Action of silylating agents on a chrysotile surface and subsequent reactions with 2-pyridine and 2-thiophene carbaldehydes

Abstract

Chrysotile fibres have been modified in two distinct steps: first, the fibers were aminated with silylating agents such as 3-aminopropyltrimethoxysilane or N-[3-(trimethoxysilyl)propyl ]ethylenediamine to give the products denoted CRI1 and CRI2, respectively. In the second step, these matrices reacted readily with 2-pyridine and 2-thiophene carbaldehydes to form CLN bonds, characteristic of a Schiff base. All immobilized materials were characterized by elemental analysis, IR spectroscopy, thermogravimetry, solid state 29Si NMR, surface area measurements and X-ray diffractometry. Nitrogen elemental analysis indicated the presence of 1.20 and 2.87 mmol g−1 of pendant groups on CRI1 and CRI2 surfaces, respectively. The experimental C/N ratios are 3.14, 2.90, 3.14 and 4.49 for modified materials CRI1L1, CRI1L2, CRI2L1 and CRI2L2, respectively. These results are in agreement with the yields of the successive reaction steps. The original chrysotile structure was maintained for the aminated modified surfaces. The surface area of prepared materials decreased with functionalization to values of <5.0 m2 g−1. All matrices obtained from reaction with aldehydes showed a CLN band at 1636 cm−1, which is related to Schiff bond formation. Products derived from the reaction with pyridine carbaldehyde showed bands associated with aromatic and aliphatic CKH stretching bands at 3050 and 2930 cm−1, respectively and pairs of bands at 1590, 1570 and 1470, 1436 cm−1 are attributed to aromatic n(CLC). These results indicate that the silylating agents are covalently bonded to the chrysotile surface. investigation of the surface reactivity of this mineral has Fig. 9 IR spectra of (a) CRI0, (b) CRI2, (c) CRI2L1, (d) CRI2L2 and (e) CRI2L2 (red).

Thermodynamics Data of Interaction of Copper Nitrate with Native and Modified Chrysotile Fibers in Aqueous Solution

“…The modified fibers were characterized by elemental analysis, thermogravimetry, and infrared spectroscopy, as recently described (35). Thus, the elemental analysis presented in Table 1 supports the argument that the immobilization took place in an effective way.…”

“…This proposal is based on the fact that the available silanol groups disposed on the silica gel surface can be covalently bonded to a series of these silylant agents, as a consequence of alcohol forming in the reaction (35).…”

A relevante potencialidade dos centros básicos nitrogenados disponíveis em polímeros inorgânicos e biopolímeros na remoção catiônica

“…Como acontece na crisotila, também o talco reage com os derivados alcoxissilanos (H 3 CO) 3 SiR [R = (CH 2 ) 3 NH 2 , (CH 2 ) 3 NH(CH 2 ) 3 NH 2 e (CH 2 ) 3 NH(CH 2 ) 3 NH(CH 2 ) 3 NH 2 . Com o primeiro material natural as cadeias pendentes reagem com aldeídos contendo outros centros bási-cos que, potencialmente, podem ampliar a capacidade em adsorver cátions 56 . Já com o talco a imobilização ocorre somente na superfície das lamelas, sem aumentar o espaçamento basal 57 .…”

Synthesis and characterization of hybrids derived from vermiculite chloropropyl and aliphatic diamines

“…In this context silica gel has been one of the most explored surfaces as shown by special investigations performed on analytical applications on preconcentration and retention of heavy cations from solutions [2][3][4], chemically bonded phases in chromatography [5] and adsorption of biological compounds [6]. However, other inorganic supports have been used as suitable supports for silylation by including metallic oxides, glasses, natural and phyllosilicates [7][8][9][10][11][12][13][14].…”

“…In this context silica gel has been one of the most explored surfaces as shown by special investigations performed on analytical applications on preconcentration and retention of heavy cations from solutions [2-4], chemically bonded phases in chromatography [5] and adsorption of biological compounds [6]. However, other inorganic supports have been used as suitable supports for silylation by including metallic oxides, glasses, natural and phyllosilicates [7][8][9][10][11][12][13][14].Framework layers of most natural clay minerals are generated by a combination of octahedral and tetrahedral sheets, normally classified in two hydrous phyllosilicates groups that have the inorganic structural arrangement in 1:1 or 2:1 layers. The first natural layered structure consists of single tetrahedral coordinated [Si 2 O 5 ](OH) 2 layer, which is connected to an edge-shared octahedral M(OH) 6 sheet where M is normally Mg 2+ or Al 3+ [15].…”