Effect of the fluidized bed drying on the structure and biosorption capability of Pb⁺² of agave epidermis

A fluidized bed drying study of agave epidermis obtained from wastes of the “pulque” manufacture was made. Drying kinetics modeling and the influence of the operation conditions on the shrinkage, microstructure and biosorption capability of Pb⁺² were studied. Drying kinetics was carried out at 50, 60, 70 and 80 °C. Six semi-empirical models were tested and diffusion approach model provided the best fits. Effective diffusivity varied from 3.73×10^-9 to 6.99×10^-9 m2s^-1, for untreated slabs (UT) and from 3.65×10^-9 to 7.74×10^-9 m2s^-1 for treated samples (T) with hydrochloric acid. Activation energy was found to be 21.22 and 23.89 kJ/mol for UT and T samples respectively. Shrinkage and the microstructure changes of T slabs were larger than UT samples. T samples dried at 70 and 80 °C showed a reduction in their Pb⁺² biosorption capability, caused by a large shrinkage and severe microstructural changes. For UT samples their biosorption capability was increased in relation with increase of the shrinkage and drying temperature. T samples dried at 50 and 60 °C improved their biosorption capability of Pb+2, while UT samples dried at 70 and 80 °C showed a better biosorption capability. These results can be useful for preparation of biosorbents.