Adsorption isotherms of benzoic acid onto activated carbon and breakthrough curves in fixed-bed columns

The adsorption isotherms of benzoic acid onto granular activated carbon at varying solution temperatures (25-55°C) and pHs (2-8) from aqueous solution were experimentally determined by batch tests. The Tóth model was found to fit all of the experimental data well. A series of column tests were performed to determine the breakthrough curves with varying bed depths (3-6 cm) and water flow rates (21.6-86.4 cm³/h). The results show that the half breakthrough time increases proportionally with increasing bed depth but decreases inverse proportionally with increasing velocity. The constant-pattern wave approach using the Freundlich isotherm model fits the experimental breakthrough curves quite successfully. A correlation was proposed to predict the volumetric mass-transfer coefficient in the liquid phase.