New synthesis strategies for effective functionalization of kaolinite and saponite with silylating agents

Silylation of clay mineral surfaces

“…When temperature increased to 185 and 195°C, APTES was intercalated into the kaolinite interlayer spaces with removal of the intercalated DMSO and subsequent condensation between APTES and kaolinite interlayer surface. In this case, the grafted APTES and the residual DMSO formed a pseudo-bilayer arrangement in the interlayer space, similar to those reported in literature (Avila et al, 2010;Tonlé et al, 2007). At 220°C, the high temperature accelerated the diffusion of APTES into the kaolinite interlayer space as well as the removal of DMSO from the interlayer space.…”

“…Similar successful grafting was also reported by Avila et al (2010), in which the grafting temperature was 200°C. Three main reflections were recorded at 1.84, 1.00 and 1.13 nm.…”

“…As indicated by literature (Avila et al, 2010;Tonlé et al, 2007Tonlé et al, , 2011, temperature was an important factor for successful silylation of kaolinite. To elucidate the influence of temperature on the grafting reaction, Yang et al (2012) conducted a series of grafting reactions on kaolinite at different temperatures (175, 185, 195 and 220°C).…”

“…More recently, Guerra et al (2012) reported that silylated kaolinite was prepared by using APTES in the medium of dry toluene under an argon atmosphere, and the basal spacing was increased from 0.71 nm (pristine kaolinite) to 1.31 nm (silylated product). The prominent difference of the basal spacings in the silylated products indicates that the reaction conditions (e.g., reaction temperature, atmosphere and solvent) have a prominent influence on the interlayer structure of silylated products (Avila et al, 2010;Kobayashi and Matsunaga, 1991;Tonlé et al, 2007Tonlé et al, , 2011.…”

“…Recently, silylation, also known as silane grafting, has proved to be an efficient way to silylate clay mineral surfaces (Avila et al, 2010;He et al, 2005). The covalent bonding between organic components and clay minerals enables a durable immobilization of the organic moieties in the silylated products (da Fonseca and Airoldi, 2003;LeBaron et al, 1999;Takahashi and Kuroda, 2011), and prevents their leaching into the surrounding solutions.…”