Adsorption of Reactive Red 120 from aqueous solutions by cetylpyridinium-bentonite

BACKGROUND: The removal of Reactive Red 120 (RR 120) from aqueous solutions using cetylpyridinium modified Resadiye bentonite (CP-bentonite) prepared by ion exchange was investigated with particular reference to the effects of temperature, pH and ionic strength on adsorption. RESULTS: Fourier transform infrared (FTIR) and thermal analysis (TG-DTG/DTA) techniques revealed that the anionic dye (RR 120) molecules replaced partly cationic surfactant species on interacting with CP-bentonite. The positive surface charge originating from the cationic surfactant species located on the external surface of the modified bentonite sample increased at low pH values. The significant amount of dye removal by CP-bentonite at high pH values proved the importance of ? and van der Waals interactions other than the electrostatic attraction in the duration of the adsorption process. The adsorption isotherms and the kinetic data were well described by the Langmuir and pseudo-second-order kinetic model, respectively. The Gibbs energy (?G), enthalpy (?H) and entropy (?S) changes in the temperature range 25-65 °C pointed out that the RR 120 uptake increased in parallel with the temperature. CONCLUSION: This study showed that the structural arrangement of cetylpyridinium ions in the CP-bentonite sample aswell as the pH, temperature and ionic strength of the bulk solution influenced the adsorption of RR 120 dye from aqueous solutions by CP-bentonite. © 2010 Society of Chemical Industry

Mechanism of the Reaction NO + H2 on the Pt(100)-hex Surface under Conditions of the Spatially Nonuniform Distribution of Reacting Species

The interaction of hydrogen with NO ads /1 × 1 islands produced by NO adsorption on the reconstructed surface Pt(100)-hex was studied by high-resolution electron energy loss spectroscopy (HREELS) and the temperature-programmed reaction (TPR) method. The islands are areas of the unreconstructed surface Pt(100)- 1 × 1 saturated with NO ads molecules. The hexagonal phase around these islands adsorbs much more hydrogen near room temperature than does the clean Pt(100)-hex surface. It is assumed that hydrogen is adsorbed on the hexagonal surface areas that are adjacent to, and are modified by, the NO ads /1 × 1 islands. The reaction of adsorbed hydrogen atoms with NO ads takes place upon heating and has the character of so-called surface explosion. The TPR peaks of the products of this reaction—nitrogen and water—occur at T des ~ 365–370 K, their full width at half-maximum being ~5–10 K. In the case of the NO ads /1 × 1 islands preactivated by heating in vacuo above the NO desorption onset temperature (375–425 K), after the admission of hydrogen at 300 K, the reaction proceeds in an autocatalytic regime and the product formation rate increases monotonically at its initial stage. In the case of activation at 375 K, during the initial, slow stage of the reaction (induction period), hydrogen reacts with nitric oxide molecules bound to structure defects (NO def ). After activation at 425 K, the induction period is characterized by the formation and consumption of imido species (NH ads ). It is assumed that NH ads formation involves N ads atoms that have resulted from NO ads dissociation on defects upon thermal activation. The induction period is followed by a rapid stage of the reaction, during which hydrogen reacts with NO 1 × 1 molecules adsorbed on 1 × 1 areas, irrespective of the activation temperature. After the completion of the reaction, the areas of the unreconstructed phase 1 × 1 are saturated with adsorbed hydrogen. The formation of H ads is accompanied by the formation of a small amount of amino species (NH 2ads )

Identifying the Liquidity Effects of Monetary Policy Shocks for a Small Open Economy: Turkey

Liquidity effect, Open economy version of NBR, Small and open economies, VAR models, E50, E52, E43,