Volume 4 Number 9 September 2019

Synthesis and Spectroscopic Determination of the Coordination Differences of Cadmium and Zinc Complexes of Dehydroacetic Acid with Pyridine and g-Picoline

Authors: Erika Martins de Carvalho ; Roselene Ribeiro Riente ; José Daniel Figueroa Villar
Pages: 81-89
Various complexes of DHA with transition-metal cations are known for their antifungal properties. Here, four novel Zn and Cd complexes were prepared via the substitution of water by pyridine andg-picoline using Zn(DHA)2(H2O)2 (2) and Cd(DHA)2(H2O)2 (3) as starting materials. The products were characterized by IR, UV, elemental analysis, TGA and NMR techniques, including correlation times and intermolecular distance measurements using the NULL pulse sequence. The experimental data were compared to the molecular modeling results using DFT and the semiempirical method PM3, confirming that the pentacoordinated Zn complexes have bipyramidal geometry while the Cd complexes have the expected octahedral geometry. These results show that substitution of Zn by Cd leads to an important modification of the coordination structure, especially when strong ligands are involved.

Chemical Characterization and Leaching Kinetics of Metals From Iron Ores

Authors: Itodo A. U. ; Eneji I. S. ; Mnenga B. O. ; Tseen M. A.
Pages: 69-80
The impact of mineral deposit on their host agricultural soil, available water bodies and near atmospheric environment is of great concern.  In this study, mineralogical characterization and leaching kinetics of metals from iron ores in Kogi States, were reported. Physicochemical parameters namely; electrical density, pH, bulk density and moisture content were also investigated. The SEM image of the iron ore appear compact with irregular shape.  XRF analysis showed that, iron ore consist of 63.44 % Fe as major element, with the oxide composition of 90.71%. The XRD analysis of iron ore unveiled the presence of magnetite (88 %), hematite (9 %) and quartz (3 %) as associated mineral. Low concentration of iron (0.77-1.70 ppm) was observed to be leached from iron ore in the acidic medium, 0.35-1.10 ppm from basic medium and 0.32-0.88 ppm in the aqueous medium, The Shrinking core, Product-layer diffusion and leaching, controlled by diffusion were the three equations used to model the leaching parameters. The leaching experimental data of iron ore fit best into the diffusion- controlled model, with R2 = 0.94 for the acidic medium Hence, the rate determining step. The analysis shows good fit for the other kinetic models.  Overall, result proved that, the environment around mining sites is chiefly contaminated by the metals leached from the ore (mineral) deposits. Hence, the need to monitor the pollution indices, the role of leaching, pollutant fate (transport and reaction) and the subsequent distribution of metals to neighboring environment.