Bull. Chem. Soc. Ethiop. 2002, 16(1), 1-7.

N. Salami^* and F.A. Adekola

Department of Chemistry, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria

(Received January 28, 2002; revised April 10, 2002)

ABSTRACT. Investigation has been carried out on the potential of a locally sourced goethite for the removal of cadmium ion from aqueous solutions using batch equilibration technique. The maximum uptake of cadmium is 6.4 ´ 10^-2 mg/g-goethite. The sorption kinetics appears to be rapid as equilibrium was attained within a period of 1 hour. The highest sorption capacity was obtained for particle size with diameter (f ) 0.09 mm. Both infrared spectrophotometric and X-ray diffraction (XRD) techniques have also provided evidence for cadmium fixation on to the surface of the goethite. The sorption mechanism appears to follow Langmuir adsorption isotherm model. The Langmuir constants K and X_m (mass of Cd²⁺ required to form monolayer on the entire surface of the goethite) were 0.096 mg/g-goethite and 0.075 mg/g-goethite, respectively.

Bull. Chem. Soc. Ethiop. 2002, 16(1), 9-35.

DIAGENESIS AND MASS TRANSFER BETWEEN PERMO-TRIASSIC SANDSTONES AND INTERBEDDED MUDSTONES, ULSTER BASIN

Wolela Ahmed^*

School of Geosciences, Queen’s University of Belfast, Belfast BT 7 1NN, Northern Ireland, UK

(Received December 8, 2000; revised April 26, 2002)

ABSTRACT. Beds of siltstone, mudstone and shale are interbedded in the Permo-Triassic sandstones of the Ulster Basin, UK, at different stratigraphic levels. The paragenetic sequences of authigenic minerals both in the sandy and fine-grained sediments (mudstones and siltstones) indicate red bed diagenetic trend. Abundant authigenic quartz overgrowths and carbonate crystals observed near the sandstone-siltstone and sandstone-mudstone contacts, indicating that pore water and mass transfer from the fine-grained sediments to sandstone facies. The fine-grained sediments are the main source of ions for the authigenesis of quartz and feldspar overgrowths and carbonate precipitation. Mechanical compaction of fine-grained sediments, influx of gravity-driven acidic meteoric pore water, dehydration water, diffusion and convection are the most important means of mass transfer and pore water circulation. Pore water migration depends upon permeability distribution and pressure difference.

Bull. Chem. Soc. Ethiop. 2002, 16(1), 37-52. 

Wolela Ahmed^*

Department of Petroleum Operations, Ministry of Mines, P.O. Box 486, Addis Ababa, Ethiopia

(Received December 8, 2000; revised April 26, 2002)

ABSTRACT. Volcanic intrusions and hydrothermal activity have modified the diagenetic minerals. In the Ulster Basin, UK, most of the authigenic mineralization in the Permo-Triassic sandstones pre-dated tertiary volcanic intrusions. The hydrothermal fluids and heat-flow from the volcanic intrusions did not affect quartz and feldspar overgrowths. However, clay mineral-transformation, illite-smectite to illite and chlorite was documented near the volcanic intrusions. Abundant actinolite, illite, chlorite, albite and laumontite cementation of the sand grains were also documented near the volcanic intrusions. The abundance of these cementing minerals decreases away from the volcanic intrusions.

In the Hartford Basin, USA, the emplacement of the volcanic intrusions took place simultaneous with sedimentation. The heat-flow from the volcanic intrusions and hydrothermal activity related to the volcanics modified the texture of authigenic minerals. Microcrystalline mosaic albite and quartz developed rather than overgrowths and crystals near the intrusions. Chlorite clumps and masses were also documented with microcrystalline mosaic albite and quartz. These features are localized near the basaltic intrusions. Laumontite is also documented near the volcanic intrusions. The reservoir characteristics of the studied sandstone formations are highly affected by the volcanic and hydrothermal fluids in the Hartford and the Ulster Basin. The porosity dropped from 27.4 to zero percent and permeability from 1350 mD to 1 mD.

Bull. Chem. Soc. Ethiop. 2002, 16(1), 53-) 64 Society of Ethiopia

Mehabaw Getahun Derebe, V.J.T. Raju and Negussie Retta^*

Department of Chemistry, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia

(Received January 4, 2002; revised March 4, 2002)

ABSTRACT. Complexes of Mn(II), Fe(III), Co(II), Ni(II) and Zn(II) with an intermediate Schiff base derived from ninhydrin and a ,L-alanine (indane-1,3-dione-2-imine-N-2-propionate, IDIP) were successfully synthesized. All complexes were distinctly colored and were characterized by elemental analysis, molar conductance, magnetic susceptibility, infrared and electronic spectral studies. The ligand (Schiff base) was shown to behave as a monobasic tridentate ONO donor. The Mn(II) and Fe(III) complexes contain only one ligand molecule plus water and chloride(s) per metal ion, while all the others contain two ligand molecules per metal ion. An octahedral geometry is proposed for the metal complexes.

A comparative anti-microbial study of the complexes was undertaken against two gram-negative bacteria, Escherichia coli and Proteus mirabilis and one gram-positive bacterium Staphylococcus aureus. It was revealed that most of the complexes and particularly Mn(II), Fe(III) and Co(II) complexes, have a much enhanced activity relative to ninhydrin against Proteus mirabilis and Staphylococcus aureus. All complexes showed a reduced activity against Escherichia coli.

Dicky D.K. Chingakule^1*+, Peter Gans² and J. Bernard Gill²

1Chemistry Department, University of Swaziland, Private Bag 4, Kwaluseni, Swaziland

A. Zanguina, M. Bayo-Bangoura , K. Bayo And G.V. Ouedraogo^*

Laboratoire De Chimie De Coordination, Ufr-Sea — Universite De Ouagadougou — 03 BP 7021 Ouagadougou 03, Burkina Faso

(Received September 10, 2001; revised February 26, 2002)

ABSTRACT. We have prepared and studied by vibrational and electronic spectrometry of a series of ferrophthalocyanine complexes with phosphine or phosphite axial ligands [PMe₃, P(OMe)₃, PPh₃, P(OPh)₃, PPh(OMe)₃ and POH(OEt)₂]. With PMe₃, P(OMe)₃ as ligands, only hexacoordinated complexes are obtained but with PPh₃, P(OPh)₃ and POH(OEt)₂ as ligands, the coordination number depends on the FePc:ligand ratio in the reaction mixture. In the ratio 1:1 the complexes thus formed are pentacoordinated and in the ratio 1:2 hexacoordinated complexes are obtained. In the electronic spectra of hexacoordinated complexes, two charge-transfer transition bands, one at ~375 nm and the other at ~421 nm can be observed. We attribute the band at 375 nm to charge-transfer from axial ligand to macrocycle (CT L_ax ® Pc) and the band at 421 nm to charge-transfer from metal to axial ligand (CT Fe ® L_ax). In the IR spectra, the position of the n _FeN4 band is linked to the coordination number; in the spectra of pentacoordinated complexes, its frequency is almost the same as that in the FePc spectrum but in hexacoordinated complexes, it moves to high frequencies.

Aman Dekebo¹, Ermias Dagne^1*, Pat Curry², Odd R. Gautun³ and Arne J. Aasen⁴

1Department of Chemistry, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia; ²Semi Arid Lands Training and Livestock Improvement Centre of Kenya, P.O. Box 301, Isiolo, Kenya; ³Department of Chemistry, University of Tromsoe, 9037 Tromsoe, Norway;

Aman Dekebo¹, Ermias Dagne^1*, Odd R. Gautun² and Arne J. Aasen³