Evaluation of the coupled reaction-adsorptionof Ca 2+ ions on ashes from sugar cane bagasse. Kinetic and thermodynamic approaches

Abstract

The adsorption of Ca2+ ions and the pozzolanic reaction between ashes from sugar cane bagasse (bio-reactant) and Ca(OH)2, are studied in the present paper. The characterization of the bio-reactant by means of XRD, specificsurface Brunauer-Emmett-Teller (BET), thermal differentialanalys is (TDA), thermo-gravimetric analysis and other physical parameters such as pignometric density, porosity,compressibility, form factor and flow velocity, is developed. A four stages mechanism is proposed to describe the pozzolanic reaction according to Zhulaev postulations. Once the reaction takes place, an 85.15% of Ca2+ is converted and the rest remains as adsorbed specie validating a dual adsorption-reaction process. The kinetics of the adsorption process can be described by means of a pseudo-firstorder model and the mechanism is controlled by the film diffusion model. The thermodynamics of the adsorption process fits to the Freundlich isotherm.