Study of Natural Clay Adsorbent Sepiolite for the Removal of Caffeine from Aqueous Solutions: Batch and Fixed-Bed Column Operation

Sepiolite reveals as a low-cost and efficient adsorbent for the adsorption of caffeine from aqueous solutions. The characterization of this material was carried out by N-2 adsorption-desorption at 77 K, Fourier transform infrared spectroscopy, thermogravimetric analysis, and electronic microscopy. Initially, batch adsorption experiments were developed in order to determine the equilibrium time and the adsorption isotherm of the system. Pseudo-first-order, Elovich equation, pseudo-second-order, and intra-particle diffusion models were applied to the experimental data to determine the adsorption kinetics. In continuous adsorption, the influence of several operation conditions (initial caffeine concentration, volumetric flow rate, and mass of adsorbent) on the shape of breakthrough curves and the mass transfer resistance was evaluated. Experimental data were fitted to the bed-depth service-time model bed-depth service-time (BDST). Through the calculation of the adsorption, parameters as breakthrough time or caffeine removal percentage can be concluded that the removal of this compound from aqueous solutions by adsorption in sepiolite beds is an alternative technique to the current methods, in order to eliminate this micropollutant.