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The behaviour of tannic acid adsorption on fluorite surface: isotherm, kinetic and thermodynamic studies

Tangarfa Mariam, Semlali Aouragh Hassan Naoul

Physicochemical Problems of Mineral Processing

2022

Vol. 58, iss. 1

77--87

Fluorite is an important mineral to produce hydrofluoric acid. As fluorite resources contain calcite as a gangue mineral, the separation between these two calcium containing minerals is difficult. Tannic acid is the most commonly used reagent as a depressant to separate fluorite from calcite by flotation. To enhance this separation, it is so primordial to understand tannic acid physicochemical reactivity via these minerals. Therefore, the aim of this work is to investigate the mechanism of tannic acid adsorption on the fluorite surface by experimental study using isotherm, kinetic and thermodynamic. Adsorption isotherm modelling results showed that the adsorption process is well described by Sips model. On the other hand, the kinetic and thermodynamic require firstly the adsorption study as a function of three main reactional parameters including initial tannic acid concentration, solution pH and temperature. This study showed that acidic pH as well as initial tannic acid concentration increase and temperature decrease promote the studied adsorption. These finding were then exploited to determine the adsorption mechanism by pseudo n order kinetic model adjustment to experimental kinetic data using nonlinear regression method. Obtained high correlation coefficient and low mean absolute error at 95 % confidence level showed good agreement of experimental kinetic data with the tested model. These results revealed that the mechanism of tannic acid adsorption onto fluorite was attributed to a chemical reaction. In addition, the thermodynamic study showed that the studied adsorption process was exothermic.