In this study, nanocomposite-implant materials with the filler materials, which are nanohydroxyapatite (nHAp) and nHAp modified by [3-(2-aminoethilamino)propyl]trimethoxysilane, using poly(methylmethacrylate) as a matrix according to the melting method, were synthesized. The nanocomposites were characterized using X-ray diffraction, Fourier transform infrared spectroscopy-attenuated total reflectance, scanning electron microscopy, transmission electron microscopy, differential thermal analysis/thermogravimetric analysis, and differential scanning calorimetry devices. Experimental results showed that the thermal stability of nanocomposites increased, and they were hemocompatible, had no negative effect on antioxidant enzymes, and had antibacterial activity. [GRAPHICS] .

The metal ion adsorption and electrokinetic properties of sepiolite modified by 3-(trimetoxysilyl)propyl metaacrylate was studied. The characterization of modified sepiolite was made by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron micrograph (SEM), and differential thermal analysis/thermogravimetry (DTA/TG). The adsorption behavior of Fe(III), Mn(II), Co(II), Zn(II), Cu(II), and Cd(II) metal ions on modified sepiolite from aqueous solutions was investigated as a function of equilibrium pH, temperature, and ionic strength. The adsorption experiments were carried out using a batch method. The initial and final concentrations of heavy metals were determined by means of atomic absorption spectrophotometry. The zeta potential of the modified sepiolite suspensions was measured as a function of metal ion concentration and equilibrium pH using a Zeta Meter 3.0. The results showed that the amount of adsorbed metal ions increased with solution pH, and that the modified sepiolite adsorbed Cu(II) and Mn(II) ions more than other metal ions. It was found that the temperature had an important effect on metal ion adsorption and that the adsorption process was endothermic in nature. Equilibrium isotherms for the adsorption of metal ions were measured experimentally. Results were analyzed by the Freundlich and Langmuir equations and determined the characteristic parameters for each adsorption isotherm. The isotherm data were reasonably well correlated by Langmuir isotherm. Maximum monolayer adsorption capacity of modified sepiolite for Cu(II), Mn(II), Zn(II), Fe(III), Co(II), and Cd(II) metal ions was calculated from 12.3x10(-5), 11.7x10(-5), 9.0x10(-5), 8.2x10(-5), 5.7x10(-5), and 1.8x10(-5)molL(-1), respectively. The affinity order of adsorption was Cu(II)>Mn(II)>Zn(II)-Fe(III)>Co(II)>Cd(II). The results indicate that modified sepiolite is good adsorbent for the removal of metal ions from aqueous solutions.

Polyphenoloxidase (PPO) from Rosmarinus officinalis L. was fractionated by ammonium sulfate ((NH4)(2)SO4) precipitation and dialysis, and then some of its kinetic properties such as optimum pH and temperature, substrate specificity, thermal inactivation, and inhibition were investigated using 4-methylcatechol, catechol, and pyrogallol as substrates. The protein content of Rosmarinus officinalis L. extracts was determined according to Bradford's method. Kinetic parameters, K (m) and V (max), were calculated from Lineweaver-Burk plots. According to V (max)/K (m) ratio, 4-methylcatechol was the most suitable substrate. The optimum temperature and pH values were 20, 30 and 30 A degrees C, and 7, 8 and 8 for 4-methylcatechol, catechol, and pyrogallol substrates, respectively. The thermal inactivation of PPO was investigated at 35, 55, and 75 A degrees C. The enzyme activity decreased with increasing temperature. The effect of different inhibitors on partly purified Rosmarinus officinalis L. PPO was spectrophotometrically investigated. For this purpose, ascorbic acid and l-cysteine were used to inhibit the activity of Rosmarinus officinalis L. PPO at different concentrations. From the experimental results, it was found that l-cysteine is a more effective inhibitor than ascorbic acid due to lower K (i) values.

This study describes an effective way for the preparation of well-dispersed poly(vinylalcohol) (PVA)/bentonite and poly(vinylalcohol)/modified bentonite nanocomposites with improved thermal properties. Nanocomposites were synthesized by effectively dispersing the inorganic nanolayers of bentonite in PVA matrix via the solution intercalation method. Bentonite was calcinated at 150 and 650 °C and modified with 3-aminopropyltrimethoxysilane (3-APT), dimethylsulfoxide (DMSO) and methanol (MeOH). The surface areas of bentonite and modified bentonite samples were measured by BET surface analyzer. In order to determine thermal stabilities of PVA and its nanocomposites, it was used thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The interactions between polymer, PVA, and filling material, bentonite were determined using Fourier transform infrared spectroscopy attenuated total reflectance (FTIR-ATR). The dispersion and exfoliation of the clay layers in PVA matrix were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The contact angles of PVA and its nanocomposites were determined for nanocomposites by sessile drop method. The activation energies were calculated using the Kissinger method. XRD and TEM results showed that bentonite layers were dispersed in nanoscale and homogenously in PVA matrix. Microscopic and XRD techniques revealed highly organized regions. Clay content up to 5 wt.% led to nanocomposites with high degree of exfoliation. Thermogravimetric analysis indicated that introduction of clay to the polymer network resulted in an increase in thermal stability. Activation energy values at both stages for PVA/bentonite nanocomposite were higher than those of pure PVA, indicating that addition of bentonite particles improves thermal stability of PVA.

Surface modification of clays has become increasingly important due to the practical applications of clays such as fillers and adsorbents. The surface modification of sepiolite with [3-(2-aminoethylamino)propyl]trimethoxysilane has been employed. The modified sepiolite surface was investigated by FTIR, XRD and 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 methoxy groups of [3-(2-aminoethylamino)propyl]trimethoxysilane. The changes on electrokinetic properties of modified sepiolite particles were studied by measuring the zeta potential of particle as a function of metal concentration and equilibrium pH of solution. It was found that the zeta potential of the clay particles was always negative independent of the metal concentration in solution. This study also provides some evidence for the adsorption of metal ions on modified sepiolite. The adsorption of metal ions onto modified sepiolite has varied with the type of metal cations. The available basic nitrogen centers covalently bonded to the sepiolite skeleton were studied for Co(II), Cu(II), Mn(II), Zn(II), Fe(III) and Cd(II) adsorption from aqueous solutions. It was found that the amount of metal ion adsorbed onto modified sepiolite increases with increase in solution equilibrium pH and temperature, whereas it generally decreases with the ionic strength. The experimental data were correlated reasonably well by the Langmuir adsorption isotherm and the isotherm parameters (q(m) and K) were calculated. The ability to adsorb the cations gave a capacity order of Zn(II) > Cu(II) similar to Co(II) > Fe(III) > Mn(II) > Cd(II) with affinities of 2.167x 10(-4), 1.870x10(-4), 1.865x10(-4), 1.193x10(4), 0.979x 10(-4) and 0.445x 10(-4) mol g(-1), respectively.

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 degrees 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 degrees 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 (RI). The Langmuir model represented the sorption process better than the Freundlich model, with R 2 values ranging from 0.9603 to 0.9977.

Nanocomposites of poly(vinyl chloride) (PVC) have been prepared by solution intercalation method using both natural and modified kaolinites. Kaolinite was modified with dimethyl sulfoxide (DMSO) to expand the interlayer basal spacing. The characterization of PVC/kaolinite nanocomposites was made by X-ray diffraction (XRD) and transmission electron microscopy (TEM); the interactions between kaolinite and PVC was discussed by FTIR-ATR; the thermal stability was determined by simultaneous DTA/TG. FTIR-ATR confirms hydrogen bonds formed between dimethyl sulfoxide molecules and the inner surface hydroxyl groups of kaolinite. XRD and TEM results give evidence that kaolinite was dramatically intercalated into nanoscale and homogenously dispersed in the PVC matrix. Thermogravimetric analysis indicated that introduction of clay to the polymer network resulted in an increase in thermal stability. Ultraviolet (UV) absorbance experiments showed that nanocomposites have a higher UV transmission than PVC film. The Kissinger method was used for calculation the decomposition activation energy. The results have shown that activation energy values at both stages for PVC/kaolinite nanocomposite are higher than those of pure PVC, indicating that addition of kaolinite particles improves thermal stability of PVC.

Surface modification of clay minerals has become increasingly important for improving the practical applications of clays such as fillers and adsorbents. An investigation was carried out on the surface modification of sepiolite with aminopropylsilyl groups in 3-aminopropyltriethoxysilane (3-APT). The zeta potential of the modified sepiolite suspensions was measured as a function of initial electrolyte concentration and equilibrium pH using a Zeta Meter 3.0 for modified sepiolite. The utility of the 3-APT-modified sepiolite was investigated as an adsorbent for removal of various heavy metal ions such as Fe, Mn, Co, Zn, Cu, Cd and Ni from aqueous solutions. The effects of various factors on the adsorption, such as pH, ionic strength and temperature of the solution were studied. The results showed that the amount adsorbed increases with solution pH in the pH range of 1.5 and 7.0; indicated that the modified sepiolite adsorbed Fe and Mn ions more than other metal ions such as Co, Zn, Cu, Cd and Ni. It was found that the temperature had an important effect on metal ion adsorption by the modified sepiolite. The adsorption isotherm has been determined and data have been analyzed according to the Langmuir and Freundlich models. (C) 2007 Elsevier B.V. All rights reserved.

Poly(vinyl chloride) (PVC)/sepiolite nanocomposites were prepared using PVC and natural, organo-modified, acidactivated, and calcined sepiolite samples through the solution intercalation method. Thermogravimetric (TG) analysis, UVvis spectrophotometry, Fourier transform infrared spectroscopy, and scanning electron microscopy were used to determine the thermal stability, optical behavior, interactions, and morphology of samples, respectively. The dispersion of sepiolite in the PVC matrix was examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The nanocomposites exhibited higher thermal stability than that of pure PVC. XRD and TEM results showed that sepiolite particles were dispersed in the nanoscaled PVC matrix. The UVvis spectra showed that the transmission of nanocomposites increased with the sepiolite content and wavelength. The thermal degradation behavior of PVC was investigated by using TG analysis under nonisothermal conditions at different heating rates under a nitrogen atmosphere. The apparent activation energy of samples was determined by using the Kissinger method. The nanocomposite showed higher activation energy than that of pure PVC. The results showed that the thermal degradation of PVC was shifted toward higher temperatures with an increase in the amount of sepiolite. (c) 2011 Wiley Periodicals, Inc. Adv Polym Techn 32: E65E82, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20271