Intersalation Reactions of Trisdiimine Metal Complexes with Montmorillonite Clay: A New Approach

Intersalation reactions of the complexes [Ni(L-L)(3)]SO(4) and [Ni(L-L)(3)]Cl(2) (L-L=1,10-phenanthroline (phen), 2,2'-bipyridyl (bpy)), with Na-montmorillonite carried out under different dynamic conditions such as ultrasonic irradiation, refluxing, autoclaving, and vigorous stirring showed that under ultrasonic irradiation, maximum adsorption of the metal complexes occurred within a period of 30 min. Metal complexes containing the phen ligand showed higher adsorption than those containing bpy. Maximum adsorption up to about three times the cation exchange capacity (CEC) of the clay was observed. Aggregated (basal spacing d(001) 12.5 ?) Na-montmorillonite, in treatment with a higher amount (>CEC) of metal complexes, formed monolayered (basal spacing d(001) 17.6 ?) species, while with predispersed clay, bilayered (basal spacing d(001)>28 ?) or pseudo-trilayer (basal spacing d(001)>32 ?) species were formed. The bilayered species were thermally stable up to 250 degrees C and above this temperature monolayered species were formed. The thermal stability of the intersalated species was higher than that of the intercalated ones. X-ray diffraction, UV-visible, IR-spectroscopy, thermal analyses, and surface area measurements were used for characterization of the products. Copyright 2001 Academic Press.     

On the Single-machine Scheduling Problem with Tardiness Penalties

The n-job, single-machine total tardiness problem is considered in this paper. A branching algorithm based on three theorems is proposed to generate a reduced set of candidate sequences. The computational results indicate that the proposed algorithm provides a smaller set of candidate sequences than the DP algorithm of Schrage and Baker.     

Adsorption and surface complexation of trimesic acid at the alpha-alumina-electrolyte interface

Adsorption kinetics, adsorption isotherms and surface complexation of trimesic acid onto alpha-alumina surfaces were investigated. Adsorption kinetics of trimesic acid with an initial concentration of 0.5 mM onto alpha-alumina surfaces were carried out in batch method in presence of 0.05 mM NaCl (aq) at pH 6 and 298.15, 303.15 and 313.15 K. Adsorption isotherms were carried out at 298.15 K, pH 5-9, and 0.05 mM NaCl (aq) by varying trimesic acid concentration from 0.01 to 0.6 mM. Three kinetics equations such as pseudo-first-order, pseudo-second-order and Ho equations were used to estimate the kinetics parameters of the adsorption of trimesic acid on the alpha-alumina surfaces. Ho equation fits the experimental kinetics data significantly better and the estimated equilibrium concentration is in excellent agreement with the experimental value. The adsorption data were fitted to Freundlich and Langmuir adsorption model and the later best fits the adsorption isotherms. Comparison of adsorption density of trimesic acid with that of benzoic and phthalic acids follows the sequence: benzoic acid < trimesic acid < phthalic acid. The negative activation energy and the Gibbs free energy for adsorption indicate that the adsorption of trimesic acid onto alpha-alumina is spontaneous and facile. DRIFT spectroscopic studies reveal that trimesate forms outer-sphere complexes with the surface hydroxyl groups that are generated onto alpha-alumina surfaces in the pH range of the study.