Zr-containing pillared interlayer clays. Part III. Influence of method of preparation on the thermal and hydrothermal stability

Bartley, Gordon; Burch, R.

doi:10.1016/s0166-9834(00)82679-2

Cited by 67 publications

(17 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The product was dried at 40~ in air and gently ground in an agate mortar. Zr-MX80 was obtained after 5 h calcination at 300~ with a heating rate of 10~ min-k Calcination at 300~ results in well-ordered Zr-pillared montmorillonites whereas temperatures >300~ cause a partial collapse of the Zr-pillars (Bartley and Burch, 1985;Matthes and Madsen, 1996).…”

Section: Preparation Of Hal Ai Hzr and Zr-mx80mentioning

confidence: 99%

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

Matthes

Madsen

Kahr

1999

Clays and clay miner.

View full text Add to dashboard Cite

Abstract--The sorption of Cd, Cu, Pb, and Zn ions by Na-rich bentonite, AI and Zr-pillared Na-rich bentonite (A1-MX80, Zr-MX80), the uncalcined hydroxy-intercalated precursors (HA1, 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 A1 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 HA1, HZr, A1, Zr-MX80, and EXM 534 and were partially nonexchangeable. 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 A1 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.

show abstract

Section: Preparation Of Hal Ai Hzr and Zr-mx80mentioning

confidence: 99%

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

Matthes

Madsen

Kahr

1999

Clays and clay miner.

View full text Add to dashboard Cite

show abstract

“…In the open literature, Occelli and Tindwa (1983) reported poor hydrothermal stability at 650~ for an A1-PILC. Bartley and Burch (1985) observed a similar behavior for Zr-PILCs and a severe loss of surface area at 730~ Similar stabilities were described by Sterte (1986) for Ti-PILCs, which show a twofold decrease of surface area between 700 ~ and 800~ Surprisingly, the steam-treated samples showed a more gradual decrease in surface area with increasing temperature and retained a surface area of about 170 mZ/g at 8000C, compared with 100 m2/g for a sample calcined in dry air at 800~ In the patent literature, Vaughan et al (1979) reported a substantial improvement of the hydrothermal stability by pillaring smectites with mixed oligocations containing A1 in combination with Si. The surface area reached 165 m2/ g after steaming at 760~ Lewis et al (1985) pillared montmorillonites with polyhedral oligosilsesquioxane compounds which, upon calcination, gave rise to twolayer silica structures between the layers.…”

Section: Introductionmentioning

confidence: 99%

Sintering of Montomorillonites Pillared by Hydroxy-Aluminum Species

Tichit

1988

Clays and clay miner.

View full text Add to dashboard Cite

Abstract--The sintering of montmorillonites pillared by hydroxy-A1 species was investigated by several techniques. The change of the microporosity of the pillared interlayer clay with temperature shows that sintering was mainly due to the loss of microporosity. On calcination of the parent clay at 760~ the X-ray powder diffraction pattern did not change; the 060 line shifted only slightly from 8.988 to 9.017 /k. The infrared (IR) spectrum suggested some dehydroxylation, but the structure appears to have been preserved. On calcination of the pillared clay at >700~ the intensity of the 001 line decreased steadily, the 060 line broadened, and the b parameter decreased slightly from 8.988 to 8.928 ,~. Fe 3+ ions apparently occupied only one site after calcination at 300~ and two sites after calcination at 700~ Smaller isomer shifts and higher quadrupole splittings in the MGssbauer spectra suggest that calcination produced more covalent bonding of Fe 3+ and a highly distorted structure. The IR spectrum was significantly modified by calcination of the sample, and the 935-and 1125-cm 1 bands disappeared and the 1035-cm -~ band broadened. These results suggest that at <700~ the pillars sintered and that the clay progressively decomposed at >750~ The pillaring-induced decrease of thermal stability of the clay was likely due to the introduction of protons during the first step of the preparation. The thermal stability of these A1-pillared interlayer complexes is comparable to that reported for hydroxy-silicoaluminum montmorillonites and fluorhectorites.

show abstract

“…A slight increase of the surface area of montmorillonite after treatment with ld/60 Zr solution was obtained with respect to the montmorillonite treated with 15d/20 solution. Bartley and Burch (1985) and Bartley (1988) reported that intercalation of the montmorillonite with fresh zirconium chloride solution had a lower surface area (117 m 2 g-l) than after treatment with Zr polymers obtained using 0.1 M ZrOC12 aged 1 d at 100 ~ (147 m 2 g-~). Similar structural characteristics of the OH-Zr-montmorillonite were obtained after 2.5 and 6.0 mmol of Zr were added per gram of montmorillonite.…”

Section: Resultsmentioning

confidence: 99%