Search

Abstract: A Hectorite sample (H) has been chemically modified with N-propyldiethylenetrimethoxysilane and bis[3-(triethoxysilyl)propyl]tetrasulfide. The resulting materials (H3TPT and HNPTM) have been characterized through elemental analysis, X-ray diffractometry, carbon nuclear magnetic resonance in the solid state, textural analysis, and thermogravimetric analysis. The adsorption experiments were performed under batch process with pH, ionic strength, contact time, and uranyl concentration as variables. The attached basic centers adsorbed uranyl cation to give maxima adsorption capacity of 5.55±0.21, 14.86±0.05, and 18.99±0.05×10−3 mmolg−1 for H, H3TPT, and HNPTM, respectively. From calorimetric determinations the quantitative thermal effects for UO2 2+/center interactions gave exothermic enthalpy (ΔintH=−6.90 to −7.88kJmol−1), negative Gibbs free energy (ΔintG=−22.34 to −24.56kJmol−1), and positive entropy (ΔintS=51.80–56.00JK−1 mol−1). These thermodynamic data confirmed the energetically favorable condition of such interaction solid/liquid for all systems. [Copyright &y& Elsevier]

Abstract: A hectorite (H) clay sample has been modified with 2-mercaptobenzimidazole (MBI) using homogeneous and heterogeneous routes. Both modification methodologies resulted in similar products, named HHOM and HHET, respectively. These materials were characterized by CO2 gas adsorption, elemental analysis, nuclear magnetic nuclei of carbon-13 and silicon-29. The effect of two variables (contact time and metal concentration) has been studied using batch technique at room temperature and pH 2.0. After achieving the best conditions for Cr(VI) adsorption, isotherms of this adsorbate on using the chosen adsorbents were obtained, which were fitted to non-linear Sips isotherm model. The maximum number of moles adsorbed was determined to be 11.63, 12.85 and 14.01mmolg−1 for H, HHOM and HHET, respectively, reflecting the maximum adsorption order of HHET >HHOM >H. The energetic effects (Δint H°, Δint G° and Δint S°) caused by chromium ion adsorption were determined through calorimetric titrations. [Copyright &y& Elsevier]

Abstract: A synthetic Na-magadiite sample has been modified by organofunctionalization process using synthetic route involved the reaction of 2-mercaptopyrimidine with 3-chloropropyltriethoxysilane. The ability of these materials to remove As(V) from aqueous solution was followed by a series of adsorption isotherms adjusted to the Langmuir equation at room temperature and pH 2.0. The kinetic parameters analyzed by the Lagergren and Elovich models gave a good fit for a pseudo-second-order reaction with k 2 in the 4.9–14.0mmol−1 min−1 range for MMPY. The adsorption process was exothermic (Δint H =−4.09 to −5.79kJmol−1) accompanied by increase in entropy (Δint S =41.29–61.80JK−1 mol−1) and Gibbs energy (Δint G =−22.34 to −24.19kJmol−1). The energetic effect caused by arsenic(V) cation adsorption was determined through calorimetric titration at the solid–liquid interface and gave a net thermal effect that enabled the calculation of the exothermic values and the equilibrium constant. [Copyright &y& Elsevier]

Abstract: Natural montmorillonite (M) and synthetic kanemite (K) have been functionalized with 1,4-bis(3-aminopropyl)piperazine reacted with methylacrylate to yield new inorganic–organic chelating materials. The original and modified materials were characterized by X-ray diffractometry, textural analysis, SEM and nuclear magnetic nuclei of carbon-13 and silicon-29. The chemically modified clay samples (M-APPMA and K-APPMA) showed modification of its physical–chemical properties including: specific area 45.0m2 g−1 (M) to 978.8m2 g−1 (M-APPMA) and 23.5m2 g−1 (K) to 898.9m2 g−1 (K-APPMA). The ability of these materials to remove thorium(IV), uranyl(VI) and europium(III) from aqueous solution was followed by a series of adsorption isotherms, which were fitted to non-linear Sips adsorption isotherm model. To achieve the best adsorption conditions the influence of pH and variation of metal concentration were investigated. The energetic effects (Δint H°, Δint G° and Δint S°) caused by metal ions adsorption were determined through calorimetric titrations. [Copyright &y& Elsevier]

Abstract: The compound 5-amino-1,3,4-thiadiazole-thiol was anchored onto analogue of heulandite by heterogeneous route. The original (HEU) and modified heulandite (HEUATT) samples were characterized through elemental analysis and nuclear magnetic nuclei of carbon-13 and silicon-29. The ability of these materials to remove Mn(II), Zn(II) and Pb(II) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation. To achieve the best adsorption conditions the influence of pH and contact time were investigated. Based on the capacity of adsorption of HEUATT to interact with metal ions, the following results were obtained 13.0, 10.1 and 7.4mmolg−1 for Pb(II), Zn(II) and Mn(II), respectively, reflecting a maximum adsorption order of Pb(II)>Zn(II)>Mn(II). The energetic effects caused by metal cation adsorption were determined through calorimetric titrations. [Copyright &y& Elsevier]

Abstract: Hybrid composite films were prepared by incorporating 0.2, 0.4 and 0.6g of natural and modified attapulgite clays particles into sodium alginate films. Attapulgite sample has been chemically modified with organofunctionalization of 3-mercaptopropyltrimethoxysilane and 3-aminopropyltriethoxysilane. These hybrid films were used for thorium adsorption from aqueous solutions under batch process with pH and Th4+ concentration as variables. The effect of attapulgite incorporation in sodium alginate films has been investigated by silicon and carbon nuclei solid-state MAS/NMR, elemental analysis, CHN, textural analysis, SEM, and mechanical properties (0–30wt% of clay samples). The reactive centers attached to the pendant chains inside the sodium alginate films can coordinate thorium(IV), by presenting and isotherm saturated at 33.70×10−5 molg−1 of this actinide. From calorimetric determinations the quantitative thermal effects for all thorium/film surfaces gave exothermic enthalpy (Δint H=−4.35 to −5.90kJmol−1), negative Gibbs free energy (Δint G=−22.62 to −24.51kJmol−1), and positive entropy (Δint S=61.18 to 62.36JK−1 mol−1). These thermodynamic data confirmed the energetically favorable condition of such interaction solid/liquid for all systems. [Copyright &y& Elsevier]

Abstract: The compound 5-amino-1,3,4-thiadiazole-thiol (ATT) was anchored onto an Amazon kanemite surface (K) by homogeneous and heterogeneous routes. Both kanemite modification methodologies resulted in similar products, named K CTT and K ATT, respectively. The modified and natural kanemite samples were characterized by textural analysis, FT-Raman, and nuclear magnetic nuclei of 29Si and 13C. Elemental analysis proved that the matrix K ATT presented a higher ATT immobilization than K CTT, with values 1.42 and 1.38mmolg−1, respectively. NMR and FT-Raman confirmed the immobilization of ATT on both surfaces. The ability of these materials to remove thorium(IV) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature and pH 4.0. The maximum number of moles adsorbed was determined to be 7.48×10−3, 9.82×10−3, and 12.94×10−3 mmolg−1 for K, K CTT, and K ATT, respectively. The energetic effects (Δint H°, Δint G°, and Δint S°) caused by metal cation adsorption were determined through calorimetric titrations. [Copyright &y& Elsevier]

Abstract: An analogue of heulandite was synthesized by using inorganic salts as a source for silicon and aluminum in the hydrothermal synthesis of the material. The resulting solid was modified by organofunctionalization with 1,4-bis(3-aminopropyl)piperazine and subsequent reaction with methylacrylate in a heterogeneous route. The original (HEU) and modified silicate (HEUAPPMA) samples were characterized by textural analysis, SEM, and nuclear magnetic nuclei of 29Si and 13C. The chemically modified silicate sample showed modification of its physical–chemical properties including specific area 459.0–978.8m2 g−1. The ability of this material to remove nickel(II), cobalt(II), and copper(II) from aqueous solutions was followed by a series of adsorption isotherms adjusted to a Sips equation. The quick adsorption process reached the equilibrium before 10, 15, and 20min for Cu(II), Ni(II), and Co(II), respectively, with maximum adsorptions at pH 4.0. Based on the capacity of adsorption of HEUAPPMA to interact with metal ions, the following results were obtained 12.9, 9.8, and 7.5mmolg−1 for Cu(II), Ni(II), and Co(II), respectively, reflecting a maximum adsorption order of Cu(II)>Ni(II)>Co(II). The energetic effects caused by metal cation adsorption were determined through calorimetric titrations. [Copyright &y& Elsevier]

Abstract: The montmorillonite clay sample from amazon region, Pará State, Brazil, was used for intercalation process with pyridine (P) and organofunctionalization with 3-aminopropyltriethoxysilane (APS). The montmorillonite-P/APS shows variation of d001 values, by changing d001 from 1.15 to 2.10nm. The original and modified samples were used for mercury cation adsorption from aqueous solution at room temperature and pH 6.0. The energetic effect caused by mercury cation adsorption was determined though calorimetric titration at the solid–liquid interface and gave a net thermal effect that enabled the calculation of the exothermic values and the equilibrium constant. [Copyright &y& Elsevier]