Physical, petrographical and geochemical data are used to constrain the mode of formation of low grade marble occurring in Nsofang and environs, in Ikom area of southeastern Nigeria. The presence of lamination, vug and cavernous structures as part of the physical features of the marble suggest possible formation at T < 100 °C under biological controls, induced during microbial metabolic activity. However, it appears this mode of formation is insignificant as the modal mineralogy of the rock frequently follow the trend: dolomite (90%) + calcite (5%) + quartz (<1%) + talc (<1%) ± phlogopite (<1%) ± Opaque mineral(s) (1%), reflecting impact of low grade metamorphism. The strong linear correlation existing between Mg/Ca and Mn/Sr components supports the participation of metamorphic dolomitization in the formation of the marble. Other elemental geochemical data revealed progressive replacement – type dolomitization as a component applicable mechanism. The intense volcanism associated with the Cameroon Volcanic Line (CVL) most likely drove the hydrothermal system and metamorphism that produced the dolomitization of precursor limestones. It appears the Cenozoic timing of the CVL coincided with the time of dolomitization, while the extrusive activities provided a source of heat and additional ions for the circulating seawater that drove the calcite-dolomite reactions of the replacement-type dolomitization model.
Titanate nanotubes (TNT) were prepared via a hydrothermal treatment of synthesized TiO2 powders in a 10 M NaOH solution at 130◦C for 24 h and subsequently washed with HCl aqueous solution of different concentrations (with water only, 0.01, 0.1 and 1 M). Samples with different contents of remnant sodium in nanotubes after heat-treatment were characterized, by high resolution transmission electron microscopy, X-ray diffraction, fourier transform infrared spectroscopy and Raman spectroscopy. The photocatalytic activity of TNT was evaluated by photocatalytic oxidation of phenol in water solution. Highly remnant sodium in nanotubes has a detrimental effect on the photocatalytic activity of titanate. This is attributed to the high concentration sodium preventing formation of the photoactive anatase phase and low concentration sodium producing surface and bulk recombination centers of photogenerated electron-hole pairs.