Christian Detellier

Preparation, Characterization, and Applications as Heavy Metals Sorbents of Covalently Grafted Thiol Functionalities on the Interlamellar Surface of Montmorillonite

A novel type of heavy metal adsorbent was prepared by the covalent grafting of a chelating sulfhydryl functionality [(3-mercaptopropyl)trimethoxysilane) in the interlamellar region of the smectite clay mineral montmorillonite. The new material (designated as thiomont) was characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, X-ray fluorescence, and 13 C solid-state NMR spectroscopy. Its approximate chemical formula was deduced to be Si 7.8 Al 3.3 Fe 0.3 Mg 0.4 O 16 (OH) 3 [OSi(OH) 2 (CH 2 ) 3 SH] 5 . Thiomont was found to be an effective adsorbent for Pb(II) and Hg(II) (70 and 65 mg of metal/g of adsorbent, respectively) but was less effective toward Cd(II) and Zn(II). Acid leaching was shown to be an effective method by which thiomont could be regenerated

STRUCTURAL STUDY OF MAYA BLUE: TEXTURAL, THERMAL AND SOLID-STATE MULTINUCLEAR MAGNETIC RESONANCE CHARACTERIZATION OF THE PALYGORSKITE-INDIGO AND SEPIOLITE-INDIGO ADDUCTS

Palygorskite-indigo and sepiolite-indigo adducts (2 wt.% indigo) were prepared by crushing the two compounds together in a mortar and heating the resulting mixtures at 150 and 120°C, respectively, for 20 h. The samples were tested chemically to ensure that they displayed the characteristic properties of Maya Blue. Textural analysis revealed that no apparent changes in microporosity occurred in sepiolite or palygorskite after thermal treatment at 120°C (sepiolite) and 150°C (palygorskite) for 20 h. Micropore measurements showed a loss of microporosity in both sepiolite and palygorskite after reaction with indigo. The TGA-DTG curves of the sepiolite-indigo and palygorskite-indigo adducts were similar to their pure clay mineral counterparts except for an additional weight loss at ∼360°C due to indigo.The 29Si CP/MAS-NMR spectrum of the heated sepiolite-indigo adduct is very reminiscent of the spectrum of dehydrated sepiolite. Crushing indigo and sepiolite together initiates a complexation, clearly seen in the 13C CP/MAS-NMR spectrum, which can be driven to completion by heat application. In contrast to the broad peaks of the pure indigo 13C CP/MAS-NMR spectrum, the sepiolite-indigo adduct spectrum consists of a well-defined series of six narrow peaks in the 120.0–125.0 ppm range. In addition, the sepiolite-indigo spectrum has two narrow, shifted peaks corresponding to the carbonyl group and the C-7 (C-16) of indigo. A model is proposed in which indigo molecules are rigidly fixed to the clay mineral surface through hydrogen bonds with edge silanol groups, and these molecules act to block the nano-tunnel entrances.

PREPARATION AND CHARACTERIZATION OF TWO DISTINCT ETHYLENE GLYCOL DERIVATIVES OF KAOLINITE

A new, well-ordered, thermally robust ethylene glycol intercalate of kaolinite was formed by refluxing the dimethyl sulfoxide intercalate of kaolinite (Kao-DMSO) with dry ethylene glycol (EG). This new phase (Kao-EG 9.4 Å) which is characterized by a d001 of 9.4 Å is distinct from a previously reported ethylene glycol intercalated phase of kaolinite (Kao-EG 10.8 Å) which has a d001 of 10.8 Å. The characterization of these two phases was studied by XRD, NMR, FTIR, and TGA/DSC. It was found that the concentration of water in the ethylene glycol reaction media played a crucial role in governing which of the phases predominated. Water favored Kao-EG 10.8 Å formation, while anhydrous conditions favored the formation of Kao-EG 9.4 Å. It is hypothesized that Kao-EG 9.4 Å is a grafted phase resulting from the product of the condensation reaction between an aluminol group on the interlamenar surface of kaolinite and the alcohol group of ethylene glycol. Ethylene glycol units would be attached to the interlamellar surface of kaolinite via Al-O-C bonds. The Kao-EG 9.4 Å phase was found to be resistant to both thermal decomposition up to 330°C and also, once formed, in the absence of interlamellar water molecules, to decomposition by hydrolysis in refluxing water.

Chemically modified kaolinite. Grafting of methoxy groups on the interlamellar aluminol surface of kaolinite

The interlayer aluminol surface of kaolinite has been modified by the reaction of methanol, at temperatures between 200 and 270 °C, with both the dimethyl sulfoside intercalate of kaolinite (Kao–DMSO) and the N-methylformamide intercalate of kaolinite (Kao-NMF). The product was a methoxy-functionalized organomineral material, which was resistant to thermal decomposition in both air and N2 atmospheres up to temperatures > 350 °C, and also to water hydrolysis. Based on results from thermal analysis, IR analysis, NMR spectroscopy (13C CP MAS, 29Si CP MAS and 27Al MAS) and elemental analysis, a structural model has been proposed, in which every third interlayer surface hydroxy group on the aluminol surface of kaolinite has been replaced by a methoxide group. The methyl groups which point away from this surface are keyed into the (SiO)6 macro-rings of the adjacent silicate surface, resulting in a non-centrosymmetric two-dimensionally ordered organomineral assembly.

Fabrication, characterization and preliminary testing of all-inorganic ultrafiltration membranes composed entirely of a naturally occurring sepiolite clay mineral

All-inorganic membranes that are composed entirely of sepiolite, a naturally occurring Mg-silicate clay mineral, have been fabricated. Pinhole-free, self-bonded membranes with transecting pores in the large mesopore to macropore size range were obtained. Characterization of the thermally treated membranes by PXRD has revealed that the sepiolite is transformed into ‘sepiolite anhydride’ by heating in air at elevated temperatures. SEM studies have subsequently shown that the air dried membranes do not develop cracks or other similar flaws even after being subjected to temperatures as high as 750 C for several hours. Calcined sepiolite membranes were tested for the ultrafiltration of high molecular weight poly(ethylene glycol) and poly(ethylene oxide) molecules in aqueous solution. The MWCO was determined to be close to 300 000 for all of the membranes that were studied in the preliminary tests. Significant membrane fouling was observed, which dramatically reduced the permeation flux rate during the ultrafiltration tests.

DEHYDRATION AND REHYDRATION OF PALYGORSKITE AND THE INFLUENCE OF WATER ON THE NANOPORES

The dehydration and rehydration processes of the clay mineral palygorskite (PFl-1) were studied by textural analysis, thermogravimetric analysis connected with mass spectrometry (TGA-MS), and 29Si and 1H solid-state NMR techniques. The TGA-MS results clearlyreveal weight losses at maxima of 70°C, 190°C, 430°C and 860°C. PFl-1 is characterized by a micropore area of 93 m2/g, corresponding to a micropore volume of 47 mm3/g. These values are also obtained for the sample heated up to 200°C for 20 h. Further heating at 300°C produces a collapse of the structure, as shown by the almost complete loss of microporosity.The 29Si NMR spectra of palygorskite show two main resonances at −92.0 and −97.5 ppm, attributed to one of the two pairs of equivalent Si nuclei in the basal plane. A minor resonance at −84.3 ppm is attributed to Q2(Si-OH) Si nuclei. The resonance at −92.0 ppm is assigned to the central Si position, while the resonance at −97.5 ppm is assigned to the edge Si sites. It is confirmed bysolid-state 29Si and 1H NMR that nearly complete rehydration is achieved by exposing palygorskite samples that have been partially dehydrated at 150°C and 300°C, to D2O or water vapor at room temperature. When the rehydration is accomplished with D2O, the atoms are disordered across all the protons sites.

Nanohybrid materials from the intercalation of imidazolium ionic liquids in kaolinite

A series of novel organic–inorganic nanohybrid materials were obtained by the intercalation in the interlamellar spaces of the clay mineral kaolinite, of ionic liquids based on imidazolium derivatives. The intercalation procedure was successfully accomplished via a melt reaction strategy using the dimethylsulfoxide–kaolinite intercalate (DMSO-K) as a precursor. 13C MAS NMR as well as XRD, TGA/DTA and FTIR studies confirmed the complete displacement of DMSO molecules by the imidazolium salts during the intercalation process. Increase of the basal spacing from 1.1 nm in DMSO-K to 1.3–1.7 nm in the nanohybrid materials was observed, indicating that imidazolium derivatives are oriented in a way such that the imidazole ring is parallel, or slightly tilted by an angle of 10–25°, with respect to the kaolinite internal surfaces. The number of moles of organic material loaded in the nanohybrids was obtained from several independent measurements. The intercalation of the imidazolium salts increases the thermal stability of the resulting material by more than 150 °C with respect to DMSO-K. After heating under air at 300 °C for two hours, XRD showed that the structure of the intercalates was kept with only a slight decrease of the intercalation ratio. The original kaolinite structure was recovered after heating the intercalate at 350 °C for an additional two hours. This observed high thermal stability is promising for the use of these nanohybrid materials as precursor for the synthesis of new nanocomposites by incorporation of polymer in kaolinite at high temperature.

Preparation and characterization of an 8.4 Aa hydrate of kaolinite

A stable 8.4 Å hydrate of kaolinite was prepared by exchanging ethylene glycol for water in the 10.8 Å intercalate of ethylene glycol in kaolinite. The hydrate of kaolinite was characterized by XRD, FTIR and TGA/DSC. From the TGA data, one can estimate that there is 0.60 water molecule per Al2Si2O5(OH)4 units. The IR data suggest a similarity of the local environment of the intercalated water in this 8.4 Å hydrate of kaolinite and the 8.4 Å hydrate of nacrite previously described by Wada (1965).

Clay-polymer nanocomposite material from the delamination of kaolinite in the presence of sodium polyacrylate.

A chemical route for the delamination of kaolinite in a polymeric matrix is reported in this work. The strategy that was used is based on mixing polyelectrolytes of opposite charges, an organic polyanion, polyacrylate, with an inorganic polycation resulting from the modification of the internal surfaces of kaolinite. The delamination was carried out by the reaction of sodium polyacrylate (PANa) with kaolinite whose internal aluminol surfaces were previously grafted with triethanolamine and subsequently quaternized with iodomethane (TOIM-K) to form an extended lamellar inorganic polycation. X-ray diffraction as well as scanning electron microscopy (SEM) confirmed the complete delamination of the kaolinite particles. 13C CP/MAS NMR showed the removal of the ammonium groups resulting from hydrolysis of the internal surfaces once exposed, and 29Si CP/MAS NMR spectra were in agreement with the retention of the 1:1 aluminosilicate kaolinite layers structures. From the thermogravimetry (TG) data, the respective percentages in mass of PA and kaolinite in the delaminated nanocomposite could be estimated to be 61% and 39%, respectively, in the conditions of the particular experiment. The procedure was repeated several times to show the reproducibility of the delamination. The interlayer functionalization of kaolinite was crucial for the success of the delamination procedure. SEM pictures show that some individual kaolinite platelets fold and form curved structures.

Reactivity of kaolinite in ionic liquids: preparation and characterization of a 1-ethyl pyridinium chloride–kaolinite intercalate

A novel class of organic–inorganic nanohybrid material was prepared by the intercalation in kaolinite of a molten organic salt (1-ethyl pyridinium chloride, EP) above its melting temperature. The intercalation proceeded at 170 °C under N2. It did not succeed when kaolinite was used as the starting material, whereas the melt intercalation process was possible when DMSO–kaolinite (DMSO-K) was used as the starting material. The amount of EP loaded in the galleries of kaolinite is 24.3% (0.574 mol of EP per unit-cell) which produces an increase of the basal spacing d001 from 1.10 nm in the case of DMSO-K to 1.35 nm. The melt intercalation process could be dramatically improved by the choice of the temperature of reaction as well as of the atmosphere. At lower temperatures (less than 140 °C), even if the reaction medium is the ionic liquid, the intercalation is not observed. This results from the non-release of DMSO from the interlamellar space of DMSO-K, a step essential for the intercalation of EP to proceed. This work indicates that the intercalation of EP and the displacement of DMSO from the interlamellar spaces of kaolinite take place concurrently, not in a sequential manner. However, the process is initially driven by the thermal removal of DMSO.