Characterization and Adsorption Properties of Chemically Modified Sepiolite

Abstract

Modification of sepiolite clay has been performed using triethoxy-3-(2-imidazolin-1-yl)propylsilane in the presence of toluene solution. The modified material was characterized by FTIR spectroscopy, XRD, and simultaneous DTA/TG analysis. It was found that the chemical bonding takes place between the hydroxyl groups and/or oxygen atoms within the structure of sepiolite and the silane group of the triethoxy-3-(2-imidazolin-1-yl)propylsilane by releasing the ethoxy groups to the solvent. Thermal decomposition of natural and modified sepiolites was carried out with a thermogravimetric analyzer. In TG and DTA analysis, during gradual heating in an oxidizing atmosphere, the modified sepiolite was oxidized, giving rise to significant exothermic peaks. The exothermic peak in the temperature range of 200−650 °C depended on the modifier loading and provided evidence of bond formation on the sepiolite surface. For natural sepiolite, a mass loss of 20.43% was observed up to 900 °C, whereas this value increased to 31.90% for modified sepiolite under oxygen atmosphere. Electrokinetic properties of the modified-sepiolite suspensions were also examined as a function of the initial electrolyte concentration and equilibrium pH using a Zeta Meter 3.0 instrument. To determine the adsorption capacity of modified sepiolite for metal ions, the experiments were examined as a function of pH, ionic strength, and temperature. The adsorption capacity of modified sepiolite increased with increasing pH and temperature, but ionic strength was found to have no significant effect. The experimental data were analyzed using the Langmuir and Freundlich adsorption models. Satisfactory agreement between the metal uptake capacities by the modified sepiolite was expressed in terms of the correlation coefficient (R 2). The Langmuir model represented the sorption process better than the Freundlich model, with R 2 values ranging from 0.9603 to 0.9977.

Nanohybrid materials from amine functionalization of sepiolite: Preparation, characterization and application as electrode modifiers for the electroanalytical detection of heavy metal ions

“…The last step occurs at 831°C and is relate to the departure of water related to structural OH, that is to the endothermal dehydroxylation of sepiolite leading to the destruction of its structure [26,43,44]. water do not undergo change, suggesting that the oorganosilane molecules are not incorporated into the channels of sepiolite but have reacted with the external Si-OH groups found on its surface [4] as expected.…”

“…For both organoclays, the aliphatic C-H stretching vibrations are found in the 3000 -2700 cm -1 region. The peaks appearing at 2946, 2837 and 2872 cm -1 are attributed to asymmetric and symmetric CH vibrations of methoxy and ethoxy groups, and to the CH 2 chains from the silane molecules [4]. The scissoring deformation mode due to CH 2 groups are found at 1490 cm …”

“…The resort to clays and clay minerals as inorganic parent support for such materials is due to their surface reactivity and ability to immobilize guest organic molecules, either within their structure or on their surface [1][2][3]. In fact, clay-based nanohybrid materials offer a wide range of applications in environmental protection [4][5][6][7][8], in catalysis [9][10], in polymer science [11][12] and in analytical electrochemistry [13][14][15][16]. In the last-mentioned application, composite materials derived from the modification of kaolinite [17][18] and smectite [19][20][21][22][23] as precursors are the most investigated, probably because these types of clay possess a layered structure favorable to intercalation processes and grafting reactions.…”

“…Sepiolite with the half-unit cell chemical formula Mg 8 Si 12 O 30 (OH) 4 (H 2 O) 4 .8H 2 O is a fibrous porous hydrated magnesium silicate [26,43,44]. Structurally, it is made up of blocks and channels extending in the fiber direction (c-axis).…”

Characterization and Some Properties of Poly(vinyl chloride)/Sepiolite Nanocomposites

“…Adsorption is due to the presence of active adsorption centers on sepiolite surfaces (oxygen atoms in the tetrahedral sheet, water molecules coordinated with the Mg 2+ ions at the edge of the structure, and silanol groups caused by the breakup of Si O Si bonds). 20,21 In previous studies, Benlikaya et al investigated the preparation and characterization of sepiolitepoly(ethyl methacrylate) and poly(2-hydroxyethyl methacrylate) nanocomposites 22 ; Xie et al, the preparation, structure, and thermomechanical properties of nylon-6 nanocomposites with lamella-and fiber-type sepiolite 23 ; Chen et al, properties of sepiolite/polyurethane nanocomposites 3 ; Ma et al, preparation of polypropylene/sepiolite nanocomposites using supercritical CO 2 -assisted mixing 24 ; Aranda et al, titania-sepiolite nanocomposites prepared by using a surfactant templating colloidal route 25 ; Santiago et al, the synthesis and swelling behavior of poly(sodium acrylate)/sepiolite superabsorbent composites and nanocomposites 26 ; and Darder et al, microfibrous chitosan-sepiolite nanocomposites. 27 In this paper, we aimed to synthesize PVC/sepiolite nanocomposites by (1) modifying the sepiolite particle surfaces with a coupling agent, acid activation, and calcination and (2) the effect of the filler/polymer ratio on properties of PVC/sepiolite nanocomposites.…”