Alumina-pillared Clay Research Articles

Enhancing the performance of alumina-pillared clay for phenol removal from water solutions and polyphenol removal from olive mill wastewater: Characterization, kinetics, adsorption performance, and mechanism

An alumina-pillared clay (Al-PILC) has been synthesized and tested for its ability to adsorb phenol from aqueous solutions, and polyphenols from Olive Mill Wastewater (OMW). The synthesis processes were investigated by varying parameters like the Al/clay ratio, with a molar ratio of [OH−]/[Al3+] = 2.4. Various techniques, including XRD, BET, XRF, FTIR, and SEM were used to characterize the resulting solids. The effect of key factors as pH, initial pollutant concentration, and contact time, were examined in order to evaluate the phenol adsorption capacities of raw clay (RC) and optimized Al-PILC10 materials. The specific surface areas of RC and Al-PILC10 were 40 and 127 m2/g, respectively, resulting in increasing the phenol adsorbed quantity from 14.15 mg/g for RC to 30.61 mg/g for Al-PILC10 clays, at pH 2 and 45 °C. Pseudo-second-order kinetics and Freundlich adsorption isotherm were suitable for describing phenol adsorption on both clays. Furthermore, Al-PILC10 exhibits an impressive removal efficiency of 76 % for polyphenols from OMW, in contrast to the 50 % achieved by RC at acidic pH. Furthermore, Al-PILC10 showcased a superior desorption rate and a favorable regeneration capacity of 64 % compared to RC (45 %), even after multiple adsorption-desorption cycles. These findings emphasize the potential of pillared clay as a cost-effective adsorbent for the efficient removal of phenol and polyphenols from wastewater.

Experimental and computational studies of sulfided NiMo supported on pillared clay: catalyst activation and guaiacol adsorption sites.

We report on intermediate (oxysulfides) and sulfided structures of NiMo supported on aluminium pillared clay (Al-PILC) during the catalyst activation process and the prefered guaiacol adsorption sites on the sulfided catalyst. In situ X-ray absorption fine structure (XAFS) together with density functional theory (DFT) calculations confirm the existence of ill-defined suboxides (MoOx, NiOx) and the well-known subsulfides (Mo2S9, Ni3S2) at the first stage which, at a later stage in the process, transform into MoS2 with two edges, oxygen-decorated Mo and Ni with zero sulfur coverage. The freshly sulfided NiMoS2 catalyst under sulfiding agents is mainly terminated by Mo-edge surface with 50% sulfur coverage (Mo-S50) with a disordered Ni-edge surface that can be assigned as NiMoS (1̄010). When exposed to an inert atmosphere such as He gas, the Mo and Ni edges evolved partially into new structures of Mo and Ni edges with zero sulfur coverage, labelled as Mo-Bare and Ni-Bare. Guaiacol is often used as a model compound for lignin and a series of calculations of guaiacol on the structural edges of a sulfided NiMoS2 catalyst show relatively good agreement between the observed and calculated inelastic neutron scattering (INS) spectra for Mo-S50, Ni-Bare, and NiMoS (1̄010) where guaiacol weakly chemisorbed via oxygen atom of OH group. The results also confirm that guaiacol is physisorbed on the basal plane of NiMoS2 in a horizontal (flat-lying) configuration via van der Waals interaction at a separation of about 3.25 Å.

The influence of cobalt loading on electrocatalytic performance toward glucose oxidation of pillared montmorillonite-supported cobalt

• Aluminum-pillared clays with different cobalt loadings were synthesized. • Modified carbon paste electrodes were tested in glucose electrooxidation. • Increase in Co loading (up to 4.13 wt%) enhanced the electrocatalytic performance. • Further increase in Co loading derogated the electrocatalytic performance. • Co 3 O 4 formation probably altered the electrocatalytic performance. In this paper, the influence of cobalt loading in pillared clay-supported cobalt materials on their electrocatalytic performance toward glucose oxidation was investigated. A series of aluminum-pillared montmorillonite clay (AP) materials with different cobalt loadings (x%CoAP, x = 1, 3, 5, and 10 wt%) was synthesized using the incipient wetness impregnation method. The X-ray powder diffraction (XRPD), inductively coupled plasma optical emission spectroscopy (ICP-OES), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy coupled with energy dispersive X-ray spectrometry (FE-SEM/EDX), high resolution transmission electron microscopy (HR-TEM) coupled with EDX, X-ray photoelectron spectroscopy (XPS), and low temperature N 2 physisorption, were employed for characterization of the materials. The incorporation of cobalt in porous structure of pillared montmorillonite was confirmed. The synthesized materials (x%CoAP) were used for modification of carbon paste (CP) electrode and tested in reaction of glucose electrooxidation. The electrochemical measurements were conducted using cyclic voltammetry and chronoamperometry in a 1 M NaOH solution, with or without glucose. The results showed that the increase of cobalt loading improved the electrode performance toward glucose. The highest current response and sensitivity were obtained for the CP-5%CoAP electrode. A lower electrode performance of CP-10%CoAP was correlated with the presence of higher quantities of Co 3 O 4 (confirmed by XRPD and XPS) in the electrode material. The mechanism and kinetics of glucose electrooxidation was studied in more details for the best performing electrode (CP-5%CoAP). It was found that the process was diffusion-controlled and the diffusion coefficient was determined. The charge transfer coefficient and catalytic rate constant were calculated. The electrode exhibited satisfactory repeatability, reproducibility, stability, and selectivity. The obtained results showed that appropriate amount of cobalt loading in pillared clay led to the obtainment of non-enzymatic electrode materials suitable for sustainable and green glucose sensors.

Catalytic photodegradation of organic compounds using TiO2/pillared clays synthesized using a nonconventional aluminum source

This study evaluates the photocatalytic degradation of 2,6-dichlorophenol (2,6-DCP), triclosan (TCS) and bisphenol A (BPA) by ultraviolet (UV) and visible (VIS) light in the presence of TiO2/catalysts synthesized by wet impregnation followed by calcination. The catalyst supports used were three alumina pillared clays (Al-PILC) synthesized using various aluminum sources and montmorillonite (Mt) as raw material. One of the Al-PILC was prepared following the conventional method (Al-PILCCM), using a commercial aluminum salt, and the other two were synthesized using a saline slag, with the aluminum used being extracted with the alkaline (Al-PILCBE) or the acid (Al-PILCAE) method. Mt was impregnated with various amounts of titanium (1, 5, 10, and 20 wt% Ti) and evaluated for the photodegradation of the aforementioned pollutants, comparing the results with those obtained using commercial anatase. Due to the higher conversion rates, 10 and 20 wt% Ti were chosen to impregnate the Al-PILC and to evaluate the photocatalytic performance. All materials were characterized by several techniques, which confirmed the successful formation of TiO2 in the anatase phase. In all cases, photodegradation was higher when using UV light and the most photodegraded pollutant was TCS (85.15 ± 0.49%), followed by 2,6-DCP (65.43 ± 0.79%) and, to a lesser degree, BPA (36.15 ± 0.65%). Al-PILC showed higher photodegradation percentages, with Al-PILCAE exhibiting the highest values for both types of light. An analysis of the photoproducts by HPLC-MS suggested that the preferred pathway for TCS and 2,6-DCP photodegradation depends on the type of light used.

One pot synthesis of aluminum pillared intercalated layered clay supported silicotungstic acid (STA/Al-PILC) catalysts

One pot synthesis of silicotungstic acid (STA) containing aluminum pillared intercalated layered clay (STA/Al-PILC) catalysts is carried out by addition of STA to aluminum pillared clay synthesis media. STA-Al Keggin type pillar agents which are formed by charge interaction among them are inserted between clay layers. Effect of parameters on catalyst structure such as pH of clay suspension, STA quantity, addition step and its isolation in buffer solution are investigated. STA addition step has a crucial role on properties of catalysts. Conservation of the layered structure of Al-PILC support in the presence of STA is seen from X-ray powder diffraction (XRD) patterns and transmission electron microscopy (TEM) images. Basal spacing values do not show much difference with respect to that of Al-PILC support which is measured as 1.85 nm. The catalyst which owes the best structural properties has 217 m2/g surface area, 0.20 cm3/g pore volume, 0.44 nm average micropore size and 3.90 nm average mesopore size with high STA loading success. Lewis acidity is dominant acid character in all catalysts. Preservation of Keggin structure of STA in PILC structures is seen by X-ray photo electron spectroscopy (XPS) with a clear W4f7/2 and W4f5/2 spin orbital doublet. The increase in STA amount leads no additional increase in STA loading. Agglomeration, which is seen clearly in TEM images, occurs when STA is added either as its powder form to Al-pillar agent media or after isolating it within the buffer solution to Al-pillar agent-clay suspension. The proposed model which assumes the placement of pillar agents between clay layers, either after coupling with each other or alone, explains effects of STA addition steps on structural properties.

A nonconventional aluminum source in the production of alumina-pillared clays for the removal of organic pollutants by adsorption

This study is the first to propose the use of aluminum saline slag as aluminum source in the synthesis of alumina pillared clays (Al-PILC). Aluminum was extracted from this waste using both alkaline and acid solutions and both were compared for preparation of the intercalation solutions used for the synthesis of Al-PILC. Variations in parameters such as [OH–]/[Al3+], Al/clay (mmol/g), clay/volume solution ratios and temperature were studied in the synthesis processes. The solids obtained were characterized by X-ray diffraction (XRD), N2 adsorption–desorption at −196 °C, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX), which confirmed that the pillaring process was successful. PILC obtained from both acid (Al-PILCAE) and alkaline (Al-PILCBE) extracts were evaluated as adsorbents for three organic pollutants, namely bisphenol A (BPA), 2,6-dichlorophenol (2,6DCP) and triclosan (TCS), in batch mode. The resulting adsorption capacities were compared with montmorillonite (Mt) and an Al-PILC prepared by the conventional method, namely, dropwise addition of an NaOH solution into an aluminum chloride solution (Al-PILCCM). In all cases, the effect of factors such as pH, initial concentration of pollutant, adsorbent dosages and contact time was studied. The kinetic and equilibrium results obtained were evaluated using both pseudo-first- and pseudo-second-order kinetics, and Langmuir, Freundlich and Sips equation isotherms for the equilibrium. The kinetic study showed that the time needed to reach equilibrium was 30, 900 and 510 min for BPA, 2,6DCP and TCS, respectively. Moreover, adsorption data showed that the Al-PILCAE and Al-PILCBE synthesized have excellent potential as adsorbents for 2,6DCP and TCS, removing 98.46% and 98.47% of these compounds, respectively.

Aluminum Pillared Clay (Al-PILC) for Adsorption of Dyes in Red Fruit Oil

Red fruit oil contains carotene, which is dark orange, so it is not very popular. Therefore, it is necessary to reduce the intensity of the color. Yesterday, in this study, the synthesis and characterization of Al-pillared clay (Al-PILC) from light and heavy clay fractions were carried out. The absorption capacity of red fruit carotene dyes was studied. The research stages included preparation, fractionation, activation, pillarization of clay with aluminum, characterization, and adsorption test for carotene dyes on red fruit. Characterization was carried out using X-ray Diffractometer (XRD) and Gas Sorption Analyzer (GSA). The results showed that basal spacing of natural clay, Al pillared heavy fraction-clay, Al pillared light fraction-clay, activated light fraction were 15.08 Å, 15.27 Å, 16.84 Å, and 16, respectively. 22 Å. The GSA results showed that the surface area and pore volume of the Al pillared light fraction-clay of 0.3 was higher than the heavy fraction. The average pore size of Al pillared light fraction-clay and the heavy fraction was found in the mesoporous range of 30-100 Å, and the adsorption isotherm is type IV. Al-pillared light fraction-clay had higher adsorption ability than a heavy fraction and light fraction before pillaring. When the pillaring agent’s concentration was 0.3 M, Al pillared heavy fraction-has absorption capacity is 58.66%, while Al pillared light fraction-clay is 90.4%.

Catalytic assessment of solid materials for the pyrolytic conversion of low-density polyethylene into fuels

Pyrolysis techniques provide an interesting way of recycling plastic wastes (PW) by transforming them into liquid fuels with high calorific values. Catalysts are employed in PW pyrolysis in order to favor cracking reactions; in that regard, cheap and abundant natural resources are being investigated as potential catalyst precursors. This article explores the pyrolysis of low-density polyethylene (LDPE) in a semibatch reactor under a reduced pressure of 300 torr and temperatures in the range of 370 °C–430 °C. Three different solid materials, an activated carbon (AC1), a commercial Fluid cracking catalyst (FCC) and an aluminum- pillared clay (Al-PILC), were tested as catalysts for the pyrolysis process. Thermogravimetric analyzes were previously performed to select the most catalytically active materials. AC1 displayed very low catalytic activity while FCC and Al-PILC displayed high activity and conversion to liquid products. Hydrocarbons ranging from C5 to C28 were identified in the liquid products as well as significant changes in their composition when FCC and Al-PILC catalyst were used. Differences in the catalytic activity of the 3 solid materials are ascribed mainly to differences in their acid properties.

Iron and molybdenum mixed oxide supported on Al-PILC for the catalytic oxidative desulfurization of dibenzothiophene in simulated diesel fuel.

In this work, three novel catalysts were prepared by 2.5, 5.0, and 10.0wt.% facile impregnation with an iron and molybdenum mixed oxide (Fe/Mo) on an aluminum pillared clay (Al-PILC) support. These materials were characterized by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), temperature programed reduction (TPR), and nitrogen (N2) physisorption at 77K. Characterizations indicated that the metal particles were dispersed on the surface of the three catalysts, and the interlayer d001 spacing of the pillared material remained unchanged after the impregnation process. The catalytic tests showed good results for DBT oxidation using the synthesized catalysts, with high turnover frequency (TOF) values, particularly for the material with 5.0wt.% Fe/Mo. Theoretical calculations were carried out at the density functional theory (DFT) level, to investigate how the DBT molecules were adsorbed onto the surface of the mixed oxide. The lowest energy proposal was obtained when both Fe and Mo were present at the active sites, indicating a possible synergistic effect of the metals on catalyst activity. Reuse tests indicated that the catalysts could be employed effectively for up to 3cycles in a row, then a decrease in activity occurred and the active sites needed to be regenerated.

Removal of pharmaceuticals and personal care products (PPCPs) from water by adsorption on aluminum pillared clay

The natural layered clay-based materials offer a sustainable approach for removal of emerging pollutants from the environment. Their low-capacity and poor-selectivity for pollutants often limit their uses. This limitation is addressed in this study with the help of Al-oxide pillaring approach. Here microporous aluminum-pillared clay (Al-PILC) was prepared from locally available Smectite clay (montmorillonite, MMT), by intercalation of Al-oxide pillars into the interlayer structure. The method increased the surface area of natural clay to 258 m2 g−1 and its porosity to 0.16 cm3 g−1. The adsorptive removal properties of prepared Al-PILC was evaluated on two selected pharmaceuticals and personal care products (PPCPs) viz. amoxicillin (AMOX) and imipramine (IMP). The results of the removal of these PPCPs were compared as a function of contact time (0–180 min), solution pH (2–12), initial concentration (0–100 mg L−1), and temperature (298–318 K). The Al-PILC adsorbs 332% more IMP and 681% more AMOX as compared to natural clay, and the maximum adsorption amounts on Al-PILC follows the order IMP > AMOX with 59.8 and 7.7 mg g−1, respectively. The kinetics of adsorption of both AMOX and IMP follow pseudo-second-order model, with intraparticle diffusion as rate-determining step. The incorporated acidic sites in clay (in form of Al2O3 pillars) enhanced its adsorption properties. These sites interacted with protonated amine and –OH groups of AMOX and the tertiary amine group of IMP. The Al-PILC exhibit effective regeneration and was reused up to three consecutive adsorption/desorption cycles. All in all, this study is expected to expand the application of Al-PILC on the adsorptive removal of the emerging pollutant from contaminated water.

Synthesis and Characterization of CPC Organomodified and Al13 Pillared Modified Bentonite

In this study, a Moroccan bentonite was used to prepare three modified clays prepared by different intercalating agents: a sodic clay (B-Na) prepared from raw clay by sodium exchange process. The homoionic sodium clay was then used to prepare an organoclay (B-CPC) by intercalation of cetyl-pyridinium chloride (CPC) and an aluminium-pillared clay (Al-PILC) by intercalation of hydroxyl-aluminium cations. The FT-IR analysis showed that the pillaring with Al13 and intercalation with CPC did not destroy the initial structure of the sodium bentonite, and some characteristic bands of the intercalating agents appears. Detailed characterization with azote gas adsorption confirmed that the specific surface area of the natural bentonite was 70 m 2 /g, and 107 m 2 /g for the B-Na when impurities are eliminated and exchanged with sodium cations. The total surface area for the Al-PILC pillared bentonite was significantly higher than that of unpillared samples and reached the value of 270 m 2 /g resulting to the increase of the adsorption sites for the N 2 gas. A considerable decrease to 7 m 2 /g of the total surface area for the B-CPC oranophilic bentonite was observed. All clay samples were classified as porous materials, the Al-PILC was a microporous material; whereas natural clays B–CPC and B-Na were mesoporous materials. The B-CPC was the clay that showed the highest (XRD) value of interlayer distance (21.7 A) corresponding to the bilayer intercalated between the clay mineral layers, and Al-PILC have a XRD peak at 19.4 A which corresponds to the Al13 intercalating pillars.

Application of raw and modified Uruguayan clays to phosphate adsorption for water remediation

ABSTRACTA raw clay from Uruguay was modified with aluminium to obtain an aluminium pillared clay (Al-PILC). The solids were characterized by scanning electron microscopy, X-ray diffraction and nitrogen adsorption-desorption isotherms. The Al-PILC retained the typical laminar structure of montmorillonite. The specific surface area and the microporous volume of the Al-PILC, 235 m2 g-1 and 0.096 cm3 g-1, respectively, were much higher than those of the clay. The phosphate adsorption capacity of the Al-PILC was higher than those of the clay. The phosphate adsorption kinetic followed the pseudo-first-order model for both, the clay and the Al-PILC, and the phosphate adsorption isotherm for the Al-PILC fit the Freundlich model.

Aluminum pillared montmorillonite clay-based self-healing coatings for corrosion protection of magnesium alloy AZ91D

In the present study, aluminum pillared montmorillonite clay was modified with cationic corrosion inhibitors Ce3+/Zr4+. The modification of the montmorillonite clay was carried out by two methods; (a) by simple mixing of inhibitor solutions along with clay by stirring for 30 min and (b) by homogenization of inhibitor solutions and clay for a very short time of 15 min followed by evacuation. The modified and as-received clays were dispersed in hybrid organic-inorganic sol-gel matrix silica sol, which were coated on magnesium alloy AZ91D and cured in air at 130 °C for 1 h. Corrosion protection ability of coatings was evaluated by electrochemical impedance spectroscopy, potentiodynamic polarization and weight loss measurements after exposure to 3.5 wt% NaCl solution for different exposure durations between 24 h to 120 h. Coatings were evaluated for their self-healing ability using scanning vibrating electrode technique for varying time duration from 1 h to 24 h. Coatings generated with the sol using the pillared montmorillonite clay after modification as described in (b) were found to exhibit better anticorrosive properties even after prolonged exposure to the corrosive medium.

Montmorillonite nanoclay-based self-healing coatings on AA 2024-T4

Cation-exchanged montmorillonite (MMT), which is an aluminum-pillared clay, was dispersed into an organic–inorganic hybrid silica matrix sol. Cationic inhibitors Ce3+/Zr4+ were introduced into montmorillonite by two methods, namely (1) physical mixing of MMT with the inhibitor solutions and (2) physical mixing for short durations and evacuation of the mixture of MMT and inhibitor solutions. Coatings using these sols were deposited on aluminum alloy AA 2024-T4 substrates, by the dip coating technique followed by thermal curing at 130°C for 1 h. TEM, BET, and XRD analyses were carried out for the inhibitor-modified montmorillonite powders. Potentiodynamic polarization and electrochemical impedance spectroscopic analyses were carried out on uncoated and coated substrates to evaluate the corrosion protection property after exposure to 3.5 wt% NaCl for varying time durations, up to 120 h. Self-healing ability was evaluated using SVET analysis by creating an artificial scribe on the surface and exposure to 3.5 wt% NaCl. Elemental mapping was carried out on scribed substrates before and after exposure to 5 wt% salt fog. Sols containing montmorillonite intercalated with cationic inhibitors when deposited on AA 2024-T4 substrates exhibited low corrosion currents after a prolonged duration of exposure to corrosion medium.

Aluminium - Cobalt-Pillared Clay for Dye Filtration Membrane

The manufacture of membrane support from cobalt aluminium pillared clay has been conducted. This research was conducted by mixing a clay suspension with pillared solution prepared from the mixture of Co(NO3)2.6H2O and AlCl3.6H2O. The molar ratio between Al and Co was 75:25 and the ratio of [OH-]/[metal] was 2. The clay suspension was stirred for 24 hours at room temperature, filtered and dried. The dried clay was then calcined at 200°C, 300°C and 400°C with a ramp rate of 2°C/min. Aluminium-cobalt-pillared clay was then characterized by XRD and GSA and moulded become a membrane support for subsequent tests on dye filtration. The XRD analysis showed that basal spacing (d001) value of aluminium cobalt was 19.49 Å, which was higher than the natural clay of 15.08Å however, the basal spacing decreased with increasing calcination temperature. The result of the GSA analysis showed that the pore diameter of the aluminium cobalt pillared clay membrane was almost the same as that of natural clay that were 34.5Å and 34.2Å, respectively. Nevertheless, the pillared clay has a more uniform pore size distribution. The results of methylene blue filtration measurements demonstrated that the membrane filter support could well which shown by a clear filtrate at all concentrations tested. The value of rejection and flux decreased with the increasing concentration of methylene blue. The values of dye rejection and water flux reached 99.89% and 5. 80 x 10-6 kg min-1, respectively but they decreased with increasing concentration of methylene blue. The results of this study indicates that the aluminium-pillared clay cobalt could be used as membrane materials especially for ultrafiltration.

A comparison of single and mixed pillared clays for zinc and chromium cations removal

In order to explore the feasibility of improving zinc and chromium ability of zirconium-aluminium pillared clays (PILC), mixed zirconium-aluminium PILC with different Zr/Al ratio (Zr/Al = 100/0, 90/10, 50/50, 10/90 and 0/100) were prepared and investigated for their ability to remove zinc and chromium from water. Single and mixed PILC were characterized with X-ray diffraction, N2 adsorption–desorption, FT-IR spectroscopy method, etc. Results indicate that, in the case of single PILC, zirconium PILC exhibited an adsorption capacity higher than aluminium PILC. In the case of mixed PILC, adsorption capacity increased as the ratio of Zr/Al increased. The influence of the pH values and the temperature on adsorption capacity was also investigated.

Combining HDC and CWPO for the removal of p-chloro-m-cresol from water under ambient-like conditions

Catalysts supported on aluminium pillared clays (Al-PILCs) using Fe and Pd or Rh as active phases have been prepared and tested for a two-step treatment of p-chloro-m-cresol (PCMC) in water by catalytic hydrodechlorination (HDC) followed by catalytic wet peroxide oxidation (CWPO) under ambient-like conditions (25°C, 1atm). Both processes were first studied independently. HDC was investigated with Pd and Rh monometallic catalysts as well as Pd-Fe and Rh-Fe bimetallic ones. The bimetallic Pd-Fe catalyst showed the best performance, allowing complete dechlorination in less than 1h reaction time. On the other hand, CWPO of PCMC with a monometallic Fe catalyst allowed complete conversion of that pollutant but with only about 33% reduction of total organic carbon (TOC) after 4h. Then, a two-step approach consisting in HDC of PCMC followed by CWPO has been tested for the first time in two different ways. The first one used a Pd-Fe bimetallic catalyst in both steps while in the second approach monometallic Pd and Fe catalysts were used for HDC and CWPO, respectively. The HDC in alkaline medium allowed reducing significantly Fe leaching. This second approach yielded complete dechlorination followed by higher mineralization (>55%) with better efficiency of H2O2 consumption.

Use of pillared clays in the preparation of washcoated clay honeycomb monoliths as support of manganese catalysts for the total oxidation of VOCs

Manganese catalysts supported by impregnation onto honeycomb monoliths extruded from commercial clay, previously coated with aluminium-pillared clay, were prepared and tested in the total combustion of propane and acetone. Samples characterization included chemical analysis, nitrogen physisorption, electron microscopies (SEM-EDS, HAADF and EELS), XRD, TPR and O2-TPD experiments. The active phase (around 5wt%), consisting of MnO2 particles as majority phase, with homogeneous size and shape, that tends to concentrate in some regions of the surface of the clay support, exhibited high efficiency to oxidize the two model VOCs investigated and stability in severe reaction conditions. Light-off temperatures as low as 225 and 330°C were found for the oxidation of acetone and propane respectively. The better performance observed in comparison to the monoliths without pillared clay was attributed to the higher active phase loading. Differences found as function of the VOC's nature and concentration were related to the different oxidation mechanisms proposed in literature, either just Mars-van Krevelen or this with also Eley-Rideal contribution, for acetone and propane respectively. These results combined with the intrinsic advantages of the honeycomb monolithic design open up new possibilities for using pillared clays as catalytic support in VOCs oxidation under more affordable conditions.

Mild microwave-assisted synthesis of aluminum-pillared bentonites

Two types of bentonites were modified using a cleaner method to prepare aluminum-pillared clays. This methodology involved a purifying stage, an intercalation process, and a microwave irradiation step at low energy power. Structural changes induced by pillaring process were demonstrated by thermal behavior, as well as morphological characterization. The effect of pillaring process on thermal stability of clays was studied, and the mass lost associated with the dehydroxylation of the octahedral clay sheets was not detected for modified bentonites. In addition, an analysis of their chemical composition and crystalline structure was also performed. Concerning industrial applications of these bentonites, two potential uses were proposed: (1) as reinforcement of different polymers matrices such as thermoplastic starch (TPS), high-density polyethylene (HDPE), and poly (styrene-b-butadiene-b-styrene), SBS; and (2) as removal agent for cadmium (Cd) species present in wastewaters. Bentonite particles reinforced thermoplastic starch matrix and increased ultraviolet barrier capacity of HDPE composites. Besides, bentonites improved the mechanical performance and modified barrier properties of SBS. Regarding effluents purification, an adequate Cd adsorption from aqueous solutions was observed (77%), proving their feasibility to be used as non-conventional removal agents.

The effect of preparation method on textural and structural properties of alumina-pillared interstratified illite-smectite

In order to study the effect of the preparation method on structural and textural properties of pillared clays, alumina-pillared bentonite clay (Al-PILC) was prepared using two different methods: the conventional and ultrasonic one, during the aging process for the pillaring solution and during the aging in the intercalation stage. Compared with the conventional treatment, the use of an ultrasonication method considerably reduces the modification time (from 24 h to 20 min) for the synthesis of the pillared clay. The characterization of solids by the elemental chemical analysis, X-ray diffraction (XRD), cation exchange capacity (CEC), N2 adsorption/desorption isotherms, scanning electron microscopy (SEM) and temperature-programmed reduction (H2-TPR) techniques showed that the use of ultrasound brings not only very similar results to those obtained with the classical method, but also present a better structural and textural properties than the clay pillared with the conventional treatment.