including metal and metal oxide nanoparticle support materials, exhibited better performance compared with the use of homogeneous catalysts, which is mainly related to their stability in hostile environments and recyclability and reusability. Various solid supports have been reported to enhance the performance of metal and metal oxide catalysts for AOPs; undoubtedly, the utilization of clay as a support is the priority under consideration and has received intensive interest. This review provides up-to-date progress on the synthesis, features, and future perspectives of clay-supported metal and metal oxide for AOPs. The methods and characteristics of metal and metal oxide incorporated into the clay structure are strongly influenced by various factors in the synthesis, including the kind of clay mineral. In addition, the benefits of nanomaterials from a green chemistry perspective are key aspects for their further considerations in various applications. Special emphasis is given to the basic schemes for clay modifications and role of clay supports for the enhanced mechanism of AOPs. The scaling-up issue is suggested for being studied to further applications at industrial scale.

Glyphosate adsorption onto porous clay heterostructure (PCH): kinetic and thermodynamic studies

The synthesis of PCH from natural bentonite produces a porous heterostructure material effective for the adsorption of glyphosate from water. The adsorption process takes place through an interaction between the silanol group of montmorillonite and/or the PCH adsorbent with the functional groups of glyphosate. The glyphosate adsorption isotherms, recorded for all the studied samples, have been established to be of Langmuir type. The kinetic of the herbicide adsorption on the PCH was best described by the pseudo-second-order model. With the increase in temperature from 25 to 50 °C, the sorption capacities of the materials studied towards glyphosate increased. The process of glyphosate adsorption was found to be endothermic and spontaneous in nature, as indicated by positive values of ΔH and negative values of ΔG. According to the results obtained, the herbicide sorption was more effective in a basic environment. The maximum amount of adsorbed glyphosate is almost doubled with PCH from 13.5 mg/g of natural clay to 27.5 mg/g of PCH.

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Hybrid Hosts Based on Sodium Alginate and Porous Clay Heterostructures for Drug Encapsulation

In this study, some hybrid materials based on sodium alginate (NaAlg) and porous clay heterostructures (PCHs) were investigated as new hosts for 5-Fluorouracil (5-FU) encapsulation. The hybrid hosts were prepared by ionotropic gelation technique using different concentrations of PCHs (1, 3, and 10 wt%) in order to identify the optimal parameters for encapsulation and drug release. The obtained hybrid materials were characterized using FTIR Spectrometry, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and UV-Vis spectrometry to investigate the interactions of the raw materials involved in the preparation of hybrid hosts, the influence of PCHs concentrations on drug encapsulation efficiency and drug release profile. All the results show that the synthesized hybrid materials were able to load a high amount of 5-FU, the encapsulation efficiency and the release profile being influenced by the concentrations of PCHs.

Al and Zr Porous Clay Heterostructures as Removal Agents of Basic Blue-41 Dye from an Artificially Polluted Solution: Regeneration Properties and Batch Design

The removal of Basic Blue-41 dye molecules was carried out by using two doped porous clay heterostructures by aluminum (Al) or zirconium (Zr) species. The proposed method of synthesis showed its efficiency, starting from Al or Zr intercalated hydrolyzed species, prior to its reaction with dodecylamine (C12 amine) and tetraethyl orthosilicate (TEOS) as a silica source. The intercalated precursors and their porous clay heterostructures (PCH) derivatives were characterized by different techniques. Solid NMR technique proved the presence of Al species into the intercalated silica between the clay sheets, and in addition to Si in different environments within the PCH materials. The Zr-PCH material exhibited a higher surface area and pore volume compared to its Al-PCH counterpart, with a mesoporous character for both materials. A maximum removed amount of 279 and 332 mg/g was achieved and deduced from the Langmuir equation. The regeneration tests revealed that the removal efficiency of Zr-PCH was retained after five regeneration runs, with a loss of 15% of the original value; meanwhile, the Al-PCH lost 45% of its efficiency after only three cycles. A single-stage batch design was proposed based on the Langmuir isotherm parameters. The increase of the removal capacity of Zr-PCH led to the reduction of the required amounts for the target removal of BB-41 dye compared to Al-PCH.

Carbon dioxide adsorption based on porous materials

Global warming due to the high concentration of anthropogenic CO2 in the atmosphere is considered one of the world's leading challenges in the 21st century as it leads to severe consequences such as climate change, extreme weather events, ocean warming, sea-level rise, declining Arctic sea ice, and the acidification of oceans. This encouraged advancing technologies that sequester carbon dioxide from the atmosphere or capture those emitted before entering the carbon cycle. Recently, CO2 capture, utilizing porous materials was established as a very favorable route, which has drawn extreme interest from scientists and engineers due to their advantages over the absorption approach. In this review, we summarize developments in porous adsorbents for CO2 capture with emphasis on recent studies. Highly efficient porous adsorption materials including metal-organic frameworks (MOFs), zeolites, mesoporous silica, clay, porous carbons, porous organic polymers (POP), and metal oxides (MO) are discussed. Besides, advanced strategies employed to increase the performance of CO2 adsorption capacity to overcome their drawbacks have been discoursed.

Catalytic Applications of Clay Minerals and Hydrotalcites

Clay minerals are the most abundant minerals on the surface of Earth [...]

The advantages of clay mineral modification methods for enhancing adsorption efficiency in wastewater treatment: a review

This review discusses the recent trends in the research over the last 30 years to use clay minerals in natural and modified forms for removing different toxic organic/inorganic pollutants. The natural and modified forms of clay minerals have an exceptional ability to remove different contaminants. However, the modification methods can improve the clay mineral adsorption properties that consequently increase more adsorption sites and functional groups to adsorb different environmental pollutants. This review shows the importance of modification methods and more extension of novel clay preparation based on nanotechnology which could raise the control of pollution. The syntheses of functionalized clays such as pillared clays and porous clay heterostructures introduce the new class of heterostructure materials with high adsorption capacity, capability, and selectivity. Due to the acceptable properties of heterostructure materials including high specific surface area, thermal and mechanical stability, and the existence of multifunctional groups to selective adsorption, this review collects more literature of research related to environmental protection issues. However, it is expected much attention to get a better understanding of the adsorption mechanism, regeneration, and recovery process of these materials.

Thermodynamic data of adsorption reveal the entry of CH4 and CO2 in a smectite clay interlayer

The ability of smectite clays to incorporate gases in their interlayers is shown to be conditioned by interlayer spacing, depending, in turn, on phyllosilicate layer composition and effective size of the charge-balancing cations. As illustrated by earlier in situ X-ray diffraction and spectroscopic characterization of the gas/clay interface, most smectites with small-size charge-balancing cations, such as Na⁺ or Ca²⁺, accommodate CO₂ and CH₄ in their interlayers only in a partially hydrated state resulting in the opening of the basal spacing, above a certain critical value. In the present study CH₄ and CO₂ adsorption isotherms were measured for Na- and Mg-exchanged montmorillonite up to 9 MPa using a manometric technique. The process of dehydration of these clays was thoroughly characterized by thermogravimetric analysis and powder X-ray diffraction. A dramatic decrease in specific surface area and methane and carbon dioxide adsorption capacities for fully dehydrated samples in comparison to partially dehydrated ones is assigned to the shrinkage of interlayer spacing resulting in its inaccessibility for the entry of CH₄ and CO₂ molecules. This observation is direct evidence of CH₄ and CO₂ adsorption capacity variation depending on the opening of smectite clay interlayer spacing.

Chitosan modified Ti-PILC supported PdOx catalysts for coupling reactions of aryl halides with terminal alkynes

Biopolymer of chitosan (CS) and titanium pillared clays (Ti-PILCs) have been combined in a hybrid as advanced supports for immobilization of PdOx=0,1 species to prepare novel PdOx=0,1@Ti-PILC/CS nano-composite catalysts. The Ti-PILC materials showed high specific surface areas and abundant meso-porous structure with many irregular pore channels caused by collapses of layered structure of clay during Ti pillaring process. Both CS chains and sub-nano sized PdOx particles were successfully incorporated into the pore channels of Ti-PILC, resulting in a decrease in both the specific surface areas and uniform distribution of pore size. Besides conventional methods characterizations, the strong interactions between PdOx species and Ti-PILC/CS support were further evidenced with positron annihilation lifetime spectroscopy studies. The resultant PdOx@Ti-PILC/CS catalyst was highly active for the coupling reactions of aryl halides with phenyl acetylenes. It was recyclable and gave excellent yield up to 13 runs with low leaching of Pd species.

Adsorption of Salmonella in Clay Minerals and Clay-Based Materials

A series of clay minerals and clay-based materials have been tested to eliminate one of the most dangerous bacteria we can find in the water: Salmonella. It has been proven that the use of clays and their PCH materials can be a suitable method for removing Salmonella from water. The results of this initial study show that all the materials analyzed have great salmonella adsorption capacities ranging from the lowest value observed in the mont-PCH sample (0.29 × 1010 CFU g−1) to the highest value observed in the natural palygorskite sample (1.52 × 1010 CFU g−1). Macroporosity, accessible external surface area, and the presence of silanol groups in the external surface of the particles appears to be the controlling factors for Salmonella adsorption capacity while it seems that the structural characteristics of the clay minerals and their respective PCH does not affect the adsorption capacity.

Adsorption of Uranium (VI) from Aqueous Solutions by Amino-functionalized Clay Minerals

Silylation of clay minerals from Cherkasy deposit (Ukraine) montmorillonite (layer silicate) and palygorskite (fibrous silicate) was performed using organosilane (3-aminopropyl)triethoxysilane (APTES). Solvents with different polarity (ethanol, toluene) were used in synthesis. The structure of modified minerals was characterized by complex of methods (X-ray powder diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption-desorption at −196 °C and thermal analysis). Studies of adsorption characteristics of APTES-modified clay minerals were carried out in relation to uranium (VI). The results indicated that modified montmorillonite and palygorskite were effective materials for water purification from UO22+.