SYNTHESIS, CHARACTERIZATION AND APPLICATION OF PVP GRAFTED SMECTITE CLAYS

FERNÁNDEZ L., SÁNCHEZ M., DE LA CRUZ C., ONTIVERO M., SANTONI D., BERTI P., ROZAS C., CRAVERO F.

Castellaneta Marina, Italia

Congreso; XIV International Clay Conference; 2009

AIPEA

In this work, polyvinylpirrolidone (PVP), a biocompatible polymer has been used to functionalize natural smectite clays (Es). PVP is a non-toxic, biocompatible polymer that forms complexes with many cations and chemical species. These characteristics make it useful to use this system in real applications such as in food and textile industry. The functionalization process required a previous attachment of an active group on the surface of the clays. Subsequently, a polymer chain was generated in situ, using vinyltrimethoxysilane (VTMS) and 1-vinyl-2-pyrrolidone (VP) as reactives. The final product is denoted as EsPVP. The obtained nanocomposite was characterized by infrared spectroscopy (IR), thermogravimetry (TGA), X-ray powder diffraction (XRD) and contact angle (θ°). The basal spacings for Es and EsPVP are 12.2 y 13.1 Å, respectively. This reflects that the interaction between PVP and clay material occur on the external surface and broken edges. Results of IR and TGA showed that the desired polymer chains have been covalently bonded to the surface of clays. New peaks at 1428 cm-1, 1620 cm-1 (attributed to VTMS) and at 1656 cm-1 (C=O double bond in PVP) were observed in the infrared spectra. The TGA curves of the clay used before and after grafting indicate that there is 6.5% (wt %) of VTMS+PVP on the external surface and broken edges of Es. One way to estimate clay hydrophilicity is to measure the contact angle. Unlike an organo-clay, the EsPVP is characterized by a lower contact angle than that of the natural clay (θEs= 25 º). In this contribution, the angles were evaluated from photographs using video enhanced image processing. Due to limitations in the technique, angles less than 10 degrees cannot be determined (θEsPVPV   < 10 º). Single batch experiments have been conducted to examine the adsorption of phenol from water by different kind of clays: Es, EsPVP and EsHDTMA.  The later clay-organic complexe was synthesized by placing quaternary ammonium cation on smectite by cation exchange, using hexadecyltrimethyl ammonium (HDTMA+) as organic cation. We adopt the following experimental condition: Co (initial phenol concentration)=100mg/l, amount of clay adsorbents=1,7gr/l, pH= 7, temperature=25 ºC, shaking time=24 hours. After centrifuging, the phenol concentration of the supernatant was measured and then the removal ratio of phenol from water was calculated. Extent of adsorption (%) of 37.37 %, 24.15 % and 14.95 % were obtained for EsPVP, EsHDTMA and Es respectively. The adsorption increment of phenol showed by the prepared EsPVP can be attributed to the presence of the specific sites on the surface developed by carbonyl groups of the grafted PVP. Keywords: smectites, grafting, PVP-phenol.