Adsorption Characteristics of Sodium Oleate onto Calcite

Abstract

Aims: The need for separation of calcite from other minerals has been a concern. Na-oleate has been found useful as a good adsorbate for separation of calcite from other minerals. The aim of present study is to investigate the effect of various mechanisms of adsorption of Na-oleate onto calcite such as contact time, pH and temperature.   Study Design: Conductivity method was used for the analysis.  Place and Duration of Study: Department of Chemistry, Federal University of Technology, Owerri, Nigeria, between February and October, 2012. Methodology: Batch adsorption experiment were carried out by introducing oleic acid into various flasks containing sodium hydroxide, NaOH solution to form sodium oleate. 1g of purified calcite was added into flasks containing Na-oleate. The specimen flasks and content were agitated for 1hr using a mechanical shaker. Each flask content was allowed to settle for further 30 min, after agitation. The content of flask was filtered with filter paper. After filtration, the conductance of each filtrate was measured. The amount of Na-oleate adsorbed onto calcite is the difference between initial and residual conductance measurement on sample. Results: The result of this study shows that initial rate of Na-oleate adsorption onto calcite conforms to first-order reaction kinetics. This study indicates that adsorption of Na- oleate onto calcite increases at low pH values than higher pH. The amount of Na-oleate adsorbed onto calcite increases gradually as temperature increases from 30 to 35 ºC. Beyond optimum temperature 40ºC, adsorption of Na-oleate on calcite decreases rapidly. The result of the analysis indicates that critical micelles concentration (cmc) changes at high pH values. Conclusion: This study indicates optimum contact time of 80 min on adsorption process of Na-oleate onto calcite. Also this study indicates that adsorption of Na-oleate onto calcite is pH dependent. Ca-oleate formation first increases with increasing Na-oleate concentration. At low pH 4 adsorption of Na-oleate onto calcite increases, whereas adsorption decreases at high pH 9. The critical micelles concentration of Na-oleate was established at concentration 9.0 x10-3 M.