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Three Locally Clays as A Surfaces for Adsorption of Cephalexin Monohydrate From Aqueous Solution: Thermodynamic and Desorption Equilibrium

The adsorption of cephalexin.H2O from aqueous solution on attapulgite, bentonite and kaolin has been studied at the human body temperature (37.5˚C) and at 5, 27, 47˚C in 0.1M hydrochloric acid (pH 1.2). The value of pH 1.2 has been chosen to simulate the pH of stomach fluid. The clays show the following order: Bentonite > attapulgite > kaolin, for their activity to adsorb cephalexin.H2O. The charged clay particles can attract molecules either by electrostatic forces, for the molecules of oppositely charged, or by inducing dipole formation in the neutral molecule. The L-shaped adsorption isotherm indicated that drug molecules arrangement in a flat geometry on the clay surface. The results indicated the applicability of Langmuir isotherm for adsorption of drug on three clays. The amount of cephalexin.H2O adsorbed on the three clays was increased with increasing pH value from 1.2 to 5. At the acidic pH, the competition between cephalexin.H2O molecules and hydronium ions results in a reduction in adsorption process. At fixed temperature and pH, the adsorption of cephalexin.H2O on the three clays was increased with increasing the ionic strength of solution. The data showed a little increase in the amount of drug adsorbed by attapulgite and bentonite with increasing temperature, so the adsorption process appeared endothermic. The reverse was observed with adsorption of cephalexin.H2O on kaolin surface (exothermic).The extent of desorption of cephalexin.H2O from the clays increased when the concentration of drug increased. This result may refer to the difficulty of desorption of the drug at low concentrations, which reflects a relatively higher adsorbate - adsorbent interaction.

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Synthesis, Characterization and Thermal Study of Some Transition Metal Complexes Derived from Quinoxaline-2,3-Dione

The present paper describes the synthesis and structural studies of new transition metal complexes of cobalt(II), nickel(II), copper(II) and cadmium(II) with two bi dentate ligands derived from quinoxaline-2,3-dione. The two ligands were fully identified by elemental analyses, FT-IR, NMR and UV-Visible spectra. The metal complexes of Co(II), Ni(II), Cu(II) and Cd(II) were isolated in the solid state after reactions of their metal chlorides with the ligands in 2:1 mole ratio. The isolated solid metal complexes were characterized with the help of elemental analyses, NMR, FT-IR and UV-Visible spectra. As well as the thermal stability of the coordinated quinoxaline polymers were tested by TG-DSC analysis and it is found that cleavage of terminal moiety was investigated, the strong coordinated bonds between oxygen donor atoms in L1 while nitrogen donor atoms of quinoxaline ring in the L2 with the metal ions. Furthermore, the thermal stability of cobalt(II), nickel(II), copper(II) and Cd(II) complexes were screened by TG-DSC analysis and the results helped us in the investigation of the proposed structure of the prepared complexes in the formula [M(L)2Cl2].XH2O and [Cd(L)2]Cl2 where L= L1 and L2 ligands derived from quinoxaline-2,3-dione.

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