Pillared Bentonite Research Articles

Photo-Fenton discoloration of the azo dye X-3B over pillared bentonites containing iron

Both Fe pillared bentonite (Fe-B) and Al-Fe pillared bentonite (Al/Fe-B) were prepared and used as heterogeneous catalysts for the photo-Fenton discoloration of azo dye X-3B under UV irradiation. The catalysts were characterized by XRD, BET and TEM. The effects of solution pH, H 2O 2 concentration, dye concentration and catalyst loading on the rate of discoloration were investigated in detail. The results indicate that the Fe-B and Al/Fe-B have high BET surface area (114.6 and 194.2 m 2/g, respectively). Both the heterogeneous photo-Fenton processes employing the Fe-B or the Al/Fe-B as catalyst exhibit higher photo-catalytic activity compared to their corresponding homogeneous photo-Fenton process. The amount of Fe ions leached from the Al/Fe-B into the solution is much lower than that leached from the Fe-B during the reaction process.

Sorption of wastewater containing reactive red X-3B on inorgano-organo pillared bentonite

Bentonite is a kind of natural clay with good exchanging ability. By exchanging its interlamellar cations with various soluble cations, such as quaternary ammonium cations and inorganic metal ions, the properties of natural bentonite can be greatly improved. In this study, hexadecyltrimethylammonium bromide (HDTMA), CaCl(2), MgCl(2), FeCl(3), AlCl(3) were used as organic and inorganic pillared materials respectively to produce several kinds of Ca-, Mg-, Fe-, Al-organo pillared bentonites. Sorption of reactive red X-3B on them was studied to determine their potential application as sorbents in wastewater treatment. The results showed that these pillared bentonites had much improved sorption properties, and that the dye solutions' pH value had some effect on the performance of these inorgano-organo pillared bentonites. Isotherms of reactive X-3B on these pillared bentonites suggested a Langmuir-type sorption mechanism.

Adsorption of humic acid onto pillared bentonite

Pillared bentonite, a clean and cost-effective adsorbent with high specific areas of 111.3 m 2/g and high basalspacing of 1.98 nm, was prepared for the removal of humic acid from water. It is effective for the removal of humic acid with a high adsorption capacity of 537 mg/g, and adsorption is favored under acid conditions. Adsorption is dependent on ionic strength and dissolved NaCl enhanced adsorption. Over 97% removal was observed under natural pH conditions from humic acid solutions containing 10 mg/L Ca 2+ or Mg 2+, which suggests that pillared bentonite can be an effective adsorbent for the removal of humic acid for drinking water purification. Pillared bentonite can be regenerated with NaOH, and the regeneration efficiency reaches 83% and 85% when the concentration of NaOH reaches 0.025 and 0.05 mol/L. The mechanism for adsorption of humic acid to pillared bentonite is discussed.

Comparative study of benzylation of benzene using benzyl chloride in the presence of pillared bentonite; ion-exchanged and pillaring solution impregnated montmorillonite K10

Montmorillonite K10 was modified with pillaring solutions of Fe, Al and Zr (K10-MPLS). The catalysts were activated at 120 and 550 °C. The resultant catalysts were used for the Friedel–Crafts benzylation of benzene with benzyl chloride under mild experimental conditions. Amongst them, K10-FePLS120 catalyst showed both high activity and selectivity for the benzylation reaction at room temperature (28 °C). The catalyst can also be reused in the benzylation for several times. The activities of these catalysts were compared with those of Fe3+-, Al3+- and Zr4+-exchanged montmorillonite K10 and Fe-, Al- and Zr-pillared bentonite catalysts. The benzylation of various monosubstituted benzenes was carried out using K10-FePLS120.

Sorption of Organic Compounds by Al and Zr-Hydroxy-Intercalated and Pillared Bentonite

AbstractOwing to their large and chemically active surface, hydroxy-intercalated and pillared clays can be potent sorbents for organic compounds. The sorption behavior of Al and Zr-hydroxy-intercalated bentonite (HAl-, HZr-MX80), Al and Zr-pillared bentonite (Al-MX80, Zr-MX80), and a commercial Al-pillared bentonite (EXM 534) for 3-chloroaniline (3-CA), atrazine (AT), and 3-chlorophenol (3-CP) was investigated. The results were compared with the sorption behavior of the untreated Na-rich bentonite (MX80) and granulated activated carbon (GAC). Also the influence of the salinity of the sorbate and the age of the sorbents was studied.Al and Zr-hydroxy-intercalated and pillared bentonites sorbed higher amounts of 3-CA, AT, and 3-CP than the untreated bentonite. The quantities sorbed related to the electron-donating properties of the sorbate and the acidity of the sorbents. Sorbed quantities increased from the hydroxy-intercalated to the pillared species, and from the Al to the Zr forms. The organic bases, 3-CA and AT, were sorbed in higher quantities than the organic acid 3-CP. For AT, the sorbents exhibited a high affinity. Aging of the samples and a high ionic strength of the sorbate reduced the sorption of 3-CA, whereas the sorption of AT was not affected greatly. The sorption capacity of GAC for organic bases was generally higher than that of the hydroxy-intercalated and pillared bentonites.The data suggest that at initial concentrations at a ppm level, 3-CA and AT can be entirely removed from aqueous solutions by Al and Zr-hydroxy-intercalated and pillared bentonites. These materials, especially Zr-pillared bentonites, represent potent alternative sorbents for atrazine, chloroanilines, and probably a wide range of other organic bases.

Sorption of Heavy-Metal Cations by Al and Zr-Hydroxy-Intercalated and Pillared Bentonite

AbstractThe sorption of Cd, Cu, Pb, and Zn ions by Na-rich bentonite, Al and Zr-pillared Na-rich bentonite (Al-MX80, Zr-MX80), the uncalcined hydroxy-intercalated precursors (HAl, HZr-MX80), and commercial Al-pillared bentonite EXM 534 was investigated. Experiments were conducted in ultrapure water and artificial leachate with varying pH. The experiments were performed over periods to 30 wk. Sorption characteristics were described with one and two-site Langmuir isotherms. The non-exchangeable quantities of heavy metals were determined by fusion of the sorbents after ion exchange with ammonium acetate.The sorption of Cd, Cu, Pb, and Zn by bentonite was dominated by cation exchange. In artificial leachate, the sorption was reduced due to competition with alkali and alkaline-earth cations. The sorption of Cu, Zn, and Pb at pH 4.9 and Cd at pH 6.9 by Al and Zr-hydroxy-intercalated and pillared MX80 was governed also by cation exchange. In contrast, the sorbed quantities of Zn at pH 6.9 exceeded the cation exchange capacity (CEC) of HAl, HZr, Al, Zr-MX80, and EXM 534 and were partially non-exchangeable. The increase of the sorption of Zn with pH and its independence of the ionic strength of the solution at neutral pH suggest a complexation of Zn ions to surface hydroxyl groups of the intercalated Al and Zr-polyhydroxo cations and pillars. This complexation is the dominating sorption mechanism. Removal of dissolved Zn from solution with time is attributed to surface precipitation. Al-hydroxy and pillared bentonites are considered potential sorbents of Zn ions from neutral pH aqueous solutions, such as waste waters and leachates.

Synthesis, characterization and catalytic activity of ruthenium containing aluminum pillared bentonites

Ruthenium containing pillared bentonites were prepared by contacting the clay with an aqueous solution containing aluminum and ruthenium salts or by cation exchange with ruthenium of an aluminum-pillared bentonite. The materials were characterized by chemical analysis, XRD, XPS, H 2-TPR, nitrogen adsorption/desorption. All the prepared samples catalyze after a reductive pretreatment the 1-butene hydrogenation. The catalytic activity is correlated to their chemical and structural properties.

Influence of Heat Treatments on the Pore and Adsorption Characteristics of Sodium Doped Alumina Pillared Bentonite

Various amounts of Na+ ions were exchanged into alumina pillared bentonite (Al-PILB) sample, by controlling the pH of the dispersion of Al-PILB and sodium chloride solution. The Na+ doped pillared clays were calcined at elevated temperatures and adsorption of nitrogen at −196°C, cyclohexane and water at ambient temperature (21 ± 1°C) by the calcined samples were conducted. The results revealed a wide size distribution of the micropores in the pillared clay. Introduction of sodium ions converted the surface of the pore walls from hydrophobic to hydrophilic and blocks some micropores, enhancing water adsorption but reducing nitrogen and cyclohexane adsorption. Existence of Na+ ions in the pores did not improve the thermal stability of the pillared clay. Calcination at high temperatures resulted in a decrease in adsorption capacity. After calcination at 700°C, cyclohexane was inaccessible to the remaining micropores in the Na+ doped pillared clays. The adsorption behavior was clearly related to the cation content as well as the calcination temperature. These results may be useful in developing desiccants and adsorbents from pillared clays for dehumidification and adsorptive cooling applications.

Preparation of hydroxy Al and [formula omitted] pillared bentonites from concentrated clay suspensions

Aluminum and aluminum iron pillared clays (PILCs) were prepared starting from concentrated (50%) aqueous or acetone suspensions of non-purified natural calcium bentonites. The PILCs were characterized by chemical analysis, X-ray diffraction, magic angle spinning NMR, and N 2 adsorption. The relative amount of Lewis and Brönsted acid sites was estimated from FT-IR spectra of adsorbed pyridine. All the PILCs prepared by this method gave highly microporous materials with micropore volumes in the range from 0.11 to 0.15 cm 3/g, and with highly ordered clay sheets (d 001=0.18 nm with peak widths of ca. 0.3 nm). The chemical composition of the products was not influenced by the nature of the solvent used in the pillaring process. Nevertheless, pillaring in acetone resulted in a faster and easier pillaring process. The obtained PILCs were more crystalline. The purity of the starting clays strongly influence the chemical and textural properties of the pillared clay. The scaling up of the process up to 500g batches using acetone as solvent is easily done and therefore, the method appears attractive for the industrial preparation of aluminum-based PILCs.

Preparation and properties of Al−B−Si composite pillared bentonite

Al−B−Si composite pillared clay was first prepared and its catalytic cracking properties for gas oil were investigated. Characterization techniques included XRD, BET and IR spectroscopy of pyridine adsorbed. It is shown by the results that the introduction of Si enhanced the catalytic activity and gasoline yield on pillared clay. Al−B−Si composite pillared clay was a better catalyst material.

Reactivity of Anisoles on Clay and Pillared Clay Surfaces

AbstractPillared bentonites were found to be efficient catalysts for the O-methyl bond cleavage of anisoles (e.g., m-methylanisole, guaiacol, and creosol) under very mild, static conditions (150°C, a few hours, inert atmosphere). The O-methyl bond cleavage led to phenolic products. Gas chromatographymass spectrometry and solid-state 13C nuclear magnetic resonance (NMR) techniques used to probe 13C-labeled anisoles revealed that dealkylation and transalkylation reactions occurred to a large extent, and that conversion was efficient at >95% after two days. Ortho- and para-isomers were observed exclusively, without any evidence of meta-substitution. Volatile products were determined by mass spectrometry to be 13CH3OH and (13CH3)2O. Magic-angle spinning 13C NMR experiments showed that the molecules were fairly mobile in the clay micropores prior to catalysis. After catalysis, cross-polarization NMR showed that molecular motion had decreased markedly. Ultraviolet-visible spectroscopy of the colored complexes suggested some quinone formation. The trend of clay reactivity was found to be: pillared bentonite ≫ acid-washed montmorillonite > untreated bentonite > pillared fluorhectorite ≃ untreated fluorhectorite.

Preparation and characterization of pillared hectorite catalysts

Reaction of natural hectorite with Al, ZrAl, and Zr polyoxycations generate pillared hectorites which after heating in air at 400 °C/4 h have Langmuir surface areas of 260–300 m 2/g thermally stable to 600–700 °C. Spectroscopic studies of sorbed pyridine indicate that these pillared hectorites (like pillared bentonites) contain both Lewis and Brønsted acid sites distributed as in the parent (acidwashed) hectorite. Above 300 °C, in vacua, pyridine is sorbed mainly on Lewis sites. Pillared hectorites are not as active as the corresponding pillared bentonites in cracking 260–426 °C boiling range gas oils but exhibit greater gasoline selectivity and minimize light gases (C 2–C 4) generation. Cracking activity depends mostly on the surface area generated by pillaring and the parent hectorite low iron content did not affect the catalyst's carbon selectivity.

New routes to the preparation of pillared montmorillonite catalysts

Clay catalysts have been prepared using reagents different from the aluminum chlorhydrate solution usually employed to pillar smectite minerals. Colloidal alumina, alumina-coated silica and solutions containing chlorhydrated complexes of zirconium and aluminum produced pillared bentonites which, upon calcination at 400 °C, formed microporous two-dimensional structures with 200 – 500 m 2 g −1 Langmuir surface area and basal spacing between 17 and 18 Å. These pillared clays contain both Bronsted and Lewis acid sites; above 300 °C, pyridine is retained predominantly on Lewis centers. The presence of zirconia seems to enhance Brönsted acidity, whereas pillaring with colloidal alumina particles increases the catalyst Lewis acidity. Cracking activity for gas oil conversion depends mainly on the surface area generated by pillaring. Pillared bentonites are more active but less selective than similarly prepared pillared hectorite catalysts.