Abstract
The dissolution of goethite samples in mineral acids from to extreme parts of Nigeria (Osogbo and Kaduna) have been investigated. The rate of dissolution was found to be slightly faster in HCl than HNO3. The higherrate of dissolution in HCl could be attributed to the complexing ability of Cl- in addition to the H+ effect while lowering effect by NO3- was attributed to adsorption of NO3 on to the goethite surface. Mononuclear complexes, especially bidentate of oxyanion are found to accelerate dissolution as opposed to binuclear complexes. A binuclearbidentate surface complex formation between NO3 - and Fe3+ was therefore proposed to account for the inhibition observed. The possible formation of Fe—Cl reduces both the surface positive charge and the repulsion between the oxide surface and protons in solution. This produced accelerated proton dissolution. The effect of temperature on theinitial dissolution rate fit into Arrhenius equation, with Kaduna goethite exhibiting higher rate than Osogbo type in both acids. The activation energies for Kaduna goethite sample are 66.11 and 82.43 kJmol-1 in 0.1M HCl and 0.1M HNO3 respectively while for Osogbo goethite sample are 54.60 and 76.32 kJmol-1 in 0.1M HCl and 0.1M HNO3 respectively. The frequency factors of 8.4 x 10-4 & 11.17 x10-4 and 5.0 x 10-5 and 3.09 x 10-3 for Kaduna and Osogbo goethite samples were obtained. @JASEM
Highlights
RESULS AND DISCUSSIONSThe release of Fe3+ was generally low for all acid concentrations and temperatures
The conventional methods of removing heavy metals from liquids include chemical precipitation, electroflotation, ion exchange, reverse osmosis and adsorption on to activated carbon (Kadrivehi and Namasivayam, 2003)
Studies on dissolution of goethite dealt with mechanism of dissolution and effect of crystal morphology on dissolution
Summary
The release of Fe3+ was generally low for all acid concentrations and temperatures. There was a general increase in the amount of goethite dissolved with increasing temperature. There is a sharp but un - linear increase in dissolved Fe3+ between 0.1 and0.5M while the effect slowed down between 0.5 and 1.0M acid concentrations. Table: Influence of concentration and temperature on dissolution of Osogbo and Kaduna goethite
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