•Substitutions improve the adsorption capacities in the following order: Cr > Ni > Mn > Co.•Adsorption isotherms is well fitted by Langmuir model and not suppressed by the presence of background electrolyte.•Inner-sphere complexation in monolayer is the dominated adsorption mode.•The adsorbed Pb(II) are in the geometry of bidentate binuclear corner-sharing, independent of the adsorption capacity.•Relationship between surface and adsorption properties was discussed by adsorption mechanism and active site density.Iron oxides are abundant in natural waters and soils and have high capacities for scavenging Pb(II) by adsorption, which affects the transport and fate of Pb on the earth's surface. We investigated the adsorption of Pb(II) on magnetites substituted with commonly incorporated transition metals such as Cr, Mn, Co, and Ni. The adsorption capacity, mechanism, and local coordination of Pb(II) were investigated by traditional macroscopic studies, i.e., acid-base titration and batch adsorption experiment, complemented with X-ray absorption fine structure (XAFS) spectrum analysis and surface complexation model (SCM). The substitution increased the surface site density, while pHpzc did not vary. Pb(II) adsorption was not suppressed by the presence of background electrolyte and improved as pH increased. The isotherms were well fit to the Langmuir adsorption model. The XAFS analysis demonstrated that Pb(II) ions were adsorbed on magnetite surface predominantly via inner-sphere complexation, where the adsorbed Pb(II) species was in bidentate binuclear corner-sharing geometry, independent of the adsorption capacity. This adsorption geometry can be applied to fit the experimental adsorption data well with the diffuse layer model (DLM). The substitutions improved the adsorption capacity in the following order: Cr > Ni > Mn > Co, and were discussed regarding the measured values of active site density and local coordination of adsorbed Pb(II). This study is the first documentation of Pb(II) adsorption on magnetite with different substitutions. The obtained results are of great significance for the understanding of Pb(II) surface complexation reactions on magnetite surface.Download high-res image (232KB)Download full-size image

•A variety of characterizations was made to investigate the composition and structure of PCHs in detail.•The clay/TEOS ratio had effect on the composition and structure of PCHs.•TEOS was both the silicon source for generating the Si framework and reaction medium.•The possibility of compositional and structural control of PCHs was discussed.Understanding the composition and structure of porous clay heterostructures (PCHs) is of great importance in clarifying the topological design and performance of PCHs in applications. In this paper, we investigated the chemical composition and structural characteristics of PCHs in detail by thermal analysis, major elements analysis, XPS, FTIR, 29Si MAS NMR, XRD, HRTEM, and nitrogen adsorption/desorption at −196 °C. Based on the characterization results, the possibility of controlling the composition and structure of PCHs was discussed. With a reduced ratio of organo-montmorillonite to tetraethylorthosilicate (i.e., clay/TEOS), the carbon content of the PCH precursors was relatively decreased due to the increase in polymerized TEOS in PCH precursors. After calcination, the progressive increase in the surface silicon contents (fSiO2-s) reflected a more intensive distribution of extra-lattice silica (i.e., the amorphous silica outside the interlayer space) in PCH. In the comparable amount of bulk silicon contents (fSiO2-b), the amorphous silica from the condensation of TEOS gradually increased, which was confirmed by FTIR and 29Si MAS NMR. HRTEM images showed a partially delaminated morphology in the PCHs synthesized with the largest clay/TEOS ratio. As the clay/TEOS ratio decreased, the interlayer distances of PCH expanded and the specific delamination was not appreciable. The mesoporosity of the PCHs gradually decreased, whereas the microporosity increased in both amount and distribution. Despite the invariant dominant pore size, the pore size distributions (PSD) of PCHs can be qualitatively controlled by altering the layer charge of the base clay, the length of the hydrophobic chains of surfactants, and the clay/TEOS ratio.Download high-res image (303KB)Download full-size image

•IOMt could simultaneously remove phenol, phosphate and Cd.•The adsorption of phenol was not affected by phosphate and Cd and vice versa.•The removal of phosphate and Cd were enhanced by synergistically adsorptions.•The types of surfactant affected adsorption capacities of IOMts.Inorganic-organic montmorillonites (IOMts) obtained by modifying polyhydroxy-aluminum (Al13)-pillared montmorillonite (AlPMt) with the cationic surfactant (C16) and zwtterionic surfactant (Z16) were investigated with the aim to remove phenol, phosphate and Cd(II) simultaneously. The structures of IOMts prepared using different surfactant doses (0.4 and 1.0CEC) strongly depended on the types and doses of the surfactants. The Al13 contents of C16 modified AlPMts (C-AlPMts) decreased with increasing C16 loading while that of Z16 modified AlPMt (Z-AlPMts) did not. In the single adsorption system, all IOMts could efficiently remove phenol and phosphate, but not Cd(II). IOMts, however, could efficiently remove all three contaminants simultaneously in the multi-contaminant adsorption system. The adsorptions of phenol on IOMts were not affected by the other two inorganic components and vice versa. Whereas the adsorptions of phosphate and Cd(II) were significantly enhanced in the multi-contaminant system, and the adsorption of one increased with increasing initial concentration of the other one, especially the adsorption of Cd(II). The enhancements of adsorption of phosphate and Cd(II) on the IOMts with higher Al13 content were much larger than that on IOMts with lower Al13 content. The adsorption mechanism for phosphate and Cd(II) uptake in the multi-contaminant system possible involve the formation of phosphate-bridged ternary complexes.

Al13 pillared montmorillonites (AlPMts) prepared with different Al/clay ratios were used to remove Cd(II) and phosphate from aqueous solution. The structure of AlPMts was characterized by X-ray diffraction (XRD), Thermogravimetric analysis (TG), and N2 adsorption–desorption. The basal spacing, intercalated amount of Al13 cations, and specific surface area of AlPMts increased with the increase of the Al/clay ratio. In the single adsorption system, with the increase of the Al/clay ratio, the adsorption of phosphate on AlPMts increased but that of Cd(II) decreased. Significantly enhanced adsorptions of Cd(II) and phosphate on AlPMts were observed in a simultaneous system. For both contaminants, the adsorption of one contaminant would increase with the increase of the initial concentration of the other one and increase in the Al/clay ratio. The enhancement of the adsorption of Cd(II) was much higher than that of phosphate on AlPMt. This suggests that the intercalated Al13 cations are the primary co-adsorption sites for phosphate and Cd(II). X-ray photoelectron spectroscopy (XPS) indicated comparable binding energy of P2p but a different binding energy of Cd3d in single and simultaneous systems. The adsorption and XPS results suggested that the formation of P-bridge ternary surface complexes was the possible adsorption mechanism for promoted uptake of Cd(II) and phosphate on AlPMt.

•The valences and occupancy for Fe and Mn in magnetite were studied by XAFS.•The Fenton activity was tested in acid orange II degradation and OH production.•The Mn enhanced activity of magnetite in Fenton reaction and Pb(II) adsorption.•The above effects were discussed with changes in structure and surface properties.In this study, a series of Mn substituted magnetites were synthesized and used in catalyzing the heterogeneous Fenton degradation of acid orange II and Pb(II) adsorption, in order to investigate the effect of Mn substitution on the reactivity of magnetite. The valence and local environment of both Fe and Mn in the spinel structure of magnetite were investigated by X-ray absorption fine structure (XAFS) spectroscopy. The incorporation of Mn did not change the valence and local structure of Fe in the synthetic magnetite, while Mn was in the valences of +2 and +3. The Mn distribution on the octahedral sites of magnetite surface increased with the increase in Mn content. The Mn introduction led to an improvement of catalytic activity of magnetite. The sample with the minimum Mn content displayed the best efficiency in OH production and the degradation of acid orange II, while the other substituted samples did not show obvious difference in their catalytic performance. The adsorption capacity of magnetite samples toward Pb(II) gradually increased with the increase in Mn content. The above influences of Mn substitution on the reactivity of magnetite were discussed in views of the variations in microstructural environment and physicochemical properties.

Silylation of clay mineral surfaces has attracted much attention due to their extensive applications in materials science and environmental engineering. Silylation of montmorillonite surfaces with 3-aminopropyltriethoxysilane was carried out in polar-protic and nonpolar solvents. The swelling property of the silylated montmorillonites was investigated by intercalating with cetyltrimethylammonium bromide. Silylated montmorillonites prepared in nonpolar solvents showed a larger amount of loaded silane and a higher extent of condensation among different silane molecules, comparing with those prepared in polar-protic solvents with high dielectric constant. Meanwhile, the silylated montmorillonites prepared in nonpolar solvents displayed poor swelling property due to the linkage between silane oligomers and clay layers, that is, the neighboring clay layers were locked by the silane oligomers. The present study demonstrated that the polarity of the solvents used had an important influence on the extent of grafting, interlayer structure, and swelling property of the silylated products. This is of high importance for synthesis and application of silylated clay minerals.Graphical abstractHighlights► Silane grafted montmorillonites have been prepared in various solvents. ► The solvent polarity has important influence on the extent of silane grafting. ► Nonpolar solvents result in a larger amount of loaded silane in silylated Mt. ► Nonpolar solvents lead to a higher degree of condensation among silane molecules. ► Silane grafted in nonpolar solvents lock the layers of silylated Mt.

Four series of substituted magnetite (Fe3−xMxO4, M = Cr, Mn, Co and Ni) were characterized by X-ray diffraction (XRD), X-ray absorption near-edge structure (XANES) spectroscopy, and thermogravimetry and differential thermal analysis (TG-DSC). XRD patterns confirmed the formation of samples with the spinel structure. XANES showed the valence and site occupancy of the substituting cations. Cr cations are in the valence of +3 and occupy the octahedral sites. The valences of Mn cation are +2 and +3. Mn2+ and Mn3+ cations preferentially entered the tetrahedral and octahedral sites, respectively. Both Co and Ni cations have a valence of +2 and mainly occupy the octahedral sites. The introduction of Cr and Ni cations obviously increases the amount of superficial hydroxyl groups. The incorporation of Mn, Co and Ni enhances the oxidation temperature of magnetite. All the four kinds of substituting cations in this study increase the temperature of phase transformation from maghemite (γ-Fe2O3) to hematite (α-Fe2O3). The mechanism of substitution changing the temperatures of oxidation and phase transformation was also discussed.Graphical abstractHighlights► The valence and coordination environment of the doping metals like Cr, Mn, Co and Ni in the magnetite. ► The influence of doping metals on the amount of surface hydroxyl. ► The influence of doping metals on the temperature of phase transformation. ► The mechanism of the doping metals influencing the phase transformation temperature.

Magnetite catalysts doped by five common transition metals (Ti, Cr, Mn, Co and Ni) on a similar level were prepared by a precipitation–oxidation method and characterized by chemical analysis, XRD, TG-DSC, BET surface area and XANES. The effects of substituting metal species on the photocatalytic performance of magnetite were investigated and compared through the UV/Fenton degradation of tetrabromobisphenol A (TBBPA). The substitution of above metals improved the heterogeneous UV/Fenton degradation of TBBPA, and the improvement extent increased in the following order: Co < Mn < Ti ≈ Ni < Cr. Fewer intermediate product species were detected in the systems with higher degradation efficiency. The distinct effects of these substituting metals on the UV/Fenton catalytic activity of magnetite were discussed in terms of reaction mechanism and surface property varieties. The substituting cations participated in the H2O2 decomposition through Haber–Weiss mechanism and enhanced separation and transfer efficiency of the photo-generated electrons and holes, both of which improved the generation of OH free radicals. Furthermore, with larger specific surface area and higher surface hydroxyl amount, substituted magnetite exhibited stronger catalytic activity for TBBPA degradation.Graphical abstractHighlights► Studied substitution improved the UV/Fenton degradation of TBBPA on magnetite. ► Some substituting cations can directly produce OH by Fenton-like reaction. ► Cr substituted magnetite is the most promising catalyst for TBBPA degradation. ► Increase in specific surface area and M-OH amount enhanced TBBPA degradation.

Recently, growing interest has been evoked in the application of transition metal substituted magnetite as heterogeneous Fenton catalyst in the degradation of organic pollutants. In the present study, the effect of substitution on the heterogeneous Fenton catalytic activity of magnetite was investigated in interfacial view. The substitution of transition metals improved the degradation of organic pollutants by accelerating the OH free radical generation and enhancing the adsorption of pollutant and H2O2. As the octahedral sites were exclusively exposed at magnetite surface, V3+ and Cr3+ occupying the octahedral sites not only participated in H2O2 decomposition to produce OH, but also quickened the electron transfer in the inverse spinel structure to reduce Fe3+ to Fe2+ with higher Fenton activity. Ti4+ , V3+ and Cr3+ increased the specific surface area and surface hydroxyl amount of magnetite, resulting in larger adsorption of methylene blue (MB) and H2O2 and accordingly faster degradation. In Ti-V co-doped magnetite, though Ti4+ was thermodynamically unfavorable for OH generation, Ti4+ showed a more prominent effect than V3+ on improving catalytic activity of magnetite, ascribed to its more significant effect on the increase of specific surface area and surface hydroxyl amount of magnetite. The catalytic efficiency was closely related to not only the nature of substituting metals, but also the pollutant characters. Due to the different adsorption behaviors, the degradation MB and acid orange II followed different degradation mechanism and was also described by different kinetics. The above results will be benefit for the application of transition metal substituted magnetite in environmental engineering.Highlights► V3+ and Cr3+ improved OH production and enhanced MB adsorption. ► Ti4+ is more positive for adsorption and catalytic activity of magnetite than V3+. ► MB adsorption enhanced with surface hydroxyl and specific surface area increase. ► The degradation of MB and AOII followed different mechanism and kinetics.

Montmorillonite (Mt) was silylated with 3-aminopropyltriethoxysilane (APTES) in a mixture of water/ethanol medium. The swelling property of the silylated product was evaluated by intercalating of cetyltrimethylammonium bromide (CTAB). Locking effect was observed in the process of silylation. The grafted silane molecules fix the interlayer height of the silylated Mt to a certain value by simultaneous condensation with the two adjacent layers. The locking effect results in the loss of swelling property of silylated Mt and only limited amount of surfactants are able to enter the galleries of the silylated products. The success of the surfactant intercalation suggests that the silylated Mt could be a carrier for the organic target matters.Graphical abstract“Locking effect” is resulted from simultaneous condensation of silane with the two adjacent Mt layers and the interlayer height of Mt can be controlled by the configurations of silanes.Highlights► Silane molecules have been grafted onto the interlayer surfaces of Mt successfully. ► The grafted silane molecules fix the interlayer height of the silylated Mt to a certain value. ► The locking effect results in the loss of swelling property of the silylated Mt.

In this paper, a series of organoclays were prepared from montmorillonites with different CEC and surfactants with different alkyl chain numbers and chain length. Then, FTIR spectroscopy using ATR, DRIFT and KBr pressed disk techniques was used to characterize the local environments of surfactant and host clays in various surfactants modified montmorillonites under wet and dry states. The present study demonstrates that the alkyl chain length and chain number have significant influences on the local environment of the intercalated surfactants. Also, this study indicates that the surface property of the resulting organoclays is affected by the loading and configuration of the intercalated surfactants. In wet state, more gauche conformers are introduced into the alkyl chains in the organoclays with low surfactant loading, evidenced by the shift of CH2 vibration to higher frequency. Meanwhile, in the case of the organo-montmorillonites with high surfactant loading, the interaction between the surfactant and silicate surface results in a re-arrangement of SiO4 tetrahedral sheets and a splitting of Si–O stretching vibration. The KBr pressed disk technique is suitable to probe the conformational ordering of the confined amine chains and the reflectance spectroscopy with ATR and/or DRIFT technique is more suitable to probe the water in organoclays. These findings are of high importance to the preparation of organoclays with proper surfactants and investigation of the microstructure of the resulting organoclays using suitable techniques.

Silylated layered double hydroxides (LDHs) were synthesized through a surfactant-free method involving an in situ condensation of silane with the surface hydroxyl group of LDHs during its reconstruction in carbonate solution. X-ray diffraction (XRD) patterns showed the silylation reaction occurred on the external surfaces of LDHs layers. The successful silylation was evidenced by 29Si cross-polarization magic-angle spinning nuclear magnetic resonance (29Si CP/MAS NMR) spectroscopy, attenuated total reflection Fourier transform infrared (ATR FTIR) spectroscopy, and infrared emission spectroscopy (IES). The ribbon shaped crystallites with a “rodlike” aggregation were observed through transmission electron microscopy (TEM) images. The aggregation was explained by the T2 and T3 types of linkage between adjacent silane molecules as indicated in the 29Si NMR spectrum. In addition, the silylated products show high thermal stability by maintained Si related bands even when the temperature was increased to 1000 °C as observed in IES spectra.

In this work, titanomagnetite was used as a heterogeneous Fenton catalyst for the degradation of methylene blue (MB). The degradation of MB on synthetic titanomagnetite at neutral pH values was studied in comparison with the adsorption of MB on titanomagnetite using UV−vis, FTIR, and the analyses of element C on titanomagnetite and DOC in reaction solution. Meanwhile, important factors affecting catalytic activity were investigated, that is, titanomagnetite load, H2O2 concentration, and reaction temperature. Titanomagnetite decomposed H2O2 yielding highly reactive hydroxyl radicals, and MB adsorbed on titanomagnetite was degraded. With the increases of titanomagnetite load, H2O2 concentration, and reaction temperature, the degradation of MB was promoted. Moreover, titanomagnetite was proved to be durable with a stable MB removal efficiency after five consecutive cycles.

3-aminopropyltriethoxysilane grafted montmorillonites were synthesized with montmorillonite, acid-activated montmorillonites and 3-aminopropyltriethoxysilane in ethanol-water mixture. The resulting products were investigated using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TG). XRD patterns demonstrated that silane was intercalated into the montmorillonite gallery, indicated by increasing basal spacings. These intercalated silanes probably adopt bilayer arrangement models within the montmorillonite and acid-activated montmorillonites interlayer spaces. TG and DTG curves indicate that acidification results in a decrease of the thermal stability of the resultant montmorillonites. Silane grafting leads to a surface property transformation of montmorillonite from hydrophilicity to lipophilicity and an increase of the thermal stability of the condensed silanes.

In this study, anionic surfactant and silane-modified hydrotalcites were synthesized through a soft chemical in situ method. The resulting materials were characterized using X-ray diffraction (XRD), high-resolution thermogravimetric analysis (HRTG), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and N2 adsorption–desorption. The Mg–Al hydrotalcite (LDH) and the only surfactant-modified hydrotalcite (LDH-2) display similar XRD patterns while both surfactant and silane-modified hydrotalcite (LDH-3) show two distinct series of reflections, corresponding to hydrotalcite and smectite-like materials, respectively. The smectite-like materials show a series of regular (001) reflections with d001=12.58 Åd001=12.58 Å. Further supporting evidence was obtained from FTIR and TG, for example, the vibration at 1198 cm−1 corresponds to SiOSi-stretching mode and the mass loss at ca. 861 °C to dehydroxylation. In LDH-2, the loaded surfactants are located in both the interlayer space and the interparticle pores with a “house of cards” structure as supported by FTIR, TG, and N2 adsorption–desorption isotherms. Both electron microscopy (SEM and TEM) micrographs and N2 adsorption–desorption isotherms show that in situ modification with surfactant and silane has a significant influence on the morphology and porous parameters of the resulting hydrotalcite materials.The XRD pattern of the both surfactant- and silane-modified hydrotalcite (LDH-3) shows a coexistence of two phases, hydrotalcite and smectite-like layered materials.

Two new materials based upon layered double hydroxides with nickel and cobalt in the brucite-like layer with and without an anionic surfactant dodecylsulfonate (DS) have been synthesized and characterized by both near-infrared and infrared spectroscopy. This work shows that large anionic surfactants can be incorporated into the interlayer of the LDHs. The presence of the carbonate anions in the interlayer and the hydroxyl surface are readily analyzed by these techniques.The two materials of Ni3 and Co3Al-layered double hydroxides show different behaviour in the near-infrared and FT-IR spectra both in terms of position and band intensity. This is an indirect indication of the incorporation transition metal ions into the brucite-like layers. The nature of the observed reflectance bands in the near-infrared spectral region 12,000–8000 cm−1 is explained in terms of the d–d electronic transitions within the divalent nickel and cobalt brucite layers. The crystal field strengths of octahedral Ni2+ and Co2+ in the synthesized layered double hydroxides are close to but smaller than those in Ni-and Co-bearing carbonate minerals.The analysis of CO32− vibrational modes ν1, ν2, ν3 and ν4 in FT-IR spectra at 1045, 885, 1350 and 760 cm−1 reveals the presence of carbonate ion in the synthetic-layered double hydroxides.

Silane grafted montmorillonites were synthesized by using 3-aminopropyltriethoxysilane and trimethylchlorosilane via two different grafting reaction systems: (a) ethanol–water mixture and (b) vapor of silane. The resulting products were investigated using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA). XRD patterns demonstrate that silane was intercalated into the montmorillonite gallery, as indicated by the increase of the basal spacing. The product prepared by vapor deposition has a larger basal spacing than that obtained from solution, due to the different extent of silane hydrolysis in various grafting systems. TGA curves indicate that the methyl groups penetrate into the siloxane clay are the primary reason for the decrease of the dehydroxylation temperature of the grafted products. 3-Aminopropyltriethoxysilane in the grafted montmorillonite adopts a bilayer arrangement while trimethylchlorosilane adopts a monolayer arrangement within the clay gallery.The intensities of stretching vibrations of CH2 in γ-APS show that product prepared in silane vapor (M-APS-2) have more silane loading than that synthesized in ethanol–water mixture (M-APS-1). This proposal is further evidenced by TG and XRD results.

X-ray photoelectron spectroscopy (XPS) in combination with X-ray diffraction (XRD) and high-resolution thermogravimetric analysis (HRTG) has been used to investigate the surfactant distribution within the organoclays prepared at different surfactant concentrations. This study demonstrates that the surfactant distribution within the organoclays depends strongly on the surfactant loadings. In the organoclays prepared at relative low surfactant concentrations, the surfactant cations mainly locate in the clay interlayer, whereas the surfactants occupy both the clay interlayer space and the interparticle pores in the organoclays prepared at high surfactant concentrations. This is in accordance with the dramatic pore volume decrease of organoclays compared to those of starting clays. XPS survey scans show that, at low surfactant concentration (<1.0 CEC), the ion exchange between Na+ and HDTMA+ is dominant, whereas both cations and ion pairs occur in the organoclays prepared at high concentrations (>1.0 CEC). High-resolution XPS spectra show that the modification of clay with surfactants has prominent influences on the binding energies of the atoms in both clays and surfactants, and nitrogen is the most sensitive to the surfactant distribution within the organoclays.

Two series of antibacterial compounds were synthesized using montmorillonite and chlorhexidine acetate (CA) by ion-exchange reaction. The resulting samples were characterized by high-resolution thermogravimetric analysis (HRTG), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and their antibacterial activity was assayed by halo method. In this study, the loaded amounts of CA in the resultant compounds were evaluated by the HRTG curves. CA adopts a lateral monolayer arrangement in the resulting samples with low CA loading, while a special state with partial overlapping of organic molecules is supposed for the resulting samples prepared at 1.0–4.0 CEC. After the intercalation with CA, the hydrophilic surfaces of montmorillonite are changed to hydrophobic ones, reflected by the frequency shift of the symmetric ν1(O-H) stretching vibration from low to high. This study shows that the interlayer cations in raw montmorillonite have little influence on the structure of the resulting samples. Antibacterial activity test against E. coli demonstrates that the antibacterial activity of the resulting samples strongly depends on the content of the loaded CA and these resulting materials show a long-term antibacterial activity that can last for at least one year.

In this study, CTAB–Al–montmorillonite complexes were synthesized by pre-modifying montmorillonite using different concentrations of surfactant (resulting in different surfactant loadings and basal spacings), then pillaring the organoclays with hydroxy-Al cations. The resultant inorganic–organic montmorillonite complexes were characterized using FTIR, with a combination of XRD, TG and chemical analysis. This study indicates that the basal spacings of the CTAB–Al–montmorillonite complexes and the amounts of Al-contained pillars strongly depend on the surfactant loadings in the clay interlayer space, resulted from the mobility variation of the intercalated surfactants. During pillaring hydroxy-Al cations into clay interlayer space, part of the intercalated surfactants were removed, resulting in a decrease of the ordering of alkyl chains and the frequency shifts of Si(Al)–O, Si–O–Al and (M–O)Td stretching vibrations. The hydrophobicity of the CTAB–Al–montmorillonite complex also strongly depends on the surfactant loading whereas that of the CTAB–Al–montmorillonite complex is relative lower than that of the corresponding organoclay, indicated by the frequency shift of the vibrations corresponding to the sorbed water and their contents estimated by TG curves. With the decrease of the sorbed water content, the frequency of the band of H–O–H bending (ν2) shifts to higher frequency while the O–H stretching vibration (ν1 and ν3) shifts to lower frequency, indicating that H2O is less hydrogen bonded. Meanwhile, the ordered conformations of the alkyl chains in CTAB–Al–montmorillonite complex decrease when compared with that of the corresponding organoclay.

The microstructure, thermal stability, surface energy, and swelling characteristics of two kinds of commercial organoclays, before and after washing treatment with a mixture of H2O/ethanol, were investigated using X-ray diffraction (XRD), thermogravimetric analysis (TG/DTG), wettability measurement, and swelling measurement. This study demonstrates that the external-surface physically adsorbed surfactant can be removed after washing treatment, resulting in an increase in thermal stability and a decrease in surface energy of the resultant organoclays. Organoclays are difficult to be introduced into a solvent when their surface energies are lower than that of the solvent. On the other hand, the organoclay with γorganoclay<γsolventγorganoclay<γsolvent is easier to be swollen and expandable by the solvent. The swelling and basal spacing measurements of the organoclays introduced into organic media indicate that the swelling factor and the interlayer swelling are two independent parameters. Both the polar character of the solvent and the swelling capacity of clay have a prominent effect on the interlayer swelling of the organoclays.The thermal stability and swelling characteristics of two commercial organoclays, before and after washing with a mixture of H2O/ethanol, were investigated using XRD, TG/DTG, wettability and swelling measurements. The external-surface physically adsorbed surfactant can be removed after washing treatment, resulting in an increase in thermal stability. The swelling and basal spacing measurements of the organoclays introduced into organic media indicate that the swelling factor and the interlayer swelling are two independent parameters. Both the polar character of the solvent and the swelling capacity of clay have a prominent effect on the interlayer swelling of the organoclays.

TiO2-PILCs were synthesized by the reaction between montmorillonite and acidic solutions of hydrolyzed TiCl4. Unlike commonly reported microporous pillared structure, a meso–microporous delaminated structure containing pillared fragments was observed in the resulting TiO2-PILC, based on the combined analyses of powder X-ray diffraction (XRD), nitrogen adsorption–desorption isotherms, chemical analysis, thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses. Air-drying after ethanol extraction (EAD) is shown to be more effective than air-drying (AD) in preserving the delaminated structure in the resultant Ti-clay. A broad XRD peak at low 2θ angle with a high d-spacing of ≈6.6 nm was firstly reported and it was proposed to be correlated with the mesoporous delaminated structure rather than the (0 0 1) reflection of intercalated/pillared periodic structure. The resulting TiO2-PILC exhibits a good thermal stability as indicated by its surface area after calcination at 600 °C. Moreover, calcination above 300 °C results in the formation of nanocrystalline anatase in the TiO2-PILC, and the grain size of anatase increases with the increment of calcination temperature. However, no phase transformation from anatase to rutile was observed even under calcination at 1000 °C. These fundamental results provide new insights about the structure of TiO2-PILC synthesized by TiCl4 hydrolysis method.

A new route for synthesis of Mg/Al layered double hydroxide (Mg6Al2(OH)16(CO3)·4H2O) has been introduced, which can be considered as a modified calcination-rehydration method. Under the hydrothermal conditions, LDHs with a high aspect ratio were synthesized and characterized by inductively coupled plasma-atom emission spectrometer (ICP-AES), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermal measurement (TG-DTG) and scanning electron microscopy (SEM). XRD patterns display the crystalline enhanced with the increase of hydrothermal temperature and aging time. TG-DTG curves show the more stable LDHs were synthesized at higher temperature. SEM images indicate the lateral size of the synthesized LDHs locates at ca. 1–6 μm and the thickness at ca. 35–60 nm. And the particle size depends strongly on the treatment temperature and aging time. A buffer solution consisted of HCO3− and CO32− keeps the pH of reaction system in a certain range and offers a low supersaturated reaction circumstance. This is of high importance for the formation of LDHs with a high aspect ratio.Layered double hydroxides with high aspect ratio were synthesized via a modified calcination-rehydration route. Rehydration of mixed oxides under suitable hydrothermal conditions shows effectiveness for preparation of stable thin sheet (ca. 35–60 nm) LDHs with a large size (ca. 1–6 μm).

•Keggin-Al30 pillared montmorillonites were successfully prepared for the first time.•Both liquid and solid-state 27Al NMR were employed to give proofs on Al30 cations.•Al30-PILM has larger specific surface area and total pore volume than Al13-PILM.Pillared interlayered clays (PILCs) draw intensive attention in the fields of chemistry and material sciences, owing to their strong surface acidity and large microporosity. These materials are superior selective heterogeneous catalysts and adsorbents. However, conventional hydroxy-aluminum pillared clays are based on Al13, which cannot provide desirable properties due to its inherent limitation of size. Herein, a convenient method has been developed to prepare Al30 PILCs from montmorillonite (Mt) and a base-hydrolyzed solution of Al (III) chloride. To the best of our knowledge, this is the first time that porous pillared interlayered Mt with large Al30 pillars (2×1×1 nm) has been successfully prepared. This fundamental work may open up entirely new avenues for developing novel PILCs as heterogeneous catalysts and porous adsorbents.

In this study, a series of vanadium doped magnetites (Fe3−xVxO4, 0 ≤ x ≤ 0.34) was synthesized by a precipitation–oxidation route and show good adsorption and catalytic activities. Powder X-ray diffraction (PXRD) and Mössbauer spectra analysis of Fe3−xVxO4 confirm the formation of magnetite, while Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy and X-ray absorption fine structure (XAFS) spectra indicate vanadium preferentially occupies the octahedral site. The valency of vanadium in magnetite is mainly +3, as inferred from FTIR and XAFS. Thermal analysis (TG–DSC) shows that the incorporation of vanadium in magnetite structure leads to an increase of superficial hydroxyl groups and a decrease in temperature of phase transformation maghemite–hematite. Vanadium incorporation can promote the adsorption of methylene blue (MB) on Fe3−xVxO4 and degradation of the dye with high degree of decolorization. The improvement of adsorption activity may be related to the increase of superficial hydroxyl. The high catalytic activity is related to the improvement of adsorption activity, the intensification of H2O2 decomposition by vanadium on the magnetite surface to produce OH and the improvement of electron transfer by vanadium to produce a more efficient regeneration of the Fenton active specie Fe2+.