New insights from modelling and estimation of mass transfer parameters in fixed-bed adsorption of Bisphenol A onto carbon materials.

Abstract

The removal of Bisphenol A, 2,2-bis (4-hydroxyphenyl) propane (BPA) in fixed-bed columns was investigated by breakthrough adsorption tests at different operation conditions and further prediction by a mathematical model to describe the adsorption-diffusion process onto two synthesized carbon porous materials. In this study, a xerogel (RFX) prepared by an optimized conventional sol-gel method and a lignin-based activated carbon (KLP) obtained via chemical activation were used in batch and fixed-bed adsorption experiments. The materials were fully characterized and their adsorptive properties were compared to those obtained with a commercial activated carbon (F400). RFX and KLP materials reached the equilibrium adsorption in only 24\u202fh, whereas F400 activated carbon required 48\u202fh. In addition, F400 and KLP adsorbents showed higher equilibrium adsorption capacity values (qe\u202f=\u202f0.40 and 0.22\u202fkg/kg, for F400 and KLP, respectively) than that obtained for the xerogel (qe\u202f=\u202f0.08\u202fkg/kg). Both synthesized carbon-adsorbents were studied in fixed-bed adsorption tests, exploring the effect of the operation conditions, e.g., initial BPA concentration (0.005-0.04\u202fkg/m3), weight of adsorbent (0.01-0.05\u202fg) and volumetric flow rate (0.2 to 1.0\u202fmL/min), on the adsorption performance of the column. All the tested adsorption columns reached the equilibrium in a very short time, due to the efficient dimensionless of the bed. Additionally, the regeneration of the exhausted adsorbent was studied, achieving the total reuse of the solids after three consecutive cycles using methanol as regeneration agent. Finally, a mathematical model based on mass conservation equations was proposed, allowing to efficiently fit the experimental BPA breakthrough curves and estimate the external and adsorbed-phase mass transfer coefficients with a high accuracy.